Add test to confirm #3922 fix

gcc/testsuite/ChangeLog:

	* rust/compile/issue-3922.rs: New test.

Signed-off-by: Pierre-Emmanuel Patry <[email protected]>

Author: P-E-P

gcc/testsuite/rust/compile/issue-3922.rs

@@ -0,0 +1,12 @@
+struct S(
+    [u8; {
+        {
+            // { dg-error "mismatched types. expected .... but got ..integer.. .E0308." "" { target *-*-* } .-1 }
+            struct Z;
+            0
+        }
+        0
+    }],
+);
+
+fn main() {}