Handle compilation error in builtin_type_shadow.rs

Author: GuillaumeGomez

tests/ui/builtin_type_shadow.rs

@@ -3,8 +3,7 @@
 
 fn foo<u32>(a: u32) -> u32 {
 //~^ builtin_type_shadow
-    42
-
+    42 //~ ERROR: mismatched type
 }
 
 fn main() {}