Repository: rust-lang/rust-analyzer
Pull request #16895 (2024-03-19 18:49:10)

Resolve whether `$pat` is `$pat_param` or not via 🌟hygiene🌟
Before we just picked the edition from the macro def which is wrong, since a macro call can produce the fragment kind from a different definition site. 

Veykril: @bors r+
bors: :pushpin: Commit 0dcf79348cace7d4d4440650f2da727edc477575 has been approved by `Veykril`

It is now in the [queue](https://bors.rust-lang.org/homu/queue/rust-analyzer) for this repository.

<!-- @bors r=Veykril 0dcf79348cace7d4d4440650f2da727edc477575 -->
<!-- homu: {"type":"Approved","sha":"0dcf79348cace7d4d4440650f2da727edc477575","approver":"Veykril","queue":"https://bors.rust-lang.org/homu/queue/rust-analyzer"} -->
bors: :hourglass: Testing commit 0dcf79348cace7d4d4440650f2da727edc477575 with merge 4febedf318329ce9c0dc6039b2c5af8e76e028b0...
<!-- homu: {"type":"BuildStarted","head_sha":"0dcf79348cace7d4d4440650f2da727edc477575","merge_sha":"4febedf318329ce9c0dc6039b2c5af8e76e028b0"} -->

Patch:
diff --git a/Cargo.lock b/Cargo.lock
index 733e119b04..7ab4e24f08 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -594,6 +594,7 @@ dependencies = [
  "rustc-hash",
  "scoped-tls",
  "smallvec",
+ "span",
  "stdx",
  "syntax",
  "test-fixture",
@@ -637,6 +638,7 @@ dependencies = [
  "pulldown-cmark",
  "pulldown-cmark-to-cmark",
  "smallvec",
+ "span",
  "stdx",
  "syntax",
  "test-fixture",
@@ -1380,6 +1382,7 @@ dependencies = [
  "semver",
  "serde",
  "serde_json",
+ "span",
  "stdx",
  "toolchain",
  "tracing",
diff --git a/crates/base-db/src/input.rs b/crates/base-db/src/input.rs
index b243b37b77..f59c4e5016 100644
--- a/crates/base-db/src/input.rs
+++ b/crates/base-db/src/input.rs
@@ -6,11 +6,12 @@
 //! actual IO. See `vfs` and `project_model` in the `rust-analyzer` crate for how
 //! actual IO is done and lowered to input.
 
-use std::{fmt, mem, ops, str::FromStr};
+use std::{fmt, mem, ops};
 
 use cfg::CfgOptions;
 use la_arena::{Arena, Idx, RawIdx};
 use rustc_hash::{FxHashMap, FxHashSet};
+use span::Edition;
 use syntax::SmolStr;
 use triomphe::Arc;
 use vfs::{file_set::FileSet, AbsPathBuf, AnchoredPath, FileId, VfsPath};
@@ -293,42 +294,11 @@ pub struct CrateData {
     pub is_proc_macro: bool,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Edition {
-    Edition2015,
-    Edition2018,
-    Edition2021,
-    Edition2024,
-}
-
-impl Edition {
-    pub const CURRENT: Edition = Edition::Edition2021;
-    pub const DEFAULT: Edition = Edition::Edition2015;
-}
-
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
 pub struct Env {
     entries: FxHashMap<String, String>,
 }
 
-impl Env {
-    pub fn new_for_test_fixture() -> Self {
-        Env {
-            entries: FxHashMap::from_iter([(
-                String::from("__ra_is_test_fixture"),
-                String::from("__ra_is_test_fixture"),
-            )]),
-        }
-    }
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-pub enum DependencyKind {
-    Normal,
-    Dev,
-    Build,
-}
-
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Dependency {
     pub crate_id: CrateId,
@@ -670,32 +640,6 @@ impl CrateData {
     }
 }
 
-impl FromStr for Edition {
-    type Err = ParseEditionError;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let res = match s {
-            "2015" => Edition::Edition2015,
-            "2018" => Edition::Edition2018,
-            "2021" => Edition::Edition2021,
-            "2024" => Edition::Edition2024,
-            _ => return Err(ParseEditionError { invalid_input: s.to_owned() }),
-        };
-        Ok(res)
-    }
-}
-
-impl fmt::Display for Edition {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str(match self {
-            Edition::Edition2015 => "2015",
-            Edition::Edition2018 => "2018",
-            Edition::Edition2021 => "2021",
-            Edition::Edition2024 => "2024",
-        })
-    }
-}
-
 impl Extend<(String, String)> for Env {
     fn extend<T: IntoIterator<Item = (String, String)>>(&mut self, iter: T) {
         self.entries.extend(iter);
@@ -722,19 +666,6 @@ impl Env {
     }
 }
 
-#[derive(Debug)]
-pub struct ParseEditionError {
-    invalid_input: String,
-}
-
-impl fmt::Display for ParseEditionError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "invalid edition: {:?}", self.invalid_input)
-    }
-}
-
-impl std::error::Error for ParseEditionError {}
-
 #[derive(Debug)]
 pub struct CyclicDependenciesError {
     path: Vec<(CrateId, Option<CrateDisplayName>)>,
diff --git a/crates/base-db/src/lib.rs b/crates/base-db/src/lib.rs
index 5dcb580723..785ff9ceff 100644
--- a/crates/base-db/src/lib.rs
+++ b/crates/base-db/src/lib.rs
@@ -14,9 +14,9 @@ use triomphe::Arc;
 pub use crate::{
     change::FileChange,
     input::{
-        CrateData, CrateDisplayName, CrateGraph, CrateId, CrateName, CrateOrigin, Dependency,
-        DependencyKind, Edition, Env, LangCrateOrigin, ProcMacroPaths, ReleaseChannel, SourceRoot,
-        SourceRootId, TargetLayoutLoadResult,
+        CrateData, CrateDisplayName, CrateGraph, CrateId, CrateName, CrateOrigin, Dependency, Env,
+        LangCrateOrigin, ProcMacroPaths, ReleaseChannel, SourceRoot, SourceRootId,
+        TargetLayoutLoadResult,
     },
 };
 pub use salsa::{self, Cancelled};
diff --git a/crates/hir-def/src/lib.rs b/crates/hir-def/src/lib.rs
index 828842de7e..46898ce542 100644
--- a/crates/hir-def/src/lib.rs
+++ b/crates/hir-def/src/lib.rs
@@ -73,7 +73,7 @@ use std::{
 use base_db::{
     impl_intern_key,
     salsa::{self, impl_intern_value_trivial},
-    CrateId, Edition,
+    CrateId,
 };
 use hir_expand::{
     builtin_attr_macro::BuiltinAttrExpander,
@@ -90,7 +90,7 @@ use hir_expand::{
 use item_tree::ExternBlock;
 use la_arena::Idx;
 use nameres::DefMap;
-use span::{AstIdNode, FileAstId, FileId, SyntaxContextId};
+use span::{AstIdNode, Edition, FileAstId, FileId, SyntaxContextId};
 use stdx::impl_from;
 use syntax::{ast, AstNode};
 
diff --git a/crates/hir-def/src/nameres.rs b/crates/hir-def/src/nameres.rs
index b56dee3efb..2d1e92c1af 100644
--- a/crates/hir-def/src/nameres.rs
+++ b/crates/hir-def/src/nameres.rs
@@ -59,14 +59,14 @@ mod tests;
 
 use std::ops::Deref;
 
-use base_db::{CrateId, Edition, FileId};
+use base_db::{CrateId, FileId};
 use hir_expand::{
     name::Name, proc_macro::ProcMacroKind, ErasedAstId, HirFileId, InFile, MacroCallId, MacroDefId,
 };
 use itertools::Itertools;
 use la_arena::Arena;
 use rustc_hash::{FxHashMap, FxHashSet};
-use span::{FileAstId, ROOT_ERASED_FILE_AST_ID};
+use span::{Edition, FileAstId, ROOT_ERASED_FILE_AST_ID};
 use stdx::format_to;
 use syntax::{ast, SmolStr};
 use triomphe::Arc;
diff --git a/crates/hir-def/src/nameres/collector.rs b/crates/hir-def/src/nameres/collector.rs
index 3d026447fb..312938e2c1 100644
--- a/crates/hir-def/src/nameres/collector.rs
+++ b/crates/hir-def/src/nameres/collector.rs
@@ -5,7 +5,7 @@
 
 use std::{cmp::Ordering, iter, mem, ops::Not};
 
-use base_db::{CrateId, Dependency, Edition, FileId};
+use base_db::{CrateId, Dependency, FileId};
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
 use hir_expand::{
@@ -22,7 +22,7 @@ use itertools::{izip, Itertools};
 use la_arena::Idx;
 use limit::Limit;
 use rustc_hash::{FxHashMap, FxHashSet};
-use span::{ErasedFileAstId, FileAstId, Span, SyntaxContextId};
+use span::{Edition, ErasedFileAstId, FileAstId, Span, SyntaxContextId};
 use stdx::always;
 use syntax::{ast, SmolStr};
 use triomphe::Arc;
diff --git a/crates/hir-def/src/nameres/path_resolution.rs b/crates/hir-def/src/nameres/path_resolution.rs
index 9e53b03728..ee29b89f3d 100644
--- a/crates/hir-def/src/nameres/path_resolution.rs
+++ b/crates/hir-def/src/nameres/path_resolution.rs
@@ -10,8 +10,8 @@
 //!
 //! `ReachedFixedPoint` signals about this.
 
