Add min_match_ergonomics_2024 feature gate

compiler/rustc_feature/src/unstable.rs

@@ -516,6 +516,9 @@ declare_features! (
     (unstable, macro_metavar_expr_concat, "1.81.0", Some(124225)),
     /// Allows `#[marker]` on certain traits allowing overlapping implementations.
     (unstable, marker_trait_attr, "1.30.0", Some(29864)),
+    /// A very restricted form of match ergonomics used over the 2024 edition transition to give
+    /// more time for T-lang to decide the final form of RFC3627.
+    (incomplete, min_match_ergonomics_2024, "CURRENT_RUSTC_VERSION", Some(123076)),
     /// A minimal, sound subset of specialization intended to be used by the
     /// standard library until the soundness issues with specialization
     /// are fixed.

compiler/rustc_span/src/symbol.rs

@@ -1218,6 +1218,7 @@ symbols! {
         min_const_generics,
         min_const_unsafe_fn,
         min_exhaustive_patterns,
+        min_match_ergonomics_2024,
         min_specialization,
         min_type_alias_impl_trait,
         minnumf128,