add a failing test

Author: dianne

tests/ui/pattern/rfc-3627-match-ergonomics-2024/migration_lint.fixed

@@ -244,4 +244,10 @@ fn main() {
     let &[migration_lint_macros::bind_ref!(a)] = &[0];
     //~^ ERROR: binding modifiers may only be written when the default binding mode is `move`
     assert_type_eq(a, &0u32);
+
+    // Test that we use the correct span when labeling a `&` whose subpattern is from an expansion.
+    let &[&migration_lint_macros::bind_ref!(a)] = &[&0];
+    //~^ ERROR: reference patterns may only be written when the default binding mode is `move` in Rust 2024
+    //~| WARN: this changes meaning in Rust 2024
+    assert_type_eq(a, &0u32);
 }

tests/ui/pattern/rfc-3627-match-ergonomics-2024/migration_lint.rs

@@ -244,4 +244,10 @@ fn main() {
     let [migration_lint_macros::bind_ref!(a)] = &[0];
     //~^ ERROR: binding modifiers may only be written when the default binding mode is `move`
     assert_type_eq(a, &0u32);
+
+    // Test that we use the correct span when labeling a `&` whose subpattern is from an expansion.
+    let [&migration_lint_macros::bind_ref!(a)] = &[&0];
+    //~^ ERROR: reference patterns may only be written when the default binding mode is `move` in Rust 2024
+    //~| WARN: this changes meaning in Rust 2024
+    assert_type_eq(a, &0u32);
 }

tests/ui/pattern/rfc-3627-match-ergonomics-2024/migration_lint.stderr

@@ -580,5 +580,26 @@ help: make the implied reference pattern explicit
 LL |     let &[migration_lint_macros::bind_ref!(a)] = &[0];
    |         +
 
-error: aborting due to 30 previous errors
+error: reference patterns may only be written when the default binding mode is `move` in Rust 2024
+  --> $DIR/auxiliary/migration_lint_macros.rs:15:22
+   |
+LL |       ($foo:ident) => {
+   |  ______________________^
+LL | |         ref $foo
+   | |________________^ reference pattern not allowed under `ref` default binding mode
+   |
+   = warning: this changes meaning in Rust 2024
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/match-ergonomics.html>
+note: matching on a reference type with a non-reference pattern changes the default binding mode
+  --> $DIR/migration_lint.rs:249:9
+   |
+LL |     let [&migration_lint_macros::bind_ref!(a)] = &[&0];
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this matches on type `&_`
+help: make the implied reference pattern explicit
+  --> $DIR/migration_lint.rs:249:9
+   |
+LL |     let &[&migration_lint_macros::bind_ref!(a)] = &[&0];
+   |         +
+
+error: aborting due to 31 previous errors