-use base_db::Edition;
 use hir_expand::{name::Name, Lookup};
+use span::Edition;
 use triomphe::Arc;
 
 use crate::{
diff --git a/crates/hir-expand/src/builtin_fn_macro.rs b/crates/hir-expand/src/builtin_fn_macro.rs
index 9fb6a0b234..fd3e4e7a4d 100644
--- a/crates/hir-expand/src/builtin_fn_macro.rs
+++ b/crates/hir-expand/src/builtin_fn_macro.rs
@@ -1,11 +1,11 @@
 //! Builtin macro
 
-use base_db::{AnchoredPath, Edition, FileId};
+use base_db::{AnchoredPath, FileId};
 use cfg::CfgExpr;
 use either::Either;
 use itertools::Itertools;
 use mbe::{parse_exprs_with_sep, parse_to_token_tree};
-use span::{Span, SpanAnchor, SyntaxContextId, ROOT_ERASED_FILE_AST_ID};
+use span::{Edition, Span, SpanAnchor, SyntaxContextId, ROOT_ERASED_FILE_AST_ID};
 use syntax::ast::{self, AstToken};
 
 use crate::{
diff --git a/crates/hir-expand/src/declarative.rs b/crates/hir-expand/src/declarative.rs
index 33643c0272..9a0b218e6d 100644
--- a/crates/hir-expand/src/declarative.rs
+++ b/crates/hir-expand/src/declarative.rs
@@ -1,8 +1,8 @@
 //! Compiled declarative macro expanders (`macro_rules!`` and `macro`)
 use std::sync::OnceLock;
 
-use base_db::{CrateId, Edition, VersionReq};
-use span::{MacroCallId, Span};
+use base_db::{CrateId, VersionReq};
+use span::{MacroCallId, Span, SyntaxContextId};
 use syntax::{ast, AstNode};
 use triomphe::Arc;
 
@@ -10,13 +10,13 @@ use crate::{
     attrs::RawAttrs,
     db::ExpandDatabase,
     hygiene::{apply_mark, Transparency},
-    tt, AstId, ExpandError, ExpandResult,
+    tt, AstId, ExpandError, ExpandResult, Lookup,
 };
 
 /// Old-style `macro_rules` or the new macros 2.0
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct DeclarativeMacroExpander {
-    pub mac: mbe::DeclarativeMacro<span::Span>,
+    pub mac: mbe::DeclarativeMacro,
     pub transparency: Transparency,
 }
 
@@ -94,8 +94,6 @@ impl DeclarativeMacroExpander {
         def_crate: CrateId,
         id: AstId<ast::Macro>,
     ) -> Arc<DeclarativeMacroExpander> {
-        let crate_data = &db.crate_graph()[def_crate];
-        let is_2021 = crate_data.edition >= Edition::Edition2021;
         let (root, map) = crate::db::parse_with_map(db, id.file_id);
         let root = root.syntax_node();
 
@@ -133,6 +131,16 @@ impl DeclarativeMacroExpander {
             )
         });
 
+        let edition = |ctx: SyntaxContextId| {
+            let crate_graph = db.crate_graph();
+            if ctx.is_root() {
+                crate_graph[def_crate].edition
+            } else {
+                let data = db.lookup_intern_syntax_context(ctx);
+                // UNWRAP-SAFETY: Only the root context has no outer expansion
+                crate_graph[data.outer_expn.unwrap().lookup(db).def.krate].edition
+            }
+        };
         let (mac, transparency) = match id.to_ptr(db).to_node(&root) {
             ast::Macro::MacroRules(macro_rules) => (
                 match macro_rules.token_tree() {
@@ -145,12 +153,11 @@ impl DeclarativeMacroExpander {
                             ),
                         );
 
-                        mbe::DeclarativeMacro::parse_macro_rules(&tt, is_2021, new_meta_vars)
+                        mbe::DeclarativeMacro::parse_macro_rules(&tt, edition, new_meta_vars)
                     }
-                    None => mbe::DeclarativeMacro::from_err(
-                        mbe::ParseError::Expected("expected a token tree".into()),
-                        is_2021,
-                    ),
+                    None => mbe::DeclarativeMacro::from_err(mbe::ParseError::Expected(
+                        "expected a token tree".into(),
+                    )),
                 },
                 transparency(&macro_rules).unwrap_or(Transparency::SemiTransparent),
             ),
@@ -163,12 +170,11 @@ impl DeclarativeMacroExpander {
                             map.span_for_range(macro_def.macro_token().unwrap().text_range()),
                         );
 
-                        mbe::DeclarativeMacro::parse_macro2(&tt, is_2021, new_meta_vars)
+                        mbe::DeclarativeMacro::parse_macro2(&tt, edition, new_meta_vars)
                     }
-                    None => mbe::DeclarativeMacro::from_err(
-                        mbe::ParseError::Expected("expected a token tree".into()),
-                        is_2021,
-                    ),
+                    None => mbe::DeclarativeMacro::from_err(mbe::ParseError::Expected(
+                        "expected a token tree".into(),
+                    )),
                 },
                 transparency(&macro_def).unwrap_or(Transparency::Opaque),
             ),
diff --git a/crates/hir-expand/src/lib.rs b/crates/hir-expand/src/lib.rs
index 5d4f7dc146..2233ae51fa 100644
--- a/crates/hir-expand/src/lib.rs
+++ b/crates/hir-expand/src/lib.rs
@@ -30,10 +30,11 @@ use triomphe::Arc;
 
 use std::{fmt, hash::Hash};
 
-use base_db::{salsa::impl_intern_value_trivial, CrateId, Edition, FileId};
+use base_db::{salsa::impl_intern_value_trivial, CrateId, FileId};
 use either::Either;
 use span::{
-    ErasedFileAstId, FileRange, HirFileIdRepr, Span, SpanAnchor, SyntaxContextData, SyntaxContextId,
+    Edition, ErasedFileAstId, FileRange, HirFileIdRepr, Span, SpanAnchor, SyntaxContextData,
+    SyntaxContextId,
 };
 use syntax::{
     ast::{self, AstNode},
@@ -53,11 +54,9 @@ use crate::{
 
 pub use crate::files::{AstId, ErasedAstId, InFile, InMacroFile, InRealFile};
 
-pub use mbe::ValueResult;
+pub use mbe::{DeclarativeMacro, ValueResult};
 pub use span::{HirFileId, MacroCallId, MacroFileId};
 
-pub type DeclarativeMacro = ::mbe::DeclarativeMacro<tt::Span>;
-
 pub mod tt {
     pub use span::Span;
     pub use tt::{DelimiterKind, Spacing};
diff --git a/crates/hir-ty/Cargo.toml b/crates/hir-ty/Cargo.toml
index a2711f8cbe..bf47374016 100644
--- a/crates/hir-ty/Cargo.toml
+++ b/crates/hir-ty/Cargo.toml
@@ -47,6 +47,7 @@ hir-expand.workspace = true
 base-db.workspace = true
 syntax.workspace = true
 limit.workspace = true
+span.workspace = true
 
 [dev-dependencies]
 expect-test = "1.4.0"
diff --git a/crates/hir-ty/src/method_resolution.rs b/crates/hir-ty/src/method_resolution.rs
index 0885d92ae8..064d317835 100644
--- a/crates/hir-ty/src/method_resolution.rs
+++ b/crates/hir-ty/src/method_resolution.rs
@@ -4,7 +4,7 @@
 //! and the corresponding code mostly in rustc_hir_analysis/check/method/probe.rs.
 use std::ops::ControlFlow;
 
-use base_db::{CrateId, Edition};
+use base_db::CrateId;
 use chalk_ir::{cast::Cast, Mutability, TyKind, UniverseIndex, WhereClause};
 use hir_def::{
     data::{adt::StructFlags, ImplData},
@@ -15,6 +15,7 @@ use hir_def::{
 use hir_expand::name::Name;
 use rustc_hash::{FxHashMap, FxHashSet};
 use smallvec::{smallvec, SmallVec};
+use span::Edition;
 use stdx::never;
 use triomphe::Arc;
 
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 9d7be9a421..15a0967b3d 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -38,7 +38,7 @@ mod display;
 use std::{iter, mem::discriminant, ops::ControlFlow};
 
 use arrayvec::ArrayVec;
-use base_db::{CrateDisplayName, CrateId, CrateOrigin, Edition, FileId};
+use base_db::{CrateDisplayName, CrateId, CrateOrigin, FileId};
 use either::Either;
 use hir_def::{
     body::{BodyDiagnostic, SyntheticSyntax},
@@ -79,6 +79,7 @@ use hir_ty::{
 use itertools::Itertools;
 use nameres::diagnostics::DefDiagnosticKind;
 use rustc_hash::FxHashSet;
+use span::Edition;
 use stdx::{impl_from, never};
 use syntax::{
     ast::{self, HasAttrs as _, HasName},
diff --git a/crates/ide/Cargo.toml b/crates/ide/Cargo.toml
index aca7d613e1..a535015a27 100644
--- a/crates/ide/Cargo.toml
+++ b/crates/ide/Cargo.toml
@@ -36,6 +36,7 @@ ide-ssr.workspace = true
 profile.workspace = true
 stdx.workspace = true
 syntax.workspace = true
+span.workspace = true
 text-edit.workspace = true
 # ide should depend only on the top-level `hir` package. if you need
 # something from some `hir-xxx` subpackage, reexport the API via `hir`.
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 11eaa88c5c..7a6c6ec41d 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -119,8 +119,8 @@ pub use ide_completion::{
 };
 pub use ide_db::{
     base_db::{
-        Cancelled, CrateGraph, CrateId, Edition, FileChange, FileId, FilePosition, FileRange,
-        SourceRoot, SourceRootId,
+        Cancelled, CrateGraph, CrateId, FileChange, FileId, FilePosition, FileRange, SourceRoot,
+        SourceRootId,
     },
     documentation::Documentation,
     label::Label,
@@ -135,6 +135,7 @@ pub use ide_diagnostics::{
     Diagnostic, DiagnosticCode, DiagnosticsConfig, ExprFillDefaultMode, Severity,
 };
 pub use ide_ssr::SsrError;
+pub use span::Edition;
 pub use syntax::{TextRange, TextSize};
 pub use text_edit::{Indel, TextEdit};
 
diff --git a/crates/mbe/src/benchmark.rs b/crates/mbe/src/benchmark.rs
index ac7f071178..4d5531ae30 100644
--- a/crates/mbe/src/benchmark.rs
+++ b/crates/mbe/src/benchmark.rs
@@ -23,7 +23,11 @@ fn benchmark_parse_macro_rules() {
         let _pt = bench("mbe parse macro rules");
         rules
             .values()
-            .map(|it| DeclarativeMacro::parse_macro_rules(it, true, true).rules.len())
+            .map(|it| {
+                DeclarativeMacro::parse_macro_rules(it, |_| span::Edition::CURRENT, true)
+                    .rules
+                    .len()
+            })
             .sum()
     };
     assert_eq!(hash, 1144);
@@ -51,10 +55,12 @@ fn benchmark_expand_macro_rules() {
     assert_eq!(hash, 69413);
 }
 
-fn macro_rules_fixtures() -> FxHashMap<String, DeclarativeMacro<Span>> {
+fn macro_rules_fixtures() -> FxHashMap<String, DeclarativeMacro> {
     macro_rules_fixtures_tt()
         .into_iter()
-        .map(|(id, tt)| (id, DeclarativeMacro::parse_macro_rules(&tt, true, true)))
+        .map(|(id, tt)| {
+            (id, DeclarativeMacro::parse_macro_rules(&tt, |_| span::Edition::CURRENT, true))
+        })
         .collect()
 }
 
@@ -80,7 +86,7 @@ fn macro_rules_fixtures_tt() -> FxHashMap<String, tt::Subtree<Span>> {
 
 /// Generate random invocation fixtures from rules
 fn invocation_fixtures(
-    rules: &FxHashMap<String, DeclarativeMacro<Span>>,
+    rules: &FxHashMap<String, DeclarativeMacro>,
 ) -> Vec<(String, tt::Subtree<Span>)> {
     let mut seed = 123456789;
     let mut res = Vec::new();
@@ -128,11 +134,7 @@ fn invocation_fixtures(
     }
     return res;
 
-    fn collect_from_op(
-        op: &Op<Span>,
-        token_trees: &mut Vec<tt::TokenTree<Span>>,
-        seed: &mut usize,
-    ) {
+    fn collect_from_op(op: &Op, token_trees: &mut Vec<tt::TokenTree<Span>>, seed: &mut usize) {
         return match op {
             Op::Var { kind, .. } => match kind.as_ref() {
                 Some(MetaVarKind::Ident) => token_trees.push(make_ident("foo")),
diff --git a/crates/mbe/src/expander.rs b/crates/mbe/src/expander.rs
index 9366048fd9..2f2c0aa6ff 100644
--- a/crates/mbe/src/expander.rs
+++ b/crates/mbe/src/expander.rs
@@ -6,22 +6,21 @@ mod matcher;
 mod transcriber;
 
 use rustc_hash::FxHashMap;
+use span::Span;
 use syntax::SmolStr;
-use tt::Span;
 
 use crate::{parser::MetaVarKind, ExpandError, ExpandResult};
 
-pub(crate) fn expand_rules<S: Span>(
-    rules: &[crate::Rule<S>],
-    input: &tt::Subtree<S>,
-    marker: impl Fn(&mut S) + Copy,
-    is_2021: bool,
+pub(crate) fn expand_rules(
+    rules: &[crate::Rule],
+    input: &tt::Subtree<Span>,
+    marker: impl Fn(&mut Span) + Copy,
     new_meta_vars: bool,
-    call_site: S,
-) -> ExpandResult<tt::Subtree<S>> {
-    let mut match_: Option<(matcher::Match<S>, &crate::Rule<S>)> = None;
+    call_site: Span,
+) -> ExpandResult<tt::Subtree<Span>> {
+    let mut match_: Option<(matcher::Match, &crate::Rule)> = None;
     for rule in rules {
-        let new_match = matcher::match_(&rule.lhs, input, is_2021);
+        let new_match = matcher::match_(&rule.lhs, input);
 
         if new_match.err.is_none() {
             // If we find a rule that applies without errors, we're done.
@@ -110,30 +109,24 @@ pub(crate) fn expand_rules<S: Span>(
 /// In other words, `Bindings` is a *multi* mapping from `SmolStr` to
 /// `tt::TokenTree`, where the index to select a particular `TokenTree` among
 /// many is not a plain `usize`, but a `&[usize]`.
-#[derive(Debug, Clone, PartialEq, Eq)]
-struct Bindings<S> {
-    inner: FxHashMap<SmolStr, Binding<S>>,
-}
-
-impl<S> Default for Bindings<S> {
-    fn default() -> Self {
-        Self { inner: Default::default() }
-    }
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+struct Bindings {
+    inner: FxHashMap<SmolStr, Binding>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
-enum Binding<S> {
-    Fragment(Fragment<S>),
-    Nested(Vec<Binding<S>>),
+enum Binding {
+    Fragment(Fragment),
+    Nested(Vec<Binding>),
     Empty,
     Missing(MetaVarKind),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
-enum Fragment<S> {
+enum Fragment {
     Empty,
     /// token fragments are just copy-pasted into the output
-    Tokens(tt::TokenTree<S>),
+    Tokens(tt::TokenTree<Span>),
     /// Expr ast fragments are surrounded with `()` on insertion to preserve
     /// precedence. Note that this impl is different from the one currently in
     /// `rustc` -- `rustc` doesn't translate fragments into token trees at all.
@@ -141,7 +134,7 @@ enum Fragment<S> {
     /// At one point in time, we tried to use "fake" delimiters here à la
     /// proc-macro delimiter=none. As we later discovered, "none" delimiters are
     /// tricky to handle in the parser, and rustc doesn't handle those either.
-    Expr(tt::Subtree<S>),
+    Expr(tt::Subtree<Span>),
     /// There are roughly two types of paths: paths in expression context, where a
     /// separator `::` between an identifier and its following generic argument list
     /// is mandatory, and paths in type context, where `::` can be omitted.
@@ -151,5 +144,5 @@ enum Fragment<S> {
     /// and is trasncribed as an expression-context path, verbatim transcription
     /// would cause a syntax error. We need to fix it up just before transcribing;
     /// see `transcriber::fix_up_and_push_path_tt()`.
-    Path(tt::Subtree<S>),
+    Path(tt::Subtree<Span>),
 }
diff --git a/crates/mbe/src/expander/matcher.rs b/crates/mbe/src/expander/matcher.rs
index eea92cfba4..3170834d54 100644
--- a/crates/mbe/src/expander/matcher.rs
+++ b/crates/mbe/src/expander/matcher.rs
@@ -62,8 +62,9 @@
 use std::rc::Rc;
 
 use smallvec::{smallvec, SmallVec};
+use span::Span;
 use syntax::SmolStr;
-use tt::{DelimSpan, Span};
+use tt::DelimSpan;
 
 use crate::{
     expander::{Binding, Bindings, ExpandResult, Fragment},
@@ -72,7 +73,7 @@ use crate::{
     ExpandError, MetaTemplate, ValueResult,
 };
 
-impl<S: Span> Bindings<S> {
+impl Bindings {
     fn push_optional(&mut self, name: &SmolStr) {
         self.inner.insert(name.clone(), Binding::Fragment(Fragment::Empty));
     }
@@ -81,14 +82,14 @@ impl<S: Span> Bindings<S> {
         self.inner.insert(name.clone(), Binding::Empty);
     }
 
-    fn bindings(&self) -> impl Iterator<Item = &Binding<S>> {
+    fn bindings(&self) -> impl Iterator<Item = &Binding> {
         self.inner.values()
     }
 }
 
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub(super) struct Match<S> {
-    pub(super) bindings: Bindings<S>,
+#[derive(Clone, Default, Debug, PartialEq, Eq)]
+pub(super) struct Match {
+    pub(super) bindings: Bindings,
     /// We currently just keep the first error and count the rest to compare matches.
     pub(super) err: Option<ExpandError>,
     pub(super) err_count: usize,
@@ -98,19 +99,7 @@ pub(super) struct Match<S> {
     pub(super) bound_count: usize,
 }
 
-impl<S> Default for Match<S> {
-    fn default() -> Self {
-        Self {
-            bindings: Default::default(),
-            err: Default::default(),
-            err_count: Default::default(),
-            unmatched_tts: Default::default(),
-            bound_count: Default::default(),
-        }
-    }
-}
-
-impl<S> Match<S> {
+impl Match {
     fn add_err(&mut self, err: ExpandError) {
         let prev_err = self.err.take();
         self.err = prev_err.or(Some(err));
@@ -119,16 +108,12 @@ impl<S> Match<S> {
 }
 
 /// Matching errors are added to the `Match`.
-pub(super) fn match_<S: Span>(
-    pattern: &MetaTemplate<S>,
-    input: &tt::Subtree<S>,
-    is_2021: bool,
-) -> Match<S> {
-    let mut res = match_loop(pattern, input, is_2021);
+pub(super) fn match_(pattern: &MetaTemplate, input: &tt::Subtree<Span>) -> Match {
+    let mut res = match_loop(pattern, input);
     res.bound_count = count(res.bindings.bindings());
     return res;
 
-    fn count<'a, S: 'a>(bindings: impl Iterator<Item = &'a Binding<S>>) -> usize {
+    fn count<'a>(bindings: impl Iterator<Item = &'a Binding>) -> usize {
         bindings
             .map(|it| match it {
                 Binding::Fragment(_) => 1,
@@ -141,10 +126,10 @@ pub(super) fn match_<S: Span>(
 }
 
 #[derive(Debug, Clone)]
-enum BindingKind<S> {
+enum BindingKind {
     Empty(SmolStr),
     Optional(SmolStr),
-    Fragment(SmolStr, Fragment<S>),
+    Fragment(SmolStr, Fragment),
     Missing(SmolStr, MetaVarKind),
     Nested(usize, usize),
 }
@@ -158,18 +143,13 @@ enum LinkNode<T> {
     Parent { idx: usize, len: usize },
 }
 
-struct BindingsBuilder<S> {
-    nodes: Vec<Vec<LinkNode<Rc<BindingKind<S>>>>>,
+#[derive(Default)]
+struct BindingsBuilder {
+    nodes: Vec<Vec<LinkNode<Rc<BindingKind>>>>,
     nested: Vec<Vec<LinkNode<usize>>>,
 }
 
-impl<S> Default for BindingsBuilder<S> {
-    fn default() -> Self {
-        Self { nodes: Default::default(), nested: Default::default() }
-    }
-}
-
-impl<S: Span> BindingsBuilder<S> {
+impl BindingsBuilder {
     fn alloc(&mut self) -> BindingsIdx {
         let idx = self.nodes.len();
         self.nodes.push(Vec::new());
@@ -206,7 +186,7 @@ impl<S: Span> BindingsBuilder<S> {
         self.nodes[idx.0].push(LinkNode::Node(Rc::new(BindingKind::Optional(var.clone()))));
     }
 
