Repository: swc-project/swc (rust)

Issue:
[Bug]: (Crash) Using private static fields with `in` operator in itself
### Describe the bug

The input program is expected to be terminated without error, but SWC fails to transpile it.

### Input code

```typescript
class x { static #y = #y in x ; }
```


### Config

_No response_

### Playground link

https://play.swc.rs/?version=1.3.14&code=H4sIAAAAAAAAA0vOSSwuVqhQqFYoLkksyUxWUK5UsAURmXlAUWuFWgCOG5gLIQAAAA%3D%3D&config=H4sIAAAAAAAAA0WMSwrDMAxE76K1t%2B0id8ghhKsEF%2F%2BQFIgxvnvlkpCdZubpdfiKh6VDRRbieUnLiicsQD6heA5VwRlm1YZRaDhQ5J10IvKyLZYidK0OUshha9PkS6pMIs%2BEeY83OUyUyueYRQdtlf7CN4zHoXzYW5D14mYeP5P5%2B3m0AAAA

### Expected behavior

`input.js` is terminated normally:
```console
$ node input.js # no error
```

### Actual behavior

SWC fails to transpile `input.js`:
<img width="436" alt="image" src="https://user-images.githubusercontent.com/68288688/200516983-eb59e784-23c0-4874-8c8d-d0973c7dd2f1.png">


### Version

1.3.14 (default SWC playground)

### Additional context

_No response_

Pull request:
fix(es): Remove `privateInObject` related setting
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**Description:**

<!-- Explain the **motivation** for making this change. What existing problem does the pull request solve? -->

private in object has already landed in ES2022 and there're many browsers supporting it, so related config can be removed. This won't be a break change for JS side as currently `serde` only checks extra fields in top level.

**BREAKING CHANGE:**

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If this PR introduces a breaking change, it must contain a notice for it to be included in the CHANGELOG. Add description or remove entirely if not breaking.

You may need to update `MIGRATION.md` for the breaking changes.
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**Related issue (if exists):**
closes #6373

Patch:
diff --git a/crates/swc/src/builder.rs b/crates/swc/src/builder.rs
index d90e954ebb..2c0780bf67 100644
--- a/crates/swc/src/builder.rs
+++ b/crates/swc/src/builder.rs
@@ -17,7 +17,6 @@ use swc_ecma_minifier::option::{terser::TerserTopLevelOptions, MinifyOptions};
 use swc_ecma_parser::Syntax;
 use swc_ecma_transforms::{
     compat,
-    compat::es2022::private_in_object,
     feature::{enable_available_feature_from_es_version, FeatureFlag},
     fixer::{fixer, paren_remover},
     helpers, hygiene,
@@ -330,7 +329,6 @@ impl<'a, 'b, P: swc_ecma_visit::Fold> PassBuilder<'a, 'b, P> {
                 paren_remover(comments.map(|v| v as &dyn Comments)),
                 self.fixer
             ),
-            Optional::new(private_in_object(), syntax.private_in_object()),
             compat_pass,
             // module / helper
             Optional::new(
diff --git a/crates/swc/src/lib.rs b/crates/swc/src/lib.rs
index 91f72096a3..d932c29574 100644
--- a/crates/swc/src/lib.rs
+++ b/crates/swc/src/lib.rs
@@ -1009,7 +1009,6 @@ impl Compiler {
                         decorators: true,
                         decorators_before_export: true,
                         import_assertions: true,
-                        private_in_object: true,
                         ..Default::default()
                     }),
                     IsModule::Bool(true),
diff --git a/crates/swc_ecma_parser/src/lib.rs b/crates/swc_ecma_parser/src/lib.rs
index adf1428d92..9fd15e210f 100644
--- a/crates/swc_ecma_parser/src/lib.rs
+++ b/crates/swc_ecma_parser/src/lib.rs
@@ -238,15 +238,6 @@ impl Syntax {
         }
     }
 
