Some minor cleanups and fixes to work with mypyc (#5473)

Author: msullivan

mypy/nodes.py

@@ -4,12 +4,12 @@
 from abc import abstractmethod
 from collections import OrderedDict, defaultdict
 from typing import (
-    Any, TypeVar, List, Tuple, cast, Set, Dict, Union, Optional, Callable, Sequence
+    Any, TypeVar, List, Tuple, cast, Set, Dict, Union, Optional, Callable, Sequence,
 )
 
 MYPY = False
 if MYPY:
-    from typing import DefaultDict
+    from typing import DefaultDict, ClassVar
 
 import mypy.strconv
 from mypy.util import short_type
@@ -48,7 +48,7 @@ def get_column(self) -> int:
         return self.column
 
 
-if False:
+if MYPY:
     # break import cycle only needed for mypy
     import mypy.types
 
@@ -630,11 +630,10 @@ def deserialize(cls, data: JsonDict) -> 'FuncDef':
         # NOTE: ret.info is set in the fixup phase.
         ret.arg_names = data['arg_names']
         ret.arg_kinds = data['arg_kinds']
-        # Mark these as 'None' so that future uses will trigger an error
-        _dummy = None  # type: Any
-        ret.arguments = _dummy
-        ret.max_pos = _dummy
-        ret.min_args = _dummy
+        # Leave these uninitialized so that future uses will trigger an error
+        del ret.arguments
+        del ret.max_pos
+        del ret.min_args
         return ret
 
 
@@ -1243,8 +1242,6 @@ def accept(self, visitor: ExpressionVisitor[T]) -> T:
 class ComplexExpr(Expression):
     """Complex literal"""
 
-    value = 0.0j
-
     def __init__(self, value: complex) -> None:
         super().__init__()
         self.value = value
@@ -2166,7 +2163,7 @@ class is generic then it will be a type constructor of higher kind.
     FLAGS = [
         'is_abstract', 'is_enum', 'fallback_to_any', 'is_named_tuple',
         'is_newtype', 'is_protocol', 'runtime_protocol'
-    ]
+    ]  # type: ClassVar[List[str]]
 
     def __init__(self, names: 'SymbolTable', defn: ClassDef, module_name: str) -> None:
         """Initialize a TypeInfo."""

mypy/server/astmerge.py

@@ -419,8 +419,6 @@ def visit_union_type(self, typ: UnionType) -> None:
     def fixup(self, node: SN) -> SN:
         if node in self.replacements:
             new = self.replacements[node]
-            # TODO: This may be unnecessary?
-            new.__dict__ = node.__dict__
             return cast(SN, new)
         return node
 

mypy/types.py

@@ -6,9 +6,13 @@
 from collections import OrderedDict
 from typing import (
     Any, TypeVar, Dict, List, Tuple, cast, Generic, Set, Optional, Union, Iterable, NamedTuple,
-    Callable, Sequence, Iterator
+    Callable, Sequence, Iterator,
 )
 
+MYPY = False
+if MYPY:
+    from typing import ClassVar
+
 import mypy.nodes
 from mypy import experiments
 from mypy.nodes import (
@@ -24,8 +28,6 @@
 
 JsonDict = Dict[str, Any]
 
-MYPY = False
-
 # If we import type_visitor in the middle of the file, mypy breaks, and if we do it
 # at the top, it breaks at runtime because of import cycle issues, so we do it at different
 # times in different places.
@@ -92,7 +94,7 @@ class TypeVarId:
     meta_level = 0  # type: int
 
     # Class variable used for allocating fresh ids for metavariables.
-    next_raw_id = 1  # type: int
+    next_raw_id = 1  # type: ClassVar[int]
 
     def __init__(self, raw_id: int, meta_level: int = 0) -> None:
         self.raw_id = raw_id