Add a test for deref projections in new pattern capture behavior

Author: meithecatte

tests/ui/closures/2229_closure_analysis/deref-mut-in-pattern.rs

@@ -0,0 +1,35 @@
+// Newly accepted examples as a result of the changes introduced in #138961.
+//
+//@ edition:2024
+//@ check-pass
+#![allow(unused_assignments)]
+
+fn f() {
+    let mut x: &mut [u8] = &mut [1, 2, 3];
+    let c = || {
+        match x {
+            [] => (),
+            _ => (),
+        }
+    };
+    x = &mut [];
+    c();
+}
+
+fn g() {
+    let mut x: &mut bool = &mut false;
+    let mut t = true;
+    let c = || {
+        match x {
+            true => (),
+            false => (),
+        }
+    };
+    x = &mut t;
+    c();
+}
+
+fn main() {
+    f();
+    g();
+}