from __future__ import annotations

from typing import Callable, Container, cast

from mypy.nodes import ARG_STAR, ARG_STAR2

from mypy.types import (

AnyType,

CallableType,

DeletedType,

ErasedType,

Instance,

LiteralType,

NoneType,

Overloaded,

Parameters,

ParamSpecType,

PartialType,

ProperType,

TupleType,

Type,

TypeAliasType,

TypedDictType,

TypeOfAny,

TypeTranslator,

TypeType,

TypeVarId,

TypeVarTupleType,

TypeVarType,

TypeVisitor,

UnboundType,

UninhabitedType,

UnionType,

UnpackType,

get_proper_type,

get_proper_types,

)

def erase_type(typ: Type) -> ProperType:

"""Erase any type variables from a type.

Also replace tuple types with the corresponding concrete types.

Examples:

A -> A

B[X] -> B[Any]

Tuple[A, B] -> tuple

Callable[[A1, A2, ...], R] -> Callable[..., Any]

Type[X] -> Type[Any]

"""

typ = get_proper_type(typ)

return typ.accept(EraseTypeVisitor())

class EraseTypeVisitor(TypeVisitor[ProperType]):

def visit_unbound_type(self, t: UnboundType) -> ProperType:

# TODO: replace with an assert after UnboundType can't leak from semantic analysis.

return AnyType(TypeOfAny.from_error)

def visit_any(self, t: AnyType) -> ProperType:

return t

def visit_none_type(self, t: NoneType) -> ProperType:

return t

def visit_uninhabited_type(self, t: UninhabitedType) -> ProperType:

return t

def visit_erased_type(self, t: ErasedType) -> ProperType:

return t

def visit_partial_type(self, t: PartialType) -> ProperType:

# Should not get here.

raise RuntimeError("Cannot erase partial types")

def visit_deleted_type(self, t: DeletedType) -> ProperType:

return t

def visit_instance(self, t: Instance) -> ProperType:

args: list[Type] = []

for tv in t.type.defn.type_vars:

# Valid erasure for *Ts is *tuple[Any, ...], not just Any.

if isinstance(tv, TypeVarTupleType):

args.append(

UnpackType(

tv.tuple_fallback.copy_modified(args=[AnyType(TypeOfAny.special_form)])

)

)

else:

args.append(AnyType(TypeOfAny.special_form))

return Instance(t.type, args, t.line)

def visit_type_var(self, t: TypeVarType) -> ProperType:

return AnyType(TypeOfAny.special_form)

def visit_param_spec(self, t: ParamSpecType) -> ProperType:

return AnyType(TypeOfAny.special_form)

def visit_parameters(self, t: Parameters) -> ProperType:

raise RuntimeError("Parameters should have been bound to a class")

def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:

# Likely, we can never get here because of aggressive erasure of types that

# can contain this, but better still return a valid replacement.

return t.tuple_fallback.copy_modified(args=[AnyType(TypeOfAny.special_form)])

def visit_unpack_type(self, t: UnpackType) -> ProperType:

return AnyType(TypeOfAny.special_form)

def visit_callable_type(self, t: CallableType) -> ProperType:

# We must preserve the fallback type for overload resolution to work.

any_type = AnyType(TypeOfAny.special_form)

return CallableType(

arg_types=[any_type, any_type],

arg_kinds=[ARG_STAR, ARG_STAR2],

arg_names=[None, None],

ret_type=any_type,

fallback=t.fallback,

is_ellipsis_args=True,

implicit=True,

)

def visit_overloaded(self, t: Overloaded) -> ProperType:

return t.fallback.accept(self)

def visit_tuple_type(self, t: TupleType) -> ProperType:

return t.partial_fallback.accept(self)

def visit_typeddict_type(self, t: TypedDictType) -> ProperType:

return t.fallback.accept(self)

def visit_literal_type(self, t: LiteralType) -> ProperType:

# The fallback for literal types should always be either

# something like int or str, or an enum class -- types that

# don't contain any TypeVars. So there's no need to visit it.

return t

def visit_union_type(self, t: UnionType) -> ProperType:

erased_items = [erase_type(item) for item in t.items]

from mypy.typeops import make_simplified_union

return make_simplified_union(erased_items)

def visit_type_type(self, t: TypeType) -> ProperType:

return TypeType.make_normalized(t.item.accept(self), line=t.line)

def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:

raise RuntimeError("Type aliases should be expanded before accepting this visitor")

def erase_typevars(t: Type, ids_to_erase: Container[TypeVarId] | None = None) -> Type:

"""Replace all type variables in a type with any,

or just the ones in the provided collection.