-    fn push_fragment(&mut self, idx: &mut BindingsIdx, var: &SmolStr, fragment: Fragment<S>) {
+    fn push_fragment(&mut self, idx: &mut BindingsIdx, var: &SmolStr, fragment: Fragment) {
         self.nodes[idx.0]
             .push(LinkNode::Node(Rc::new(BindingKind::Fragment(var.clone(), fragment))));
     }
@@ -227,11 +207,11 @@ impl<S: Span> BindingsBuilder<S> {
         idx.0 = new_idx;
     }
 
-    fn build(self, idx: &BindingsIdx) -> Bindings<S> {
+    fn build(self, idx: &BindingsIdx) -> Bindings {
         self.build_inner(&self.nodes[idx.0])
     }
 
-    fn build_inner(&self, link_nodes: &[LinkNode<Rc<BindingKind<S>>>]) -> Bindings<S> {
+    fn build_inner(&self, link_nodes: &[LinkNode<Rc<BindingKind>>]) -> Bindings {
         let mut bindings = Bindings::default();
         let mut nodes = Vec::new();
         self.collect_nodes(link_nodes, &mut nodes);
@@ -281,7 +261,7 @@ impl<S: Span> BindingsBuilder<S> {
         &'a self,
         id: usize,
         len: usize,
-        nested_refs: &mut Vec<&'a [LinkNode<Rc<BindingKind<S>>>]>,
+        nested_refs: &mut Vec<&'a [LinkNode<Rc<BindingKind>>]>,
     ) {
         self.nested[id].iter().take(len).for_each(|it| match it {
             LinkNode::Node(id) => nested_refs.push(&self.nodes[*id]),
@@ -289,7 +269,7 @@ impl<S: Span> BindingsBuilder<S> {
         });
     }
 
-    fn collect_nested(&self, idx: usize, nested_idx: usize, nested: &mut Vec<Bindings<S>>) {
+    fn collect_nested(&self, idx: usize, nested_idx: usize, nested: &mut Vec<Bindings>) {
         let last = &self.nodes[idx];
         let mut nested_refs: Vec<&[_]> = Vec::new();
         self.nested[nested_idx].iter().for_each(|it| match *it {
@@ -300,7 +280,7 @@ impl<S: Span> BindingsBuilder<S> {
         nested.extend(nested_refs.into_iter().map(|iter| self.build_inner(iter)));
     }
 
-    fn collect_nodes_ref<'a>(&'a self, id: usize, len: usize, nodes: &mut Vec<&'a BindingKind<S>>) {
+    fn collect_nodes_ref<'a>(&'a self, id: usize, len: usize, nodes: &mut Vec<&'a BindingKind>) {
         self.nodes[id].iter().take(len).for_each(|it| match it {
             LinkNode::Node(it) => nodes.push(it),
             LinkNode::Parent { idx, len } => self.collect_nodes_ref(*idx, *len, nodes),
@@ -309,8 +289,8 @@ impl<S: Span> BindingsBuilder<S> {
 
     fn collect_nodes<'a>(
         &'a self,
-        link_nodes: &'a [LinkNode<Rc<BindingKind<S>>>],
-        nodes: &mut Vec<&'a BindingKind<S>>,
+        link_nodes: &'a [LinkNode<Rc<BindingKind>>],
+        nodes: &mut Vec<&'a BindingKind>,
     ) {
         link_nodes.iter().for_each(|it| match it {
             LinkNode::Node(it) => nodes.push(it),
@@ -320,22 +300,22 @@ impl<S: Span> BindingsBuilder<S> {
 }
 
 #[derive(Debug, Clone)]
-struct MatchState<'t, S> {
+struct MatchState<'t> {
     /// The position of the "dot" in this matcher
-    dot: OpDelimitedIter<'t, S>,
+    dot: OpDelimitedIter<'t>,
 
     /// Token subtree stack
     /// When matching against matchers with nested delimited submatchers (e.g., `pat ( pat ( .. )
     /// pat ) pat`), we need to keep track of the matchers we are descending into. This stack does
     /// that where the bottom of the stack is the outermost matcher.
-    stack: SmallVec<[OpDelimitedIter<'t, S>; 4]>,
+    stack: SmallVec<[OpDelimitedIter<'t>; 4]>,
 
     /// The "parent" matcher position if we are in a repetition. That is, the matcher position just
     /// before we enter the repetition.
-    up: Option<Box<MatchState<'t, S>>>,
+    up: Option<Box<MatchState<'t>>>,
 
     /// The separator if we are in a repetition.
-    sep: Option<Separator<S>>,
+    sep: Option<Separator>,
 
     /// The KleeneOp of this sequence if we are in a repetition.
     sep_kind: Option<RepeatKind>,
@@ -347,7 +327,7 @@ struct MatchState<'t, S> {
     bindings: BindingsIdx,
 
     /// Cached result of meta variable parsing
-    meta_result: Option<(TtIter<'t, S>, ExpandResult<Option<Fragment<S>>>)>,
+    meta_result: Option<(TtIter<'t, Span>, ExpandResult<Option<Fragment>>)>,
 
     /// Is error occurred in this state, will `poised` to "parent"
     is_error: bool,
@@ -372,18 +352,17 @@ struct MatchState<'t, S> {
 /// - `bb_items`: the set of items that are waiting for the black-box parser.
 /// - `error_items`: the set of items in errors, used for error-resilient parsing
 #[inline]
-fn match_loop_inner<'t, S: Span>(
-    src: TtIter<'t, S>,
-    stack: &[TtIter<'t, S>],
-    res: &mut Match<S>,
-    bindings_builder: &mut BindingsBuilder<S>,
-    cur_items: &mut SmallVec<[MatchState<'t, S>; 1]>,
-    bb_items: &mut SmallVec<[MatchState<'t, S>; 1]>,
-    next_items: &mut Vec<MatchState<'t, S>>,
-    eof_items: &mut SmallVec<[MatchState<'t, S>; 1]>,
-    error_items: &mut SmallVec<[MatchState<'t, S>; 1]>,
-    is_2021: bool,
-    delim_span: tt::DelimSpan<S>,
+fn match_loop_inner<'t>(
+    src: TtIter<'t, Span>,
+    stack: &[TtIter<'t, Span>],
+    res: &mut Match,
+    bindings_builder: &mut BindingsBuilder,
+    cur_items: &mut SmallVec<[MatchState<'t>; 1]>,
+    bb_items: &mut SmallVec<[MatchState<'t>; 1]>,
+    next_items: &mut Vec<MatchState<'t>>,
+    eof_items: &mut SmallVec<[MatchState<'t>; 1]>,
+    error_items: &mut SmallVec<[MatchState<'t>; 1]>,
+    delim_span: tt::DelimSpan<Span>,
 ) {
     macro_rules! try_push {
         ($items: expr, $it:expr) => {
@@ -494,7 +473,7 @@ fn match_loop_inner<'t, S: Span>(
             OpDelimited::Op(Op::Var { kind, name, .. }) => {
                 if let &Some(kind) = kind {
                     let mut fork = src.clone();
-                    let match_res = match_meta_var(kind, &mut fork, is_2021, delim_span);
+                    let match_res = match_meta_var(kind, &mut fork, delim_span);
                     match match_res.err {
                         None => {
                             // Some meta variables are optional (e.g. vis)
@@ -607,10 +586,10 @@ fn match_loop_inner<'t, S: Span>(
     }
 }
 
-fn match_loop<S: Span>(pattern: &MetaTemplate<S>, src: &tt::Subtree<S>, is_2021: bool) -> Match<S> {
+fn match_loop(pattern: &MetaTemplate, src: &tt::Subtree<Span>) -> Match {
     let span = src.delimiter.delim_span();
     let mut src = TtIter::new(src);
-    let mut stack: SmallVec<[TtIter<'_, S>; 1]> = SmallVec::new();
+    let mut stack: SmallVec<[TtIter<'_, Span>; 1]> = SmallVec::new();
     let mut res = Match::default();
     let mut error_recover_item = None;
 
@@ -647,7 +626,6 @@ fn match_loop<S: Span>(pattern: &MetaTemplate<S>, src: &tt::Subtree<S>, is_2021:
             &mut next_items,
             &mut eof_items,
             &mut error_items,
-            is_2021,
             span,
         );
         stdx::always!(cur_items.is_empty());
@@ -758,12 +736,11 @@ fn match_loop<S: Span>(pattern: &MetaTemplate<S>, src: &tt::Subtree<S>, is_2021:
     }
 }
 
-fn match_meta_var<S: Span>(
+fn match_meta_var(
     kind: MetaVarKind,
-    input: &mut TtIter<'_, S>,
-    is_2021: bool,
-    delim_span: DelimSpan<S>,
-) -> ExpandResult<Option<Fragment<S>>> {
+    input: &mut TtIter<'_, Span>,
+    delim_span: DelimSpan<Span>,
+) -> ExpandResult<Option<Fragment>> {
     let fragment = match kind {
         MetaVarKind::Path => {
             return input.expect_fragment(parser::PrefixEntryPoint::Path).map(|it| {
@@ -771,8 +748,7 @@ fn match_meta_var<S: Span>(
             });
         }
         MetaVarKind::Ty => parser::PrefixEntryPoint::Ty,
-        MetaVarKind::Pat if is_2021 => parser::PrefixEntryPoint::PatTop,
-        MetaVarKind::Pat => parser::PrefixEntryPoint::Pat,
+        MetaVarKind::Pat => parser::PrefixEntryPoint::PatTop,
         MetaVarKind::PatParam => parser::PrefixEntryPoint::Pat,
         MetaVarKind::Stmt => parser::PrefixEntryPoint::Stmt,
         MetaVarKind::Block => parser::PrefixEntryPoint::Block,
@@ -846,7 +822,7 @@ fn match_meta_var<S: Span>(
     input.expect_fragment(fragment).map(|it| it.map(Fragment::Tokens))
 }
 
