Repository: ruby/prism
Pull request #2632 (2024-03-25 19:33:27)

Freeze internal parts, again
Fixes https://github.com/ruby/prism/issues/2532, again


Patch:
diff --git a/config.yml b/config.yml
index d9e39460..bb1dd6e6 100644
--- a/config.yml
+++ b/config.yml
@@ -626,6 +626,13 @@ flags:
       - name: HEXADECIMAL
         comment: "0x prefix"
     comment: Flags for integer nodes that correspond to the base of the integer.
+  - name: InterpolatedStringNodeFlags
+    values:
+      - name: FROZEN
+        comment: "frozen by virtue of a `frozen_string_literal: true` comment or `--enable-frozen-string-literal`"
+      - name: MUTABLE
+        comment: "mutable by virtue of a `frozen_string_literal: false` comment or `--disable-frozen-string-literal`"
+    comment: Flags for interpolated string nodes that indicated mutability if they are also marked as literals.
   - name: KeywordHashNodeFlags
     values:
       - name: SYMBOL_KEYS
@@ -2260,6 +2267,9 @@ nodes:
           ^^^^^^^^^^^^^^^^
   - name: InterpolatedStringNode
     fields:
+      - name: flags
+        type: flags
+        kind: InterpolatedStringNodeFlags
       - name: opening_loc
         type: location?
       - name: parts
diff --git a/lib/prism/node_ext.rb b/lib/prism/node_ext.rb
index 4ec7c301..86745440 100644
--- a/lib/prism/node_ext.rb
+++ b/lib/prism/node_ext.rb
@@ -55,6 +55,7 @@ module Prism
     def to_interpolated
       InterpolatedStringNode.new(
         source,
+        frozen? ? InterpolatedStringNodeFlags::FROZEN : 0,
         opening_loc,
         [copy(opening_loc: nil, closing_loc: nil, location: content_loc)],
         closing_loc,
diff --git a/src/prism.c b/src/prism.c
index cca0e028..cd3a3955 100644
--- a/src/prism.c
+++ b/src/prism.c
@@ -4281,6 +4281,7 @@ pm_interpolated_regular_expression_node_create(pm_parser_t *parser, const pm_tok
     *node = (pm_interpolated_regular_expression_node_t) {
         {
             .type = PM_INTERPOLATED_REGULAR_EXPRESSION_NODE,
+            .flags = PM_NODE_FLAG_STATIC_LITERAL,
             .location = {
                 .start = opening->start,
                 .end = NULL,
@@ -4302,6 +4303,15 @@ pm_interpolated_regular_expression_node_append(pm_interpolated_regular_expressio
     if (node->base.location.end < part->location.end) {
         node->base.location.end = part->location.end;
     }
+
+    if (PM_NODE_TYPE_P(part, PM_STRING_NODE)) {
+        pm_node_flag_set(part, PM_NODE_FLAG_STATIC_LITERAL | PM_STRING_FLAGS_FROZEN);
+    }
+
+    if (!PM_NODE_FLAG_P(part, PM_NODE_FLAG_STATIC_LITERAL)) {
+        pm_node_flag_unset((pm_node_t *) node, PM_NODE_FLAG_STATIC_LITERAL);
+    }
+
     pm_node_list_append(&node->parts, part);
 }
 
@@ -4312,6 +4322,38 @@ pm_interpolated_regular_expression_node_closing_set(pm_parser_t *parser, pm_inte
     pm_node_flag_set((pm_node_t *)node, pm_regular_expression_flags_create(parser, closing));
 }
 
+/**
+ * Append a part to an InterpolatedStringNode node.
+ */
+static inline void
+pm_interpolated_string_node_append(pm_parser_t *parser, pm_interpolated_string_node_t *node, pm_node_t *part) {
+    if (node->parts.size == 0 && node->opening_loc.start == NULL) {
+        node->base.location.start = part->location.start;
+    }
+
+    if (PM_NODE_TYPE_P(part, PM_STRING_NODE)) {
+        pm_node_flag_set(part, PM_NODE_FLAG_STATIC_LITERAL | PM_STRING_FLAGS_FROZEN);
+    }
+
+    if (!PM_NODE_FLAG_P(part, PM_NODE_FLAG_STATIC_LITERAL)) {
+        pm_node_flag_unset((pm_node_t *) node, PM_NODE_FLAG_STATIC_LITERAL | PM_INTERPOLATED_STRING_NODE_FLAGS_FROZEN | PM_INTERPOLATED_STRING_NODE_FLAGS_MUTABLE);
+    }
+
+    pm_node_list_append(&node->parts, part);
+    node->base.location.end = MAX(node->base.location.end, part->location.end);
+
+    if (PM_NODE_FLAG_P(node, PM_NODE_FLAG_STATIC_LITERAL)) {
+        switch (parser->frozen_string_literal) {
+            case PM_OPTIONS_FROZEN_STRING_LITERAL_DISABLED:
+                pm_node_flag_set((pm_node_t *) node, PM_INTERPOLATED_STRING_NODE_FLAGS_MUTABLE);
+                break;
+            case PM_OPTIONS_FROZEN_STRING_LITERAL_ENABLED:
+                pm_node_flag_set((pm_node_t *) node, PM_INTERPOLATED_STRING_NODE_FLAGS_FROZEN);
+                break;
+        }
+    }
+}
+
 /**
  * Allocate and initialize a new InterpolatedStringNode node.
  */
@@ -4322,6 +4364,7 @@ pm_interpolated_string_node_create(pm_parser_t *parser, const pm_token_t *openin
     *node = (pm_interpolated_string_node_t) {
         {
             .type = PM_INTERPOLATED_STRING_NODE,
+            .flags = PM_NODE_FLAG_STATIC_LITERAL,
             .location = {
                 .start = opening->start,
                 .end = closing->end,
@@ -4333,30 +4376,43 @@ pm_interpolated_string_node_create(pm_parser_t *parser, const pm_token_t *openin
     };
 
     if (parts != NULL) {
-        node->parts = *parts;
+        for (size_t index = 0; index < parts->size; index++) {
+            pm_interpolated_string_node_append(parser, node, parts->nodes[index]);
+        }
     }
 
     return node;
 }
 
 /**
- * Append a part to an InterpolatedStringNode node.
+ * Set the closing token of the given InterpolatedStringNode node.
  */
-static inline void
-pm_interpolated_string_node_append(pm_interpolated_string_node_t *node, pm_node_t *part) {
+static void
+pm_interpolated_string_node_closing_set(pm_interpolated_string_node_t *node, const pm_token_t *closing) {
+    node->closing_loc = PM_OPTIONAL_LOCATION_TOKEN_VALUE(closing);
+    node->base.location.end = closing->end;
+}
+
+static void
+pm_interpolated_symbol_node_append(pm_interpolated_symbol_node_t *node, pm_node_t *part) {
     if (node->parts.size == 0 && node->opening_loc.start == NULL) {
         node->base.location.start = part->location.start;
     }
 
+    if (PM_NODE_TYPE_P(part, PM_STRING_NODE)) {
+        pm_node_flag_set(part, PM_NODE_FLAG_STATIC_LITERAL | PM_STRING_FLAGS_FROZEN);
+    }
+
+    if (!PM_NODE_FLAG_P(part, PM_NODE_FLAG_STATIC_LITERAL)) {
+        pm_node_flag_unset((pm_node_t *) node, PM_NODE_FLAG_STATIC_LITERAL);
+    }
+
     pm_node_list_append(&node->parts, part);
-    node->base.location.end = part->location.end;
+    node->base.location.end = MAX(node->base.location.end, part->location.end);
 }
 
-/**
- * Set the closing token of the given InterpolatedStringNode node.
- */
 static void
-pm_interpolated_string_node_closing_set(pm_interpolated_string_node_t *node, const pm_token_t *closing) {
+pm_interpolated_symbol_node_closing_loc_set(pm_interpolated_symbol_node_t *node, const pm_token_t *closing) {
     node->closing_loc = PM_OPTIONAL_LOCATION_TOKEN_VALUE(closing);
     node->base.location.end = closing->end;
 }
@@ -4371,6 +4427,7 @@ pm_interpolated_symbol_node_create(pm_parser_t *parser, const pm_token_t *openin
     *node = (pm_interpolated_symbol_node_t) {
         {
             .type = PM_INTERPOLATED_SYMBOL_NODE,
+            .flags = PM_NODE_FLAG_STATIC_LITERAL,
             .location = {
                 .start = opening->start,
                 .end = closing->end,
@@ -4382,22 +4439,14 @@ pm_interpolated_symbol_node_create(pm_parser_t *parser, const pm_token_t *openin
     };
 
     if (parts != NULL) {
-        node->parts = *parts;
+        for (size_t index = 0; index < parts->size; index++) {
+            pm_interpolated_symbol_node_append(node, parts->nodes[index]);
+        }
     }
 
     return node;
 }
 
-static inline void
-pm_interpolated_symbol_node_append(pm_interpolated_symbol_node_t *node, pm_node_t *part) {
-    if (node->parts.size == 0 && node->opening_loc.start == NULL) {
-        node->base.location.start = part->location.start;
-    }
-
-    pm_node_list_append(&node->parts, part);
-    node->base.location.end = part->location.end;
-}
-
 /**
  * Allocate a new InterpolatedXStringNode node.
  */
@@ -4423,6 +4472,10 @@ pm_interpolated_xstring_node_create(pm_parser_t *parser, const pm_token_t *openi
 
 static inline void
 pm_interpolated_xstring_node_append(pm_interpolated_x_string_node_t *node, pm_node_t *part) {
+    if (PM_NODE_TYPE_P(part, PM_STRING_NODE)) {
+        pm_node_flag_set(part, PM_NODE_FLAG_STATIC_LITERAL | PM_STRING_FLAGS_FROZEN);
+    }
+
     pm_node_list_append(&node->parts, part);
     node->base.location.end = part->location.end;
 }
@@ -10853,11 +10906,15 @@ parser_lex(pm_parser_t *parser) {
                         // the list of newlines.
                         if (parser->heredoc_end == NULL) {
                             pm_newline_list_append(&parser->newline_list, breakpoint);
+                            parser->current.end = breakpoint + 1;
+                            breakpoint = pm_strpbrk(parser, parser->current.end, breakpoints, parser->end - parser->current.end, false);
+                            break;
                         }
 
                         parser->current.end = breakpoint + 1;
-                        breakpoint = pm_strpbrk(parser, parser->current.end, breakpoints, parser->end - parser->current.end, false);
-                        break;
+                        parser_flush_heredoc_end(parser);
+                        pm_regexp_token_buffer_flush(parser, &token_buffer);
+                        LEX(PM_TOKEN_STRING_CONTENT);
                     case '\\': {
                         // If we hit escapes, then we need to treat the next
                         // token literally. In this case we'll skip past the
@@ -14100,14 +14157,12 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
             return (pm_node_t *) pm_string_node_to_symbol_node(parser, (pm_string_node_t *) part, &opening, &parser->previous);
         }
 
-        // Create a node_list first. We'll use this to check if it should be an
-        // InterpolatedSymbolNode or a SymbolNode.
-        pm_node_list_t node_list = { 0 };
-        if (part) pm_node_list_append(&node_list, part);
+        pm_interpolated_symbol_node_t *symbol = pm_interpolated_symbol_node_create(parser, &opening, NULL, &opening);
+        if (part) pm_interpolated_symbol_node_append(symbol, part);
 
         while (!match2(parser, PM_TOKEN_STRING_END, PM_TOKEN_EOF)) {
             if ((part = parse_string_part(parser)) != NULL) {
-                pm_node_list_append(&node_list, part);
+                pm_interpolated_symbol_node_append(symbol, part);
             }
         }
 
@@ -14118,7 +14173,8 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
             expect1(parser, PM_TOKEN_STRING_END, PM_ERR_SYMBOL_TERM_INTERPOLATED);
         }
 
-        return (pm_node_t *) pm_interpolated_symbol_node_create(parser, &opening, &node_list, &parser->previous);
+        pm_interpolated_symbol_node_closing_loc_set(symbol, &parser->previous);
+        return (pm_node_t *) symbol;
     }
 
     pm_token_t content;
@@ -14139,14 +14195,14 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
         // In this case, the best way we have to represent this is as an
         // interpolated string node, so that's what we'll do here.
         if (match1(parser, PM_TOKEN_STRING_CONTENT)) {
-            pm_node_list_t parts = { 0 };
+            pm_interpolated_symbol_node_t *symbol = pm_interpolated_symbol_node_create(parser, &opening, NULL, &opening);
             pm_token_t bounds = not_provided(parser);
 
             pm_node_t *part = (pm_node_t *) pm_string_node_create_unescaped(parser, &bounds, &content, &bounds, &unescaped);
-            pm_node_list_append(&parts, part);
+            pm_interpolated_symbol_node_append(symbol, part);
 
             part = (pm_node_t *) pm_string_node_create_unescaped(parser, &bounds, &parser->current, &bounds, &parser->current_string);
-            pm_node_list_append(&parts, part);
+            pm_interpolated_symbol_node_append(symbol, part);
 
             if (next_state != PM_LEX_STATE_NONE) {
                 lex_state_set(parser, next_state);
@@ -14154,7 +14210,9 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
 
             parser_lex(parser);
             expect1(parser, PM_TOKEN_STRING_END, PM_ERR_SYMBOL_TERM_DYNAMIC);
-            return (pm_node_t *) pm_interpolated_symbol_node_create(parser, &opening, &parts, &parser->previous);
+
+            pm_interpolated_symbol_node_closing_loc_set(symbol, &parser->previous);
+            return (pm_node_t *) symbol;
         }
     } else {
         content = (pm_token_t) { .type = PM_TOKEN_STRING_CONTENT, .start = parser->previous.end, .end = parser->previous.end };
@@ -15322,6 +15380,8 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
 
                 expect1(parser, PM_TOKEN_STRING_END, PM_ERR_STRING_LITERAL_EOF);
                 node = (pm_node_t *) pm_interpolated_string_node_create(parser, &opening, &parts, &parser->previous);
+
+                pm_node_list_free(&parts);
             } else if (accept1(parser, PM_TOKEN_LABEL_END) && !state_is_arg_labeled) {
                 node = (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped, parse_symbol_encoding(parser, &unescaped));
             } else if (match1(parser, PM_TOKEN_EOF)) {
@@ -15376,6 +15436,8 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
                     expect1(parser, PM_TOKEN_STRING_END, PM_ERR_STRING_INTERPOLATED_TERM);
                     node = (pm_node_t *) pm_interpolated_string_node_create(parser, &opening, &parts, &parser->previous);
                 }
+
+                pm_node_list_free(&parts);
             }
         } else {
             // If we get here, then the first part of the string is not plain
@@ -15399,6 +15461,8 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
                 expect1(parser, PM_TOKEN_STRING_END, PM_ERR_STRING_INTERPOLATED_TERM);
                 node = (pm_node_t *) pm_interpolated_string_node_create(parser, &opening, &parts, &parser->previous);
             }
+
+            pm_node_list_free(&parts);
         }
 
         if (current == NULL) {
@@ -15427,11 +15491,11 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
                 pm_token_t bounds = not_provided(parser);
 
                 pm_interpolated_string_node_t *container = pm_interpolated_string_node_create(parser, &bounds, NULL, &bounds);
-                pm_interpolated_string_node_append(container, current);
+                pm_interpolated_string_node_append(parser, container, current);
                 current = (pm_node_t *) container;
             }
 
-            pm_interpolated_string_node_append((pm_interpolated_string_node_t *) current, node);
+            pm_interpolated_string_node_append(parser, (pm_interpolated_string_node_t *) current, node);
         }
     }
 
@@ -16007,6 +16071,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                     node = (pm_node_t *) cast;
                 } else {
                     pm_interpolated_string_node_t *cast = pm_interpolated_string_node_create(parser, &opening, &parts, &opening);
+                    pm_node_list_free(&parts);
 
                     lex_mode_pop(parser);
                     expect1(parser, PM_TOKEN_HEREDOC_END, PM_ERR_HEREDOC_TERM);
@@ -17365,15 +17430,15 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                             // If we hit string content and the current node is
                             // an interpolated string, then we need to append
                             // the string content to the list of child nodes.
-                            pm_interpolated_string_node_append((pm_interpolated_string_node_t *) current, string);
+                            pm_interpolated_string_node_append(parser, (pm_interpolated_string_node_t *) current, string);
                         } else if (PM_NODE_TYPE_P(current, PM_STRING_NODE)) {
                             // If we hit string content and the current node is
                             // a string node, then we need to convert the
                             // current node into an interpolated string and add
                             // the string content to the list of child nodes.
                             pm_interpolated_string_node_t *interpolated = pm_interpolated_string_node_create(parser, &opening, NULL, &closing);
-                            pm_interpolated_string_node_append(interpolated, current);
-                            pm_interpolated_string_node_append(interpolated, string);
+                            pm_interpolated_string_node_append(parser, interpolated, current);
+                            pm_interpolated_string_node_append(parser, interpolated, string);
                             current = (pm_node_t *) interpolated;
                         } else {
                             assert(false && "unreachable");
@@ -17398,7 +17463,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                             pm_token_t opening = not_provided(parser);
                             pm_token_t closing = not_provided(parser);
                             pm_interpolated_string_node_t *interpolated = pm_interpolated_string_node_create(parser, &opening, NULL, &closing);
-                            pm_interpolated_string_node_append(interpolated, current);
+                            pm_interpolated_string_node_append(parser, interpolated, current);
                             current = (pm_node_t *) interpolated;
                         } else {
                             // If we hit an embedded variable and the current
@@ -17407,7 +17472,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                         }
 
                         pm_node_t *part = parse_string_part(parser);
-                        pm_interpolated_string_node_append((pm_interpolated_string_node_t *) current, part);
+                        pm_interpolated_string_node_append(parser, (pm_interpolated_string_node_t *) current, part);
                         break;
                     }
                     case PM_TOKEN_EMBEXPR_BEGIN: {
@@ -17427,7 +17492,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                             pm_token_t opening = not_provided(parser);
                             pm_token_t closing = not_provided(parser);
                             pm_interpolated_string_node_t *interpolated = pm_interpolated_string_node_create(parser, &opening, NULL, &closing);
-                            pm_interpolated_string_node_append(interpolated, current);
+                            pm_interpolated_string_node_append(parser, interpolated, current);
                             current = (pm_node_t *) interpolated;
                         } else if (PM_NODE_TYPE_P(current, PM_INTERPOLATED_STRING_NODE)) {
                             // If we hit an embedded expression and the current
@@ -17438,7 +17503,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                         }
 
                         pm_node_t *part = parse_string_part(parser);
-                        pm_interpolated_string_node_append((pm_interpolated_string_node_t *) current, part);
+                        pm_interpolated_string_node_append(parser, (pm_interpolated_string_node_t *) current, part);
                         break;
                     }
                     default:


