Add test that triggers ICE

Author: Nadrieril

tests/ui/pattern/auxiliary/match_ergonomics_2024_macros.rs

@@ -0,0 +1,11 @@
+//@ compile-flags: --edition 2024 -Z unstable-options
+
+// This contains a binding in edition 2024, so if matched with a reference binding mode it will end
+// up with a `mut ref mut` binding mode. We use this to test the migration lint on patterns with
+// mixed editions.
+#[macro_export]
+macro_rules! mixed_edition_pat {
+    () => {
+        Some(mut _x)
+    };
+}

tests/ui/pattern/match_ergonomics_2024.rs

@@ -1,9 +1,12 @@
 //@ edition: 2021
 //@ run-rustfix
+//@ aux-build:match_ergonomics_2024_macros.rs
 #![feature(mut_preserve_binding_mode_2024, ref_pat_eat_one_layer_2024)]
 #![allow(incomplete_features, unused)]
 #![forbid(rust_2024_incompatible_pat)]
 
+extern crate match_ergonomics_2024_macros;
+
 struct Foo(u8);
 
 fn main() {
@@ -38,4 +41,11 @@ fn main() {
     let s = Struct { a: 0, b: 0, c: 0 };
     let Struct { a, mut b, c } = &s;
     //~^ ERROR: the semantics of this pattern will change in edition 2024
+
+    match &(Some(0), Some(0)) {
+        // The two patterns are the same syntactically, but because they're defined in different
+        // editions they don't mean the same thing.
+        (Some(mut _x), match_ergonomics_2024_macros::mixed_edition_pat!()) => {}
+        _ => {}
+    }
 }