-fn collect_vars<S: Span>(collector_fun: &mut impl FnMut(SmolStr), pattern: &MetaTemplate<S>) {
+fn collect_vars(collector_fun: &mut impl FnMut(SmolStr), pattern: &MetaTemplate) {
     for op in pattern.iter() {
         match op {
             Op::Var { name, .. } => collector_fun(name.clone()),
@@ -859,11 +835,11 @@ fn collect_vars<S: Span>(collector_fun: &mut impl FnMut(SmolStr), pattern: &Meta
         }
     }
 }
-impl<S: Span> MetaTemplate<S> {
-    fn iter_delimited_with(&self, delimiter: tt::Delimiter<S>) -> OpDelimitedIter<'_, S> {
+impl MetaTemplate {
+    fn iter_delimited_with(&self, delimiter: tt::Delimiter<Span>) -> OpDelimitedIter<'_> {
         OpDelimitedIter { inner: &self.0, idx: 0, delimited: delimiter }
     }
-    fn iter_delimited(&self, span: tt::DelimSpan<S>) -> OpDelimitedIter<'_, S> {
+    fn iter_delimited(&self, span: tt::DelimSpan<Span>) -> OpDelimitedIter<'_> {
         OpDelimitedIter {
             inner: &self.0,
             idx: 0,
@@ -873,27 +849,27 @@ impl<S: Span> MetaTemplate<S> {
 }
 
 #[derive(Debug, Clone, Copy)]
-enum OpDelimited<'a, S> {
-    Op(&'a Op<S>),
+enum OpDelimited<'a> {
+    Op(&'a Op),
     Open,
     Close,
 }
 
 #[derive(Debug, Clone, Copy)]
-struct OpDelimitedIter<'a, S> {
-    inner: &'a [Op<S>],
-    delimited: tt::Delimiter<S>,
+struct OpDelimitedIter<'a> {
+    inner: &'a [Op],
+    delimited: tt::Delimiter<Span>,
     idx: usize,
 }
 
-impl<'a, S: Span> OpDelimitedIter<'a, S> {
+impl<'a> OpDelimitedIter<'a> {
     fn is_eof(&self) -> bool {
         let len = self.inner.len()
             + if self.delimited.kind != tt::DelimiterKind::Invisible { 2 } else { 0 };
         self.idx >= len
     }
 
-    fn peek(&self) -> Option<OpDelimited<'a, S>> {
+    fn peek(&self) -> Option<OpDelimited<'a>> {
         match self.delimited.kind {
             tt::DelimiterKind::Invisible => self.inner.get(self.idx).map(OpDelimited::Op),
             _ => match self.idx {
@@ -909,8 +885,8 @@ impl<'a, S: Span> OpDelimitedIter<'a, S> {
     }
 }
 
-impl<'a, S: Span> Iterator for OpDelimitedIter<'a, S> {
-    type Item = OpDelimited<'a, S>;
+impl<'a> Iterator for OpDelimitedIter<'a> {
+    type Item = OpDelimited<'a>;
 
     fn next(&mut self) -> Option<Self::Item> {
         let res = self.peek();
@@ -926,8 +902,8 @@ impl<'a, S: Span> Iterator for OpDelimitedIter<'a, S> {
     }
 }
 
-impl<S: Span> TtIter<'_, S> {
-    fn expect_separator(&mut self, separator: &Separator<S>) -> bool {
+impl TtIter<'_, Span> {
+    fn expect_separator(&mut self, separator: &Separator) -> bool {
         let mut fork = self.clone();
         let ok = match separator {
             Separator::Ident(lhs) => match fork.expect_ident_or_underscore() {
@@ -957,7 +933,7 @@ impl<S: Span> TtIter<'_, S> {
         ok
     }
 
-    fn expect_tt(&mut self) -> Result<tt::TokenTree<S>, ()> {
+    fn expect_tt(&mut self) -> Result<tt::TokenTree<Span>, ()> {
         if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) = self.peek_n(0) {
             if punct.char == '\'' {
                 self.expect_lifetime()
@@ -976,7 +952,7 @@ impl<S: Span> TtIter<'_, S> {
         }
     }
 
-    fn expect_lifetime(&mut self) -> Result<tt::TokenTree<S>, ()> {
+    fn expect_lifetime(&mut self) -> Result<tt::TokenTree<Span>, ()> {
         let punct = self.expect_single_punct()?;
         if punct.char != '\'' {
             return Err(());
@@ -997,7 +973,7 @@ impl<S: Span> TtIter<'_, S> {
         .into())
     }
 
-    fn eat_char(&mut self, c: char) -> Option<tt::TokenTree<S>> {
+    fn eat_char(&mut self, c: char) -> Option<tt::TokenTree<Span>> {
         let mut fork = self.clone();
         match fork.expect_char(c) {
             Ok(_) => {
diff --git a/crates/mbe/src/expander/transcriber.rs b/crates/mbe/src/expander/transcriber.rs
index 6d3055da28..5e6e45f152 100644
--- a/crates/mbe/src/expander/transcriber.rs
+++ b/crates/mbe/src/expander/transcriber.rs
@@ -1,8 +1,9 @@
 //! Transcriber takes a template, like `fn $ident() {}`, a set of bindings like
 //! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
 
+use span::Span;
 use syntax::SmolStr;
-use tt::{Delimiter, Span};
+use tt::Delimiter;
 
 use crate::{
     expander::{Binding, Bindings, Fragment},
@@ -10,8 +11,8 @@ use crate::{
     CountError, ExpandError, ExpandResult, MetaTemplate,
 };
 
-impl<S: Span> Bindings<S> {
-    fn get(&self, name: &str) -> Result<&Binding<S>, ExpandError> {
+impl Bindings {
+    fn get(&self, name: &str) -> Result<&Binding, ExpandError> {
         match self.inner.get(name) {
             Some(binding) => Ok(binding),
             None => Err(ExpandError::UnresolvedBinding(Box::new(Box::from(name)))),
@@ -21,10 +22,10 @@ impl<S: Span> Bindings<S> {
     fn get_fragment(
         &self,
         name: &str,
-        mut span: S,
+        mut span: Span,
         nesting: &mut [NestingState],
-        marker: impl Fn(&mut S),
-    ) -> Result<Fragment<S>, ExpandError> {
+        marker: impl Fn(&mut Span),
+    ) -> Result<Fragment, ExpandError> {
         macro_rules! binding_err {
             ($($arg:tt)*) => { ExpandError::binding_error(format!($($arg)*)) };
         }
@@ -134,15 +135,15 @@ impl<S: Span> Bindings<S> {
     }
 }
 
-pub(super) fn transcribe<S: Span>(
-    template: &MetaTemplate<S>,
-    bindings: &Bindings<S>,
-    marker: impl Fn(&mut S) + Copy,
+pub(super) fn transcribe(
+    template: &MetaTemplate,
+    bindings: &Bindings,
+    marker: impl Fn(&mut Span) + Copy,
     new_meta_vars: bool,
-    call_site: S,
-) -> ExpandResult<tt::Subtree<S>> {
+    call_site: Span,
+) -> ExpandResult<tt::Subtree<Span>> {
     let mut ctx = ExpandCtx { bindings, nesting: Vec::new(), new_meta_vars, call_site };
-    let mut arena: Vec<tt::TokenTree<S>> = Vec::new();
+    let mut arena: Vec<tt::TokenTree<Span>> = Vec::new();
     expand_subtree(&mut ctx, template, None, &mut arena, marker)
 }
 
@@ -158,20 +159,20 @@ struct NestingState {
 }
 
 #[derive(Debug)]
-struct ExpandCtx<'a, S> {
-    bindings: &'a Bindings<S>,
+struct ExpandCtx<'a> {
+    bindings: &'a Bindings,
     nesting: Vec<NestingState>,
     new_meta_vars: bool,
-    call_site: S,
+    call_site: Span,
 }
 
-fn expand_subtree<S: Span>(
-    ctx: &mut ExpandCtx<'_, S>,
-    template: &MetaTemplate<S>,
-    delimiter: Option<Delimiter<S>>,
-    arena: &mut Vec<tt::TokenTree<S>>,
-    marker: impl Fn(&mut S) + Copy,
-) -> ExpandResult<tt::Subtree<S>> {
+fn expand_subtree(
+    ctx: &mut ExpandCtx<'_>,
+    template: &MetaTemplate,
+    delimiter: Option<Delimiter<Span>>,
+    arena: &mut Vec<tt::TokenTree<Span>>,
+    marker: impl Fn(&mut Span) + Copy,
+) -> ExpandResult<tt::Subtree<Span>> {
     // remember how many elements are in the arena now - when returning, we want to drain exactly how many elements we added. This way, the recursive uses of the arena get their own "view" of the arena, but will reuse the allocation
     let start_elements = arena.len();
     let mut err = None;
@@ -332,12 +333,12 @@ fn expand_subtree<S: Span>(
     }
 }
 
-fn expand_var<S: Span>(
-    ctx: &mut ExpandCtx<'_, S>,
+fn expand_var(
+    ctx: &mut ExpandCtx<'_>,
     v: &SmolStr,
-    id: S,
-    marker: impl Fn(&mut S),
-) -> ExpandResult<Fragment<S>> {
+    id: Span,
+    marker: impl Fn(&mut Span),
+) -> ExpandResult<Fragment> {
     // We already handle $crate case in mbe parser
     debug_assert!(v != "crate");
 
@@ -378,15 +379,15 @@ fn expand_var<S: Span>(
     }
 }
 
-fn expand_repeat<S: Span>(
-    ctx: &mut ExpandCtx<'_, S>,
-    template: &MetaTemplate<S>,
+fn expand_repeat(
+    ctx: &mut ExpandCtx<'_>,
+    template: &MetaTemplate,
     kind: RepeatKind,
-    separator: &Option<Separator<S>>,
-    arena: &mut Vec<tt::TokenTree<S>>,
-    marker: impl Fn(&mut S) + Copy,
-) -> ExpandResult<Fragment<S>> {
-    let mut buf: Vec<tt::TokenTree<S>> = Vec::new();
+    separator: &Option<Separator>,
+    arena: &mut Vec<tt::TokenTree<Span>>,
+    marker: impl Fn(&mut Span) + Copy,
+) -> ExpandResult<Fragment> {
+    let mut buf: Vec<tt::TokenTree<Span>> = Vec::new();
     ctx.nesting.push(NestingState { idx: 0, at_end: false, hit: false });
     // Dirty hack to make macro-expansion terminate.
     // This should be replaced by a proper macro-by-example implementation
@@ -478,11 +479,7 @@ fn expand_repeat<S: Span>(
     ExpandResult { value: Fragment::Tokens(tt), err }
 }
 
