Function fix_instance

mypy/typeanal.py:2066–2114

Fix a malformed instance by replacing all type arguments with TypeVar default or Any. Also emit a suitable error if this is not due to implicit Any's.

(
    t: Instance,
    fail: MsgCallback,
    note: MsgCallback,
    disallow_any: bool,
    options: Options,
    use_generic_error: bool = False,
    unexpanded_type: Type | None = None,
)

def fix_instance(
    t: Instance,
    fail: MsgCallback,
    note: MsgCallback,
    disallow_any: bool,
    options: Options,
    use_generic_error: bool = False,
    unexpanded_type: Type | None = None,
) -> None:
    """Fix a malformed instance by replacing all type arguments with TypeVar default or Any.

    Also emit a suitable error if this is not due to implicit Any's.
    """
    arg_count = len(t.args)
    min_tv_count = sum(not tv.has_default() for tv in t.type.defn.type_vars)
    max_tv_count = len(t.type.type_vars)
    if arg_count < min_tv_count or arg_count > max_tv_count:
        # Don't use existing args if arg_count doesn't match
        if arg_count > max_tv_count:
            # Already wrong arg count error, don't emit missing type parameters error as well.
            disallow_any = False
        t.args = ()

    args: list[Type] = [*(t.args[:max_tv_count])]
    any_type: AnyType | None = None
    env: dict[TypeVarId, Type] = {}

    for tv, arg in itertools.zip_longest(t.type.defn.type_vars, t.args, fillvalue=None):
        if tv is None:
            continue
        if arg is None:
            if tv.has_default():
                arg = tv.default
            else:
                if any_type is None:
                    fullname = None if use_generic_error else t.type.fullname
                    any_type = get_omitted_any(
                        disallow_any, fail, note, t, options, fullname, unexpanded_type
                    )
                arg = any_type
            args.append(arg)
        env[tv.id] = arg
    t.args = tuple(args)
    fix_type_var_tuple_argument(t)
    if not t.type.has_type_var_tuple_type:
        with state.strict_optional_set(True):
            fixed = expand_type(t, env)
        assert isinstance(fixed, Instance)
        t.args = fixed.args


def instantiate_type_alias(