Emit errors on invalid defaulted TypeVar constructions #2429
Description
Summary
When a TypeVar has a default, there are some bounds/constraints that may be invalid. ty should emit an error for these cases. This is probably already part of the typing conformance suite somewhere, but I couldn't find an existing issue for it, so I figured I'd open one.
From these links:
https://typing.python.org/en/latest/spec/generics.html#bound-rules
https://typing.python.org/en/latest/spec/generics.html#constraint-rules
from typing import TypeVar
T1 = TypeVar("T1", bound=int)
Ok = TypeVar("Ok", default=T1, bound=float) # Valid
AlsoOk = TypeVar("AlsoOk", default=T1, bound=int) # Valid
Invalid = TypeVar("Invalid", default=T1, bound=str) # Invalid: int is not assignable to str
T2 = TypeVar("T2", bound=int)
Invalid1 = TypeVar("Invalid1", float, str, default=T2) # Invalid: upper bound int is incompatible with constraints float or str
T3 = TypeVar("T3", int, str)
AlsoOk1 = TypeVar("AlsoOk1", int, str, bool, default=T3) # Valid
AlsoInvalid = TypeVar("AlsoInvalid", bool, complex, default=T3) # Invalid: {bool, complex} is not a superset of {int, str}Currently none of the Invalid lines give an error.
Version
ty 0.0.11 (830cb9c 2026-01-09)