-fn push_fragment<S: Span>(
-    ctx: &ExpandCtx<'_, S>,
-    buf: &mut Vec<tt::TokenTree<S>>,
-    fragment: Fragment<S>,
-) {
+fn push_fragment(ctx: &ExpandCtx<'_>, buf: &mut Vec<tt::TokenTree<Span>>, fragment: Fragment) {
     match fragment {
         Fragment::Tokens(tt::TokenTree::Subtree(tt)) => push_subtree(buf, tt),
         Fragment::Expr(sub) => {
@@ -494,7 +491,7 @@ fn push_fragment<S: Span>(
     }
 }
 
-fn push_subtree<S>(buf: &mut Vec<tt::TokenTree<S>>, tt: tt::Subtree<S>) {
+fn push_subtree(buf: &mut Vec<tt::TokenTree<Span>>, tt: tt::Subtree<Span>) {
     match tt.delimiter.kind {
         tt::DelimiterKind::Invisible => buf.extend(Vec::from(tt.token_trees)),
         _ => buf.push(tt.into()),
@@ -504,10 +501,10 @@ fn push_subtree<S>(buf: &mut Vec<tt::TokenTree<S>>, tt: tt::Subtree<S>) {
 /// Inserts the path separator `::` between an identifier and its following generic
 /// argument list, and then pushes into the buffer. See [`Fragment::Path`] for why
 /// we need this fixup.
-fn fix_up_and_push_path_tt<S: Span>(
-    ctx: &ExpandCtx<'_, S>,
-    buf: &mut Vec<tt::TokenTree<S>>,
-    subtree: tt::Subtree<S>,
+fn fix_up_and_push_path_tt(
+    ctx: &ExpandCtx<'_>,
+    buf: &mut Vec<tt::TokenTree<Span>>,
+    subtree: tt::Subtree<Span>,
 ) {
     stdx::always!(matches!(subtree.delimiter.kind, tt::DelimiterKind::Invisible));
     let mut prev_was_ident = false;
@@ -546,11 +543,7 @@ fn fix_up_and_push_path_tt<S: Span>(
 
 /// Handles `${count(t, depth)}`. `our_depth` is the recursion depth and `count_depth` is the depth
 /// defined by the metavar expression.
-fn count<S>(
-    binding: &Binding<S>,
-    depth_curr: usize,
-    depth_max: usize,
-) -> Result<usize, CountError> {
+fn count(binding: &Binding, depth_curr: usize, depth_max: usize) -> Result<usize, CountError> {
     match binding {
         Binding::Nested(bs) => {
             if depth_curr == depth_max {
@@ -564,8 +557,8 @@ fn count<S>(
     }
 }
 
-fn count_old<S>(
-    binding: &Binding<S>,
+fn count_old(
+    binding: &Binding,
     our_depth: usize,
     count_depth: Option<usize>,
 ) -> Result<usize, CountError> {
diff --git a/crates/mbe/src/lib.rs b/crates/mbe/src/lib.rs
index 62fdce3689..3a85351266 100644
--- a/crates/mbe/src/lib.rs
+++ b/crates/mbe/src/lib.rs
@@ -17,8 +17,8 @@ mod tt_iter;
 #[cfg(test)]
 mod benchmark;
 
+use span::{Edition, Span, SyntaxContextId};
 use stdx::impl_from;
-use tt::Span;
 
 use std::fmt;
 
@@ -127,32 +127,29 @@ impl fmt::Display for CountError {
 /// `tt::TokenTree`, but there's a crucial difference: in macro rules, `$ident`
 /// and `$()*` have special meaning (see `Var` and `Repeat` data structures)
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub struct DeclarativeMacro<S> {
-    rules: Box<[Rule<S>]>,
-    // This is used for correctly determining the behavior of the pat fragment
-    // FIXME: This should be tracked by hygiene of the fragment identifier!
-    is_2021: bool,
+pub struct DeclarativeMacro {
+    rules: Box<[Rule]>,
     err: Option<Box<ParseError>>,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-struct Rule<S> {
-    lhs: MetaTemplate<S>,
-    rhs: MetaTemplate<S>,
+struct Rule {
+    lhs: MetaTemplate,
+    rhs: MetaTemplate,
 }
 
-impl<S: Span> DeclarativeMacro<S> {
-    pub fn from_err(err: ParseError, is_2021: bool) -> DeclarativeMacro<S> {
-        DeclarativeMacro { rules: Box::default(), is_2021, err: Some(Box::new(err)) }
+impl DeclarativeMacro {
+    pub fn from_err(err: ParseError) -> DeclarativeMacro {
+        DeclarativeMacro { rules: Box::default(), err: Some(Box::new(err)) }
     }
 
     /// The old, `macro_rules! m {}` flavor.
     pub fn parse_macro_rules(
-        tt: &tt::Subtree<S>,
-        is_2021: bool,
+        tt: &tt::Subtree<Span>,
+        edition: impl Copy + Fn(SyntaxContextId) -> Edition,
         // FIXME: Remove this once we drop support for rust 1.76 (defaults to true then)
         new_meta_vars: bool,
-    ) -> DeclarativeMacro<S> {
+    ) -> DeclarativeMacro {
         // Note: this parsing can be implemented using mbe machinery itself, by
         // matching against `$($lhs:tt => $rhs:tt);*` pattern, but implementing
         // manually seems easier.
@@ -161,7 +158,7 @@ impl<S: Span> DeclarativeMacro<S> {
         let mut err = None;
 
         while src.len() > 0 {
-            let rule = match Rule::parse(&mut src, true, new_meta_vars) {
+            let rule = match Rule::parse(edition, &mut src, true, new_meta_vars) {
                 Ok(it) => it,
                 Err(e) => {
                     err = Some(Box::new(e));
@@ -184,16 +181,16 @@ impl<S: Span> DeclarativeMacro<S> {
             }
         }
 
-        DeclarativeMacro { rules: rules.into_boxed_slice(), is_2021, err }
+        DeclarativeMacro { rules: rules.into_boxed_slice(), err }
     }
 
     /// The new, unstable `macro m {}` flavor.
     pub fn parse_macro2(
-        tt: &tt::Subtree<S>,
-        is_2021: bool,
+        tt: &tt::Subtree<Span>,
+        edition: impl Copy + Fn(SyntaxContextId) -> Edition,
         // FIXME: Remove this once we drop support for rust 1.76 (defaults to true then)
         new_meta_vars: bool,
-    ) -> DeclarativeMacro<S> {
+    ) -> DeclarativeMacro {
         let mut src = TtIter::new(tt);
         let mut rules = Vec::new();
         let mut err = None;
@@ -201,7 +198,7 @@ impl<S: Span> DeclarativeMacro<S> {
         if tt::DelimiterKind::Brace == tt.delimiter.kind {
             cov_mark::hit!(parse_macro_def_rules);
             while src.len() > 0 {
-                let rule = match Rule::parse(&mut src, true, new_meta_vars) {
+                let rule = match Rule::parse(edition, &mut src, true, new_meta_vars) {
                     Ok(it) => it,
                     Err(e) => {
                         err = Some(Box::new(e));
@@ -220,7 +217,7 @@ impl<S: Span> DeclarativeMacro<S> {
             }
         } else {
             cov_mark::hit!(parse_macro_def_simple);
-            match Rule::parse(&mut src, false, new_meta_vars) {
+            match Rule::parse(edition, &mut src, false, new_meta_vars) {
                 Ok(rule) => {
                     if src.len() != 0 {
                         err = Some(Box::new(ParseError::expected("remaining tokens in macro def")));
@@ -240,7 +237,7 @@ impl<S: Span> DeclarativeMacro<S> {
             }
         }
 
-        DeclarativeMacro { rules: rules.into_boxed_slice(), is_2021, err }
+        DeclarativeMacro { rules: rules.into_boxed_slice(), err }
     }
 
     pub fn err(&self) -> Option<&ParseError> {
@@ -249,18 +246,19 @@ impl<S: Span> DeclarativeMacro<S> {
 
     pub fn expand(
         &self,
-        tt: &tt::Subtree<S>,
-        marker: impl Fn(&mut S) + Copy,
+        tt: &tt::Subtree<Span>,
+        marker: impl Fn(&mut Span) + Copy,
         new_meta_vars: bool,
-        call_site: S,
-    ) -> ExpandResult<tt::Subtree<S>> {
-        expander::expand_rules(&self.rules, tt, marker, self.is_2021, new_meta_vars, call_site)
+        call_site: Span,
+    ) -> ExpandResult<tt::Subtree<Span>> {
+        expander::expand_rules(&self.rules, tt, marker, new_meta_vars, call_site)
     }
 }
 
-impl<S: Span> Rule<S> {
+impl Rule {
     fn parse(
-        src: &mut TtIter<'_, S>,
+        edition: impl Copy + Fn(SyntaxContextId) -> Edition,
+        src: &mut TtIter<'_, Span>,
         expect_arrow: bool,
         new_meta_vars: bool,
     ) -> Result<Self, ParseError> {
@@ -271,14 +269,14 @@ impl<S: Span> Rule<S> {
         }
         let rhs = src.expect_subtree().map_err(|()| ParseError::expected("expected subtree"))?;
 
-        let lhs = MetaTemplate::parse_pattern(lhs)?;
-        let rhs = MetaTemplate::parse_template(rhs, new_meta_vars)?;
+        let lhs = MetaTemplate::parse_pattern(edition, lhs)?;
+        let rhs = MetaTemplate::parse_template(edition, rhs, new_meta_vars)?;
 
         Ok(crate::Rule { lhs, rhs })
     }
 }
 
-fn validate<S: Span>(pattern: &MetaTemplate<S>) -> Result<(), ParseError> {
+fn validate(pattern: &MetaTemplate) -> Result<(), ParseError> {
     for op in pattern.iter() {
         match op {
             Op::Subtree { tokens, .. } => validate(tokens)?,
diff --git a/crates/mbe/src/parser.rs b/crates/mbe/src/parser.rs
index afdbbef231..eaf2fd8c27 100644
--- a/crates/mbe/src/parser.rs
+++ b/crates/mbe/src/parser.rs
@@ -2,8 +2,8 @@
 //! trees.
 
 use smallvec::{smallvec, SmallVec};
+use span::{Edition, Span, SyntaxContextId};
 use syntax::SmolStr;
-use tt::Span;
 
 use crate::{tt_iter::TtIter, ParseError};
 
