"""Verify properties of type arguments, like 'int' in C[int] being valid.

This must happen after semantic analysis since there can be placeholder

types until the end of semantic analysis, and these break various type

operations, including subtype checks.

"""

from __future__ import annotations

from typing import Callable

from mypy import errorcodes as codes, message_registry

from mypy.errorcodes import ErrorCode

from mypy.errors import Errors

from mypy.messages import format_type

from mypy.mixedtraverser import MixedTraverserVisitor

from mypy.nodes import ARG_STAR, Block, ClassDef, Context, FakeInfo, FuncItem, MypyFile

from mypy.options import Options

from mypy.scope import Scope

from mypy.subtypes import is_same_type, is_subtype

from mypy.types import (

AnyType,

CallableType,

Instance,

Parameters,

ParamSpecType,

TupleType,

Type,

TypeAliasType,

TypeOfAny,

TypeVarLikeType,

TypeVarTupleType,

TypeVarType,

UnboundType,

UnpackType,

flatten_nested_tuples,

get_proper_type,

get_proper_types,

split_with_prefix_and_suffix,

)

class TypeArgumentAnalyzer(MixedTraverserVisitor):

def __init__(

self,

errors: Errors,

options: Options,

is_typeshed_file: bool,

named_type: Callable[[str, list[Type]], Instance],

) -> None:

super().__init__()

self.errors = errors

self.options = options

self.is_typeshed_file = is_typeshed_file

self.named_type = named_type

self.scope = Scope()

# Should we also analyze function definitions, or only module top-levels?

self.recurse_into_functions = True

# Keep track of the type aliases already visited. This is needed to avoid

# infinite recursion on types like A = Union[int, List[A]].

self.seen_aliases: set[TypeAliasType] = set()

def visit_mypy_file(self, o: MypyFile) -> None:

self.errors.set_file(o.path, o.fullname, scope=self.scope, options=self.options)

with self.scope.module_scope(o.fullname):

super().visit_mypy_file(o)

def visit_func(self, defn: FuncItem) -> None:

if not self.recurse_into_functions:

return

with self.scope.function_scope(defn):

super().visit_func(defn)

def visit_class_def(self, defn: ClassDef) -> None:

with self.scope.class_scope(defn.info):

super().visit_class_def(defn)

def visit_block(self, o: Block) -> None:

if not o.is_unreachable:

super().visit_block(o)

def visit_type_alias_type(self, t: TypeAliasType) -> None:

super().visit_type_alias_type(t)

if t in self.seen_aliases:

# Avoid infinite recursion on recursive type aliases.

# Note: it is fine to skip the aliases we have already seen in non-recursive

# types, since errors there have already been reported.

return

self.seen_aliases.add(t)

assert t.alias is not None, f"Unfixed type alias {t.type_ref}"

is_error = self.validate_args(t.alias.name, tuple(t.args), t.alias.alias_tvars, t)

if not is_error:

# If there was already an error for the alias itself, there is no point in checking

# the expansion, most likely it will result in the same kind of error.

get_proper_type(t).accept(self)

def visit_tuple_type(self, t: TupleType) -> None:

t.items = flatten_nested_tuples(t.items)

# We could also normalize Tuple[*tuple[X, ...]] -> tuple[X, ...] like in

# expand_type() but we can't do this here since it is not a translator visitor,

# and we need to return an Instance instead of TupleType.

super().visit_tuple_type(t)

def visit_callable_type(self, t: CallableType) -> None:

super().visit_callable_type(t)

# Normalize trivial unpack in var args as *args: *tuple[X, ...] -> *args: X

if t.is_var_arg:

star_index = t.arg_kinds.index(ARG_STAR)

star_type = t.arg_types[star_index]

if isinstance(star_type, UnpackType):

p_type = get_proper_type(star_type.type)

if isinstance(p_type, Instance):

assert p_type.type.fullname == "builtins.tuple"

t.arg_types[star_index] = p_type.args[0]

def visit_instance(self, t: Instance) -> None:

super().visit_instance(t)

# Type argument counts were checked in the main semantic analyzer pass. We assume

# that the counts are correct here.

info = t.type

if isinstance(info, FakeInfo):

return # https://github.com/python/mypy/issues/11079

self.validate_args(info.name, t.args, info.defn.type_vars, t)

if t.type.fullname == "builtins.tuple" and len(t.args) == 1:

# Normalize Tuple[*Tuple[X, ...], ...] -> Tuple[X, ...]

arg = t.args[0]

if isinstance(arg, UnpackType):

unpacked = get_proper_type(arg.type)

if isinstance(unpacked, Instance):

assert unpacked.type.fullname == "builtins.tuple"

t.args = unpacked.args

def validate_args(

self, name: str, args: tuple[Type, ...], type_vars: list[TypeVarLikeType], ctx: Context