-    pub fn private_in_object(self) -> bool {
-        match self {
-            Syntax::Es(EsConfig {
-                private_in_object, ..
-            }) => private_in_object,
-            Syntax::Typescript(_) => true,
-        }
-    }
-
     pub(crate) fn allow_super_outside_method(self) -> bool {
         match self {
             Syntax::Es(EsConfig {
@@ -321,9 +312,6 @@ pub struct EsConfig {
     #[serde(default)]
     pub import_assertions: bool,
 
-    #[serde(default, rename = "privateInObject")]
-    pub private_in_object: bool,
-
     #[serde(default, rename = "allowSuperOutsideMethod")]
     pub allow_super_outside_method: bool,
 
diff --git a/crates/swc_ecma_parser/src/parser/expr.rs b/crates/swc_ecma_parser/src/parser/expr.rs
index 3f73a9a70a..6ab3787668 100644
--- a/crates/swc_ecma_parser/src/parser/expr.rs
+++ b/crates/swc_ecma_parser/src/parser/expr.rs
@@ -487,7 +487,7 @@ impl<I: Tokens> Parser<I> {
             }
         }
 
-        if self.input.syntax().private_in_object() && eat!(self, '#') {
+        if eat!(self, '#') {
             let id = self.parse_ident_name()?;
             return Ok(Box::new(Expr::PrivateName(PrivateName {
                 span: span!(self, start),


Test patch:
diff --git a/crates/swc/tests/fixture/issues-6xxx/6373/input/.swcrc b/crates/swc/tests/fixture/issues-6xxx/6373/input/.swcrc
new file mode 100644
index 0000000000..129a48e782
--- /dev/null
+++ b/crates/swc/tests/fixture/issues-6xxx/6373/input/.swcrc
@@ -0,0 +1,12 @@
+{
+    "jsc": {
+      "parser": {
+        "syntax": "ecmascript"
+      },
+      "target": "es5"
+    },
+    "module": {
+      "type": "es6"
+    },
+    "isModule": true
+}
\ No newline at end of file
diff --git a/crates/swc/tests/fixture/issues-6xxx/6373/input/input.js b/crates/swc/tests/fixture/issues-6xxx/6373/input/input.js
new file mode 100644
index 0000000000..949565dcd4
--- /dev/null
+++ b/crates/swc/tests/fixture/issues-6xxx/6373/input/input.js
@@ -0,0 +1,1 @@
+class x { static #y = #y in x ; }
\ No newline at end of file
diff --git a/crates/swc/tests/fixture/issues-6xxx/6373/output/input.js b/crates/swc/tests/fixture/issues-6xxx/6373/output/input.js
new file mode 100644
index 0000000000..e59f2a3523
--- /dev/null
+++ b/crates/swc/tests/fixture/issues-6xxx/6373/output/input.js
@@ -0,0 +1,9 @@
+import _class_call_check from "@swc/helpers/src/_class_call_check.mjs";
+var x = function x() {
+    "use strict";
+    _class_call_check(this, x);
+};
+var _y = {
+    writable: true,
+    value: x === x
+};
diff --git a/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.1.normal.js b/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.1.normal.js
index b070e32e71..54cebaf32e 100644
--- a/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.1.normal.js
+++ b/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.1.normal.js
@@ -1,10 +1,9 @@
 //// [privateNameInInExpressionUnused.ts]
-var _brand_check_brand = new WeakSet();
 class Foo {
     #unused;
-    #brand = void _brand_check_brand.add(this);
+    #brand;
     isFoo(v) {
         // This should count as using/reading '#brand'
-        return _brand_check_brand.has(v);
+        return #brand in v;
     }
 }
diff --git a/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.2.minified.js b/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.2.minified.js
index 2cbd89df2d..62c9d362c2 100644
--- a/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.2.minified.js
+++ b/crates/swc/tests/tsc-references/privateNameInInExpressionUnused.2.minified.js
@@ -1,2 +1,1 @@
 //// [privateNameInInExpressionUnused.ts]
-new WeakSet();
diff --git a/crates/swc_ecma_parser/tests/test262-error-references/fail/c3731145e0e65d1d.js.stderr b/crates/swc_ecma_parser/tests/test262-error-references/fail/c3731145e0e65d1d.js.stderr
index 834ca3cda8..03085de602 100644
--- a/crates/swc_ecma_parser/tests/test262-error-references/fail/c3731145e0e65d1d.js.stderr
+++ b/crates/swc_ecma_parser/tests/test262-error-references/fail/c3731145e0e65d1d.js.stderr
@@ -1,7 +1,6 @@
 
