fixup! Adds expr_2024 migration lit

Signed-off-by: Vincenzo Palazzo <[email protected]>

compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs

@@ -41,12 +41,14 @@ declare_lint! {
     ///
     /// ### Explanation
     ///
-    /// Rust [editions] allow the language to evolve without breaking
-    /// backwards compatibility. This lint catches code that uses new keywords
-    /// that are added to the language that are used as identifiers (such as a
-    /// variable name, function name, etc.). If you switch the compiler to a
-    /// new edition without updating the code, then it will fail to compile if
-    /// you are using a new keyword as an identifier.
+    /// Rust [editions] allow the language to evolve without breaking backwards compatibility.
+    /// This lint catches code that uses [macro matcher fragment specifiers] that have changes
+    /// the syntax in the edition 2024. If you switch the compiler to a
+    /// new edition without updating the code, your macros may behave differently.
+    ///
+    /// In the edition 2024, the `expr` fragment specifier `expr`
+    /// will also match `const { ... }` blocks. To keep the old behavior, you should use the
+    /// `expr_2021`.
     ///
     /// This lint solves the problem automatically. It is "allow" by default
     /// because the code is perfectly valid in older editions. The [`cargo
@@ -56,6 +58,7 @@ declare_lint! {
     /// a new edition.
     ///
     /// [editions]: https://doc.rust-lang.org/edition-guide/
+    /// [macro matcher fragment specifiers]: https://doc.rust-lang.org/nightly/edition-guide/rust-2024/macro-fragment-specifiers.html
     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
     pub EDITION_2024_EXPR_FRAGMENT_SPECIFIER,
     Allow,