mypy/copytype.py

from __future__ import annotations

from typing import Any, cast

from mypy.types import (
    AnyType,
    CallableType,
    DeletedType,
    ErasedType,
    Instance,
    LiteralType,
    NoneType,
    Overloaded,
    Parameters,
    ParamSpecType,
    PartialType,
    ProperType,
    TupleType,
    TypeAliasType,
    TypedDictType,
    TypeType,
    TypeVarTupleType,
    TypeVarType,
    UnboundType,
    UninhabitedType,
    UnionType,
    UnpackType,
)

# type_visitor needs to be imported after types
from mypy.type_visitor import TypeVisitor  # isort: skip


def copy_type(t: ProperType) -> ProperType:
    """Create a shallow copy of a type.

    This can be used to mutate the copy with truthiness information.

    Classes compiled with mypyc don't support copy.copy(), so we need
    a custom implementation.
    """
    return t.accept(TypeShallowCopier())


class TypeShallowCopier(TypeVisitor[ProperType]):
    def visit_unbound_type(self, t: UnboundType) -> ProperType:
        return t

    def visit_any(self, t: AnyType) -> ProperType:
        return self.copy_common(t, AnyType(t.type_of_any, t.source_any, t.missing_import_name))

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

    def visit_uninhabited_type(self, t: UninhabitedType) -> ProperType:
        dup = UninhabitedType(t.is_noreturn)
        dup.ambiguous = t.ambiguous
        return self.copy_common(t, dup)

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

    def visit_deleted_type(self, t: DeletedType) -> ProperType:
        return self.copy_common(t, DeletedType(t.source))

    def visit_instance(self, t: Instance) -> ProperType:
        dup = Instance(t.type, t.args, last_known_value=t.last_known_value)
        dup.invalid = t.invalid
        return self.copy_common(t, dup)

    def visit_type_var(self, t: TypeVarType) -> ProperType:
        dup = TypeVarType(
            t.name,
            t.fullname,
            t.id,
            values=t.values,
            upper_bound=t.upper_bound,
            variance=t.variance,
        )
        return self.copy_common(t, dup)

    def visit_param_spec(self, t: ParamSpecType) -> ProperType:
        dup = ParamSpecType(t.name, t.fullname, t.id, t.flavor, t.upper_bound, prefix=t.prefix)
        return self.copy_common(t, dup)

    def visit_parameters(self, t: Parameters) -> ProperType:
        dup = Parameters(
            t.arg_types,
            t.arg_kinds,
            t.arg_names,
            variables=t.variables,
            is_ellipsis_args=t.is_ellipsis_args,
        )
        return self.copy_common(t, dup)

    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
        dup = TypeVarTupleType(t.name, t.fullname, t.id, t.upper_bound)
        return self.copy_common(t, dup)

    def visit_unpack_type(self, t: UnpackType) -> ProperType:
        dup = UnpackType(t.type)
        return self.copy_common(t, dup)

    def visit_partial_type(self, t: PartialType) -> ProperType:
        return self.copy_common(t, PartialType(t.type, t.var, t.value_type))

    def visit_callable_type(self, t: CallableType) -> ProperType:
        return self.copy_common(t, t.copy_modified())

    def visit_tuple_type(self, t: TupleType) -> ProperType:
        return self.copy_common(t, TupleType(t.items, t.partial_fallback, implicit=t.implicit))

    def visit_typeddict_type(self, t: TypedDictType) -> ProperType:
        return self.copy_common(t, TypedDictType(t.items, t.required_keys, t.fallback))

    def visit_literal_type(self, t: LiteralType) -> ProperType:
        return self.copy_common(t, LiteralType(value=t.value, fallback=t.fallback))

    def visit_union_type(self, t: UnionType) -> ProperType:
        return self.copy_common(t, UnionType(t.items))

    def visit_overloaded(self, t: Overloaded) -> ProperType:
        return self.copy_common(t, Overloaded(items=t.items))

    def visit_type_type(self, t: TypeType) -> ProperType:
        # Use cast since the type annotations in TypeType are imprecise.
        return self.copy_common(t, TypeType(cast(Any, t.item)))

    def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:
        assert False, "only ProperTypes supported"

    def copy_common(self, t: ProperType, t2: ProperType) -> ProperType:
        t2.line = t.line
        t2.column = t.column
        t2.can_be_false = t.can_be_false
        t2.can_be_true = t.can_be_true
        return t2