-  x Unexpected token `#`. Expected this, import, async, function, [ for array literal, { for object literal, @ for decorator, function, class, null, true, false, number, bigint, string, regexp, `
-  | for template literal, (, or an identifier
+  x Expected ident
    ,-[$DIR/tests/test262-parser/fail/c3731145e0e65d1d.js:1:1]
  1 | #=
-   : ^
+   :  ^
    `----
diff --git a/crates/swc_ecma_transforms_compat/tests/es2015_new_target.rs b/crates/swc_ecma_transforms_compat/tests/es2015_new_target.rs
index 5a165b66d8..01b30f8e08 100644
--- a/crates/swc_ecma_transforms_compat/tests/es2015_new_target.rs
+++ b/crates/swc_ecma_transforms_compat/tests/es2015_new_target.rs
@@ -2,7 +2,6 @@ use std::{fs::read_to_string, path::PathBuf};
 
 use serde::Deserialize;
 use swc_common::{chain, Mark};
-use swc_ecma_parser::{EsConfig, Syntax};
 use swc_ecma_transforms_base::pass::noop;
 use swc_ecma_transforms_compat::{
     es2015::{arrow, classes, new_target::new_target},
@@ -96,10 +95,7 @@ fn fixture(input: PathBuf) {
 
     let output = input.parent().unwrap().join("output.js");
     test_fixture(
-        Syntax::Es(EsConfig {
-            private_in_object: true,
-            ..Default::default()
-        }),
+        Default::default(),
         &|t| get_passes(t, &options.plugins),
         &input,
         &output,
diff --git a/crates/swc_ecma_transforms_compat/tests/es2022_private_in_object.rs b/crates/swc_ecma_transforms_compat/tests/es2022_private_in_object.rs
index 22acd2c7ca..cb19d148a4 100644
--- a/crates/swc_ecma_transforms_compat/tests/es2022_private_in_object.rs
+++ b/crates/swc_ecma_transforms_compat/tests/es2022_private_in_object.rs
@@ -2,7 +2,6 @@ use std::path::PathBuf;
 
 use serde::Deserialize;
 use swc_common::chain;
-use swc_ecma_parser::{EsConfig, Syntax};
 use swc_ecma_transforms_base::pass::noop;
 use swc_ecma_transforms_compat::{
     es2015::classes,
@@ -32,10 +31,7 @@ fn fixture(input: PathBuf) {
 
     let output = parent.join("output.js");
     test_fixture(
-        Syntax::Es(EsConfig {
-            private_in_object: true,
-            ..Default::default()
-        }),
+        Default::default(),
         &|t| {
             let mut pass: Box<dyn Fold> = Box::new(noop());
 
diff --git a/crates/swc_ecma_transforms_typescript/tests/strip_correctness.rs b/crates/swc_ecma_transforms_typescript/tests/strip_correctness.rs
index d58fb74ef4..19122dc9dc 100644
--- a/crates/swc_ecma_transforms_typescript/tests/strip_correctness.rs
+++ b/crates/swc_ecma_transforms_typescript/tests/strip_correctness.rs
@@ -236,7 +236,6 @@ fn identity(entry: PathBuf) {
                 decorators: true,
                 decorators_before_export: true,
                 export_default_from: true,
-                private_in_object: true,
                 import_assertions: true,
                 allow_super_outside_method: true,
                 ..Default::default()