Eliminate all mypyc warnings when compiling mypy (#6638)

This was a big obstacle that made me reluctant to set up CI.

Author: msullivan

mypy/checkexpr.py

@@ -1495,7 +1495,7 @@ def infer_overload_return_type(self,
             # We try returning a precise type if we can. If not, we give up and just return 'Any'.
             if all_same_types(return_types):
                 return return_types[0], inferred_types[0]
-            elif all_same_types(erase_type(typ) for typ in return_types):
+            elif all_same_types([erase_type(typ) for typ in return_types]):
                 return erase_type(return_types[0]), erase_type(inferred_types[0])
             else:
                 return self.check_call(callee=AnyType(TypeOfAny.special_form),
@@ -3113,8 +3113,9 @@ def visit_generator_expr(self, e: GeneratorExpr) -> Type:
     def check_generator_or_comprehension(self, gen: GeneratorExpr,
                                          type_name: str,
                                          id_for_messages: str,
-                                         additional_args: List[Type] = []) -> Type:
+                                         additional_args: Optional[List[Type]] = None) -> Type:
         """Type check a generator expression or a list comprehension."""
+        additional_args = additional_args or []
         with self.chk.binder.frame_context(can_skip=True, fall_through=0):
             self.check_for_comp(gen)
 
@@ -3734,8 +3735,7 @@ def any_causes_overload_ambiguity(items: List[CallableType],
     return False
 
 
-def all_same_types(types: Iterable[Type]) -> bool:
-    types = list(types)
+def all_same_types(types: List[Type]) -> bool:
     if len(types) == 0:
         return True
     return all(is_same_type(t, types[0]) for t in types[1:])

mypy/fastparse.py

@@ -40,6 +40,10 @@
 from mypy.options import Options
 
 try:
+    # pull this into a final variable to make mypyc be quiet about the
+    # the default argument warning
+    PY_MINOR_VERSION = sys.version_info[1]  # type: Final
+
     # Check if we can use the stdlib ast module instead of typed_ast.
     if sys.version_info >= (3, 8):
         import ast as ast3
@@ -64,7 +68,7 @@
         )
 
         def ast3_parse(source: Union[str, bytes], filename: str, mode: str,
-                       feature_version: int = sys.version_info[1]) -> AST:
+                       feature_version: int = PY_MINOR_VERSION) -> AST:
             return ast3.parse(source, filename, mode,
                               type_comments=True,  # This works the magic
                               feature_version=feature_version)
@@ -92,7 +96,7 @@ def ast3_parse(source: Union[str, bytes], filename: str, mode: str,
         )
 
         def ast3_parse(source: Union[str, bytes], filename: str, mode: str,
-                       feature_version: int = sys.version_info[1]) -> AST:
+                       feature_version: int = PY_MINOR_VERSION) -> AST:
             return ast3.parse(source, filename, mode, feature_version=feature_version)
 
         # These don't exist before 3.8

mypy/ipc.py

@@ -15,6 +15,7 @@
 MYPY = False
 if MYPY:
     from typing import Type
+    from typing_extensions import Final
 
 from types import TracebackType
 
@@ -179,7 +180,7 @@ def __exit__(self,
 
 class IPCServer(IPCBase):
 
-    BUFFER_SIZE = 2**16
+    BUFFER_SIZE = 2**16  # type: Final
 
     def __init__(self, name: str, timeout: Optional[float] = None) -> None:
         if sys.platform == 'win32':

mypy/messages.py

@@ -921,7 +921,7 @@ def incompatible_conditional_function_def(self, defn: FuncDef) -> None:
     def cannot_instantiate_abstract_class(self, class_name: str,
                                           abstract_attributes: List[str],
                                           context: Context) -> None:
-        attrs = format_string_list("'%s'" % a for a in abstract_attributes)
+        attrs = format_string_list(["'%s'" % a for a in abstract_attributes])
         self.fail("Cannot instantiate abstract class '%s' with abstract "
                   "attribute%s %s" % (class_name, plural_s(abstract_attributes),
                                    attrs),
@@ -1507,8 +1507,7 @@ def plural_s(s: Union[int, Sequence[Any]]) -> str:
         return ''
 
 
-def format_string_list(s: Iterable[str]) -> str:
-    lst = list(s)
+def format_string_list(lst: List[str]) -> str:
     assert len(lst) > 0
     if len(lst) == 1:
         return lst[0]

mypy/newsemanal/typeanal.py

@@ -1219,7 +1219,7 @@ def __init__(self) -> None:
         super().__init__(self.combine_lists_strategy)
 
     def query_types(self, types: Iterable[Type]) -> List[Type]:
-        return self.strategy(t.accept(self) for t in types) + list(types)
+        return self.strategy([t.accept(self) for t in types]) + list(types)
 
     @classmethod
     def combine_lists_strategy(cls, it: Iterable[List[Type]]) -> List[Type]:

mypy/nodes.py

@@ -2996,8 +2996,8 @@ def __str__(self) -> str:
         return '\n'.join(a)
 
     def copy(self) -> 'SymbolTable':
-        return SymbolTable((key, node.copy())
-                           for key, node in self.items())
+        return SymbolTable([(key, node.copy())
+                            for key, node in self.items()])
 
     def serialize(self, fullname: str) -> JsonDict:
         data = {'.class': 'SymbolTable'}  # type: JsonDict

mypy/report.py

@@ -419,7 +419,8 @@ def __init__(self, reports: Reports, output_dir: str) -> None:
     # XML doesn't like control characters, but they are sometimes
     # legal in source code (e.g. comments, string literals).
     # Tabs (#x09) are allowed in XML content.
-    control_fixer = str.maketrans(''.join(chr(i) for i in range(32) if i != 9), '?' * 31)
+    control_fixer = str.maketrans(
+        ''.join(chr(i) for i in range(32) if i != 9), '?' * 31)  # type: Final
 
     def on_file(self,
                 tree: MypyFile,

mypy/stubdoc.py

@@ -24,7 +24,7 @@
 class ArgSig:
     """Signature info for a single argument."""
 
-    _TYPE_RE = re.compile(r'^[a-zA-Z_][\w\[\], ]*(\.[a-zA-Z_][\w\[\], ]*)*$')
+    _TYPE_RE = re.compile(r'^[a-zA-Z_][\w\[\], ]*(\.[a-zA-Z_][\w\[\], ]*)*$')  # type: Final
 
     def __init__(self, name: str, type: Optional[str] = None, default: bool = False):
         self.name = name

mypy/typeanal.py

@@ -1243,7 +1243,7 @@ def __init__(self) -> None:
         super().__init__(self.combine_lists_strategy)
 
     def query_types(self, types: Iterable[Type]) -> List[Type]:
-        return self.strategy(t.accept(self) for t in types) + list(types)
+        return self.strategy([t.accept(self) for t in types]) + list(types)
 
     @classmethod
     def combine_lists_strategy(cls, it: Iterable[List[Type]]) -> List[Type]: