test: cover compatibility function return tokens

tests/test_validate_typecheck_diagnostics.py

@@ -114,6 +114,12 @@ class ValidateTypecheckDiagnosticsTests(unittest.TestCase):
             MODULE.EXPECTED,
         )
 
+    def test_includes_compatibility_function_extra_return_tokens_fixture(self):
+        self.assertIn(
+            "tests/typecheck_function_compat_return_extra_tokens_bad.claro",
+            MODULE.EXPECTED,
+        )
+
     def test_includes_empty_compatibility_method_return_fixture(self):
         self.assertIn(
             "tests/typecheck_method_compat_empty_return_bad.claro",

tests/typecheck_function_compat_return_extra_tokens_bad.claro

@@ -0,0 +1,3 @@
+TEACH square TAKES amount RETURNS NUMBER
+    RETURN amount extra
+LEARNED