regression test for spurrious "help: store this in the heap"

Closes #82446

Author: notriddle

src/test/ui/box/issue-82446.rs

@@ -0,0 +1,15 @@
+// https://github.com/rust-lang/rust/issues/82446
+// Spurious 'help: store this in the heap' regression test
+trait MyTrait {}
+
+struct Foo {
+    val: Box<dyn MyTrait>
+}
+
+fn make_it(val: &Box<dyn MyTrait>) {
+    Foo {
+        val //~ ERROR [E0308]
+    };
+}
+
+fn main() {}

src/test/ui/box/issue-82446.stderr

@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-82446.rs:11:9
+   |
+LL |         val
+   |         ^^^ expected struct `Box`, found reference
+   |
+   = note: expected struct `Box<(dyn MyTrait + 'static)>`
+           found reference `&Box<(dyn MyTrait + 'static)>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.