Add missing TypedDict special case to checkmember.py (#18604)

Fixes #18600

mypy/checkexpr.py

@@ -15,7 +15,12 @@
 import mypy.errorcodes as codes
 from mypy import applytype, erasetype, join, message_registry, nodes, operators, types
 from mypy.argmap import ArgTypeExpander, map_actuals_to_formals, map_formals_to_actuals
-from mypy.checkmember import analyze_member_access, freeze_all_type_vars, type_object_type
+from mypy.checkmember import (
+    analyze_member_access,
+    freeze_all_type_vars,
+    type_object_type,
+    typeddict_callable,
+)
 from mypy.checkstrformat import StringFormatterChecker
 from mypy.erasetype import erase_type, remove_instance_last_known_values, replace_meta_vars
 from mypy.errors import ErrorWatcher, report_internal_error
@@ -955,20 +960,7 @@ def typeddict_callable(self, info: TypeInfo) -> CallableType:
         Note it is not safe to move this to type_object_type() since it will crash
         on plugin-generated TypedDicts, that may not have the special_alias.
         """
-        assert info.special_alias is not None
-        target = info.special_alias.target
-        assert isinstance(target, ProperType) and isinstance(target, TypedDictType)
-        expected_types = list(target.items.values())
-        kinds = [ArgKind.ARG_NAMED] * len(expected_types)
-        names = list(target.items.keys())
-        return CallableType(
-            expected_types,
-            kinds,
-            names,
-            target,
-            self.named_type("builtins.type"),
-            variables=info.defn.type_vars,
-        )
+        return typeddict_callable(info, self.named_type)
 
     def typeddict_callable_from_context(self, callee: TypedDictType) -> CallableType:
         return CallableType(

mypy/checkmember.py

@@ -20,6 +20,7 @@
     ARG_STAR2,
     EXCLUDED_ENUM_ATTRIBUTES,
     SYMBOL_FUNCBASE_TYPES,
+    ArgKind,
     Context,
     Decorator,
     FuncBase,
@@ -1148,8 +1149,16 @@ def analyze_class_attribute_access(
         )
         return AnyType(TypeOfAny.from_error)
 
+    # TODO: some logic below duplicates analyze_ref_expr in checkexpr.py
     if isinstance(node.node, TypeInfo):
-        return type_object_type(node.node, mx.named_type)
+        if node.node.typeddict_type:
+            # We special-case TypedDict, because they don't define any constructor.
+            return typeddict_callable(node.node, mx.named_type)
+        elif node.node.fullname == "types.NoneType":
+            # We special case NoneType, because its stub definition is not related to None.
+            return TypeType(NoneType())
+        else:
+            return type_object_type(node.node, mx.named_type)
 
     if isinstance(node.node, MypyFile):
         # Reference to a module object.
@@ -1330,6 +1339,31 @@ class B(A[str]): pass
     return t
 
 
+def typeddict_callable(info: TypeInfo, named_type: Callable[[str], Instance]) -> CallableType:
+    """Construct a reasonable type for a TypedDict type in runtime context.
+
+    If it appears as a callee, it will be special-cased anyway, e.g. it is
+    also allowed to accept a single positional argument if it is a dict literal.
+
+    Note it is not safe to move this to type_object_type() since it will crash
+    on plugin-generated TypedDicts, that may not have the special_alias.
+    """
+    assert info.special_alias is not None
+    target = info.special_alias.target
+    assert isinstance(target, ProperType) and isinstance(target, TypedDictType)
+    expected_types = list(target.items.values())
+    kinds = [ArgKind.ARG_NAMED] * len(expected_types)
+    names = list(target.items.keys())
+    return CallableType(
+        expected_types,
+        kinds,
+        names,
+        target,
+        named_type("builtins.type"),
+        variables=info.defn.type_vars,
+    )
+
+
 def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> ProperType:
     """Return the type of a type object.
 

test-data/unit/check-typeddict.test

@@ -4118,3 +4118,23 @@ Func = TypedDict('Func', {
 })
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]
+
+[case testTypedDictNestedInClassAndInherited]
+from typing_extensions import TypedDict
+
+class Base:
+    class Params(TypedDict):
+        name: str
+
+class Derived(Base):
+    pass
+
+class DerivedOverride(Base):
+    class Params(Base.Params):
+        pass
+
+Base.Params(name="Robert")
+Derived.Params(name="Robert")
+DerivedOverride.Params(name="Robert")
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]