Optimization: Enable always defined attributes in Type subclasses

mypy/types.py

@@ -198,7 +198,7 @@ def deserialize_type(data: JsonDict | str) -> Type:
 class Type(mypy.nodes.Context):
  """Abstract base class for all types."""
 
- __slots__ = ("can_be_true", "can_be_false")
+ __slots__ = ("_can_be_true", "_can_be_false")
  # 'can_be_true' and 'can_be_false' mean whether the value of the
  # expression can be true or false in a boolean context. They are useful
  # when inferring the type of logic expressions like `x and y`.
@@ -211,8 +211,29 @@ class Type(mypy.nodes.Context):
 
  def __init__(self, line: int = -1, column: int = -1) -> None:
  super().__init__(line, column)
- self.can_be_true = self.can_be_true_default()
- self.can_be_false = self.can_be_false_default()
+ # Value of these can be -1 (use the default, lazy init), 0 (false) or 1 (true)
+ self._can_be_true = -1
+ self._can_be_false = -1
+
+ @property
+ def can_be_true(self) -> bool:
+ if self._can_be_true == -1: # Lazy init helps mypyc
+ self._can_be_true = self.can_be_true_default()
+ return bool(self._can_be_true)
+
+ @can_be_true.setter
+ def can_be_true(self, v: bool) -> None:
+ self._can_be_true = v
+
+ @property
+ def can_be_false(self) -> bool:
+ if self._can_be_false == -1: # Lazy init helps mypyc
+ self._can_be_false = self.can_be_false_default()
+ return bool(self._can_be_false)
+
+ @can_be_false.setter
+ def can_be_false(self, v: bool) -> None:
+ self._can_be_false = v
 
  def can_be_true_default(self) -> bool:
  return True
@@ -261,10 +282,10 @@ def __init__(
  line: int = -1,
  column: int = -1,
  ) -> None:
+ super().__init__(line, column)
  self.alias = alias
  self.args = args
  self.type_ref: str | None = None
- super().__init__(line, column)
 
  def _expand_once(self) -> Type:
  """Expand to the target type exactly once.
@@ -1421,7 +1442,7 @@ class FunctionLike(ProperType):
 
  def __init__(self, line: int = -1, column: int = -1) -> None:
  super().__init__(line, column)
- self.can_be_false = False
+ self._can_be_false = False
 
  @abstractmethod
  def is_type_obj(self) -> bool:
@@ -2180,10 +2201,10 @@ def __init__(
  column: int = -1,
  implicit: bool = False,
  ) -> None:
+ super().__init__(line, column)
  self.partial_fallback = fallback
  self.items = items
  self.implicit = implicit
- super().__init__(line, column)
 
  def can_be_true_default(self) -> bool:
  if self.can_be_any_bool():
@@ -2492,8 +2513,8 @@ class LiteralType(ProperType):
  def __init__(
  self, value: LiteralValue, fallback: Instance, line: int = -1, column: int = -1
  ) -> None:
- self.value = value
  super().__init__(line, column)
+ self.value = value
  self.fallback = fallback
  self._hash = -1 # Cached hash value