Test patch:
diff --git a/test/prism/snapshots/alias.txt b/test/prism/snapshots/alias.txt
index 687082d8..a952e96f 100644
--- a/test/prism/snapshots/alias.txt
+++ b/test/prism/snapshots/alias.txt
@@ -57,7 +57,7 @@
         │   │   ├── opening_loc: (7,6)-(7,8) = ":\""
         │   │   ├── parts: (length: 2)
         │   │   │   ├── @ StringNode (location: (7,8)-(7,11))
-        │   │   │   │   ├── flags: ∅
+        │   │   │   │   ├── flags: frozen
         │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   ├── content_loc: (7,8)-(7,11) = "abc"
         │   │   │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/dash_heredocs.txt b/test/prism/snapshots/dash_heredocs.txt
index 9af3acf9..bd2b05ea 100644
--- a/test/prism/snapshots/dash_heredocs.txt
+++ b/test/prism/snapshots/dash_heredocs.txt
@@ -79,10 +79,11 @@
         │   ├── closing_loc: (23,0)-(24,0) = "  EOF\n"
         │   └── unescaped: "  a\n  b\n"
         ├── @ InterpolatedStringNode (location: (25,0)-(25,8))
+        │   ├── flags: ∅
         │   ├── opening_loc: (25,0)-(25,8) = "<<-\"EOF\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (26,0)-(27,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (26,0)-(27,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -104,17 +105,18 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (27,3)-(27,4) = "}"
         │   │   └── @ StringNode (location: (27,4)-(28,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (27,4)-(28,0) = "\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n"
         │   └── closing_loc: (28,0)-(29,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (30,0)-(30,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (30,0)-(30,6) = "<<-EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (31,0)-(32,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (31,0)-(32,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -136,7 +138,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (32,3)-(32,4) = "}"
         │   │   └── @ StringNode (location: (32,4)-(33,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (32,4)-(33,0) = "\n"
         │   │       ├── closing_loc: ∅
@@ -184,10 +186,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (49,7)-(49,11))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (49,7)-(49,11) = "<<-B"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (52,0)-(53,2))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (52,0)-(53,2) = "  b\n  "
         │   │           │   │   ├── closing_loc: ∅
@@ -202,7 +205,7 @@
         │   │           │   │   │           └── value: 2
         │   │           │   │   └── closing_loc: (54,2)-(54,3) = "}"
         │   │           │   └── @ StringNode (location: (54,3)-(55,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (54,3)-(55,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -228,10 +231,11 @@
             │   ├── flags: ∅
             │   └── arguments: (length: 1)
             │       └── @ InterpolatedStringNode (location: (57,7)-(57,11))
+            │           ├── flags: ∅
             │           ├── opening_loc: (57,7)-(57,11) = "<<-B"
             │           ├── parts: (length: 3)
             │           │   ├── @ StringNode (location: (60,0)-(61,2))
-            │           │   │   ├── flags: ∅
+            │           │   │   ├── flags: frozen
             │           │   │   ├── opening_loc: ∅
             │           │   │   ├── content_loc: (60,0)-(61,2) = "  b\n  "
             │           │   │   ├── closing_loc: ∅
@@ -246,7 +250,7 @@
             │           │   │   │           └── value: 2
             │           │   │   └── closing_loc: (62,3)-(62,4) = "}"
             │           │   └── @ StringNode (location: (62,4)-(63,0))
-            │           │       ├── flags: ∅
+            │           │       ├── flags: frozen
             │           │       ├── opening_loc: ∅
             │           │       ├── content_loc: (62,4)-(63,0) = "\n"
             │           │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/dos_endings.txt b/test/prism/snapshots/dos_endings.txt
index c5b962f2..1ae15e1e 100644
--- a/test/prism/snapshots/dos_endings.txt
+++ b/test/prism/snapshots/dos_endings.txt
@@ -15,16 +15,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (1,5)-(2,12))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: ∅
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (1,5)-(1,9))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: (1,5)-(1,6) = "\""
         │   │           │   │   ├── content_loc: (1,6)-(1,8) = "hi"
         │   │           │   │   ├── closing_loc: (1,8)-(1,9) = "\""
         │   │           │   │   └── unescaped: "hi"
         │   │           │   └── @ StringNode (location: (2,5)-(2,12))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: (2,5)-(2,6) = "\""
         │   │           │       ├── content_loc: (2,6)-(2,11) = "there"
         │   │           │       ├── closing_loc: (2,11)-(2,12) = "\""
@@ -81,16 +82,17 @@
             │   │           ├── flags: ∅
             │   │           ├── receiver:
             │   │           │   @ InterpolatedStringNode (location: (17,8)-(17,14))
+            │   │           │   ├── flags: ∅
             │   │           │   ├── opening_loc: (17,8)-(17,14) = "<<~EOF"
             │   │           │   ├── parts: (length: 2)
             │   │           │   │   ├── @ StringNode (location: (18,0)-(19,0))
-            │   │           │   │   │   ├── flags: ∅
+            │   │           │   │   │   ├── flags: frozen
             │   │           │   │   │   ├── opening_loc: ∅
             │   │           │   │   │   ├── content_loc: (18,0)-(19,0) = "\r\n"
             │   │           │   │   │   ├── closing_loc: ∅
             │   │           │   │   │   └── unescaped: "\n"
             │   │           │   │   └── @ StringNode (location: (19,0)-(20,0))
-            │   │           │   │       ├── flags: ∅
+            │   │           │   │       ├── flags: frozen
             │   │           │   │       ├── opening_loc: ∅
             │   │           │   │       ├── content_loc: (19,0)-(20,0) = "    baz\r\n"
             │   │           │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/dstring.txt b/test/prism/snapshots/dstring.txt
index ad395f8a..3978a2f0 100644
--- a/test/prism/snapshots/dstring.txt
+++ b/test/prism/snapshots/dstring.txt
@@ -10,10 +10,11 @@
         │   ├── closing_loc: (2,5)-(2,6) = "\""
         │   └── unescaped: "foo\n  bar"
         ├── @ InterpolatedStringNode (location: (4,0)-(5,9))
+        │   ├── flags: ∅
         │   ├── opening_loc: (4,0)-(4,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (4,1)-(5,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (4,1)-(5,2) = "foo\n  "
         │   │   │   ├── closing_loc: ∅
@@ -36,16 +37,17 @@
         │   │       └── closing_loc: (5,7)-(5,8) = "}"
         │   └── closing_loc: (5,8)-(5,9) = "\""
         ├── @ InterpolatedStringNode (location: (7,0)-(9,2))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (7,0)-(8,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: (7,0)-(7,1) = "\""
         │   │   │   ├── content_loc: (7,1)-(8,1) = "fo\no"
         │   │   │   ├── closing_loc: (8,1)-(8,2) = "\""
         │   │   │   └── unescaped: "fo\no"
         │   │   └── @ StringNode (location: (8,3)-(9,2))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (8,3)-(8,4) = "\""
         │   │       ├── content_loc: (8,4)-(9,1) = "ba\nr"
         │   │       ├── closing_loc: (9,1)-(9,2) = "\""
diff --git a/test/prism/snapshots/heredocs_leading_whitespace.txt b/test/prism/snapshots/heredocs_leading_whitespace.txt
index 332dfa29..dbcb0d5a 100644
--- a/test/prism/snapshots/heredocs_leading_whitespace.txt
+++ b/test/prism/snapshots/heredocs_leading_whitespace.txt
@@ -28,32 +28,34 @@
         │   ├── closing_loc: (19,0)-(20,0) = "  FOO\n"
         │   └── unescaped: "a\nb\n"
         ├── @ InterpolatedStringNode (location: (21,0)-(21,10))
+        │   ├── flags: ∅
         │   ├── opening_loc: (21,0)-(21,10) = "<<~'  FOO'"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (22,0)-(23,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (22,0)-(23,0) = "a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (23,0)-(24,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (23,0)-(24,0) = "b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (24,0)-(25,0) = "     FOO\n"
         └── @ InterpolatedStringNode (location: (26,0)-(26,10))
+            ├── flags: ∅
             ├── opening_loc: (26,0)-(26,10) = "<<~'  FOO'"
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (27,0)-(28,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (27,0)-(28,0) = "a\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "a\n"
             │   └── @ StringNode (location: (28,0)-(29,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (28,0)-(29,0) = "b\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/heredocs_nested.txt b/test/prism/snapshots/heredocs_nested.txt
index 1717aadb..f830b028 100644
--- a/test/prism/snapshots/heredocs_nested.txt
+++ b/test/prism/snapshots/heredocs_nested.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(12,4))
     └── body: (length: 2)
         ├── @ InterpolatedStringNode (location: (1,0)-(1,7))
+        │   ├── flags: ∅
         │   ├── opening_loc: (1,0)-(1,7) = "<<~RUBY"
         │   ├── parts: (length: 4)
         │   │   ├── @ StringNode (location: (2,0)-(3,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (2,0)-(3,0) = "pre\n"
         │   │   │   ├── closing_loc: ∅
@@ -25,19 +26,20 @@
         │   │   │   │           └── unescaped: "  hello\n"
         │   │   │   └── closing_loc: (7,0)-(7,1) = "}"
         │   │   ├── @ StringNode (location: (7,1)-(8,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (7,1)-(8,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   └── @ StringNode (location: (8,0)-(9,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (8,0)-(9,0) = "post\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "post\n"
         │   └── closing_loc: (9,0)-(10,0) = "RUBY\n"
         └── @ InterpolatedStringNode (location: (12,0)-(12,4))
+            ├── flags: ∅
             ├── opening_loc: (12,0)-(12,4) = "<<-A"
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (13,0)-(21,1))
@@ -46,6 +48,7 @@
             │   │   │   @ StatementsNode (location: (14,0)-(14,4))
             │   │   │   └── body: (length: 1)
             │   │   │       └── @ InterpolatedStringNode (location: (14,0)-(14,4))
+            │   │   │           ├── flags: ∅
             │   │   │           ├── opening_loc: (14,0)-(14,4) = "<<-B"
             │   │   │           ├── parts: (length: 2)
             │   │   │           │   ├── @ EmbeddedStatementsNode (location: (15,0)-(19,1))
@@ -54,6 +57,7 @@
             │   │   │           │   │   │   @ StatementsNode (location: (16,0)-(16,4))
             │   │   │           │   │   │   └── body: (length: 1)
             │   │   │           │   │   │       └── @ InterpolatedStringNode (location: (16,0)-(16,4))
+            │   │   │           │   │   │           ├── flags: ∅
             │   │   │           │   │   │           ├── opening_loc: (16,0)-(16,4) = "<<-C"
             │   │   │           │   │   │           ├── parts: (length: 2)
             │   │   │           │   │   │           │   ├── @ EmbeddedStatementsNode (location: (17,0)-(17,4))
@@ -66,7 +70,7 @@
             │   │   │           │   │   │           │   │   │           └── value: 3
             │   │   │           │   │   │           │   │   └── closing_loc: (17,3)-(17,4) = "}"
             │   │   │           │   │   │           │   └── @ StringNode (location: (17,4)-(18,0))
-            │   │   │           │   │   │           │       ├── flags: ∅
+            │   │   │           │   │   │           │       ├── flags: frozen
             │   │   │           │   │   │           │       ├── opening_loc: ∅
             │   │   │           │   │   │           │       ├── content_loc: (17,4)-(18,0) = "\n"
             │   │   │           │   │   │           │       ├── closing_loc: ∅
@@ -74,7 +78,7 @@
             │   │   │           │   │   │           └── closing_loc: (18,0)-(19,0) = "C\n"
             │   │   │           │   │   └── closing_loc: (19,0)-(19,1) = "}"
             │   │   │           │   └── @ StringNode (location: (19,1)-(20,0))
-            │   │   │           │       ├── flags: ∅
+            │   │   │           │       ├── flags: frozen
             │   │   │           │       ├── opening_loc: ∅
             │   │   │           │       ├── content_loc: (19,1)-(20,0) = "\n"
             │   │   │           │       ├── closing_loc: ∅
@@ -82,7 +86,7 @@
             │   │   │           └── closing_loc: (20,0)-(21,0) = "B\n"
             │   │   └── closing_loc: (21,0)-(21,1) = "}"
             │   └── @ StringNode (location: (21,1)-(22,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (21,1)-(22,0) = "\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/heredocs_with_ignored_newlines.txt b/test/prism/snapshots/heredocs_with_ignored_newlines.txt
index cdc0b4fa..0f964ec2 100644
--- a/test/prism/snapshots/heredocs_with_ignored_newlines.txt
+++ b/test/prism/snapshots/heredocs_with_ignored_newlines.txt
@@ -10,58 +10,59 @@
         │   ├── closing_loc: (2,0)-(3,0) = "HERE\n"
         │   └── unescaped: ""
         └── @ InterpolatedStringNode (location: (4,0)-(4,8))
+            ├── flags: ∅
             ├── opening_loc: (4,0)-(4,8) = "<<~THERE"
             ├── parts: (length: 9)
             │   ├── @ StringNode (location: (5,0)-(6,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (5,0)-(6,0) = "  way over\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "way over\n"
             │   ├── @ StringNode (location: (6,0)-(7,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (6,0)-(7,0) = "  <<HERE\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "<<HERE\n"
             │   ├── @ StringNode (location: (7,0)-(8,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (7,0)-(8,0) = "    not here\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "  not here\n"
             │   ├── @ StringNode (location: (8,0)-(9,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (8,0)-(9,0) = "  HERE\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "HERE\n"
             │   ├── @ StringNode (location: (9,0)-(10,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (9,0)-(10,0) = "\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "\n"
             │   ├── @ StringNode (location: (10,0)-(11,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (10,0)-(11,0) = "  <<~BUT\\\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "<<~BUT"
             │   ├── @ StringNode (location: (11,0)-(12,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (11,0)-(12,0) = "    but\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "  but\n"
             │   ├── @ StringNode (location: (12,0)-(13,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (12,0)-(13,0) = "  BUT\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "BUT\n"
             │   └── @ StringNode (location: (13,0)-(14,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (13,0)-(14,0) = "    there\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/lambda.txt b/test/prism/snapshots/lambda.txt
index f9e82c88..0864b103 100644
--- a/test/prism/snapshots/lambda.txt
+++ b/test/prism/snapshots/lambda.txt
@@ -46,10 +46,11 @@
         │   │   │   │       ├── name_loc: (5,3)-(5,5) = "x:"
         │   │   │   │       └── value:
         │   │   │   │           @ InterpolatedStringNode (location: (5,6)-(5,13))
+        │   │   │   │           ├── flags: ∅
         │   │   │   │           ├── opening_loc: (5,6)-(5,7) = "\""
         │   │   │   │           ├── parts: (length: 2)
         │   │   │   │           │   ├── @ StringNode (location: (5,7)-(5,8))
-        │   │   │   │           │   │   ├── flags: ∅
+        │   │   │   │           │   │   ├── flags: frozen
         │   │   │   │           │   │   ├── opening_loc: ∅
         │   │   │   │           │   │   ├── content_loc: (5,7)-(5,8) = "b"
         │   │   │   │           │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/method_calls.txt b/test/prism/snapshots/method_calls.txt
index 370686e9..de9ba71a 100644
--- a/test/prism/snapshots/method_calls.txt
+++ b/test/prism/snapshots/method_calls.txt
@@ -1669,6 +1669,7 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (109,4)-(109,29))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (109,4)-(109,5) = "\""
         │   │           ├── parts: (length: 1)
         │   │           │   └── @ EmbeddedStatementsNode (location: (109,5)-(109,28))
@@ -2237,6 +2238,7 @@
         │   ├── closing_loc: ∅
         │   └── block: ∅
         ├── @ InterpolatedStringNode (location: (145,0)-(145,17))
+        │   ├── flags: ∅
         │   ├── opening_loc: (145,0)-(145,1) = "\""
         │   ├── parts: (length: 1)
         │   │   └── @ EmbeddedStatementsNode (location: (145,1)-(145,16))
@@ -2272,6 +2274,7 @@
         │   │       └── closing_loc: (145,15)-(145,16) = "}"
         │   └── closing_loc: (145,16)-(145,17) = "\""
         ├── @ InterpolatedStringNode (location: (147,0)-(147,8))
+        │   ├── flags: ∅
         │   ├── opening_loc: (147,0)-(147,1) = "\""
         │   ├── parts: (length: 1)
         │   │   └── @ EmbeddedStatementsNode (location: (147,1)-(147,7))
@@ -2425,7 +2428,7 @@
             │                   │   ├── opening_loc: (156,5)-(156,6) = "\""
             │                   │   ├── parts: (length: 2)
             │                   │   │   ├── @ StringNode (location: (156,6)-(156,7))
-            │                   │   │   │   ├── flags: ∅
+            │                   │   │   │   ├── flags: frozen
             │                   │   │   │   ├── opening_loc: ∅
             │                   │   │   │   ├── content_loc: (156,6)-(156,7) = "c"
             │                   │   │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/methods.txt b/test/prism/snapshots/methods.txt
index ac21bbae..24567d24 100644
--- a/test/prism/snapshots/methods.txt
+++ b/test/prism/snapshots/methods.txt
@@ -1237,10 +1237,11 @@
         │   │   @ StatementsNode (location: (136,12)-(136,26))
         │   │   └── body: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (136,12)-(136,26))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (136,12)-(136,13) = "\""
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (136,13)-(136,16))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (136,13)-(136,16) = "foo"
         │   │           │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/modules.txt b/test/prism/snapshots/modules.txt
index aef3875d..1a0eb632 100644
--- a/test/prism/snapshots/modules.txt
+++ b/test/prism/snapshots/modules.txt
@@ -24,10 +24,11 @@
         │   ├── end_keyword_loc: (1,15)-(1,18) = "end"
         │   └── name: :A
         ├── @ InterpolatedStringNode (location: (3,0)-(3,18))
+        │   ├── flags: ∅
         │   ├── opening_loc: (3,0)-(3,3) = "%Q{"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (3,3)-(3,7))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (3,3)-(3,7) = "aaa "
         │   │   │   ├── closing_loc: ∅
@@ -49,7 +50,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (3,12)-(3,13) = "}"
         │   │   └── @ StringNode (location: (3,13)-(3,17))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (3,13)-(3,17) = " ccc"
         │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/regex.txt b/test/prism/snapshots/regex.txt
index 9e19bbb1..d07ab8c5 100644
--- a/test/prism/snapshots/regex.txt
+++ b/test/prism/snapshots/regex.txt
@@ -39,7 +39,7 @@
         │   ├── opening_loc: (7,0)-(7,1) = "/"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (7,1)-(7,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (7,1)-(7,5) = "aaa "
         │   │   │   ├── closing_loc: ∅
@@ -55,7 +55,7 @@
         │   ├── opening_loc: (9,0)-(9,1) = "/"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (9,1)-(9,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (9,1)-(9,5) = "aaa "
         │   │   │   ├── closing_loc: ∅
@@ -77,7 +77,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (9,10)-(9,11) = "}"
         │   │   └── @ StringNode (location: (9,11)-(9,15))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (9,11)-(9,15) = " ccc"
         │   │       ├── closing_loc: ∅
@@ -192,7 +192,7 @@
         │   ├── opening_loc: (30,0)-(30,1) = "/"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (30,1)-(30,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (30,1)-(30,5) = "aaa "
         │   │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/difficult0_.txt b/test/prism/snapshots/seattlerb/difficult0_.txt
index 251a8012..8ba30ccf 100644
--- a/test/prism/snapshots/seattlerb/difficult0_.txt
+++ b/test/prism/snapshots/seattlerb/difficult0_.txt
@@ -35,16 +35,17 @@
             │           │   │   ├── flags: ∅
             │           │   │   └── arguments: (length: 1)
             │           │   │       └── @ InterpolatedStringNode (location: (1,9)-(4,4))