@@ -21,30 +21,39 @@ use crate::{tt_iter::TtIter, ParseError};
 /// Stuff to the right is a [`MetaTemplate`] template which is used to produce
 /// output.
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub(crate) struct MetaTemplate<S>(pub(crate) Box<[Op<S>]>);
+pub(crate) struct MetaTemplate(pub(crate) Box<[Op]>);
 
-impl<S: Span> MetaTemplate<S> {
-    pub(crate) fn parse_pattern(pattern: &tt::Subtree<S>) -> Result<Self, ParseError> {
-        MetaTemplate::parse(pattern, Mode::Pattern, false)
+impl MetaTemplate {
+    pub(crate) fn parse_pattern(
+        edition: impl Copy + Fn(SyntaxContextId) -> Edition,
+        pattern: &tt::Subtree<Span>,
+    ) -> Result<Self, ParseError> {
+        MetaTemplate::parse(edition, pattern, Mode::Pattern, false)
     }
 
     pub(crate) fn parse_template(
-        template: &tt::Subtree<S>,
+        edition: impl Copy + Fn(SyntaxContextId) -> Edition,
+        template: &tt::Subtree<Span>,
         new_meta_vars: bool,
     ) -> Result<Self, ParseError> {
-        MetaTemplate::parse(template, Mode::Template, new_meta_vars)
+        MetaTemplate::parse(edition, template, Mode::Template, new_meta_vars)
     }
 
-    pub(crate) fn iter(&self) -> impl Iterator<Item = &Op<S>> {
+    pub(crate) fn iter(&self) -> impl Iterator<Item = &Op> {
         self.0.iter()
     }
 
-    fn parse(tt: &tt::Subtree<S>, mode: Mode, new_meta_vars: bool) -> Result<Self, ParseError> {
+    fn parse(
+        edition: impl Copy + Fn(SyntaxContextId) -> Edition,
+        tt: &tt::Subtree<Span>,
+        mode: Mode,
+        new_meta_vars: bool,
+    ) -> Result<Self, ParseError> {
         let mut src = TtIter::new(tt);
 
         let mut res = Vec::new();
         while let Some(first) = src.peek_n(0) {
-            let op = next_op(first, &mut src, mode, new_meta_vars)?;
+            let op = next_op(edition, first, &mut src, mode, new_meta_vars)?;
             res.push(op);
         }
 
@@ -53,15 +62,15 @@ impl<S: Span> MetaTemplate<S> {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub(crate) enum Op<S> {
+pub(crate) enum Op {
     Var {
         name: SmolStr,
         kind: Option<MetaVarKind>,
-        id: S,
+        id: Span,
     },
     Ignore {
         name: SmolStr,
-        id: S,
+        id: Span,
     },
     Index {
         depth: usize,
@@ -75,17 +84,17 @@ pub(crate) enum Op<S> {
         depth: Option<usize>,
     },
     Repeat {
-        tokens: MetaTemplate<S>,
+        tokens: MetaTemplate,
         kind: RepeatKind,
-        separator: Option<Separator<S>>,
+        separator: Option<Separator>,
     },
     Subtree {
-        tokens: MetaTemplate<S>,
-        delimiter: tt::Delimiter<S>,
+        tokens: MetaTemplate,
+        delimiter: tt::Delimiter<Span>,
     },
-    Literal(tt::Literal<S>),
-    Punct(SmallVec<[tt::Punct<S>; 3]>),
-    Ident(tt::Ident<S>),
+    Literal(tt::Literal<Span>),
+    Punct(SmallVec<[tt::Punct<Span>; 3]>),
+    Ident(tt::Ident<Span>),
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -114,15 +123,15 @@ pub(crate) enum MetaVarKind {
 }
 
 #[derive(Clone, Debug, Eq)]
-pub(crate) enum Separator<S> {
-    Literal(tt::Literal<S>),
-    Ident(tt::Ident<S>),
-    Puncts(SmallVec<[tt::Punct<S>; 3]>),
+pub(crate) enum Separator {
+    Literal(tt::Literal<Span>),
+    Ident(tt::Ident<Span>),
+    Puncts(SmallVec<[tt::Punct<Span>; 3]>),
 }
 
 // Note that when we compare a Separator, we just care about its textual value.
-impl<S> PartialEq for Separator<S> {
-    fn eq(&self, other: &Separator<S>) -> bool {
+impl PartialEq for Separator {
+    fn eq(&self, other: &Separator) -> bool {
         use Separator::*;
 
         match (self, other) {
@@ -144,12 +153,13 @@ enum Mode {
     Template,
 }
 
-fn next_op<S: Span>(
-    first_peeked: &tt::TokenTree<S>,
-    src: &mut TtIter<'_, S>,
+fn next_op(
+    edition: impl Copy + Fn(SyntaxContextId) -> Edition,
+    first_peeked: &tt::TokenTree<Span>,
+    src: &mut TtIter<'_, Span>,
     mode: Mode,
     new_meta_vars: bool,
-) -> Result<Op<S>, ParseError> {
+) -> Result<Op, ParseError> {
     let res = match first_peeked {
         tt::TokenTree::Leaf(tt::Leaf::Punct(p @ tt::Punct { char: '$', .. })) => {
             src.next().expect("first token already peeked");
@@ -162,7 +172,7 @@ fn next_op<S: Span>(
                 tt::TokenTree::Subtree(subtree) => match subtree.delimiter.kind {
                     tt::DelimiterKind::Parenthesis => {
                         let (separator, kind) = parse_repeat(src)?;
-                        let tokens = MetaTemplate::parse(subtree, mode, new_meta_vars)?;
+                        let tokens = MetaTemplate::parse(edition, subtree, mode, new_meta_vars)?;
                         Op::Repeat { tokens, separator, kind }
                     }
                     tt::DelimiterKind::Brace => match mode {
@@ -189,13 +199,13 @@ fn next_op<S: Span>(
                         Op::Ident(tt::Ident { text: "$crate".into(), span: ident.span })
                     }
                     tt::Leaf::Ident(ident) => {
-                        let kind = eat_fragment_kind(src, mode)?;
+                        let kind = eat_fragment_kind(edition, src, mode)?;
                         let name = ident.text.clone();
                         let id = ident.span;
                         Op::Var { name, kind, id }
                     }
                     tt::Leaf::Literal(lit) if is_boolean_literal(lit) => {
-                        let kind = eat_fragment_kind(src, mode)?;
+                        let kind = eat_fragment_kind(edition, src, mode)?;
                         let name = lit.text.clone();
                         let id = lit.span;
                         Op::Var { name, kind, id }
@@ -233,15 +243,16 @@ fn next_op<S: Span>(
 
         tt::TokenTree::Subtree(subtree) => {
             src.next().expect("first token already peeked");
-            let tokens = MetaTemplate::parse(subtree, mode, new_meta_vars)?;
+            let tokens = MetaTemplate::parse(edition, subtree, mode, new_meta_vars)?;
             Op::Subtree { tokens, delimiter: subtree.delimiter }
         }
     };
     Ok(res)
 }
 
-fn eat_fragment_kind<S: Span>(
-    src: &mut TtIter<'_, S>,
+fn eat_fragment_kind(
+    edition: impl Copy + Fn(SyntaxContextId) -> Edition,
+    src: &mut TtIter<'_, Span>,
     mode: Mode,
 ) -> Result<Option<MetaVarKind>, ParseError> {
     if let Mode::Pattern = mode {
@@ -252,7 +263,10 @@ fn eat_fragment_kind<S: Span>(
         let kind = match ident.text.as_str() {
             "path" => MetaVarKind::Path,
             "ty" => MetaVarKind::Ty,
-            "pat" => MetaVarKind::Pat,
+            "pat" => match edition(ident.span.ctx) {
+                Edition::Edition2015 | Edition::Edition2018 => MetaVarKind::PatParam,
+                Edition::Edition2021 | Edition::Edition2024 => MetaVarKind::Pat,
+            },
             "pat_param" => MetaVarKind::PatParam,
             "stmt" => MetaVarKind::Stmt,
             "block" => MetaVarKind::Block,
@@ -271,13 +285,11 @@ fn eat_fragment_kind<S: Span>(
     Ok(None)
 }
 
-fn is_boolean_literal<S>(lit: &tt::Literal<S>) -> bool {
+fn is_boolean_literal(lit: &tt::Literal<Span>) -> bool {
     matches!(lit.text.as_str(), "true" | "false")
 }
 
-fn parse_repeat<S: Span>(
-    src: &mut TtIter<'_, S>,
-) -> Result<(Option<Separator<S>>, RepeatKind), ParseError> {
+fn parse_repeat(src: &mut TtIter<'_, Span>) -> Result<(Option<Separator>, RepeatKind), ParseError> {
     let mut separator = Separator::Puncts(SmallVec::new());
     for tt in src {
         let tt = match tt {
@@ -314,7 +326,7 @@ fn parse_repeat<S: Span>(
     Err(ParseError::InvalidRepeat)
 }
 
-fn parse_metavar_expr<S: Span>(new_meta_vars: bool, src: &mut TtIter<'_, S>) -> Result<Op<S>, ()> {
+fn parse_metavar_expr(new_meta_vars: bool, src: &mut TtIter<'_, Span>) -> Result<Op, ()> {
     let func = src.expect_ident()?;
     let args = src.expect_subtree()?;
 
@@ -352,7 +364,7 @@ fn parse_metavar_expr<S: Span>(new_meta_vars: bool, src: &mut TtIter<'_, S>) ->
     Ok(op)
 }
 
-fn parse_depth<S: Span>(src: &mut TtIter<'_, S>) -> Result<usize, ()> {
+fn parse_depth(src: &mut TtIter<'_, Span>) -> Result<usize, ()> {
     if src.len() == 0 {
         Ok(0)
     } else if let tt::Leaf::Literal(lit) = src.expect_literal()? {
@@ -363,7 +375,7 @@ fn parse_depth<S: Span>(src: &mut TtIter<'_, S>) -> Result<usize, ()> {
     }
 }
 
-fn try_eat_comma<S: Span>(src: &mut TtIter<'_, S>) -> bool {
+fn try_eat_comma(src: &mut TtIter<'_, Span>) -> bool {
     if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: ',', .. }))) = src.peek_n(0) {
         let _ = src.next();
         return true;
diff --git a/crates/project-model/Cargo.toml b/crates/project-model/Cargo.toml
index 139689975d..097ee1f75c 100644
--- a/crates/project-model/Cargo.toml
+++ b/crates/project-model/Cargo.toml
@@ -25,6 +25,7 @@ itertools.workspace = true
 
