typeddict check for multiple inheritance fails with type aliases

[A5rocks]

Bug Report

Mypy thinks a type alias isn't a typeddict.

To Reproduce

from typing import TypedDict, Unpack

class A(TypedDict, total=False):
    y: int
class B(TypedDict, total=False):
    x: str

D = B

class C(A, D):  # E: All bases of a new TypedDict must be TypedDict types  
    pass

Expected Behavior

no errors

Actual Behavior

main.py:10: error: All bases of a new TypedDict must be TypedDict types  [misc]
Found 1 error in 1 file (checked 1 source file)

Your Environment

Checked using mypy-play.

• Mypy version used: 1.15
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.12

[sterliakov]

mypy/mypy/semanal_typeddict.py

Lines 611 to 616 in 4b1a255

	def is_typeddict(self, expr: Expression) -> bool:
	return (
	isinstance(expr, RefExpr)
	and isinstance(expr.node, TypeInfo)
	and expr.node.typeddict_type is not None
	)