Typevar defaults not applied to new style type alias

[cdce8p]

Bug Report

To Reproduce

class A[L = int, M = str]: ...
type TD2 = A[float]

def func(a: TD2) -> None:
    reveal_type(a)

Expected Behavior

note: Revealed type is "test.A[builtins.float, builtins.str]"

Actual Behavior

note: Revealed type is "test.A[builtins.float]"

Your Environment

• Mypy version used: mypy 1.16.0+dev.616e1865c1e0024d181ac915d2f1576113ed2cd8 (compiled: no)
• Python version used: 3.13