 # local deps
 base-db.workspace = true
+span.workspace = true
 cfg.workspace = true
 paths = { workspace = true, features = ["serde1"] }
 stdx.workspace = true
diff --git a/crates/project-model/src/cargo_workspace.rs b/crates/project-model/src/cargo_workspace.rs
index 4f6bac08f6..957366b610 100644
--- a/crates/project-model/src/cargo_workspace.rs
+++ b/crates/project-model/src/cargo_workspace.rs
@@ -4,13 +4,13 @@ use std::ops;
 use std::str::from_utf8;
 
 use anyhow::Context;
-use base_db::Edition;
 use cargo_metadata::{CargoOpt, MetadataCommand};
 use la_arena::{Arena, Idx};
 use paths::{AbsPath, AbsPathBuf, Utf8PathBuf};
 use rustc_hash::{FxHashMap, FxHashSet};
 use serde::Deserialize;
 use serde_json::from_value;
+use span::Edition;
 use toolchain::Tool;
 
 use crate::{utf8_stdout, InvocationLocation, ManifestPath, Sysroot};
diff --git a/crates/project-model/src/project_json.rs b/crates/project-model/src/project_json.rs
index 0b6e8caf5d..512588cc8f 100644
--- a/crates/project-model/src/project_json.rs
+++ b/crates/project-model/src/project_json.rs
@@ -49,11 +49,12 @@
 //! user explores them belongs to that extension (it's totally valid to change
 //! rust-project.json over time via configuration request!)
 
-use base_db::{CrateDisplayName, CrateId, CrateName, Dependency, Edition};
+use base_db::{CrateDisplayName, CrateId, CrateName, Dependency};
 use la_arena::RawIdx;
 use paths::{AbsPath, AbsPathBuf, Utf8PathBuf};
 use rustc_hash::FxHashMap;
 use serde::{de, Deserialize};
+use span::Edition;
 
 use crate::cfg_flag::CfgFlag;
 
diff --git a/crates/project-model/src/workspace.rs b/crates/project-model/src/workspace.rs
index c6642efca2..1556e9b549 100644
--- a/crates/project-model/src/workspace.rs
+++ b/crates/project-model/src/workspace.rs
@@ -6,13 +6,14 @@ use std::{collections::VecDeque, fmt, fs, iter, str::FromStr, sync};
 
 use anyhow::{format_err, Context};
 use base_db::{
-    CrateDisplayName, CrateGraph, CrateId, CrateName, CrateOrigin, Dependency, Edition, Env,
-    FileId, LangCrateOrigin, ProcMacroPaths, TargetLayoutLoadResult,
+    CrateDisplayName, CrateGraph, CrateId, CrateName, CrateOrigin, Dependency, Env, FileId,
+    LangCrateOrigin, ProcMacroPaths, TargetLayoutLoadResult,
 };
 use cfg::{CfgAtom, CfgDiff, CfgOptions};
 use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::{FxHashMap, FxHashSet};
 use semver::Version;
+use span::Edition;
 use stdx::always;
 use toolchain::Tool;
 use triomphe::Arc;
diff --git a/crates/span/src/lib.rs b/crates/span/src/lib.rs
index 6b849ce373..c9109c72d0 100644
--- a/crates/span/src/lib.rs
+++ b/crates/span/src/lib.rs
@@ -16,6 +16,56 @@ pub use self::{
 pub use syntax::{TextRange, TextSize};
 pub use vfs::FileId;
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Edition {
+    Edition2015,
+    Edition2018,
+    Edition2021,
+    Edition2024,
+}
+
+impl Edition {
+    pub const CURRENT: Edition = Edition::Edition2021;
+    pub const DEFAULT: Edition = Edition::Edition2015;
+}
+
+#[derive(Debug)]
+pub struct ParseEditionError {
+    invalid_input: String,
+}
+
+impl std::error::Error for ParseEditionError {}
+impl fmt::Display for ParseEditionError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "invalid edition: {:?}", self.invalid_input)
+    }
+}
+
+impl std::str::FromStr for Edition {
+    type Err = ParseEditionError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let res = match s {
+            "2015" => Edition::Edition2015,
+            "2018" => Edition::Edition2018,
+            "2021" => Edition::Edition2021,
+            "2024" => Edition::Edition2024,
+            _ => return Err(ParseEditionError { invalid_input: s.to_owned() }),
+        };
+        Ok(res)
+    }
+}
+
+impl fmt::Display for Edition {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(match self {
+            Edition::Edition2015 => "2015",
+            Edition::Edition2018 => "2018",
+            Edition::Edition2021 => "2021",
+            Edition::Edition2024 => "2024",
+        })
+    }
+}
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct FilePosition {
     pub file_id: FileId,


Test patch:
diff --git a/crates/hir-def/src/macro_expansion_tests/mbe.rs b/crates/hir-def/src/macro_expansion_tests/mbe.rs
index 965f329acb..c5c26e26bc 100644
--- a/crates/hir-def/src/macro_expansion_tests/mbe.rs
+++ b/crates/hir-def/src/macro_expansion_tests/mbe.rs
@@ -1449,6 +1449,7 @@ ok!();
 #[test]
 fn test_new_std_matches() {
     check(
+        //- edition:2021
         r#"
 macro_rules! matches {
     ($expression:expr, $pattern:pat $(if $guard:expr)? $(,)?) => {
@@ -1480,6 +1481,90 @@ fn main() {
     );
 }
 
+#[test]
+fn test_hygienic_pat() {
+    check(
+        r#"
+//- /new.rs crate:new deps:old edition:2015
+old::make!();
+fn main() {
+    matches!(0, 0 | 1 if true);
+}
+//- /old.rs crate:old edition:2021
+#[macro_export]
+macro_rules! make {
+    () => {
+        macro_rules! matches {
+            ($expression:expr, $pattern:pat if $guard:expr ) => {
+                match $expression {
+                    $pattern if $guard => true,
+                    _ => false
+                }
+            };
+        }
+    }
+}
+ "#,
+        expect![[r#"
+macro_rules !matches {
+    ($expression: expr, $pattern: pat if $guard: expr) = > {
+        match $expression {
+            $pattern if $guard = > true , _ = > false
+        }
+    }
+    ;
+}
+fn main() {
+    match 0 {
+        0|1 if true =>true , _=>false
+    };
+}
+"#]],
+    );
+    check(
+        r#"
+//- /new.rs crate:new deps:old edition:2021
+old::make!();
+fn main() {
+    matches/*+errors*/!(0, 0 | 1 if true);
+}
+//- /old.rs crate:old edition:2015
+#[macro_export]
+macro_rules! make {
+    () => {
+        macro_rules! matches {
+            ($expression:expr, $pattern:pat if $guard:expr ) => {
+                match $expression {
+                    $pattern if $guard => true,
+                    _ => false
+                }
+            };
+        }
+    }
+}
+ "#,
+        expect![[r#"
+macro_rules !matches {
+    ($expression: expr, $pattern: pat if $guard: expr) = > {
+        match $expression {
+            $pattern if $guard = > true , _ = > false
+        }
+    }
+    ;
+}
+fn main() {
+    /* error: unexpected token in input *//* parse error: expected expression */
+/* parse error: expected FAT_ARROW */
+/* parse error: expected `,` */
+/* parse error: expected pattern */
+match 0 {
+        0 if $guard=>true , _=>false
+    };
+}
+"#]],
+    );
+}
+
 #[test]
 fn test_dollar_crate_lhs_is_not_meta() {
     check(
diff --git a/crates/test-fixture/src/lib.rs b/crates/test-fixture/src/lib.rs
index 8cf65d11c6..b20315eefc 100644
--- a/crates/test-fixture/src/lib.rs
+++ b/crates/test-fixture/src/lib.rs
@@ -2,8 +2,8 @@
 use std::{iter, mem, ops::Not, str::FromStr, sync};
 
 use base_db::{
-    CrateDisplayName, CrateGraph, CrateId, CrateName, CrateOrigin, Dependency, Edition, Env,
-    FileChange, FileSet, LangCrateOrigin, SourceDatabaseExt, SourceRoot, Version, VfsPath,
+    CrateDisplayName, CrateGraph, CrateId, CrateName, CrateOrigin, Dependency, Env, FileChange,
+    FileSet, LangCrateOrigin, SourceDatabaseExt, SourceRoot, Version, VfsPath,
 };
 use cfg::CfgOptions;
 use hir_expand::{
@@ -14,7 +14,7 @@ use hir_expand::{
     },
 };
 use rustc_hash::FxHashMap;
-use span::{FileId, FilePosition, FileRange, Span};
+use span::{Edition, FileId, FilePosition, FileRange, Span};
 use test_utils::{
     extract_range_or_offset, Fixture, FixtureWithProjectMeta, RangeOrOffset, CURSOR_MARKER,
     ESCAPED_CURSOR_MARKER,
@@ -137,7 +137,10 @@ impl ChangeFixture {
         let mut crate_deps = Vec::new();
         let mut default_crate_root: Option<FileId> = None;
         let mut default_cfg = CfgOptions::default();
-        let mut default_env = Env::new_for_test_fixture();
+        let mut default_env = Env::from_iter([(
+            String::from("__ra_is_test_fixture"),
+            String::from("__ra_is_test_fixture"),
+        )]);
 
         let mut file_set = FileSet::default();
         let mut current_source_root_kind = SourceRootKind::Local;
@@ -262,7 +265,10 @@ impl ChangeFixture {
                 None,
                 Default::default(),
                 Default::default(),
-                Env::new_for_test_fixture(),
+                Env::from_iter([(
+                    String::from("__ra_is_test_fixture"),
+                    String::from("__ra_is_test_fixture"),
+                )]),
                 false,
                 CrateOrigin::Lang(LangCrateOrigin::Core),
             );
@@ -298,7 +304,10 @@ impl ChangeFixture {
                 None,
                 Default::default(),
                 Default::default(),
-                Env::new_for_test_fixture(),
+                Env::from_iter([(
+                    String::from("__ra_is_test_fixture"),
+                    String::from("__ra_is_test_fixture"),
+                )]),
                 true,
                 CrateOrigin::Local { repo: None, name: None },
             );