Fix crash when function annotation has more args than function (#1812)

Author: ddfisher

mypy/semanal.py

@@ -542,7 +542,7 @@ def check_function_signature(self, fdef: FuncItem) -> None:
             extra_anys = [AnyType()] * (len(fdef.arguments) - len(sig.arg_types))
             sig.arg_types.extend(extra_anys)
         elif len(sig.arg_types) > len(fdef.arguments):
-            self.fail('Type signature has too many arguments', fdef)
+            self.fail('Type signature has too many arguments', fdef, blocker=True)
 
     def visit_class_def(self, defn: ClassDef) -> None:
         self.clean_up_bases_and_infer_type_variables(defn)

test-data/unit/check-fastparse.test

@@ -154,3 +154,19 @@ def f(a,        # type: A
 [builtins fixtures/dict.py]
 [out]
 main: note: In function "f":
+
+[case testFasterParseTooManyArgumentsAnnotation]
+# options: fast_parser
+def f():  # E: Type signature has too many arguments
+    # type: (int) -> None
+    pass
+[out]
+main: note: In function "f":
+
+[case testFasterParseTooFewArgumentsAnnotation]
+# options: fast_parser
+def f(x):  # E: Type signature has too few arguments
+    # type: () -> None
+    pass
+[out]
+main: note: In function "f":