+            │           │   │           ├── flags: ∅
             │           │   │           ├── opening_loc: (1,9)-(1,10) = "'"
             │           │   │           ├── parts: (length: 2)
             │           │   │           │   ├── @ StringNode (location: (1,10)-(2,0))
-            │           │   │           │   │   ├── flags: ∅
+            │           │   │           │   │   ├── flags: frozen
             │           │   │           │   │   ├── opening_loc: ∅
             │           │   │           │   │   ├── content_loc: (1,10)-(2,0) = "b\n"
             │           │   │           │   │   ├── closing_loc: ∅
             │           │   │           │   │   └── unescaped: "b\n"
             │           │   │           │   └── @ StringNode (location: (4,0)-(4,3))
-            │           │   │           │       ├── flags: ∅
+            │           │   │           │       ├── flags: frozen
             │           │   │           │       ├── opening_loc: ∅
             │           │   │           │       ├── content_loc: (4,0)-(4,3) = "  c"
             │           │   │           │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/dstr_evstr.txt b/test/prism/snapshots/seattlerb/dstr_evstr.txt
index ce692238..8d771e88 100644
--- a/test/prism/snapshots/seattlerb/dstr_evstr.txt
+++ b/test/prism/snapshots/seattlerb/dstr_evstr.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,12))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,12))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (1,1)-(1,7))
diff --git a/test/prism/snapshots/seattlerb/dstr_lex_state.txt b/test/prism/snapshots/seattlerb/dstr_lex_state.txt
index 0e7f8ff8..c4c0ef04 100644
--- a/test/prism/snapshots/seattlerb/dstr_lex_state.txt
+++ b/test/prism/snapshots/seattlerb/dstr_lex_state.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,8))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,8))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 1)
             │   └── @ EmbeddedStatementsNode (location: (1,1)-(1,7))
diff --git a/test/prism/snapshots/seattlerb/dstr_str.txt b/test/prism/snapshots/seattlerb/dstr_str.txt
index 42bd37a1..70b5752c 100644
--- a/test/prism/snapshots/seattlerb/dstr_str.txt
+++ b/test/prism/snapshots/seattlerb/dstr_str.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,10))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,10))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (1,1)-(1,7))
@@ -19,7 +20,7 @@
             │   │   │           └── unescaped: "a"
             │   │   └── closing_loc: (1,6)-(1,7) = "}"
             │   └── @ StringNode (location: (1,7)-(1,9))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,7)-(1,9) = " b"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/evstr_evstr.txt b/test/prism/snapshots/seattlerb/evstr_evstr.txt
index ef7545c2..9c801299 100644
--- a/test/prism/snapshots/seattlerb/evstr_evstr.txt
+++ b/test/prism/snapshots/seattlerb/evstr_evstr.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,10))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,10))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (1,1)-(1,5))
diff --git a/test/prism/snapshots/seattlerb/evstr_str.txt b/test/prism/snapshots/seattlerb/evstr_str.txt
index 214491d6..54319e61 100644
--- a/test/prism/snapshots/seattlerb/evstr_str.txt
+++ b/test/prism/snapshots/seattlerb/evstr_str.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,8))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,8))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (1,1)-(1,5))
@@ -23,7 +24,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,4)-(1,5) = "}"
             │   └── @ StringNode (location: (1,5)-(1,7))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,5)-(1,7) = " b"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_nested.txt b/test/prism/snapshots/seattlerb/heredoc_nested.txt
index 4734068b..26d533a3 100644
--- a/test/prism/snapshots/seattlerb/heredoc_nested.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_nested.txt
@@ -7,6 +7,7 @@
             ├── flags: ∅
             ├── elements: (length: 2)
             │   ├── @ InterpolatedStringNode (location: (1,1)-(1,4))
+            │   │   ├── flags: ∅
             │   │   ├── opening_loc: (1,1)-(1,4) = "<<A"
             │   │   ├── parts: (length: 3)
             │   │   │   ├── @ EmbeddedStatementsNode (location: (2,0)-(2,6))
@@ -22,13 +23,13 @@
             │   │   │   │   │           └── unescaped: "b\n"
             │   │   │   │   └── closing_loc: (2,5)-(2,6) = "}"
             │   │   │   ├── @ StringNode (location: (2,6)-(3,0))
-            │   │   │   │   ├── flags: ∅
+            │   │   │   │   ├── flags: frozen
             │   │   │   │   ├── opening_loc: ∅
             │   │   │   │   ├── content_loc: (2,6)-(3,0) = "\n"
             │   │   │   │   ├── closing_loc: ∅
             │   │   │   │   └── unescaped: "\n"
             │   │   │   └── @ StringNode (location: (5,0)-(6,0))
-            │   │   │       ├── flags: ∅
+            │   │   │       ├── flags: frozen
             │   │   │       ├── opening_loc: ∅
             │   │   │       ├── content_loc: (5,0)-(6,0) = "a\n"
             │   │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly.txt
index 48f830be..9bab044a 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly.txt
@@ -9,22 +9,23 @@
             ├── name_loc: (1,0)-(1,1) = "a"
             ├── value:
             │   @ InterpolatedStringNode (location: (1,4)-(1,12))
+            │   ├── flags: ∅
             │   ├── opening_loc: (1,4)-(1,12) = "<<~\"EOF\""
             │   ├── parts: (length: 3)
             │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (2,0)-(3,0) = "  x\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "x\n"
             │   │   ├── @ StringNode (location: (3,0)-(4,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (3,0)-(4,0) = "  y\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "y\n"
             │   │   └── @ StringNode (location: (4,0)-(5,0))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (4,0)-(5,0) = "  z\n"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_line_plus_interpolation.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_line_plus_interpolation.txt
index 3a4ea011..e12014af 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_line_plus_interpolation.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_line_plus_interpolation.txt
@@ -23,10 +23,11 @@
             │   │           ├── flags: ∅
             │   │           ├── receiver:
             │   │           │   @ InterpolatedStringNode (location: (1,8)-(1,14))
+            │   │           │   ├── flags: ∅
             │   │           │   ├── opening_loc: (1,8)-(1,14) = "<<~EOF"
             │   │           │   ├── parts: (length: 3)
             │   │           │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │           │   │   │   ├── flags: ∅
+            │   │           │   │   │   ├── flags: frozen
             │   │           │   │   │   ├── opening_loc: ∅
             │   │           │   │   │   ├── content_loc: (2,0)-(3,0) = "\n"
             │   │           │   │   │   ├── closing_loc: ∅
@@ -48,7 +49,7 @@
             │   │           │   │   │   │           └── block: ∅
             │   │           │   │   │   └── closing_loc: (3,9)-(3,10) = "}"
             │   │           │   │   └── @ StringNode (location: (3,10)-(4,0))
-            │   │           │   │       ├── flags: ∅
+            │   │           │   │       ├── flags: frozen
             │   │           │   │       ├── opening_loc: ∅
             │   │           │   │       ├── content_loc: (3,10)-(4,0) = "baz\n"
             │   │           │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_lines.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_lines.txt
index 533f8ac4..8596647e 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_lines.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly_blank_lines.txt
@@ -9,22 +9,23 @@
             ├── name_loc: (1,0)-(1,1) = "a"
             ├── value:
             │   @ InterpolatedStringNode (location: (1,4)-(1,10))
+            │   ├── flags: ∅
             │   ├── opening_loc: (1,4)-(1,10) = "<<~EOF"
             │   ├── parts: (length: 3)
             │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (2,0)-(3,0) = "  x\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "x\n"
             │   │   ├── @ StringNode (location: (3,0)-(4,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (3,0)-(4,0) = "\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "\n"
             │   │   └── @ StringNode (location: (4,0)-(5,0))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (4,0)-(5,0) = "  z\n"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly_interp.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly_interp.txt
index 31360286..d34f89ff 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly_interp.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly_interp.txt
@@ -9,16 +9,17 @@
             ├── name_loc: (1,0)-(1,1) = "a"
             ├── value:
             │   @ InterpolatedStringNode (location: (1,4)-(1,10))
+            │   ├── flags: ∅
             │   ├── opening_loc: (1,4)-(1,10) = "<<~EOF"
             │   ├── parts: (length: 5)
             │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (2,0)-(3,0) = "      w\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "    w\n"
             │   │   ├── @ StringNode (location: (3,0)-(3,3))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (3,0)-(3,3) = "  x"
             │   │   │   ├── closing_loc: ∅
@@ -33,13 +34,13 @@
             │   │   │   │           └── value: 42
             │   │   │   └── closing_loc: (3,7)-(3,8) = "}"
             │   │   ├── @ StringNode (location: (3,8)-(4,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (3,8)-(4,0) = " y\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: " y\n"
             │   │   └── @ StringNode (location: (4,0)-(5,0))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (4,0)-(5,0) = "    z\n"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs.txt
index 8a058191..311d7bc1 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs.txt
@@ -9,16 +9,17 @@
             ├── name_loc: (1,0)-(1,1) = "a"
             ├── value:
             │   @ InterpolatedStringNode (location: (1,4)-(1,12))
+            │   ├── flags: ∅
             │   ├── opening_loc: (1,4)-(1,12) = "<<~\"EOF\""
             │   ├── parts: (length: 2)
             │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (2,0)-(3,0) = "        blah blah\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "blah blah\n"
             │   │   └── @ StringNode (location: (3,0)-(4,0))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (3,0)-(4,0) = "\t blah blah\n"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs_extra.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs_extra.txt
index af85f11e..3150f807 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs_extra.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly_tabs_extra.txt
@@ -9,16 +9,17 @@
             ├── name_loc: (1,0)-(1,1) = "a"
             ├── value:
             │   @ InterpolatedStringNode (location: (1,4)-(1,12))
+            │   ├── flags: ∅
             │   ├── opening_loc: (1,4)-(1,12) = "<<~\"EOF\""
             │   ├── parts: (length: 2)
             │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (2,0)-(3,0) = "  blah blah\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "blah blah\n"
             │   │   └── @ StringNode (location: (3,0)-(4,0))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (3,0)-(4,0) = " \tblah blah\n"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_squiggly_visually_blank_lines.txt b/test/prism/snapshots/seattlerb/heredoc_squiggly_visually_blank_lines.txt
index 3cba13a9..85c3d2df 100644
--- a/test/prism/snapshots/seattlerb/heredoc_squiggly_visually_blank_lines.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_squiggly_visually_blank_lines.txt
@@ -9,22 +9,23 @@
             ├── name_loc: (1,0)-(1,1) = "a"
             ├── value:
             │   @ InterpolatedStringNode (location: (1,4)-(1,10))
+            │   ├── flags: ∅
             │   ├── opening_loc: (1,4)-(1,10) = "<<~EOF"
             │   ├── parts: (length: 3)
             │   │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (2,0)-(3,0) = "  x\n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "x\n"
             │   │   ├── @ StringNode (location: (3,0)-(4,0))
-            │   │   │   ├── flags: ∅
+            │   │   │   ├── flags: frozen
             │   │   │   ├── opening_loc: ∅
             │   │   │   ├── content_loc: (3,0)-(4,0) = " \n"
             │   │   │   ├── closing_loc: ∅
             │   │   │   └── unescaped: "\n"
             │   │   └── @ StringNode (location: (4,0)-(5,0))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (4,0)-(5,0) = "  z\n"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes.txt b/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes.txt
index 0067e498..c4be1244 100644
--- a/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,5))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,5))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,5) = "<<EOS"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (2,0)-(2,5))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (2,0)-(2,5) = "foo\\r"
             │   │   ├── closing_loc: ∅
@@ -18,7 +19,7 @@
             │   │       @ InstanceVariableReadNode (location: (2,6)-(2,10))
             │   │       └── name: :@bar
             │   └── @ StringNode (location: (2,10)-(3,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (2,10)-(3,0) = "\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes_windows.txt b/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes_windows.txt
index 7eb04bdb..c2290cec 100644
--- a/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes_windows.txt
+++ b/test/prism/snapshots/seattlerb/heredoc_with_interpolation_and_carriage_return_escapes_windows.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,5))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,5))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,5) = "<<EOS"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (2,0)-(2,5))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (2,0)-(2,5) = "foo\\r"
             │   │   ├── closing_loc: ∅
@@ -18,7 +19,7 @@
             │   │       @ InstanceVariableReadNode (location: (2,6)-(2,10))
             │   │       └── name: :@bar
             │   └── @ StringNode (location: (2,10)-(3,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (2,10)-(3,0) = "\r\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/parse_line_dstr_escaped_newline.txt b/test/prism/snapshots/seattlerb/parse_line_dstr_escaped_newline.txt
index e135d31a..aada5a94 100644
--- a/test/prism/snapshots/seattlerb/parse_line_dstr_escaped_newline.txt
+++ b/test/prism/snapshots/seattlerb/parse_line_dstr_escaped_newline.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(3,4))
     └── body: (length: 2)
         ├── @ InterpolatedStringNode (location: (1,0)-(2,2))
+        │   ├── flags: ∅
         │   ├── opening_loc: (1,0)-(1,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (1,1)-(1,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (1,1)-(1,4) = "a\\n"
         │   │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/parse_line_dstr_soft_newline.txt b/test/prism/snapshots/seattlerb/parse_line_dstr_soft_newline.txt
index 4415cbcc..7ef56acb 100644
--- a/test/prism/snapshots/seattlerb/parse_line_dstr_soft_newline.txt
+++ b/test/prism/snapshots/seattlerb/parse_line_dstr_soft_newline.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(4,4))
     └── body: (length: 2)
         ├── @ InterpolatedStringNode (location: (1,0)-(3,2))
+        │   ├── flags: ∅
         │   ├── opening_loc: (1,0)-(1,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (1,1)-(2,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (1,1)-(2,0) = "a\n"
         │   │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/parse_line_evstr_after_break.txt b/test/prism/snapshots/seattlerb/parse_line_evstr_after_break.txt
index 9cb200e9..82f461e3 100644
--- a/test/prism/snapshots/seattlerb/parse_line_evstr_after_break.txt
+++ b/test/prism/snapshots/seattlerb/parse_line_evstr_after_break.txt
@@ -4,15 +4,17 @@
     @ StatementsNode (location: (1,0)-(2,6))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(2,6))
+            ├── flags: ∅
             ├── opening_loc: ∅
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (1,0)-(1,3))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: (1,0)-(1,1) = "\""
             │   │   ├── content_loc: (1,1)-(1,2) = "a"
             │   │   ├── closing_loc: (1,2)-(1,3) = "\""
             │   │   └── unescaped: "a"
             │   └── @ InterpolatedStringNode (location: (2,0)-(2,6))
+            │       ├── flags: ∅
             │       ├── opening_loc: (2,0)-(2,1) = "\""
             │       ├── parts: (length: 1)
             │       │   └── @ EmbeddedStatementsNode (location: (2,1)-(2,5))
diff --git a/test/prism/snapshots/seattlerb/parse_line_heredoc_evstr.txt b/test/prism/snapshots/seattlerb/parse_line_heredoc_evstr.txt
index 1a51e369..b251b2b3 100644
--- a/test/prism/snapshots/seattlerb/parse_line_heredoc_evstr.txt
+++ b/test/prism/snapshots/seattlerb/parse_line_heredoc_evstr.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,4))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,4))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,4) = "<<-A"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (2,0)-(3,0) = "a\n"
             │   │   ├── closing_loc: ∅
@@ -29,7 +30,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (3,3)-(3,4) = "}"
             │   └── @ StringNode (location: (3,4)-(4,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (3,4)-(4,0) = "\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/pct_w_heredoc_interp_nested.txt b/test/prism/snapshots/seattlerb/pct_w_heredoc_interp_nested.txt
index 946f08bc..c4bc53b7 100644
--- a/test/prism/snapshots/seattlerb/pct_w_heredoc_interp_nested.txt
+++ b/test/prism/snapshots/seattlerb/pct_w_heredoc_interp_nested.txt
@@ -13,6 +13,7 @@
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "1"
             │   ├── @ InterpolatedStringNode (location: (1,6)-(1,12))
+            │   │   ├── flags: ∅
             │   │   ├── opening_loc: ∅
             │   │   ├── parts: (length: 1)
             │   │   │   └── @ EmbeddedStatementsNode (location: (1,6)-(1,12))
diff --git a/test/prism/snapshots/seattlerb/qsymbols_interp.txt b/test/prism/snapshots/seattlerb/qsymbols_interp.txt
index 23c39302..97bc6754 100644
--- a/test/prism/snapshots/seattlerb/qsymbols_interp.txt
+++ b/test/prism/snapshots/seattlerb/qsymbols_interp.txt
@@ -16,7 +16,7 @@
             │   │   ├── opening_loc: ∅
             │   │   ├── parts: (length: 2)
             │   │   │   ├── @ StringNode (location: (1,5)-(1,6))
-            │   │   │   │   ├── flags: ∅
+            │   │   │   │   ├── flags: frozen
             │   │   │   │   ├── opening_loc: ∅
             │   │   │   │   ├── content_loc: (1,5)-(1,6) = "b"
             │   │   │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_evstr.txt b/test/prism/snapshots/seattlerb/str_evstr.txt
index 24b4bdaa..7010ad0a 100644
--- a/test/prism/snapshots/seattlerb/str_evstr.txt
+++ b/test/prism/snapshots/seattlerb/str_evstr.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,8))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,8))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (1,1)-(1,3))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,3) = "a "
             │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_evstr_escape.txt b/test/prism/snapshots/seattlerb/str_evstr_escape.txt
index c14c39ee..3867574c 100644
--- a/test/prism/snapshots/seattlerb/str_evstr_escape.txt
+++ b/test/prism/snapshots/seattlerb/str_evstr_escape.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,16))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,16))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,1)-(1,3))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,3) = "a "
             │   │   ├── closing_loc: ∅
@@ -29,7 +30,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,6)-(1,7) = "}"
             │   └── @ StringNode (location: (1,7)-(1,15))
-            │       ├── flags: forced_utf8_encoding
+            │       ├── flags: forced_utf8_encoding, frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,7)-(1,15) = "\\302\\275"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_heredoc_interp.txt b/test/prism/snapshots/seattlerb/str_heredoc_interp.txt
index cdb5e7e8..bb7bbba2 100644
--- a/test/prism/snapshots/seattlerb/str_heredoc_interp.txt
+++ b/test/prism/snapshots/seattlerb/str_heredoc_interp.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,4))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,4))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,4) = "<<\"\""
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (2,0)-(2,4))
@@ -23,7 +24,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (2,3)-(2,4) = "}"
             │   └── @ StringNode (location: (2,4)-(4,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (2,4)-(4,0) = "\nblah2\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_interp_ternary_or_label.txt b/test/prism/snapshots/seattlerb/str_interp_ternary_or_label.txt
index 474c42eb..5a2f435e 100644
--- a/test/prism/snapshots/seattlerb/str_interp_ternary_or_label.txt
+++ b/test/prism/snapshots/seattlerb/str_interp_ternary_or_label.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,23))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,23))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 1)
             │   └── @ EmbeddedStatementsNode (location: (1,1)-(1,22))
diff --git a/test/prism/snapshots/seattlerb/str_lit_concat_bad_encodings.txt b/test/prism/snapshots/seattlerb/str_lit_concat_bad_encodings.txt
index b841407c..0066f66e 100644
--- a/test/prism/snapshots/seattlerb/str_lit_concat_bad_encodings.txt
+++ b/test/prism/snapshots/seattlerb/str_lit_concat_bad_encodings.txt
@@ -4,16 +4,17 @@
     @ StatementsNode (location: (1,0)-(2,66))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(2,66))
+            ├── flags: ∅
             ├── opening_loc: ∅
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (1,0)-(1,62))
-            │   │   ├── flags: forced_utf8_encoding
+            │   │   ├── flags: forced_utf8_encoding, frozen
             │   │   ├── opening_loc: (1,0)-(1,1) = "\""
             │   │   ├── content_loc: (1,1)-(1,61) = "\\xE3\\xD3\\x8B\\xE3\\x83\\xBC\\x83\\xE3\\x83\\xE3\\x82\\xB3\\xA3\\x82\\x99"
             │   │   ├── closing_loc: (1,61)-(1,62) = "\""
             │   │   └── unescaped: "\xE3Ӌー\x83\xE3\x83コ\xA3\x82\x99"
             │   └── @ StringNode (location: (2,8)-(2,66))
-            │       ├── flags: forced_utf8_encoding
+            │       ├── flags: forced_utf8_encoding, frozen
             │       ├── opening_loc: (2,8)-(2,9) = "\""
             │       ├── content_loc: (2,9)-(2,65) = "\\xE3\\x83\\xB3\\xE3\\x83\\x8F\\xE3\\x82\\x9A\\xC3\\xBD;foo@bar.com"
             │       ├── closing_loc: (2,65)-(2,66) = "\""
diff --git a/test/prism/snapshots/seattlerb/str_pct_Q_nested.txt b/test/prism/snapshots/seattlerb/str_pct_Q_nested.txt
index 92ee7a9c..1db0e762 100644
--- a/test/prism/snapshots/seattlerb/str_pct_Q_nested.txt
+++ b/test/prism/snapshots/seattlerb/str_pct_Q_nested.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,26))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,26))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,3) = "%Q["
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,3)-(1,11))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,3)-(1,11) = "before ["
             │   │   ├── closing_loc: ∅
@@ -29,7 +30,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,17)-(1,18) = "}"
             │   └── @ StringNode (location: (1,18)-(1,25))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,18)-(1,25) = "] after"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_pct_nested_nested.txt b/test/prism/snapshots/seattlerb/str_pct_nested_nested.txt
index b9c39c9a..22c30318 100644
--- a/test/prism/snapshots/seattlerb/str_pct_nested_nested.txt
+++ b/test/prism/snapshots/seattlerb/str_pct_nested_nested.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,20))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,20))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,2) = "%{"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,2)-(1,5))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,2)-(1,5) = " { "
             │   │   ├── closing_loc: ∅
@@ -18,6 +19,7 @@
             │   │   │   @ StatementsNode (location: (1,8)-(1,14))
             │   │   │   └── body: (length: 1)
             │   │   │       └── @ InterpolatedStringNode (location: (1,8)-(1,14))
+            │   │   │           ├── flags: ∅
             │   │   │           ├── opening_loc: (1,8)-(1,9) = "\""
             │   │   │           ├── parts: (length: 1)
             │   │   │           │   └── @ EmbeddedStatementsNode (location: (1,9)-(1,13))
@@ -32,7 +34,7 @@
             │   │   │           └── closing_loc: (1,13)-(1,14) = "\""
             │   │   └── closing_loc: (1,15)-(1,16) = "}"
             │   └── @ StringNode (location: (1,16)-(1,19))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,16)-(1,19) = " } "
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_str.txt b/test/prism/snapshots/seattlerb/str_str.txt
index f183980f..f3f1213a 100644
--- a/test/prism/snapshots/seattlerb/str_str.txt
+++ b/test/prism/snapshots/seattlerb/str_str.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,10))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,10))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (1,1)-(1,3))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,3) = "a "
             │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/str_str_str.txt b/test/prism/snapshots/seattlerb/str_str_str.txt
index 68873d81..b01f2b57 100644
--- a/test/prism/snapshots/seattlerb/str_str_str.txt
+++ b/test/prism/snapshots/seattlerb/str_str_str.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,12))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,12))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,1)-(1,3))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,3) = "a "
             │   │   ├── closing_loc: ∅
@@ -25,7 +26,7 @@
             │   │   │           └── unescaped: "b"
             │   │   └── closing_loc: (1,8)-(1,9) = "}"
             │   └── @ StringNode (location: (1,9)-(1,11))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,9)-(1,11) = " c"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/words_interp.txt b/test/prism/snapshots/seattlerb/words_interp.txt
index dfead7d3..1175a6f4 100644
--- a/test/prism/snapshots/seattlerb/words_interp.txt
+++ b/test/prism/snapshots/seattlerb/words_interp.txt
@@ -7,6 +7,7 @@
             ├── flags: ∅
             ├── elements: (length: 1)
             │   └── @ InterpolatedStringNode (location: (1,3)-(1,8))
+            │       ├── flags: ∅
             │       ├── opening_loc: ∅
             │       ├── parts: (length: 2)
             │       │   ├── @ EmbeddedStatementsNode (location: (1,3)-(1,7))
@@ -19,7 +20,7 @@
             │       │   │   │           └── value: 1
             │       │   │   └── closing_loc: (1,6)-(1,7) = "}"
             │       │   └── @ StringNode (location: (1,7)-(1,8))
-            │       │       ├── flags: ∅
+            │       │       ├── flags: frozen
             │       │       ├── opening_loc: ∅
             │       │       ├── content_loc: (1,7)-(1,8) = "b"
             │       │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/spanning_heredoc.txt b/test/prism/snapshots/spanning_heredoc.txt
index 90297d22..c89daaed 100644
--- a/test/prism/snapshots/spanning_heredoc.txt
+++ b/test/prism/snapshots/spanning_heredoc.txt
@@ -36,13 +36,13 @@
         │   │           │       │   ├── opening_loc: (4,13)-(4,14) = "/"
         │   │           │       │   ├── parts: (length: 2)
         │   │           │       │   │   ├── @ StringNode (location: (4,14)-(4,16))
-        │   │           │       │   │   │   ├── flags: ∅
+        │   │           │       │   │   │   ├── flags: frozen
         │   │           │       │   │   │   ├── opening_loc: ∅
         │   │           │       │   │   │   ├── content_loc: (4,14)-(4,16) = "b\\"
         │   │           │       │   │   │   ├── closing_loc: ∅
         │   │           │       │   │   │   └── unescaped: "b"
         │   │           │       │   │   └── @ StringNode (location: (7,0)-(7,1))
-        │   │           │       │   │       ├── flags: ∅
+        │   │           │       │   │       ├── flags: frozen
         │   │           │       │   │       ├── opening_loc: ∅
         │   │           │       │   │       ├── content_loc: (7,0)-(7,1) = "b"
         │   │           │       │   │       ├── closing_loc: ∅
@@ -76,16 +76,17 @@
         │   │       │   ├── closing_loc: (12,0)-(13,0) = "A\n"
         │   │       │   └── unescaped: "c\n"
         │   │       └── @ InterpolatedStringNode (location: (10,9)-(13,2))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (10,9)-(10,10) = "\""
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (10,10)-(10,12))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (10,10)-(10,12) = "d\\"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "d"
         │   │           │   └── @ StringNode (location: (13,0)-(13,1))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (13,0)-(13,1) = "d"
         │   │           │       ├── closing_loc: ∅
@@ -111,16 +112,17 @@
         │   │       │   ├── closing_loc: (18,0)-(19,0) = "A\n"
         │   │       │   └── unescaped: "e\n"
         │   │       └── @ InterpolatedStringNode (location: (16,9)-(19,2))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (16,9)-(16,12) = "%q["
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (16,12)-(16,14))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (16,12)-(16,14) = "f\\"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "f\\\n"
         │   │           │   └── @ StringNode (location: (19,0)-(19,1))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (19,0)-(19,1) = "f"
         │   │           │       ├── closing_loc: ∅
@@ -146,16 +148,17 @@
         │   │       │   ├── closing_loc: (24,0)-(25,0) = "A\n"
         │   │       │   └── unescaped: "g\n"
         │   │       └── @ InterpolatedStringNode (location: (22,9)-(25,2))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (22,9)-(22,12) = "%Q["
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (22,12)-(22,14))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (22,12)-(22,14) = "h\\"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "h"
         │   │           │   └── @ StringNode (location: (25,0)-(25,1))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (25,0)-(25,1) = "h"
         │   │           │       ├── closing_loc: ∅
@@ -220,16 +223,17 @@
         │   │           ├── flags: ∅
         │   │           ├── elements: (length: 1)
         │   │           │   └── @ InterpolatedStringNode (location: (35,12)-(38,1))
+        │   │           │       ├── flags: ∅
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── parts: (length: 2)
         │   │           │       │   ├── @ StringNode (location: (35,12)-(35,14))
-        │   │           │       │   │   ├── flags: ∅
+        │   │           │       │   │   ├── flags: frozen
         │   │           │       │   │   ├── opening_loc: ∅
         │   │           │       │   │   ├── content_loc: (35,12)-(35,14) = "l\\"
         │   │           │       │   │   ├── closing_loc: ∅
         │   │           │       │   │   └── unescaped: "l\n"
         │   │           │       │   └── @ StringNode (location: (38,0)-(38,1))
-        │   │           │       │       ├── flags: ∅
+        │   │           │       │       ├── flags: frozen
         │   │           │       │       ├── opening_loc: ∅
         │   │           │       │       ├── content_loc: (38,0)-(38,1) = "l"
         │   │           │       │       ├── closing_loc: ∅
@@ -299,13 +303,13 @@
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── parts: (length: 2)
         │   │           │       │   ├── @ StringNode (location: (48,12)-(48,14))
-        │   │           │       │   │   ├── flags: ∅
+        │   │           │       │   │   ├── flags: frozen
         │   │           │       │   │   ├── opening_loc: ∅
         │   │           │       │   │   ├── content_loc: (48,12)-(48,14) = "p\\"
         │   │           │       │   │   ├── closing_loc: ∅
         │   │           │       │   │   └── unescaped: "p\n"
         │   │           │       │   └── @ StringNode (location: (48,12)-(48,14))
-        │   │           │       │       ├── flags: ∅
+        │   │           │       │       ├── flags: frozen
         │   │           │       │       ├── opening_loc: ∅
         │   │           │       │       ├── content_loc: (48,12)-(48,14) = "p\\"
         │   │           │       │       ├── closing_loc: ∅
@@ -331,13 +335,13 @@
         │   │   │   ├── opening_loc: (53,5)-(53,6) = "/"
         │   │   │   ├── parts: (length: 2)
         │   │   │   │   ├── @ StringNode (location: (53,6)-(53,7))
-        │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   ├── content_loc: (53,6)-(53,7) = "\\"
         │   │   │   │   │   ├── closing_loc: ∅
         │   │   │   │   │   └── unescaped: ""
         │   │   │   │   └── @ StringNode (location: (55,0)-(55,6))
-        │   │   │   │       ├── flags: ∅
+        │   │   │   │       ├── flags: frozen
         │   │   │   │       ├── opening_loc: ∅
         │   │   │   │       ├── content_loc: (55,0)-(55,6) = "(?<a>)"
         │   │   │   │       ├── closing_loc: ∅
@@ -373,13 +377,13 @@
         │   ├── opening_loc: (57,5)-(57,7) = ":'"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (57,7)-(58,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (57,7)-(58,0) = "a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (59,0)-(59,1))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (59,0)-(59,1) = "b"
         │   │       ├── closing_loc: ∅
@@ -395,13 +399,13 @@
             ├── opening_loc: (61,5)-(61,7) = ":\""
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (61,7)-(62,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (61,7)-(62,0) = "a\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "a\n"
             │   └── @ StringNode (location: (63,0)-(63,1))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (63,0)-(63,1) = "b"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/strings.txt b/test/prism/snapshots/strings.txt
index 40a05ce0..632d2ac3 100644
--- a/test/prism/snapshots/strings.txt
+++ b/test/prism/snapshots/strings.txt
@@ -93,6 +93,7 @@
         │   ├── closing_loc: (29,5)-(29,6) = "`"
         │   └── unescaped: "abc"
         ├── @ InterpolatedStringNode (location: (31,0)-(31,8))
+        │   ├── flags: ∅
         │   ├── opening_loc: (31,0)-(31,1) = "\""
         │   ├── parts: (length: 1)
         │   │   └── @ EmbeddedVariableNode (location: (31,1)-(31,7))
@@ -108,10 +109,11 @@
         │   ├── closing_loc: (33,5)-(33,6) = "\\"
         │   └── unescaped: "abc"
         ├── @ InterpolatedStringNode (location: (35,0)-(35,17))
+        │   ├── flags: ∅
         │   ├── opening_loc: (35,0)-(35,2) = "%{"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (35,2)-(35,6))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (35,2)-(35,6) = "aaa "
         │   │   │   ├── closing_loc: ∅
@@ -133,7 +135,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (35,11)-(35,12) = "}"
         │   │   └── @ StringNode (location: (35,12)-(35,16))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (35,12)-(35,16) = " ccc"
         │   │       ├── closing_loc: ∅
@@ -207,10 +209,11 @@
         │   ├── closing_loc: (53,6)-(53,7) = "\""
         │   └── unescaped: "\#@---"
         ├── @ InterpolatedStringNode (location: (55,0)-(55,16))
+        │   ├── flags: ∅
         │   ├── opening_loc: (55,0)-(55,1) = "\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (55,1)-(55,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (55,1)-(55,5) = "aaa "
         │   │   │   ├── closing_loc: ∅
@@ -232,7 +235,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (55,10)-(55,11) = "}"
         │   │   └── @ StringNode (location: (55,11)-(55,15))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (55,11)-(55,15) = " ccc"
         │   │       ├── closing_loc: ∅
@@ -334,10 +337,11 @@
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a"
         │   │   ├── @ InterpolatedStringNode (location: (67,5)-(67,11))
+        │   │   │   ├── flags: ∅
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── parts: (length: 3)
         │   │   │   │   ├── @ StringNode (location: (67,5)-(67,6))
-        │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   ├── content_loc: (67,5)-(67,6) = "b"
         │   │   │   │   │   ├── closing_loc: ∅
@@ -359,7 +363,7 @@
         │   │   │   │   │   │           └── block: ∅
         │   │   │   │   │   └── closing_loc: (67,9)-(67,10) = "}"
         │   │   │   │   └── @ StringNode (location: (67,10)-(67,11))
-        │   │   │   │       ├── flags: ∅
+        │   │   │   │       ├── flags: frozen
         │   │   │   │       ├── opening_loc: ∅
         │   │   │   │       ├── content_loc: (67,10)-(67,11) = "d"
         │   │   │   │       ├── closing_loc: ∅
@@ -432,6 +436,7 @@
         │   ├── closing_loc: (79,14)-(79,15) = "'"
         │   └── unescaped: "\\ foo \\ bar"
         ├── @ InterpolatedStringNode (location: (81,0)-(81,7))
+        │   ├── flags: ∅
         │   ├── opening_loc: (81,0)-(81,1) = "\""
         │   ├── parts: (length: 1)
         │   │   └── @ EmbeddedVariableNode (location: (81,1)-(81,6))
@@ -441,6 +446,7 @@
         │   │           └── name: :$foo
         │   └── closing_loc: (81,6)-(81,7) = "\""
         ├── @ InterpolatedStringNode (location: (83,0)-(83,7))
+        │   ├── flags: ∅
         │   ├── opening_loc: (83,0)-(83,1) = "\""
         │   ├── parts: (length: 1)
         │   │   └── @ EmbeddedVariableNode (location: (83,1)-(83,6))
@@ -492,16 +498,17 @@
         │   ├── closing_loc: ∅
         │   └── unescaped: "a"
         ├── @ InterpolatedStringNode (location: (99,0)-(99,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (99,0)-(99,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: (99,0)-(99,1) = "?"
         │   │   │   ├── content_loc: (99,1)-(99,2) = "a"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a"
         │   │   └── @ StringNode (location: (99,3)-(99,6))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (99,3)-(99,4) = "\""
         │   │       ├── content_loc: (99,4)-(99,5) = "a"
         │   │       ├── closing_loc: (99,5)-(99,6) = "\""
diff --git a/test/prism/snapshots/symbols.txt b/test/prism/snapshots/symbols.txt
index c34be74b..dbd3a4d0 100644
--- a/test/prism/snapshots/symbols.txt
+++ b/test/prism/snapshots/symbols.txt
@@ -33,7 +33,7 @@
         │   ├── opening_loc: (5,0)-(5,2) = ":\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (5,2)-(5,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (5,2)-(5,5) = "abc"
         │   │   │   ├── closing_loc: ∅
@@ -234,7 +234,7 @@
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── parts: (length: 2)
         │   │   │   │   ├── @ StringNode (location: (39,5)-(39,6))
-        │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   ├── content_loc: (39,5)-(39,6) = "b"
         │   │   │   │   │   ├── closing_loc: ∅
@@ -262,7 +262,7 @@
         │   │   │   │   │   │           └── value: 2
         │   │   │   │   │   └── closing_loc: (39,14)-(39,15) = "}"
         │   │   │   │   └── @ StringNode (location: (39,15)-(39,16))
-        │   │   │   │       ├── flags: ∅
+        │   │   │   │       ├── flags: frozen
         │   │   │   │       ├── opening_loc: ∅
         │   │   │   │       ├── content_loc: (39,15)-(39,16) = "c"
         │   │   │   │       ├── closing_loc: ∅
@@ -272,7 +272,7 @@
         │   │       ├── opening_loc: ∅
         │   │       ├── parts: (length: 3)
         │   │       │   ├── @ StringNode (location: (39,17)-(39,18))
-        │   │       │   │   ├── flags: ∅
+        │   │       │   │   ├── flags: frozen
         │   │       │   │   ├── opening_loc: ∅
         │   │       │   │   ├── content_loc: (39,17)-(39,18) = "d"
         │   │       │   │   ├── closing_loc: ∅
@@ -287,7 +287,7 @@
         │   │       │   │   │           └── value: 3
         │   │       │   │   └── closing_loc: (39,21)-(39,22) = "}"
         │   │       │   └── @ StringNode (location: (39,22)-(39,23))
-        │   │       │       ├── flags: ∅
+        │   │       │       ├── flags: frozen
         │   │       │       ├── opening_loc: ∅
         │   │       │       ├── content_loc: (39,22)-(39,23) = "f"
         │   │       │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/tilde_heredocs.txt b/test/prism/snapshots/tilde_heredocs.txt
index fd369a64..f50f915a 100644
--- a/test/prism/snapshots/tilde_heredocs.txt
+++ b/test/prism/snapshots/tilde_heredocs.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(94,6))
     └── body: (length: 19)
         ├── @ InterpolatedStringNode (location: (1,0)-(1,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (1,0)-(1,6) = "<<~EOF"
         │   ├── parts: (length: 4)
         │   │   ├── @ StringNode (location: (2,0)-(3,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (2,0)-(3,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -22,13 +23,13 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (3,3)-(3,4) = "}"
         │   │   ├── @ StringNode (location: (3,4)-(4,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (3,4)-(4,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   └── @ StringNode (location: (4,0)-(5,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (4,0)-(5,0) = "  a\n"