) -> bool:

if any(isinstance(v, TypeVarTupleType) for v in type_vars):

prefix = next(i for (i, v) in enumerate(type_vars) if isinstance(v, TypeVarTupleType))

tvt = type_vars[prefix]

assert isinstance(tvt, TypeVarTupleType)

start, middle, end = split_with_prefix_and_suffix(

tuple(args), prefix, len(type_vars) - prefix - 1

)

args = start + (TupleType(list(middle), tvt.tuple_fallback),) + end

is_error = False

for (i, arg), tvar in zip(enumerate(args), type_vars):

if isinstance(tvar, TypeVarType):

if isinstance(arg, ParamSpecType):

# TODO: Better message

is_error = True

self.fail(f'Invalid location for ParamSpec "{arg.name}"', ctx)

self.note(

"You can use ParamSpec as the first argument to Callable, e.g., "

"'Callable[{}, int]'".format(arg.name),

ctx,

)

continue

if tvar.values:

if isinstance(arg, TypeVarType):

if self.in_type_alias_expr:

# Type aliases are allowed to use unconstrained type variables

# error will be checked at substitution point.

continue

arg_values = arg.values

if not arg_values:

is_error = True

self.fail(

message_registry.INVALID_TYPEVAR_AS_TYPEARG.format(arg.name, name),

ctx,

code=codes.TYPE_VAR,

)

continue

else:

arg_values = [arg]

if self.check_type_var_values(name, arg_values, tvar.name, tvar.values, ctx):

is_error = True

# Check against upper bound. Since it's object the vast majority of the time,

# add fast path to avoid a potentially slow subtype check.

upper_bound = tvar.upper_bound

object_upper_bound = (

type(upper_bound) is Instance

and upper_bound.type.fullname == "builtins.object"

)

if not object_upper_bound and not is_subtype(arg, upper_bound):

if self.in_type_alias_expr and isinstance(arg, TypeVarType):

# Type aliases are allowed to use unconstrained type variables

# error will be checked at substitution point.

continue

is_error = True

self.fail(

message_registry.INVALID_TYPEVAR_ARG_BOUND.format(

format_type(arg, self.options),

name,

format_type(upper_bound, self.options),

),

ctx,

code=codes.TYPE_VAR,

)

elif isinstance(tvar, ParamSpecType):

if not isinstance(

get_proper_type(arg), (ParamSpecType, Parameters, AnyType, UnboundType)

):

self.fail(

"Can only replace ParamSpec with a parameter types list or"

f" another ParamSpec, got {format_type(arg, self.options)}",

ctx,

)

return is_error

def visit_unpack_type(self, typ: UnpackType) -> None:

super().visit_unpack_type(typ)

proper_type = get_proper_type(typ.type)

if isinstance(proper_type, TupleType):

return

if isinstance(proper_type, TypeVarTupleType):

return

# TODO: this should probably be .has_base("builtins.tuple"), also elsewhere. This is

# tricky however, since this needs map_instance_to_supertype() available in many places.

if isinstance(proper_type, Instance) and proper_type.type.fullname == "builtins.tuple":

return

if not isinstance(proper_type, (UnboundType, AnyType)):

# Avoid extra errors if there were some errors already. Also interpret plain Any

# as tuple[Any, ...] (this is better for the code in type checker).

self.fail(

message_registry.INVALID_UNPACK.format(format_type(proper_type, self.options)),

typ.type,

code=codes.VALID_TYPE,

)

typ.type = self.named_type("builtins.tuple", [AnyType(TypeOfAny.from_error)])

def check_type_var_values(

self, name: str, actuals: list[Type], arg_name: str, valids: list[Type], context: Context

) -> bool:

is_error = False

for actual in get_proper_types(actuals):

# We skip UnboundType here, since they may appear in defn.bases,

# the error will be caught when visiting info.bases, that have bound type

# variables.

if not isinstance(actual, (AnyType, UnboundType)) and not any(

is_same_type(actual, value) for value in valids

):

is_error = True

if len(actuals) > 1 or not isinstance(actual, Instance):

self.fail(

message_registry.INVALID_TYPEVAR_ARG_VALUE.format(name),

context,

code=codes.TYPE_VAR,

)

else:

class_name = f'"{name}"'

actual_type_name = f'"{actual.type.name}"'

self.fail(

message_registry.INCOMPATIBLE_TYPEVAR_VALUE.format(

arg_name, class_name, actual_type_name

),

context,

code=codes.TYPE_VAR,

)

return is_error

def fail(self, msg: str, context: Context, *, code: ErrorCode | None = None) -> None:

self.errors.report(context.line, context.column, msg, code=code)

def note(self, msg: str, context: Context, *, code: ErrorCode | None = None) -> None:

self.errors.report(context.line, context.column, msg, severity="note", code=code)