"""

def erase_id(id: TypeVarId) -> bool:

if ids_to_erase is None:

return True

return id in ids_to_erase

return t.accept(TypeVarEraser(erase_id, AnyType(TypeOfAny.special_form)))

def replace_meta_vars(t: Type, target_type: Type) -> Type:

"""Replace unification variables in a type with the target type."""

return t.accept(TypeVarEraser(lambda id: id.is_meta_var(), target_type))

class TypeVarEraser(TypeTranslator):

"""Implementation of type erasure"""

def __init__(self, erase_id: Callable[[TypeVarId], bool], replacement: Type) -> None:

self.erase_id = erase_id

self.replacement = replacement

def visit_type_var(self, t: TypeVarType) -> Type:

if self.erase_id(t.id):

return self.replacement

return t

# TODO: below two methods duplicate some logic with expand_type().

# In fact, we may want to refactor this whole visitor to use expand_type().

def visit_instance(self, t: Instance) -> Type:

result = super().visit_instance(t)

assert isinstance(result, ProperType) and isinstance(result, Instance)

if t.type.fullname == "builtins.tuple":

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

arg = result.args[0]

if isinstance(arg, UnpackType):

unpacked = get_proper_type(arg.type)

if isinstance(unpacked, Instance):

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

return unpacked

return result

def visit_tuple_type(self, t: TupleType) -> Type:

result = super().visit_tuple_type(t)

assert isinstance(result, ProperType) and isinstance(result, TupleType)

if len(result.items) == 1:

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

item = result.items[0]

if isinstance(item, UnpackType):

unpacked = get_proper_type(item.type)

if isinstance(unpacked, Instance):

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

if result.partial_fallback.type.fullname != "builtins.tuple":

# If it is a subtype (like named tuple) we need to preserve it,

# this essentially mimics the logic in tuple_fallback().

return result.partial_fallback.accept(self)

return unpacked

return result

def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:

if self.erase_id(t.id):

return t.tuple_fallback.copy_modified(args=[self.replacement])

return t

def visit_param_spec(self, t: ParamSpecType) -> Type:

if self.erase_id(t.id):

return self.replacement

return t

def visit_type_alias_type(self, t: TypeAliasType) -> Type:

# Type alias target can't contain bound type variables (not bound by the type

# alias itself), so it is safe to just erase the arguments.

return t.copy_modified(args=[a.accept(self) for a in t.args])

def remove_instance_last_known_values(t: Type) -> Type:

return t.accept(LastKnownValueEraser())

class LastKnownValueEraser(TypeTranslator):

"""Removes the Literal[...] type that may be associated with any

Instance types."""

def visit_instance(self, t: Instance) -> Type:

if not t.last_known_value and not t.args:

return t

return t.copy_modified(args=[a.accept(self) for a in t.args], last_known_value=None)

def visit_type_alias_type(self, t: TypeAliasType) -> Type:

# Type aliases can't contain literal values, because they are

# always constructed as explicit types.

return t

def visit_union_type(self, t: UnionType) -> Type:

new = cast(UnionType, super().visit_union_type(t))

# Erasure can result in many duplicate items; merge them.

# Call make_simplified_union only on lists of instance types

# that all have the same fullname, to avoid simplifying too

# much.

instances = [item for item in new.items if isinstance(get_proper_type(item), Instance)]

# Avoid merge in simple cases such as optional types.

if len(instances) > 1:

instances_by_name: dict[str, list[Instance]] = {}

p_new_items = get_proper_types(new.items)

for p_item in p_new_items:

if isinstance(p_item, Instance) and not p_item.args:

instances_by_name.setdefault(p_item.type.fullname, []).append(p_item)

merged: list[Type] = []

for item in new.items:

orig_item = item

item = get_proper_type(item)

if isinstance(item, Instance) and not item.args:

types = instances_by_name.get(item.type.fullname)

if types is not None:

if len(types) == 1:

merged.append(item)

else:

from mypy.typeops import make_simplified_union

merged.append(make_simplified_union(types))

del instances_by_name[item.type.fullname]

else:

merged.append(orig_item)

return UnionType.make_union(merged)

return new