         │   │       ├── closing_loc: ∅
@@ -41,28 +42,30 @@
         │   ├── closing_loc: (9,0)-(10,0) = "EOF\n"
         │   └── unescaped: "a\n"
         ├── @ InterpolatedStringNode (location: (11,0)-(11,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (11,0)-(11,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (12,0)-(13,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (12,0)-(13,0) = "\ta\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\ta\n"
         │   │   ├── @ StringNode (location: (13,0)-(14,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (13,0)-(14,0) = "  b\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "b\n"
         │   │   └── @ StringNode (location: (14,0)-(15,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (14,0)-(15,0) = "\t\tc\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\t\tc\n"
         │   └── closing_loc: (15,0)-(16,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (17,0)-(17,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (17,0)-(17,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ EmbeddedStatementsNode (location: (18,2)-(18,6))
@@ -75,17 +78,18 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (18,5)-(18,6) = "}"
         │   │   └── @ StringNode (location: (18,6)-(19,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (18,6)-(19,0) = " a\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: " a\n"
         │   └── closing_loc: (19,0)-(20,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (21,0)-(21,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (21,0)-(21,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (22,0)-(22,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (22,0)-(22,4) = "  a "
         │   │   │   ├── closing_loc: ∅
@@ -100,17 +104,18 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (22,7)-(22,8) = "}"
         │   │   └── @ StringNode (location: (22,8)-(23,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (22,8)-(23,0) = "\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n"
         │   └── closing_loc: (23,0)-(24,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (25,0)-(25,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (25,0)-(25,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (26,0)-(27,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (26,0)-(27,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -125,17 +130,18 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (27,4)-(27,5) = "}"
         │   │   └── @ StringNode (location: (27,5)-(28,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (27,5)-(28,0) = "\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n"
         │   └── closing_loc: (28,0)-(29,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (30,0)-(30,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (30,0)-(30,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (31,0)-(32,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (31,0)-(32,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -150,55 +156,58 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (32,5)-(32,6) = "}"
         │   │   └── @ StringNode (location: (32,6)-(33,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (32,6)-(33,0) = "\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n"
         │   └── closing_loc: (33,0)-(34,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (35,0)-(35,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (35,0)-(35,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (36,0)-(37,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (36,0)-(37,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (37,0)-(38,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (37,0)-(38,0) = "  b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (38,0)-(39,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (40,0)-(40,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (40,0)-(40,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (41,0)-(42,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (41,0)-(42,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (42,0)-(43,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (42,0)-(43,0) = "   b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: " b\n"
         │   └── closing_loc: (43,0)-(44,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (45,0)-(45,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (45,0)-(45,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (46,0)-(47,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (46,0)-(47,0) = "\t\t\ta\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\ta\n"
         │   │   └── @ StringNode (location: (47,0)-(48,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (47,0)-(48,0) = "\t\tb\n"
         │   │       ├── closing_loc: ∅
@@ -211,136 +220,143 @@
         │   ├── closing_loc: (52,0)-(53,0) = "EOF\n"
         │   └── unescaped: "a \#{1}\n"
         ├── @ InterpolatedStringNode (location: (54,0)-(54,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (54,0)-(54,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (55,0)-(56,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (55,0)-(56,0) = "\ta\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (56,0)-(57,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (56,0)-(57,0) = "\t b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: " b\n"
         │   └── closing_loc: (57,0)-(58,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (59,0)-(59,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (59,0)-(59,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (60,0)-(61,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (60,0)-(61,0) = "\t a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: " a\n"
         │   │   └── @ StringNode (location: (61,0)-(62,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (61,0)-(62,0) = "\tb\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (62,0)-(63,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (64,0)-(64,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (64,0)-(64,6) = "<<~EOF"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (65,0)-(66,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (65,0)-(66,0) = "  \ta\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (66,0)-(67,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (66,0)-(67,0) = "        b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (67,0)-(68,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (69,0)-(69,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (69,0)-(69,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (70,0)-(71,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (70,0)-(71,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   ├── @ StringNode (location: (71,0)-(72,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (71,0)-(72,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   └── @ StringNode (location: (72,0)-(73,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (72,0)-(73,0) = "  b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (73,0)-(74,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (75,0)-(75,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (75,0)-(75,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (76,0)-(77,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (76,0)-(77,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   ├── @ StringNode (location: (77,0)-(78,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (77,0)-(78,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   └── @ StringNode (location: (78,0)-(79,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (78,0)-(79,0) = "  b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (79,0)-(80,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (81,0)-(81,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (81,0)-(81,6) = "<<~EOF"
         │   ├── parts: (length: 5)
         │   │   ├── @ StringNode (location: (82,0)-(83,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (82,0)-(83,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   ├── @ StringNode (location: (83,0)-(84,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (83,0)-(84,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   ├── @ StringNode (location: (84,0)-(85,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (84,0)-(85,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   ├── @ StringNode (location: (85,0)-(86,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (85,0)-(86,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   └── @ StringNode (location: (86,0)-(87,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (86,0)-(87,0) = "  b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (87,0)-(88,0) = "EOF\n"
         ├── @ InterpolatedStringNode (location: (89,0)-(89,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (89,0)-(89,6) = "<<~EOF"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (90,0)-(91,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (90,0)-(91,0) = "\n"
         │   │   │   ├── closing_loc: ∅
@@ -355,13 +371,14 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (91,5)-(91,6) = "}"
         │   │   └── @ StringNode (location: (91,6)-(92,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (91,6)-(92,0) = "a\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "a\n"
         │   └── closing_loc: (92,0)-(93,0) = "    EOF\n"
         └── @ InterpolatedStringNode (location: (94,0)-(94,6))
+            ├── flags: ∅
             ├── opening_loc: (94,0)-(94,6) = "<<~EOT"
             ├── parts: (length: 3)
             │   ├── @ EmbeddedStatementsNode (location: (95,2)-(95,6))
@@ -374,13 +391,13 @@
             │   │   │           └── value: 1
             │   │   └── closing_loc: (95,5)-(95,6) = "}"
             │   ├── @ StringNode (location: (95,6)-(96,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (95,6)-(96,0) = "\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "\n"
             │   └── @ StringNode (location: (96,0)-(97,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (96,0)-(97,0) = "\tb\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/undef.txt b/test/prism/snapshots/undef.txt
index 6031119a..e59ace92 100644
--- a/test/prism/snapshots/undef.txt
+++ b/test/prism/snapshots/undef.txt
@@ -90,7 +90,7 @@
         │   │       ├── opening_loc: (15,6)-(15,8) = ":\""
         │   │       ├── parts: (length: 2)
         │   │       │   ├── @ StringNode (location: (15,8)-(15,11))
-        │   │       │   │   ├── flags: ∅
+        │   │       │   │   ├── flags: frozen
         │   │       │   │   ├── opening_loc: ∅
         │   │       │   │   ├── content_loc: (15,8)-(15,11) = "abc"
         │   │       │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/unparser/corpus/literal/assignment.txt b/test/prism/snapshots/unparser/corpus/literal/assignment.txt
index 3a458b83..99c8daf3 100644
--- a/test/prism/snapshots/unparser/corpus/literal/assignment.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/assignment.txt
@@ -910,10 +910,11 @@
         │   ├── name_loc: (39,0)-(39,1) = "x"
         │   ├── value:
         │   │   @ InterpolatedStringNode (location: (39,4)-(39,14))
+        │   │   ├── flags: ∅
         │   │   ├── opening_loc: (39,4)-(39,14) = "<<-HEREDOC"
         │   │   ├── parts: (length: 3)
         │   │   │   ├── @ StringNode (location: (40,0)-(40,2))
-        │   │   │   │   ├── flags: ∅
+        │   │   │   │   ├── flags: frozen
         │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   ├── content_loc: (40,0)-(40,2) = "  "
         │   │   │   │   ├── closing_loc: ∅
@@ -923,7 +924,7 @@
         │   │   │   │   ├── statements: ∅
         │   │   │   │   └── closing_loc: (40,4)-(40,5) = "}"
         │   │   │   └── @ StringNode (location: (40,5)-(41,0))
-        │   │   │       ├── flags: ∅
+        │   │   │       ├── flags: frozen
         │   │   │       ├── opening_loc: ∅
         │   │   │       ├── content_loc: (40,5)-(41,0) = "\n"
         │   │   │       ├── closing_loc: ∅
@@ -945,10 +946,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (42,4)-(42,14))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (42,4)-(42,14) = "<<-HEREDOC"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (43,0)-(43,2))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (43,0)-(43,2) = "  "
         │   │           │   │   ├── closing_loc: ∅
@@ -958,7 +960,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (43,4)-(43,5) = "}"
         │   │           │   └── @ StringNode (location: (43,5)-(44,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (43,5)-(44,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -981,10 +983,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (45,6)-(45,16))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (45,6)-(45,16) = "<<-HEREDOC"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (46,0)-(46,2))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (46,0)-(46,2) = "  "
         │   │           │   │   ├── closing_loc: ∅
@@ -994,7 +997,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (46,4)-(46,5) = "}"
         │   │           │   └── @ StringNode (location: (46,5)-(47,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (46,5)-(47,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -1015,10 +1018,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (48,2)-(48,12))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (48,2)-(48,12) = "<<-HEREDOC"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (49,0)-(49,2))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (49,0)-(49,2) = "  "
         │   │           │   │   ├── closing_loc: ∅
@@ -1028,7 +1032,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (49,4)-(49,5) = "}"
         │   │           │   └── @ StringNode (location: (49,5)-(50,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (49,5)-(50,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -1054,10 +1058,11 @@
             ├── operator_loc: (51,3)-(51,6) = "||="
             └── value:
                 @ InterpolatedStringNode (location: (51,7)-(51,17))
+                ├── flags: ∅
                 ├── opening_loc: (51,7)-(51,17) = "<<-HEREDOC"
                 ├── parts: (length: 3)
                 │   ├── @ StringNode (location: (52,0)-(52,2))
-                │   │   ├── flags: ∅
+                │   │   ├── flags: frozen
                 │   │   ├── opening_loc: ∅
                 │   │   ├── content_loc: (52,0)-(52,2) = "  "
                 │   │   ├── closing_loc: ∅
@@ -1067,7 +1072,7 @@
                 │   │   ├── statements: ∅
                 │   │   └── closing_loc: (52,4)-(52,5) = "}"
                 │   └── @ StringNode (location: (52,5)-(53,0))
-                │       ├── flags: ∅
+                │       ├── flags: frozen
                 │       ├── opening_loc: ∅
                 │       ├── content_loc: (52,5)-(53,0) = "\n"
                 │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/unparser/corpus/literal/def.txt b/test/prism/snapshots/unparser/corpus/literal/def.txt
index da285d89..f3ef6c38 100644
--- a/test/prism/snapshots/unparser/corpus/literal/def.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/def.txt
@@ -1154,10 +1154,11 @@
         │   │   @ StatementsNode (location: (127,2)-(127,12))
         │   │   └── body: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (127,2)-(127,12))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (127,2)-(127,12) = "<<-HEREDOC"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (128,0)-(128,4))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (128,0)-(128,4) = "    "
         │   │           │   │   ├── closing_loc: ∅
@@ -1167,7 +1168,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (128,6)-(128,7) = "}"
         │   │           │   └── @ StringNode (location: (128,7)-(129,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (128,7)-(129,0) = "\n"
         │   │           │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/unparser/corpus/literal/dstr.txt b/test/prism/snapshots/unparser/corpus/literal/dstr.txt
index 2f8e5da6..e60a309b 100644
--- a/test/prism/snapshots/unparser/corpus/literal/dstr.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/dstr.txt
@@ -12,6 +12,7 @@
         │   │   @ StatementsNode (location: (2,2)-(2,8))
         │   │   └── body: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (2,2)-(2,8))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (2,2)-(2,3) = "\""
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ EmbeddedStatementsNode (location: (2,3)-(2,6))
@@ -19,7 +20,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (2,5)-(2,6) = "}"
         │   │           │   └── @ StringNode (location: (2,6)-(2,7))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (2,6)-(2,7) = "a"
         │   │           │       ├── closing_loc: ∅
@@ -36,10 +37,11 @@
         │   │   @ StatementsNode (location: (5,2)-(10,3))
         │   │   └── body: (length: 2)
         │   │       ├── @ InterpolatedStringNode (location: (5,2)-(5,12))
+        │   │       │   ├── flags: ∅
         │   │       │   ├── opening_loc: (5,2)-(5,12) = "<<-HEREDOC"
         │   │       │   ├── parts: (length: 3)
         │   │       │   │   ├── @ StringNode (location: (6,0)-(7,0))
-        │   │       │   │   │   ├── flags: ∅
+        │   │       │   │   │   ├── flags: frozen
         │   │       │   │   │   ├── opening_loc: ∅
         │   │       │   │   │   ├── content_loc: (6,0)-(7,0) = "a\n"
         │   │       │   │   │   ├── closing_loc: ∅
@@ -49,7 +51,7 @@
         │   │       │   │   │   ├── statements: ∅
         │   │       │   │   │   └── closing_loc: (7,2)-(7,3) = "}"
         │   │       │   │   └── @ StringNode (location: (7,3)-(9,0))
-        │   │       │   │       ├── flags: ∅
+        │   │       │   │       ├── flags: frozen
         │   │       │   │       ├── opening_loc: ∅
         │   │       │   │       ├── content_loc: (7,3)-(9,0) = "a\nb\n"
         │   │       │   │       ├── closing_loc: ∅
@@ -68,10 +70,11 @@
         │   ├── consequent: ∅
         │   └── end_keyword_loc: (11,0)-(11,3) = "end"
         ├── @ InterpolatedStringNode (location: (12,0)-(12,10))
+        │   ├── flags: ∅
         │   ├── opening_loc: (12,0)-(12,10) = "<<-HEREDOC"
         │   ├── parts: (length: 7)
         │   │   ├── @ StringNode (location: (13,0)-(14,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (13,0)-(14,0) = "\\\#{}\\\#{}\n"
         │   │   │   ├── closing_loc: ∅
@@ -81,7 +84,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (14,2)-(14,3) = "}"
         │   │   ├── @ StringNode (location: (14,3)-(15,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (14,3)-(15,0) = "\n"
         │   │   │   ├── closing_loc: ∅
@@ -91,7 +94,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (15,2)-(15,3) = "}"
         │   │   ├── @ StringNode (location: (15,3)-(16,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (15,3)-(16,0) = "\n"
         │   │   │   ├── closing_loc: ∅
@@ -101,7 +104,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (16,2)-(16,3) = "}"
         │   │   └── @ StringNode (location: (16,3)-(17,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (16,3)-(17,0) = "\n"
         │   │       ├── closing_loc: ∅
@@ -110,6 +113,7 @@
         ├── @ RescueModifierNode (location: (18,0)-(18,21))
         │   ├── expression:
         │   │   @ InterpolatedStringNode (location: (18,0)-(18,10))
+        │   │   ├── flags: ∅
         │   │   ├── opening_loc: (18,0)-(18,10) = "<<-HEREDOC"
         │   │   ├── parts: (length: 2)
         │   │   │   ├── @ EmbeddedStatementsNode (location: (19,0)-(19,3))
@@ -117,7 +121,7 @@
         │   │   │   │   ├── statements: ∅
         │   │   │   │   └── closing_loc: (19,2)-(19,3) = "}"
         │   │   │   └── @ StringNode (location: (19,3)-(21,0))
-        │   │   │       ├── flags: ∅
+        │   │   │       ├── flags: frozen
         │   │   │       ├── opening_loc: ∅
         │   │   │       ├── content_loc: (19,3)-(21,0) = "\na\n"
         │   │   │       ├── closing_loc: ∅
@@ -127,10 +131,11 @@
         │   └── rescue_expression:
         │       @ NilNode (location: (18,18)-(18,21))
         ├── @ InterpolatedStringNode (location: (22,0)-(22,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (22,0)-(22,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (22,1)-(22,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (22,1)-(22,2) = "a"
         │   │   │   ├── closing_loc: ∅
@@ -142,10 +147,11 @@
         │   │           └── number: 1
         │   └── closing_loc: (22,5)-(22,6) = "\""
         ├── @ InterpolatedStringNode (location: (23,0)-(23,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (23,0)-(23,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (23,1)-(23,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (23,1)-(23,2) = "a"
         │   │   │   ├── closing_loc: ∅
@@ -157,10 +163,11 @@
         │   │           └── name: :$a
         │   └── closing_loc: (23,5)-(23,6) = "\""
