Cache type_object_type()

Author: ilevkivskyi

mypy/checker.py

@@ -397,6 +397,7 @@ def __init__(
         self.is_stub = tree.is_stub
         self.is_typeshed_stub = tree.is_typeshed_file(options)
         self.inferred_attribute_types = None
+        self.allow_constructor_cache = True
 
         # If True, process function definitions. If False, don't. This is used
         # for processing module top levels in fine-grained incremental mode.
@@ -500,12 +501,16 @@ def check_first_pass(self) -> None:
                         )
 
     def check_second_pass(
-        self, todo: Sequence[DeferredNode | FineGrainedDeferredNode] | None = None
+        self,
+        todo: Sequence[DeferredNode | FineGrainedDeferredNode] | None = None,
+        *,
+        allow_constructor_cache: bool = True,
     ) -> bool:
         """Run second or following pass of type checking.
 
         This goes through deferred nodes, returning True if there were any.
         """
+        self.allow_constructor_cache = allow_constructor_cache
         self.recurse_into_functions = True
         with state.strict_optional_set(self.options.strict_optional), checker_state.set(self):
             if not todo and not self.deferred_nodes:

mypy/checker_shared.py

@@ -137,6 +137,7 @@ class TypeCheckerSharedApi(CheckerPluginInterface):
     module_refs: set[str]
     scope: CheckerScope
     checking_missing_await: bool
+    allow_constructor_cache: bool
 
     @property
     @abstractmethod

mypy/nodes.py

@@ -3022,6 +3022,7 @@ class is generic then it will be a type constructor of higher kind.
         "dataclass_transform_spec",
         "is_type_check_only",
         "deprecated",
+        "type_object_type",
     )
 
     _fullname: str  # Fully qualified name
@@ -3178,6 +3179,10 @@ class is generic then it will be a type constructor of higher kind.
     # The type's deprecation message (in case it is deprecated)
     deprecated: str | None
 
+    # Cached value of class constructor type, i.e. the type of class object when it
+    # appears in runtime context.
+    type_object_type: mypy.types.FunctionLike | None
+
     FLAGS: Final = [
         "is_abstract",
         "is_enum",
@@ -3236,6 +3241,7 @@ def __init__(self, names: SymbolTable, defn: ClassDef, module_name: str) -> None
         self.dataclass_transform_spec = None
         self.is_type_check_only = False
         self.deprecated = None
+        self.type_object_type = None
 
     def add_type_vars(self) -> None:
         self.has_type_var_tuple_type = False

mypy/server/update.py

@@ -1025,10 +1025,10 @@ def key(node: FineGrainedDeferredNode) -> int:
     # We seem to need additional passes in fine-grained incremental mode.
     checker.pass_num = 0
     checker.last_pass = 3
-    more = checker.check_second_pass(nodes)
+    more = checker.check_second_pass(nodes, allow_constructor_cache=False)
     while more:
         more = False
-        if graph[module_id].type_checker().check_second_pass():
+        if graph[module_id].type_checker().check_second_pass(allow_constructor_cache=False):
             more = True
 
     if manager.options.export_types:

mypy/typeops.py

@@ -11,6 +11,7 @@
 from collections.abc import Iterable, Sequence
 from typing import Any, Callable, TypeVar, cast
 
+from mypy.checker_state import checker_state
 from mypy.copytype import copy_type
 from mypy.expandtype import expand_type, expand_type_by_instance
 from mypy.maptype import map_instance_to_supertype
@@ -145,6 +146,15 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
     where ... are argument types for the __init__/__new__ method (without the self
     argument). Also, the fallback type will be 'type' instead of 'function'.
     """
+    allow_cache = (
+        checker_state.type_checker is not None
+        and checker_state.type_checker.allow_constructor_cache
+    )
+
+    if info.type_object_type is not None:
+        if allow_cache:
+            return info.type_object_type
+        info.type_object_type = None
 
     # We take the type from whichever of __init__ and __new__ is first
     # in the MRO, preferring __init__ if there is a tie.
@@ -189,7 +199,10 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
                     is_bound=True,
                     fallback=named_type("builtins.function"),
                 )
-                return class_callable(sig, info, fallback, None, is_new=False)
+                result: FunctionLike = class_callable(sig, info, fallback, None, is_new=False)
+                if allow_cache:
+                    info.type_object_type = result
+                return result
 
         # Otherwise prefer __init__ in a tie. It isn't clear that this
         # is the right thing, but __new__ caused problems with
@@ -204,7 +217,10 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
         assert isinstance(method.type, ProperType)
         assert isinstance(method.type, FunctionLike)  # is_valid_constructor() ensures this
         t = method.type
-    return type_object_type_from_function(t, info, method.info, fallback, is_new)
+    result = type_object_type_from_function(t, info, method.info, fallback, is_new)
+    if allow_cache:
+        info.type_object_type = result
+    return result
 
 
 def is_valid_constructor(n: SymbolNode | None) -> bool: