Don't report unused type ignores in typeshed (#1920)

Author: ddfisher

mypy/checker.py

@@ -145,8 +145,7 @@ def visit_file(self, file_node: MypyFile, path: str) -> None:
         self.globals = file_node.names
         self.weak_opts = file_node.weak_opts
         self.enter_partial_types()
-        # gross, but no other clear way to tell
-        self.is_typeshed_stub = self.is_stub and 'typeshed' in os.path.normpath(path).split(os.sep)
+        self.is_typeshed_stub = self.errors.is_typeshed_file(path)
 
         for d in file_node.defs:
             self.accept(d)

mypy/errors.py

@@ -206,12 +206,17 @@ def add_error_info(self, info: ErrorInfo) -> None:
 
     def generate_unused_ignore_notes(self) -> None:
         for file, ignored_lines in self.ignored_lines.items():
-            for line in ignored_lines - self.used_ignored_lines[file]:
-                # Don't use report since add_error_info will ignore the error!
-                info = ErrorInfo(self.import_context(), file, None, None,
-                                 line, 'note', "unused 'type: ignore' comment",
-                                 False, False)
-                self.error_info.append(info)
+            if not self.is_typeshed_file(file):
+                for line in ignored_lines - self.used_ignored_lines[file]:
+                    # Don't use report since add_error_info will ignore the error!
+                    info = ErrorInfo(self.import_context(), file, None, None,
+                                    line, 'note', "unused 'type: ignore' comment",
+                                    False, False)
+                    self.error_info.append(info)
+
+    def is_typeshed_file(self, file: str) -> bool:
+        # gross, but no other clear way to tell
+        return 'typeshed' in os.path.normpath(file).split(os.sep)
 
     def num_messages(self) -> int:
         """Return the number of generated messages."""