         ├── @ InterpolatedStringNode (location: (24,0)-(24,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (24,0)-(24,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (24,1)-(24,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (24,1)-(24,2) = "a"
         │   │   │   ├── closing_loc: ∅
@@ -172,10 +179,11 @@
         │   │           └── name: :@a
         │   └── closing_loc: (24,5)-(24,6) = "\""
         ├── @ InterpolatedStringNode (location: (25,0)-(25,7))
+        │   ├── flags: ∅
         │   ├── opening_loc: (25,0)-(25,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (25,1)-(25,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (25,1)-(25,2) = "a"
         │   │   │   ├── closing_loc: ∅
@@ -201,10 +209,11 @@
         │   │               ├── flags: ∅
         │   │               └── arguments: (length: 1)
         │   │                   └── @ InterpolatedStringNode (location: (27,9)-(27,19))
+        │   │                       ├── flags: ∅
         │   │                       ├── opening_loc: (27,9)-(27,19) = "<<-HEREDOC"
         │   │                       ├── parts: (length: 3)
         │   │                       │   ├── @ StringNode (location: (28,0)-(28,4))
-        │   │                       │   │   ├── flags: ∅
+        │   │                       │   │   ├── flags: frozen
         │   │                       │   │   ├── opening_loc: ∅
         │   │                       │   │   ├── content_loc: (28,0)-(28,4) = "    "
         │   │                       │   │   ├── closing_loc: ∅
@@ -219,7 +228,7 @@
         │   │                       │   │   │           └── value: 42
         │   │                       │   │   └── closing_loc: (28,8)-(28,9) = "}"
         │   │                       │   └── @ StringNode (location: (28,9)-(29,0))
-        │   │                       │       ├── flags: ∅
+        │   │                       │       ├── flags: frozen
         │   │                       │       ├── opening_loc: ∅
         │   │                       │       ├── content_loc: (28,9)-(29,0) = "\n"
         │   │                       │       ├── closing_loc: ∅
@@ -239,10 +248,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (31,4)-(31,14))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (31,4)-(31,14) = "<<-HEREDOC"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (32,0)-(32,2))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (32,0)-(32,2) = "  "
         │   │           │   │   ├── closing_loc: ∅
@@ -264,7 +274,7 @@
         │   │           │   │   │           └── block: ∅
         │   │           │   │   └── closing_loc: (32,7)-(32,8) = "}"
         │   │           │   └── @ StringNode (location: (32,8)-(33,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (32,8)-(33,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -284,10 +294,11 @@
             │   ├── flags: ∅
             │   └── arguments: (length: 1)
             │       └── @ InterpolatedStringNode (location: (34,4)-(34,14))
+            │           ├── flags: ∅
             │           ├── opening_loc: (34,4)-(34,14) = "<<-HEREDOC"
             │           ├── parts: (length: 3)
             │           │   ├── @ StringNode (location: (35,0)-(35,2))
-            │           │   │   ├── flags: ∅
+            │           │   │   ├── flags: frozen
             │           │   │   ├── opening_loc: ∅
             │           │   │   ├── content_loc: (35,0)-(35,2) = "  "
             │           │   │   ├── closing_loc: ∅
@@ -309,7 +320,7 @@
             │           │   │   │           └── block: ∅
             │           │   │   └── closing_loc: (35,7)-(35,8) = "}"
             │           │   └── @ StringNode (location: (35,8)-(36,0))
-            │           │       ├── flags: ∅
+            │           │       ├── flags: frozen
             │           │       ├── opening_loc: ∅
             │           │       ├── content_loc: (35,8)-(36,0) = "\n"
             │           │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/unparser/corpus/literal/literal.txt b/test/prism/snapshots/unparser/corpus/literal/literal.txt
index ba7dd70b..dcf00bf4 100644
--- a/test/prism/snapshots/unparser/corpus/literal/literal.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/literal.txt
@@ -16,10 +16,11 @@
         │   │   │   │   └── unescaped: "foo"
         │   │   │   ├── value:
         │   │   │   │   @ InterpolatedStringNode (location: (1,11)-(1,21))
+        │   │   │   │   ├── flags: ∅
         │   │   │   │   ├── opening_loc: (1,11)-(1,21) = "<<-HEREDOC"
         │   │   │   │   ├── parts: (length: 3)
         │   │   │   │   │   ├── @ StringNode (location: (2,0)-(2,2))
-        │   │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   │   ├── content_loc: (2,0)-(2,2) = "  "
         │   │   │   │   │   │   ├── closing_loc: ∅
@@ -29,7 +30,7 @@
         │   │   │   │   │   │   ├── statements: ∅
         │   │   │   │   │   │   └── closing_loc: (2,4)-(2,5) = "}"
         │   │   │   │   │   └── @ StringNode (location: (2,5)-(3,0))
-        │   │   │   │   │       ├── flags: ∅
+        │   │   │   │   │       ├── flags: frozen
         │   │   │   │   │       ├── opening_loc: ∅
         │   │   │   │   │       ├── content_loc: (2,5)-(3,0) = "\n"
         │   │   │   │   │       ├── closing_loc: ∅
@@ -121,10 +122,11 @@
         │   │   │   ├── flags: ∅
         │   │   │   └── arguments: (length: 1)
         │   │   │       └── @ InterpolatedStringNode (location: (6,2)-(6,12))
+        │   │   │           ├── flags: ∅
         │   │   │           ├── opening_loc: (6,2)-(6,12) = "<<-HEREDOC"
         │   │   │           ├── parts: (length: 3)
         │   │   │           │   ├── @ StringNode (location: (7,0)-(7,2))
-        │   │   │           │   │   ├── flags: ∅
+        │   │   │           │   │   ├── flags: frozen
         │   │   │           │   │   ├── opening_loc: ∅
         │   │   │           │   │   ├── content_loc: (7,0)-(7,2) = "  "
         │   │   │           │   │   ├── closing_loc: ∅
@@ -134,7 +136,7 @@
         │   │   │           │   │   ├── statements: ∅
         │   │   │           │   │   └── closing_loc: (7,4)-(7,5) = "}"
         │   │   │           │   └── @ StringNode (location: (7,5)-(8,0))
-        │   │   │           │       ├── flags: ∅
+        │   │   │           │       ├── flags: frozen
         │   │   │           │       ├── opening_loc: ∅
         │   │   │           │       ├── content_loc: (7,5)-(8,0) = "\n"
         │   │   │           │       ├── closing_loc: ∅
@@ -191,10 +193,11 @@
         │   │   │   │   └── unescaped: "foo"
         │   │   │   ├── value:
         │   │   │   │   @ InterpolatedStringNode (location: (10,11)-(10,21))
+        │   │   │   │   ├── flags: ∅
         │   │   │   │   ├── opening_loc: (10,11)-(10,21) = "<<-HEREDOC"
         │   │   │   │   ├── parts: (length: 3)
         │   │   │   │   │   ├── @ StringNode (location: (11,0)-(11,2))
-        │   │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   │   ├── content_loc: (11,0)-(11,2) = "  "
         │   │   │   │   │   │   ├── closing_loc: ∅
@@ -204,7 +207,7 @@
         │   │   │   │   │   │   ├── statements: ∅
         │   │   │   │   │   │   └── closing_loc: (11,4)-(11,5) = "}"
         │   │   │   │   │   └── @ StringNode (location: (11,5)-(12,0))
-        │   │   │   │   │       ├── flags: ∅
+        │   │   │   │   │       ├── flags: frozen
         │   │   │   │   │       ├── opening_loc: ∅
         │   │   │   │   │       ├── content_loc: (11,5)-(12,0) = "\n"
         │   │   │   │   │       ├── closing_loc: ∅
@@ -259,6 +262,7 @@
         │   │       └── operator_loc: (13,16)-(13,18) = "**"
         │   └── closing_loc: (13,22)-(13,23) = "}"
         ├── @ InterpolatedStringNode (location: (14,0)-(14,14))
+        │   ├── flags: ∅
         │   ├── opening_loc: (14,0)-(14,1) = "\""
         │   ├── parts: (length: 5)
         │   │   ├── @ EmbeddedVariableNode (location: (14,1)-(14,4))
@@ -267,7 +271,7 @@
         │   │   │       @ InstanceVariableReadNode (location: (14,2)-(14,4))
         │   │   │       └── name: :@a
         │   │   ├── @ StringNode (location: (14,4)-(14,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (14,4)-(14,5) = " "
         │   │   │   ├── closing_loc: ∅
@@ -278,7 +282,7 @@
         │   │   │       @ ClassVariableReadNode (location: (14,6)-(14,9))
         │   │   │       └── name: :@@a
         │   │   ├── @ StringNode (location: (14,9)-(14,10))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (14,9)-(14,10) = " "
         │   │   │   ├── closing_loc: ∅
@@ -355,26 +359,28 @@
         │           ├── flags: decimal
         │           └── value: 1
         ├── @ InterpolatedStringNode (location: (28,0)-(28,11))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (28,0)-(28,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: (28,0)-(28,1) = "\""
         │   │   │   ├── content_loc: (28,1)-(28,4) = "foo"
         │   │   │   ├── closing_loc: (28,4)-(28,5) = "\""
         │   │   │   └── unescaped: "foo"
         │   │   └── @ StringNode (location: (28,6)-(28,11))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (28,6)-(28,7) = "\""
         │   │       ├── content_loc: (28,7)-(28,10) = "bar"
         │   │       ├── closing_loc: (28,10)-(28,11) = "\""
         │   │       └── unescaped: "bar"
         │   └── closing_loc: ∅
         ├── @ InterpolatedStringNode (location: (29,0)-(29,15))
+        │   ├── flags: ∅
         │   ├── opening_loc: (29,0)-(29,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (29,1)-(29,8))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (29,1)-(29,8) = "foobar "
         │   │   │   ├── closing_loc: ∅
@@ -397,10 +403,11 @@
         │   │       └── closing_loc: (29,13)-(29,14) = "}"
         │   └── closing_loc: (29,14)-(29,15) = "\""
         ├── @ InterpolatedStringNode (location: (30,0)-(30,12))
+        │   ├── flags: ∅
         │   ├── opening_loc: (30,0)-(30,1) = "\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (30,1)-(30,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (30,1)-(30,4) = "foo"
         │   │   │   ├── closing_loc: ∅
@@ -415,17 +422,18 @@
         │   │   │   │           └── value: 1
         │   │   │   └── closing_loc: (30,7)-(30,8) = "}"
         │   │   └── @ StringNode (location: (30,8)-(30,11))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (30,8)-(30,11) = "bar"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "bar"
         │   └── closing_loc: (30,11)-(30,12) = "\""
         ├── @ InterpolatedStringNode (location: (31,0)-(31,9))
+        │   ├── flags: ∅
         │   ├── opening_loc: (31,0)-(31,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (31,1)-(31,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (31,1)-(31,5) = "\\\\\\\\"
         │   │   │   ├── closing_loc: ∅
@@ -436,6 +444,7 @@
         │   │       └── closing_loc: (31,7)-(31,8) = "}"
         │   └── closing_loc: (31,8)-(31,9) = "\""
         ├── @ InterpolatedStringNode (location: (32,0)-(32,9))
+        │   ├── flags: ∅
         │   ├── opening_loc: (32,0)-(32,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ EmbeddedStatementsNode (location: (32,1)-(32,4))
@@ -443,17 +452,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (32,3)-(32,4) = "}"
         │   │   └── @ StringNode (location: (32,4)-(32,8))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (32,4)-(32,8) = "\\\#{}"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\#{}"
         │   └── closing_loc: (32,8)-(32,9) = "\""
         ├── @ InterpolatedStringNode (location: (33,0)-(33,9))
+        │   ├── flags: ∅
         │   ├── opening_loc: (33,0)-(33,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (33,1)-(33,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (33,1)-(33,5) = "\\\#{}"
         │   │   │   ├── closing_loc: ∅
@@ -497,7 +507,7 @@
         │   ├── opening_loc: (39,0)-(39,1) = "`"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (39,1)-(39,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (39,1)-(39,4) = "foo"
         │   │   │   ├── closing_loc: ∅
@@ -582,7 +592,7 @@
         │   ├── opening_loc: (51,0)-(51,1) = "/"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (51,1)-(51,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (51,1)-(51,4) = "foo"
         │   │   │   ├── closing_loc: ∅
@@ -601,7 +611,7 @@
         │   ├── opening_loc: (52,0)-(52,1) = "/"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (52,1)-(52,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (52,1)-(52,4) = "foo"
         │   │   │   ├── closing_loc: ∅
@@ -660,7 +670,7 @@
         │   ├── opening_loc: (58,0)-(58,2) = ":\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (58,2)-(58,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (58,2)-(58,5) = "foo"
         │   │   │   ├── closing_loc: ∅
@@ -682,7 +692,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (58,10)-(58,11) = "}"
         │   │   └── @ StringNode (location: (58,11)-(58,14))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (58,11)-(58,14) = "baz"
         │   │       ├── closing_loc: ∅
@@ -1081,6 +1091,7 @@
         │   │       └── operator_loc: (80,6)-(80,8) = "=>"
         │   └── closing_loc: (80,11)-(80,12) = "}"
         ├── @ InterpolatedStringNode (location: (81,0)-(82,7))
+        │   ├── flags: ∅
         │   ├── opening_loc: (81,0)-(81,1) = "\""
         │   ├── parts: (length: 4)
         │   │   ├── @ EmbeddedStatementsNode (location: (81,1)-(81,4))
@@ -1088,7 +1099,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (81,3)-(81,4) = "}"
         │   │   ├── @ StringNode (location: (81,4)-(82,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (81,4)-(82,0) = "\n"
         │   │   │   ├── closing_loc: ∅
@@ -1098,7 +1109,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (82,2)-(82,3) = "}"
         │   │   └── @ StringNode (location: (82,3)-(82,6))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (82,3)-(82,6) = "\\na"
         │   │       ├── closing_loc: ∅
@@ -1121,6 +1132,7 @@
         │       │   @ StatementsNode (location: (84,2)-(85,7))
         │       │   └── body: (length: 1)
         │       │       └── @ InterpolatedStringNode (location: (84,2)-(85,7))
+        │       │           ├── flags: ∅
         │       │           ├── opening_loc: (84,2)-(84,3) = "\""
         │       │           ├── parts: (length: 4)
         │       │           │   ├── @ EmbeddedStatementsNode (location: (84,3)-(84,6))
@@ -1128,7 +1140,7 @@
         │       │           │   │   ├── statements: ∅
         │       │           │   │   └── closing_loc: (84,5)-(84,6) = "}"
         │       │           │   ├── @ StringNode (location: (84,6)-(85,0))
-        │       │           │   │   ├── flags: ∅
+        │       │           │   │   ├── flags: frozen
         │       │           │   │   ├── opening_loc: ∅
         │       │           │   │   ├── content_loc: (84,6)-(85,0) = "\n"
         │       │           │   │   ├── closing_loc: ∅
@@ -1138,7 +1150,7 @@
         │       │           │   │   ├── statements: ∅
         │       │           │   │   └── closing_loc: (85,2)-(85,3) = "}"
         │       │           │   └── @ StringNode (location: (85,3)-(85,6))
-        │       │           │       ├── flags: ∅
+        │       │           │       ├── flags: frozen
         │       │           │       ├── opening_loc: ∅
         │       │           │       ├── content_loc: (85,3)-(85,6) = "\\na"
         │       │           │       ├── closing_loc: ∅
@@ -1156,7 +1168,7 @@
             ├── opening_loc: (89,0)-(89,1) = "`"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (89,1)-(90,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (89,1)-(90,0) = "  x\n"
             │   │   ├── closing_loc: ∅
@@ -1178,7 +1190,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (90,5)-(90,6) = "}"
             │   └── @ StringNode (location: (90,6)-(91,1))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (90,6)-(91,1) = "\n#"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/unparser/corpus/semantic/dstr.txt b/test/prism/snapshots/unparser/corpus/semantic/dstr.txt
index 5ab954b6..499bf59d 100644
--- a/test/prism/snapshots/unparser/corpus/semantic/dstr.txt
+++ b/test/prism/snapshots/unparser/corpus/semantic/dstr.txt
@@ -40,10 +40,11 @@
         │   ├── closing_loc: (19,0)-(20,0) = "DOC\n"
         │   └── unescaped: "  a\n"
         ├── @ InterpolatedStringNode (location: (21,0)-(21,5))
+        │   ├── flags: ∅
         │   ├── opening_loc: (21,0)-(21,5) = "<<DOC"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (22,0)-(23,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (22,0)-(23,2) = "  a\n  "
         │   │   │   ├── closing_loc: ∅
@@ -53,17 +54,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (23,4)-(23,5) = "}"
         │   │   └── @ StringNode (location: (23,5)-(24,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (23,5)-(24,0) = "\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n"
         │   └── closing_loc: (24,0)-(25,0) = "DOC\n"
         ├── @ InterpolatedStringNode (location: (26,0)-(26,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (26,0)-(26,6) = "<<~DOC"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (27,0)-(28,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (27,0)-(28,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -73,17 +75,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (28,4)-(28,5) = "}"
         │   │   └── @ StringNode (location: (28,5)-(29,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (28,5)-(29,0) = "\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n"
         │   └── closing_loc: (29,0)-(30,0) = "DOC\n"
         ├── @ InterpolatedStringNode (location: (31,0)-(31,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (31,0)-(31,6) = "<<~DOC"
         │   ├── parts: (length: 4)
         │   │   ├── @ StringNode (location: (32,0)-(33,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (32,0)-(33,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
@@ -93,29 +96,30 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (33,4)-(33,5) = "}"
         │   │   ├── @ StringNode (location: (33,5)-(34,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (33,5)-(34,0) = "\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "\n"
         │   │   └── @ StringNode (location: (34,0)-(35,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (34,0)-(35,0) = "  b\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n"
         │   └── closing_loc: (35,0)-(36,0) = "DOC\n"
         ├── @ InterpolatedStringNode (location: (37,0)-(37,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (37,0)-(37,6) = "<<~DOC"
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (38,0)-(39,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (38,0)-(39,0) = "  a\n"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a\n"
         │   │   └── @ StringNode (location: (39,0)-(40,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (39,0)-(40,0) = "    b\n"
         │   │       ├── closing_loc: ∅
@@ -140,6 +144,7 @@
         │   ├── closing_loc: (56,0)-(57,0) = "DOC\n"
         │   └── unescaped: " a\\nb\n"
         ├── @ InterpolatedStringNode (location: (58,0)-(58,5))
+        │   ├── flags: ∅
         │   ├── opening_loc: (58,0)-(58,5) = "<<DOC"
         │   ├── parts: (length: 4)
         │   │   ├── @ EmbeddedStatementsNode (location: (59,0)-(59,3))
@@ -147,7 +152,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (59,2)-(59,3) = "}"
         │   │   ├── @ StringNode (location: (59,3)-(60,1))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (59,3)-(60,1) = "a\n "
         │   │   │   ├── closing_loc: ∅
@@ -157,17 +162,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (60,3)-(60,4) = "}"
         │   │   └── @ StringNode (location: (60,4)-(61,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (60,4)-(61,0) = "a\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "a\n"
         │   └── closing_loc: (61,0)-(62,0) = "DOC\n"
         ├── @ InterpolatedStringNode (location: (63,0)-(63,5))
+        │   ├── flags: ∅
         │   ├── opening_loc: (63,0)-(63,5) = "<<DOC"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (64,0)-(64,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (64,0)-(64,2) = "  "
         │   │   │   ├── closing_loc: ∅
@@ -177,17 +183,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (64,4)-(64,5) = "}"
         │   │   └── @ StringNode (location: (64,5)-(66,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (64,5)-(66,0) = "\n  \\\#{}\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\n  \#{}\n"
         │   └── closing_loc: (66,0)-(67,0) = "DOC\n"
         ├── @ InterpolatedStringNode (location: (68,0)-(68,5))
+        │   ├── flags: ∅
         │   ├── opening_loc: (68,0)-(68,5) = "<<DOC"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (69,0)-(69,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (69,0)-(69,2) = " a"
         │   │   │   ├── closing_loc: ∅
@@ -197,13 +204,14 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (69,4)-(69,5) = "}"
         │   │   └── @ StringNode (location: (69,5)-(71,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (69,5)-(71,0) = "b\n c\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "b\n c\n"
         │   └── closing_loc: (71,0)-(72,0) = "DOC\n"
         ├── @ InterpolatedStringNode (location: (73,0)-(73,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (73,0)-(73,6) = "<<~DOC"
         │   ├── parts: (length: 2)
         │   │   ├── @ EmbeddedStatementsNode (location: (74,2)-(74,5))
@@ -211,7 +219,7 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (74,4)-(74,5) = "}"
         │   │   └── @ StringNode (location: (74,5)-(75,0))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (74,5)-(75,0) = "\n"
         │   │       ├── closing_loc: ∅
@@ -226,6 +234,7 @@
         │   │   @ StatementsNode (location: (78,2)-(78,8))
         │   │   └── body: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (78,2)-(78,8))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (78,2)-(78,8) = "<<~DOC"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ EmbeddedStatementsNode (location: (79,4)-(79,7))
@@ -233,7 +242,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (79,6)-(79,7) = "}"
         │   │           │   └── @ StringNode (location: (79,7)-(80,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (79,7)-(80,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -250,10 +259,11 @@
         │   │   @ StatementsNode (location: (84,2)-(84,8))
         │   │   └── body: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (84,2)-(84,8))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (84,2)-(84,8) = "<<~DOC"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (85,0)-(85,5))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (85,0)-(85,5) = "    b"
         │   │           │   │   ├── closing_loc: ∅
@@ -263,7 +273,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (85,7)-(85,8) = "}"
         │   │           │   └── @ StringNode (location: (85,8)-(86,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (85,8)-(86,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -280,6 +290,7 @@
         │   │   @ StatementsNode (location: (90,2)-(90,8))
         │   │   └── body: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (90,2)-(90,8))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (90,2)-(90,8) = "<<~DOC"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ EmbeddedStatementsNode (location: (91,4)-(91,7))
@@ -287,7 +298,7 @@
         │   │           │   │   ├── statements: ∅
         │   │           │   │   └── closing_loc: (91,6)-(91,7) = "}"
         │   │           │   └── @ StringNode (location: (91,7)-(92,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (91,7)-(92,0) = "a\n"
         │   │           │       ├── closing_loc: ∅
@@ -312,6 +323,7 @@
         │   ├── consequent: ∅
         │   └── end_keyword_loc: (101,0)-(101,3) = "end"
         ├── @ InterpolatedStringNode (location: (103,0)-(103,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (103,0)-(103,1) = "\""
         │   ├── parts: (length: 2)
         │   │   ├── @ EmbeddedStatementsNode (location: (103,1)-(103,4))
@@ -319,17 +331,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (103,3)-(103,4) = "}"
         │   │   └── @ StringNode (location: (103,4)-(103,5))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (103,4)-(103,5) = "a"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "a"
         │   └── closing_loc: (103,5)-(103,6) = "\""
         ├── @ InterpolatedStringNode (location: (105,0)-(105,12))
+        │   ├── flags: ∅
         │   ├── opening_loc: (105,0)-(105,2) = "%("
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (105,2)-(105,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (105,2)-(105,5) = "\\n\""
         │   │   │   ├── closing_loc: ∅
@@ -339,17 +352,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (105,7)-(105,8) = "}"
         │   │   └── @ StringNode (location: (105,8)-(105,11))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (105,8)-(105,11) = "\"\\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\"\n"
         │   └── closing_loc: (105,11)-(105,12) = ")"
         ├── @ InterpolatedStringNode (location: (107,0)-(107,14))
+        │   ├── flags: ∅
         │   ├── opening_loc: (107,0)-(107,3) = "%Q("
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (107,3)-(107,7))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (107,3)-(107,7) = "-\\n\""
         │   │   │   ├── closing_loc: ∅
@@ -359,17 +373,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (107,9)-(107,10) = "}"
         │   │   └── @ StringNode (location: (107,10)-(107,13))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (107,10)-(107,13) = "\"\\n"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\"\n"
         │   └── closing_loc: (107,13)-(107,14) = ")"
         ├── @ InterpolatedStringNode (location: (109,0)-(111,2))
+        │   ├── flags: ∅
         │   ├── opening_loc: (109,0)-(109,1) = "\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (109,1)-(110,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (109,1)-(110,0) = "a\n"
         │   │   │   ├── closing_loc: ∅
@@ -379,17 +394,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (110,2)-(110,3) = "}"
         │   │   └── @ StringNode (location: (110,3)-(111,1))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (110,3)-(111,1) = "\nb"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\nb"
         │   └── closing_loc: (111,1)-(111,2) = "\""
         ├── @ InterpolatedStringNode (location: (113,0)-(114,2))
+        │   ├── flags: ∅
         │   ├── opening_loc: (113,0)-(113,1) = "\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (113,1)-(113,4))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (113,1)-(113,4) = "a\\n"
         │   │   │   ├── closing_loc: ∅
@@ -399,17 +415,18 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (113,6)-(113,7) = "}"
         │   │   └── @ StringNode (location: (113,7)-(114,1))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (113,7)-(114,1) = "\nb"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\nb"
         │   └── closing_loc: (114,1)-(114,2) = "\""
         ├── @ InterpolatedStringNode (location: (116,0)-(117,7))
+        │   ├── flags: ∅
         │   ├── opening_loc: (116,0)-(116,1) = "\""
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (116,1)-(117,0))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (116,1)-(117,0) = "a\n"
         │   │   │   ├── closing_loc: ∅
@@ -419,22 +436,24 @@
         │   │   │   ├── statements: ∅
         │   │   │   └── closing_loc: (117,2)-(117,3) = "}"
         │   │   └── @ StringNode (location: (117,3)-(117,6))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (117,3)-(117,6) = "\\nb"
         │   │       ├── closing_loc: ∅
         │   │       └── unescaped: "\nb"
         │   └── closing_loc: (117,6)-(117,7) = "\""
         ├── @ InterpolatedStringNode (location: (119,0)-(120,5))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ StringNode (location: (119,0)-(119,3))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: (119,0)-(119,1) = "'"
         │   │   │   ├── content_loc: (119,1)-(119,2) = "a"
         │   │   │   ├── closing_loc: (119,2)-(119,3) = "'"
         │   │   │   └── unescaped: "a"
         │   │   └── @ InterpolatedStringNode (location: (120,0)-(120,5))
+        │   │       ├── flags: ∅
         │   │       ├── opening_loc: (120,0)-(120,1) = "\""
         │   │       ├── parts: (length: 1)
         │   │       │   └── @ EmbeddedStatementsNode (location: (120,1)-(120,4))
@@ -444,35 +463,38 @@
         │   │       └── closing_loc: (120,4)-(120,5) = "\""
         │   └── closing_loc: ∅
         ├── @ InterpolatedStringNode (location: (122,0)-(122,8))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (122,0)-(122,2))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: (122,0)-(122,1) = "\""
         │   │   │   ├── content_loc: (122,1)-(122,1) = ""
         │   │   │   ├── closing_loc: (122,1)-(122,2) = "\""
         │   │   │   └── unescaped: ""
         │   │   ├── @ StringNode (location: (122,3)-(122,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: (122,3)-(122,4) = "\""
         │   │   │   ├── content_loc: (122,4)-(122,4) = ""
         │   │   │   ├── closing_loc: (122,4)-(122,5) = "\""
         │   │   │   └── unescaped: ""
         │   │   └── @ StringNode (location: (122,6)-(122,8))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (122,6)-(122,7) = "\""
         │   │       ├── content_loc: (122,7)-(122,7) = ""
         │   │       ├── closing_loc: (122,7)-(122,8) = "\""
         │   │       └── unescaped: ""
         │   └── closing_loc: ∅
         ├── @ InterpolatedStringNode (location: (124,0)-(124,12))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ InterpolatedStringNode (location: (124,0)-(124,8))
+        │   │   │   ├── flags: ∅
         │   │   │   ├── opening_loc: (124,0)-(124,1) = "\""
         │   │   │   ├── parts: (length: 2)
         │   │   │   │   ├── @ StringNode (location: (124,1)-(124,2))
-        │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   ├── content_loc: (124,1)-(124,2) = "a"
         │   │   │   │   │   ├── closing_loc: ∅
@@ -487,20 +509,22 @@
         │   │   │   │       └── closing_loc: (124,6)-(124,7) = "}"
         │   │   │   └── closing_loc: (124,7)-(124,8) = "\""
         │   │   └── @ StringNode (location: (124,9)-(124,12))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (124,9)-(124,10) = "\""
         │   │       ├── content_loc: (124,10)-(124,11) = "b"
         │   │       ├── closing_loc: (124,11)-(124,12) = "\""
         │   │       └── unescaped: "b"
         │   └── closing_loc: ∅
         ├── @ InterpolatedStringNode (location: (125,0)-(125,10))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ InterpolatedStringNode (location: (125,0)-(125,6))
+        │   │   │   ├── flags: ∅
         │   │   │   ├── opening_loc: (125,0)-(125,1) = "\""
         │   │   │   ├── parts: (length: 2)
         │   │   │   │   ├── @ StringNode (location: (125,1)-(125,2))
-        │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   ├── content_loc: (125,1)-(125,2) = "a"
         │   │   │   │   │   ├── closing_loc: ∅
@@ -512,20 +536,22 @@
         │   │   │   │           └── name: :@a
         │   │   │   └── closing_loc: (125,5)-(125,6) = "\""
         │   │   └── @ StringNode (location: (125,7)-(125,10))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (125,7)-(125,8) = "\""
         │   │       ├── content_loc: (125,8)-(125,9) = "b"
         │   │       ├── closing_loc: (125,9)-(125,10) = "\""
         │   │       └── unescaped: "b"
         │   └── closing_loc: ∅
         ├── @ InterpolatedStringNode (location: (126,0)-(126,10))
+        │   ├── flags: ∅
         │   ├── opening_loc: ∅
         │   ├── parts: (length: 2)
         │   │   ├── @ InterpolatedStringNode (location: (126,0)-(126,6))
+        │   │   │   ├── flags: ∅
         │   │   │   ├── opening_loc: (126,0)-(126,1) = "\""
         │   │   │   ├── parts: (length: 2)
         │   │   │   │   ├── @ StringNode (location: (126,1)-(126,2))
-        │   │   │   │   │   ├── flags: ∅
+        │   │   │   │   │   ├── flags: frozen
         │   │   │   │   │   ├── opening_loc: ∅
         │   │   │   │   │   ├── content_loc: (126,1)-(126,2) = "a"
         │   │   │   │   │   ├── closing_loc: ∅
@@ -537,20 +563,22 @@
         │   │   │   │           └── name: :$a
         │   │   │   └── closing_loc: (126,5)-(126,6) = "\""
         │   │   └── @ StringNode (location: (126,7)-(126,10))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: (126,7)-(126,8) = "\""
         │   │       ├── content_loc: (126,8)-(126,9) = "b"
         │   │       ├── closing_loc: (126,9)-(126,10) = "\""
         │   │       └── unescaped: "b"
         │   └── closing_loc: ∅
         └── @ InterpolatedStringNode (location: (127,0)-(127,11))
+            ├── flags: ∅
             ├── opening_loc: ∅
             ├── parts: (length: 2)
             │   ├── @ InterpolatedStringNode (location: (127,0)-(127,7))
+            │   │   ├── flags: ∅
             │   │   ├── opening_loc: (127,0)-(127,1) = "\""
             │   │   ├── parts: (length: 2)
             │   │   │   ├── @ StringNode (location: (127,1)-(127,2))
-            │   │   │   │   ├── flags: ∅
+            │   │   │   │   ├── flags: frozen
             │   │   │   │   ├── opening_loc: ∅
             │   │   │   │   ├── content_loc: (127,1)-(127,2) = "a"
             │   │   │   │   ├── closing_loc: ∅
@@ -562,7 +590,7 @@
             │   │   │           └── name: :@@a
             │   │   └── closing_loc: (127,6)-(127,7) = "\""
             │   └── @ StringNode (location: (127,8)-(127,11))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: (127,8)-(127,9) = "\""
             │       ├── content_loc: (127,9)-(127,10) = "b"
             │       ├── closing_loc: (127,10)-(127,11) = "\""
diff --git a/test/prism/snapshots/unparser/corpus/semantic/literal.txt b/test/prism/snapshots/unparser/corpus/semantic/literal.txt
index 59e02be6..ef666890 100644
--- a/test/prism/snapshots/unparser/corpus/semantic/literal.txt
+++ b/test/prism/snapshots/unparser/corpus/semantic/literal.txt
@@ -55,7 +55,7 @@
         │   │   │   │           └── name: :@bar
         │   │   │   └── closing_loc: (11,9)-(11,10) = "}"
         │   │   └── @ StringNode (location: (11,10)-(11,13))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (11,10)-(11,13) = "baz"
         │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/array_symbols_interp.txt b/test/prism/snapshots/whitequark/array_symbols_interp.txt
index 7583ad88..2437486b 100644
--- a/test/prism/snapshots/whitequark/array_symbols_interp.txt
+++ b/test/prism/snapshots/whitequark/array_symbols_interp.txt
@@ -41,7 +41,7 @@
             │       ├── opening_loc: ∅
             │       ├── parts: (length: 2)
             │       │   ├── @ StringNode (location: (3,3)-(3,6))
-            │       │   │   ├── flags: ∅
+            │       │   │   ├── flags: frozen
             │       │   │   ├── opening_loc: ∅
             │       │   │   ├── content_loc: (3,3)-(3,6) = "foo"
             │       │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/array_words_interp.txt b/test/prism/snapshots/whitequark/array_words_interp.txt
index c2f23d2b..c3ae9a0c 100644
--- a/test/prism/snapshots/whitequark/array_words_interp.txt
+++ b/test/prism/snapshots/whitequark/array_words_interp.txt
@@ -13,6 +13,7 @@
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "foo"
         │   │   └── @ InterpolatedStringNode (location: (1,7)-(1,13))
+        │   │       ├── flags: ∅
         │   │       ├── opening_loc: ∅
         │   │       ├── parts: (length: 1)
         │   │       │   └── @ EmbeddedStatementsNode (location: (1,7)-(1,13))
@@ -44,6 +45,7 @@
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "foo"
             │   └── @ InterpolatedStringNode (location: (3,7)-(3,21))
+            │       ├── flags: ∅
             │       ├── opening_loc: ∅
             │       ├── parts: (length: 3)
             │       │   ├── @ EmbeddedStatementsNode (location: (3,7)-(3,13))
@@ -63,7 +65,7 @@
             │       │   │   │           └── block: ∅
             │       │   │   └── closing_loc: (3,12)-(3,13) = "}"
             │       │   ├── @ StringNode (location: (3,13)-(3,16))
-            │       │   │   ├── flags: ∅
+            │       │   │   ├── flags: frozen
             │       │   │   ├── opening_loc: ∅
             │       │   │   ├── content_loc: (3,13)-(3,16) = "foo"
             │       │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/bug_435.txt b/test/prism/snapshots/whitequark/bug_435.txt
index e08874fa..42f9a49c 100644
--- a/test/prism/snapshots/whitequark/bug_435.txt
+++ b/test/prism/snapshots/whitequark/bug_435.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,14))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,14))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 1)
             │   └── @ EmbeddedStatementsNode (location: (1,1)-(1,13))
diff --git a/test/prism/snapshots/whitequark/bug_466.txt b/test/prism/snapshots/whitequark/bug_466.txt
index 3f65dee0..4167c223 100644
--- a/test/prism/snapshots/whitequark/bug_466.txt
+++ b/test/prism/snapshots/whitequark/bug_466.txt
@@ -15,6 +15,7 @@
             │   ├── flags: ∅
             │   └── arguments: (length: 1)
             │       └── @ InterpolatedStringNode (location: (1,4)-(1,19))
+            │           ├── flags: ∅
             │           ├── opening_loc: (1,4)-(1,5) = "\""
             │           ├── parts: (length: 1)
             │           │   └── @ EmbeddedStatementsNode (location: (1,5)-(1,18))
diff --git a/test/prism/snapshots/whitequark/bug_473.txt b/test/prism/snapshots/whitequark/bug_473.txt
index 96991ebe..028b6a51 100644
--- a/test/prism/snapshots/whitequark/bug_473.txt
+++ b/test/prism/snapshots/whitequark/bug_473.txt
@@ -15,6 +15,7 @@
             │   ├── flags: ∅
             │   └── arguments: (length: 1)
             │       └── @ InterpolatedStringNode (location: (1,2)-(1,9))
+            │           ├── flags: ∅
             │           ├── opening_loc: (1,2)-(1,3) = "\""
             │           ├── parts: (length: 1)
             │           │   └── @ EmbeddedStatementsNode (location: (1,3)-(1,8))
diff --git a/test/prism/snapshots/whitequark/bug_480.txt b/test/prism/snapshots/whitequark/bug_480.txt
index f0a2a312..ed6ba407 100644
--- a/test/prism/snapshots/whitequark/bug_480.txt
+++ b/test/prism/snapshots/whitequark/bug_480.txt
@@ -15,6 +15,7 @@
             │   ├── flags: ∅
             │   └── arguments: (length: 1)
             │       └── @ InterpolatedStringNode (location: (1,2)-(1,12))
+            │           ├── flags: ∅
             │           ├── opening_loc: (1,2)-(1,3) = "\""
             │           ├── parts: (length: 2)
             │           │   ├── @ EmbeddedStatementsNode (location: (1,3)-(1,6))
diff --git a/test/prism/snapshots/whitequark/bug_interp_single.txt b/test/prism/snapshots/whitequark/bug_interp_single.txt
index 6a9d56b5..74af8607 100644
--- a/test/prism/snapshots/whitequark/bug_interp_single.txt
+++ b/test/prism/snapshots/whitequark/bug_interp_single.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(3,8))
     └── body: (length: 2)
         ├── @ InterpolatedStringNode (location: (1,0)-(1,6))
+        │   ├── flags: ∅
         │   ├── opening_loc: (1,0)-(1,1) = "\""
         │   ├── parts: (length: 1)
         │   │   └── @ EmbeddedStatementsNode (location: (1,1)-(1,5))
@@ -20,6 +21,7 @@
             ├── flags: ∅
             ├── elements: (length: 1)
             │   └── @ InterpolatedStringNode (location: (3,3)-(3,7))
+            │       ├── flags: ∅
             │       ├── opening_loc: ∅
             │       ├── parts: (length: 1)
             │       │   └── @ EmbeddedStatementsNode (location: (3,3)-(3,7))
diff --git a/test/prism/snapshots/whitequark/dedenting_heredoc.txt b/test/prism/snapshots/whitequark/dedenting_heredoc.txt
index 49c44549..acb79e83 100644
--- a/test/prism/snapshots/whitequark/dedenting_heredoc.txt
+++ b/test/prism/snapshots/whitequark/dedenting_heredoc.txt
@@ -15,10 +15,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (1,2)-(1,8))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (1,2)-(1,8) = "<<~\"E\""
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (2,0)-(3,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (2,0)-(3,0) = "    x\n"
         │   │           │   │   ├── closing_loc: ∅
@@ -36,7 +37,7 @@
         │   │           │   │   │           └── unescaped: "  y"
         │   │           │   │   └── closing_loc: (3,9)-(3,10) = "}"
         │   │           │   └── @ StringNode (location: (3,10)-(4,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (3,10)-(4,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -56,10 +57,11 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (6,2)-(6,8))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (6,2)-(6,8) = "<<~\"E\""
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (7,0)-(8,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (7,0)-(8,0) = "    x\n"
         │   │           │   │   ├── closing_loc: ∅
@@ -81,7 +83,7 @@
         │   │           │   │   │           └── block: ∅
         │   │           │   │   └── closing_loc: (8,7)-(8,8) = "}"
         │   │           │   └── @ StringNode (location: (8,8)-(9,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (8,8)-(9,0) = "\n"
         │   │           │       ├── closing_loc: ∅
@@ -101,16 +103,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (11,2)-(11,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (11,2)-(11,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (12,0)-(13,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (12,0)-(13,0) = "\tx\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "x\n"
         │   │           │   └── @ StringNode (location: (13,0)-(14,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (13,0)-(14,0) = "        y\n"
         │   │           │       ├── closing_loc: ∅
