attrs plugin does not support generic type

Bug Report

The mypy attrs plugin has custom support for attrs.evolve, which has different code branches for regular and generic types (starting here).

It admits attrs.has as a type guard for attrs.evolve if the original type is Any, but not if it's a generic type parameter T with no type bound.

To Reproduce

On python 3.12 (so lacking copy.replace):

def replace[T](value: T, **kwargs: Any) -> T:
    if attrs.has(type(value)):
        return attrs.evolve(value, **kwargs)
    else:
        raise NotImplementedError(f"replace is not implemented for {type(value)}")

Mypy reports, error: Argument 1 to "evolve" has a variable type "T" not bound to an attrs class [misc]

(In the actual code I'd do something else in other branches; this is intended as a replacement for copy.replace on python < 3.13, supporting different types besides attrs classes.)

Using the attr.AttrInstance protocol also doesn't work, which means I can't define my own type guard wrapping attrs.has. This code results in the same mypy error:

def replace[T: attrs.AttrsInstance](value: T, **kwargs: Any) -> T:
    return attrs.evolve(value, **kwargs)

However, this code works (and is a viable workaround):

def replace[T](value: T, **kwargs: Any) -> T:
    val2: Any = value
    if attrs.has(type(val2)):
        return attrs.evolve(val2, **kwargs)
    else:
        raise NotImplementedError(f"replace is not implemented for {type(value)}")

Expected Behavior

Mypy should honor attrs.has as a type guard for attrs.evolve, whether the original type is generic or any other kind.

• Mypy version used: 1.15.0
• Python version used: 3.12.10

Start in mypy/plugins/attrs.py around the attrs.evolve handling at line 914, then run the provided Python 3.12 generic example against mypy 1.15.0 to observe the diagnostic. Trace how attrs.has is recognized for Any versus an unbound type parameter, and confirm completion when the generic example is accepted without the variable-type error while preserving the expected return type.