add tests

Author: wyattscarpenter

test-data/unit/check-errorcodes.test

@@ -394,6 +394,19 @@ def f() -> None:
 def g():
     pass
 
+[case testErrorCodeUntypedDecorator]
+# flags: --disallow-untyped-decorators --warn-unused-ignores
+def d(f): return f
+
+@d  # E: Untyped decorator makes function "x" untyped  [untyped-decorator]
+def x() -> int: return 1
+@d # type: ignore
+def y() -> int: return 2
+@d # type: ignore[untyped-decorator]
+def best() -> int: return 3
+@d # type: ignore[misc]  # E: Unused "type: ignore" comment, use narrower [untyped-decorator] instead of [misc] code  [unused-ignore]
+def z() -> int: return 4
+
 [case testErrorCodeIndexing]
 from typing import Dict
 x: Dict[int, int]