@@ -130,16 +133,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (16,2)-(16,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (16,2)-(16,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (17,0)-(18,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (17,0)-(18,0) = "\tx\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "\tx\n"
         │   │           │   └── @ StringNode (location: (18,0)-(19,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (18,0)-(19,0) = "    y\n"
         │   │           │       ├── closing_loc: ∅
@@ -159,16 +163,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (21,2)-(21,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (21,2)-(21,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (22,0)-(23,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (22,0)-(23,0) = "    \tx\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "x\n"
         │   │           │   └── @ StringNode (location: (23,0)-(24,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (23,0)-(24,0) = "        y\n"
         │   │           │       ├── closing_loc: ∅
@@ -188,16 +193,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (26,2)-(26,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (26,2)-(26,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (27,0)-(28,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (27,0)-(28,0) = "        \tx\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "\tx\n"
         │   │           │   └── @ StringNode (location: (28,0)-(29,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (28,0)-(29,0) = "\ty\n"
         │   │           │       ├── closing_loc: ∅
@@ -217,16 +223,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (31,2)-(31,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (31,2)-(31,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (32,0)-(33,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (32,0)-(33,0) = "    x\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "  x\n"
         │   │           │   └── @ StringNode (location: (33,0)-(34,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (33,0)-(34,0) = "  \\\ty\n"
         │   │           │       ├── closing_loc: ∅
@@ -246,16 +253,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (36,2)-(36,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (36,2)-(36,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (37,0)-(38,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (37,0)-(38,0) = "    x\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "  x\n"
         │   │           │   └── @ StringNode (location: (38,0)-(39,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (38,0)-(39,0) = "  \\  y\n"
         │   │           │       ├── closing_loc: ∅
@@ -294,22 +302,23 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (44,2)-(44,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (44,2)-(44,6) = "<<~E"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (45,0)-(46,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (45,0)-(46,0) = "  x\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "  x\n"
         │   │           │   ├── @ StringNode (location: (46,0)-(47,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (46,0)-(47,0) = "\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "\n"
         │   │           │   └── @ StringNode (location: (47,0)-(48,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (47,0)-(48,0) = "y\n"
         │   │           │       ├── closing_loc: ∅
@@ -329,22 +338,23 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (50,2)-(50,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (50,2)-(50,6) = "<<~E"
         │   │           ├── parts: (length: 3)
         │   │           │   ├── @ StringNode (location: (51,0)-(52,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (51,0)-(52,0) = "  x\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "x\n"
         │   │           │   ├── @ StringNode (location: (52,0)-(53,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (52,0)-(53,0) = "    \n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "  \n"
         │   │           │   └── @ StringNode (location: (53,0)-(54,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (53,0)-(54,0) = "  y\n"
         │   │           │       ├── closing_loc: ∅
@@ -364,16 +374,17 @@
         │   │   ├── flags: ∅
         │   │   └── arguments: (length: 1)
         │   │       └── @ InterpolatedStringNode (location: (56,2)-(56,6))
+        │   │           ├── flags: ∅
         │   │           ├── opening_loc: (56,2)-(56,6) = "<<~E"
         │   │           ├── parts: (length: 2)
         │   │           │   ├── @ StringNode (location: (57,0)-(58,0))
-        │   │           │   │   ├── flags: ∅
+        │   │           │   │   ├── flags: frozen
         │   │           │   │   ├── opening_loc: ∅
         │   │           │   │   ├── content_loc: (57,0)-(58,0) = "  x\n"
         │   │           │   │   ├── closing_loc: ∅
         │   │           │   │   └── unescaped: "x\n"
         │   │           │   └── @ StringNode (location: (58,0)-(59,0))
-        │   │           │       ├── flags: ∅
+        │   │           │       ├── flags: frozen
         │   │           │       ├── opening_loc: ∅
         │   │           │       ├── content_loc: (58,0)-(59,0) = "    y\n"
         │   │           │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/dedenting_interpolating_heredoc_fake_line_continuation.txt b/test/prism/snapshots/whitequark/dedenting_interpolating_heredoc_fake_line_continuation.txt
index cc5be3d9..8d093fda 100644
--- a/test/prism/snapshots/whitequark/dedenting_interpolating_heredoc_fake_line_continuation.txt
+++ b/test/prism/snapshots/whitequark/dedenting_interpolating_heredoc_fake_line_continuation.txt
@@ -4,16 +4,17 @@
     @ StatementsNode (location: (1,0)-(1,8))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,8))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,8) = "<<~'FOO'"
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (2,0)-(3,0) = "  baz\\\\\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "baz\\\\\n"
             │   └── @ StringNode (location: (3,0)-(4,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (3,0)-(4,0) = "  qux\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/dedenting_non_interpolating_heredoc_line_continuation.txt b/test/prism/snapshots/whitequark/dedenting_non_interpolating_heredoc_line_continuation.txt
index d9f7fe2e..d43d313e 100644
--- a/test/prism/snapshots/whitequark/dedenting_non_interpolating_heredoc_line_continuation.txt
+++ b/test/prism/snapshots/whitequark/dedenting_non_interpolating_heredoc_line_continuation.txt
@@ -4,16 +4,17 @@
     @ StatementsNode (location: (1,0)-(1,8))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,8))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,8) = "<<~'FOO'"
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (2,0)-(3,0) = "  baz\\\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "baz\\\n"
             │   └── @ StringNode (location: (3,0)-(4,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (3,0)-(4,0) = "  qux\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/endless_method_command_syntax.txt b/test/prism/snapshots/whitequark/endless_method_command_syntax.txt
index 334fb39d..4ec57ccd 100644
--- a/test/prism/snapshots/whitequark/endless_method_command_syntax.txt
+++ b/test/prism/snapshots/whitequark/endless_method_command_syntax.txt
@@ -296,10 +296,11 @@
         │   │           ├── keyword_loc: (13,38)-(13,44) = "rescue"
         │   │           └── rescue_expression:
         │   │               @ InterpolatedStringNode (location: (13,45)-(13,60))
+        │   │               ├── flags: ∅
         │   │               ├── opening_loc: (13,45)-(13,46) = "\""
         │   │               ├── parts: (length: 2)
         │   │               │   ├── @ StringNode (location: (13,46)-(13,55))
-        │   │               │   │   ├── flags: ∅
+        │   │               │   │   ├── flags: frozen
         │   │               │   │   ├── opening_loc: ∅
         │   │               │   │   ├── content_loc: (13,46)-(13,55) = "instance "
         │   │               │   │   ├── closing_loc: ∅
@@ -365,10 +366,11 @@
             │           ├── keyword_loc: (15,43)-(15,49) = "rescue"
             │           └── rescue_expression:
             │               @ InterpolatedStringNode (location: (15,50)-(15,62))
+            │               ├── flags: ∅
             │               ├── opening_loc: (15,50)-(15,51) = "\""
             │               ├── parts: (length: 2)
             │               │   ├── @ StringNode (location: (15,51)-(15,57))
-            │               │   │   ├── flags: ∅
+            │               │   │   ├── flags: frozen
             │               │   │   ├── opening_loc: ∅
             │               │   │   ├── content_loc: (15,51)-(15,57) = "class "
             │               │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/non_lvar_injecting_match.txt b/test/prism/snapshots/whitequark/non_lvar_injecting_match.txt
index 2df571e8..584e997d 100644
--- a/test/prism/snapshots/whitequark/non_lvar_injecting_match.txt
+++ b/test/prism/snapshots/whitequark/non_lvar_injecting_match.txt
@@ -20,7 +20,7 @@
             │   │   │   │           └── value: 1
             │   │   │   └── closing_loc: (1,4)-(1,5) = "}"
             │   │   └── @ StringNode (location: (1,5)-(1,18))
-            │   │       ├── flags: ∅
+            │   │       ├── flags: frozen
             │   │       ├── opening_loc: ∅
             │   │       ├── content_loc: (1,5)-(1,18) = "(?<match>bar)"
             │   │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/parser_bug_640.txt b/test/prism/snapshots/whitequark/parser_bug_640.txt
index a9d3f957..15757683 100644
--- a/test/prism/snapshots/whitequark/parser_bug_640.txt
+++ b/test/prism/snapshots/whitequark/parser_bug_640.txt
@@ -4,16 +4,17 @@
     @ StatementsNode (location: (1,0)-(1,6))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,6))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,6) = "<<~FOO"
             ├── parts: (length: 2)
             │   ├── @ StringNode (location: (2,0)-(3,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (2,0)-(3,0) = "  baz\\\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "baz"
             │   └── @ StringNode (location: (3,0)-(4,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (3,0)-(4,0) = "  qux\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/parser_drops_truncated_parts_of_squiggly_heredoc.txt b/test/prism/snapshots/whitequark/parser_drops_truncated_parts_of_squiggly_heredoc.txt
index d9744355..018d7916 100644
--- a/test/prism/snapshots/whitequark/parser_drops_truncated_parts_of_squiggly_heredoc.txt
+++ b/test/prism/snapshots/whitequark/parser_drops_truncated_parts_of_squiggly_heredoc.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,7))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,7))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,7) = "<<~HERE"
             ├── parts: (length: 2)
             │   ├── @ EmbeddedStatementsNode (location: (2,2)-(2,5))
@@ -11,7 +12,7 @@
             │   │   ├── statements: ∅
             │   │   └── closing_loc: (2,4)-(2,5) = "}"
             │   └── @ StringNode (location: (2,5)-(3,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (2,5)-(3,0) = "\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/regex_interp.txt b/test/prism/snapshots/whitequark/regex_interp.txt
index ee8caf22..0a6db4cf 100644
--- a/test/prism/snapshots/whitequark/regex_interp.txt
+++ b/test/prism/snapshots/whitequark/regex_interp.txt
@@ -8,7 +8,7 @@
             ├── opening_loc: (1,0)-(1,1) = "/"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,1)-(1,4))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,4) = "foo"
             │   │   ├── closing_loc: ∅
@@ -30,7 +30,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,9)-(1,10) = "}"
             │   └── @ StringNode (location: (1,10)-(1,13))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,10)-(1,13) = "baz"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/ruby_bug_11990.txt b/test/prism/snapshots/whitequark/ruby_bug_11990.txt
index 43c04e55..0a5fba14 100644
--- a/test/prism/snapshots/whitequark/ruby_bug_11990.txt
+++ b/test/prism/snapshots/whitequark/ruby_bug_11990.txt
@@ -15,16 +15,17 @@
             │   ├── flags: ∅
             │   └── arguments: (length: 1)
             │       └── @ InterpolatedStringNode (location: (1,2)-(1,12))
+            │           ├── flags: ∅
             │           ├── opening_loc: ∅
             │           ├── parts: (length: 2)
             │           │   ├── @ StringNode (location: (1,2)-(1,6))
-            │           │   │   ├── flags: ∅
+            │           │   │   ├── flags: frozen
             │           │   │   ├── opening_loc: (1,2)-(1,6) = "<<~E"
             │           │   │   ├── content_loc: (2,0)-(3,0) = "  x\n"
             │           │   │   ├── closing_loc: (3,0)-(4,0) = "E\n"
             │           │   │   └── unescaped: "x\n"
             │           │   └── @ StringNode (location: (1,7)-(1,12))
-            │           │       ├── flags: ∅
+            │           │       ├── flags: frozen
             │           │       ├── opening_loc: (1,7)-(1,8) = "\""
             │           │       ├── content_loc: (1,8)-(1,11) = "  y"
             │           │       ├── closing_loc: (1,11)-(1,12) = "\""
diff --git a/test/prism/snapshots/whitequark/slash_newline_in_heredocs.txt b/test/prism/snapshots/whitequark/slash_newline_in_heredocs.txt
index 8d6fce2b..ba1fce0c 100644
--- a/test/prism/snapshots/whitequark/slash_newline_in_heredocs.txt
+++ b/test/prism/snapshots/whitequark/slash_newline_in_heredocs.txt
@@ -10,22 +10,23 @@
         │   ├── closing_loc: (5,0)-(6,0) = "E\n"
         │   └── unescaped: "    1     2\n    3\n"
         └── @ InterpolatedStringNode (location: (8,0)-(8,4))
+            ├── flags: ∅
             ├── opening_loc: (8,0)-(8,4) = "<<~E"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (9,0)-(10,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (9,0)-(10,0) = "    1 \\\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "1 "
             │   ├── @ StringNode (location: (10,0)-(11,0))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (10,0)-(11,0) = "    2\n"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "2\n"
             │   └── @ StringNode (location: (11,0)-(12,0))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (11,0)-(12,0) = "    3\n"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/string_concat.txt b/test/prism/snapshots/whitequark/string_concat.txt
index 38ea0c74..f7f7bf97 100644
--- a/test/prism/snapshots/whitequark/string_concat.txt
+++ b/test/prism/snapshots/whitequark/string_concat.txt
@@ -4,13 +4,15 @@
     @ StatementsNode (location: (1,0)-(1,14))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,14))
+            ├── flags: ∅
             ├── opening_loc: ∅
             ├── parts: (length: 2)
             │   ├── @ InterpolatedStringNode (location: (1,0)-(1,8))
+            │   │   ├── flags: ∅
             │   │   ├── opening_loc: (1,0)-(1,1) = "\""
             │   │   ├── parts: (length: 2)
             │   │   │   ├── @ StringNode (location: (1,1)-(1,4))
-            │   │   │   │   ├── flags: ∅
+            │   │   │   │   ├── flags: frozen
             │   │   │   │   ├── opening_loc: ∅
             │   │   │   │   ├── content_loc: (1,1)-(1,4) = "foo"
             │   │   │   │   ├── closing_loc: ∅
@@ -22,7 +24,7 @@
             │   │   │           └── name: :@a
             │   │   └── closing_loc: (1,7)-(1,8) = "\""
             │   └── @ StringNode (location: (1,9)-(1,14))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: (1,9)-(1,10) = "\""
             │       ├── content_loc: (1,10)-(1,13) = "bar"
             │       ├── closing_loc: (1,13)-(1,14) = "\""
diff --git a/test/prism/snapshots/whitequark/string_dvar.txt b/test/prism/snapshots/whitequark/string_dvar.txt
index 123b36e0..9d042325 100644
--- a/test/prism/snapshots/whitequark/string_dvar.txt
+++ b/test/prism/snapshots/whitequark/string_dvar.txt
@@ -4,6 +4,7 @@
     @ StatementsNode (location: (1,0)-(1,14))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,14))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 5)
             │   ├── @ EmbeddedVariableNode (location: (1,1)-(1,4))
@@ -12,7 +13,7 @@
             │   │       @ InstanceVariableReadNode (location: (1,2)-(1,4))
             │   │       └── name: :@a
             │   ├── @ StringNode (location: (1,4)-(1,5))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,4)-(1,5) = " "
             │   │   ├── closing_loc: ∅
@@ -23,7 +24,7 @@
             │   │       @ ClassVariableReadNode (location: (1,6)-(1,9))
             │   │       └── name: :@@a
             │   ├── @ StringNode (location: (1,9)-(1,10))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,9)-(1,10) = " "
             │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/string_interp.txt b/test/prism/snapshots/whitequark/string_interp.txt
index a83323a0..597e8c5d 100644
--- a/test/prism/snapshots/whitequark/string_interp.txt
+++ b/test/prism/snapshots/whitequark/string_interp.txt
@@ -4,10 +4,11 @@
     @ StatementsNode (location: (1,0)-(1,14))
     └── body: (length: 1)
         └── @ InterpolatedStringNode (location: (1,0)-(1,14))
+            ├── flags: ∅
             ├── opening_loc: (1,0)-(1,1) = "\""
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,1)-(1,4))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,4) = "foo"
             │   │   ├── closing_loc: ∅
@@ -29,7 +30,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,9)-(1,10) = "}"
             │   └── @ StringNode (location: (1,10)-(1,13))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,10)-(1,13) = "baz"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/symbol_interp.txt b/test/prism/snapshots/whitequark/symbol_interp.txt
index c108addd..a9b8dfcb 100644
--- a/test/prism/snapshots/whitequark/symbol_interp.txt
+++ b/test/prism/snapshots/whitequark/symbol_interp.txt
@@ -7,7 +7,7 @@
             ├── opening_loc: (1,0)-(1,2) = ":\""
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,2)-(1,5))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,2)-(1,5) = "foo"
             │   │   ├── closing_loc: ∅
@@ -29,7 +29,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,10)-(1,11) = "}"
             │   └── @ StringNode (location: (1,11)-(1,14))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,11)-(1,14) = "baz"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/undef.txt b/test/prism/snapshots/whitequark/undef.txt
index 5e6b5c7b..163cc2e8 100644
--- a/test/prism/snapshots/whitequark/undef.txt
+++ b/test/prism/snapshots/whitequark/undef.txt
@@ -21,7 +21,7 @@
             │       ├── opening_loc: (1,17)-(1,19) = ":\""
             │       ├── parts: (length: 2)
             │       │   ├── @ StringNode (location: (1,19)-(1,22))
-            │       │   │   ├── flags: ∅
+            │       │   │   ├── flags: frozen
             │       │   │   ├── opening_loc: ∅
             │       │   │   ├── content_loc: (1,19)-(1,22) = "foo"
             │       │   │   ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/xstring_interp.txt b/test/prism/snapshots/whitequark/xstring_interp.txt
index e9543098..0676ea96 100644
--- a/test/prism/snapshots/whitequark/xstring_interp.txt
+++ b/test/prism/snapshots/whitequark/xstring_interp.txt
@@ -7,7 +7,7 @@
             ├── opening_loc: (1,0)-(1,1) = "`"
             ├── parts: (length: 3)
             │   ├── @ StringNode (location: (1,1)-(1,4))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: frozen
             │   │   ├── opening_loc: ∅
             │   │   ├── content_loc: (1,1)-(1,4) = "foo"
             │   │   ├── closing_loc: ∅
@@ -29,7 +29,7 @@
             │   │   │           └── block: ∅
             │   │   └── closing_loc: (1,9)-(1,10) = "}"
             │   └── @ StringNode (location: (1,10)-(1,13))
-            │       ├── flags: ∅
+            │       ├── flags: frozen
             │       ├── opening_loc: ∅
             │       ├── content_loc: (1,10)-(1,13) = "baz"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/xstring.txt b/test/prism/snapshots/xstring.txt
index 04b4cbf6..1a177026 100644
--- a/test/prism/snapshots/xstring.txt
+++ b/test/prism/snapshots/xstring.txt
@@ -13,7 +13,7 @@
         │   ├── opening_loc: (3,0)-(3,1) = "`"
         │   ├── parts: (length: 3)
         │   │   ├── @ StringNode (location: (3,1)-(3,5))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: frozen
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── content_loc: (3,1)-(3,5) = "foo "
         │   │   │   ├── closing_loc: ∅
@@ -35,7 +35,7 @@
         │   │   │   │           └── block: ∅
         │   │   │   └── closing_loc: (3,10)-(3,11) = "}"
         │   │   └── @ StringNode (location: (3,11)-(3,15))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: frozen
         │   │       ├── opening_loc: ∅
         │   │       ├── content_loc: (3,11)-(3,15) = " baz"
         │   │       ├── closing_loc: ∅