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Merged
youknowone merged 2 commits into from
Feb 4, 2026
Merged

support | operation between typing.Union and strings #6983

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3d99a79
remove duplicated _call_typing_func_object() functions
Feb 4, 2026
411f549
support | operation between typing.Union and strings
Feb 2, 2026
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support | operation between typing.Union and strings 
Adds support for performing '|' operation between Union objects and
strings, e.g. forward type references.

For example following code:

    from typing import Union

    U1 = Union[int, str]
    U1 | "float"

The result of the operation above becomes:

   int | str | ForwardRef('float')
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@elmjag
Elmir Jagudin authored and elmjag committed Feb 4, 2026
commit 411f549bbea0306cca9afb048e18d9da1a189669
1 change: 0 additions & 1 deletion Lib/test/test_typing.py
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Expand Up @@ -2281,7 +2281,6 @@ class Ints(enum.IntEnum):
self.assertEqual(Union[Literal[1], Literal[Ints.B], Literal[True]].__args__,
(Literal[1], Literal[Ints.B], Literal[True]))

@unittest.expectedFailure # TODO: RUSTPYTHON; AssertionError: types.UnionType[int, str] | float != types.UnionType[int, str, float]
def test_allow_non_types_in_or(self):
# gh-140348: Test that using | with a Union object allows things that are
# not allowed by is_unionable().
Expand Down
7 changes: 1 addition & 6 deletions crates/vm/src/builtins/type.rs
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Expand Up @@ -2048,12 +2048,7 @@ pub(crate) fn call_slot_new(
}

pub(crate) fn or_(zelf: PyObjectRef, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
if !union_::is_unionable(zelf.clone(), vm) || !union_::is_unionable(other.clone(), vm) {
return Ok(vm.ctx.not_implemented());
}

let tuple = PyTuple::new_ref(vec![zelf, other], &vm.ctx);
union_::make_union(&tuple, vm)
union_::or_op(zelf, other, vm)
}

fn take_next_base(bases: &mut [Vec<PyTypeRef>]) -> Option<PyTypeRef> {
Expand Down
34 changes: 32 additions & 2 deletions crates/vm/src/builtins/union.rs
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Expand Up @@ -8,7 +8,7 @@ use crate::{
convert::ToPyObject,
function::PyComparisonValue,
protocol::{PyMappingMethods, PyNumberMethods},
stdlib::typing::TypeAliasType,
stdlib::typing::{TypeAliasType, call_typing_func_object},
types::{AsMapping, AsNumber, Comparable, GetAttr, Hashable, PyComparisonOp, Representable},
};
use alloc::fmt;
Expand Down Expand Up @@ -193,7 +193,7 @@ impl PyUnion {
}
}

pub fn is_unionable(obj: PyObjectRef, vm: &VirtualMachine) -> bool {
fn is_unionable(obj: PyObjectRef, vm: &VirtualMachine) -> bool {
let cls = obj.class();
cls.is(vm.ctx.types.none_type)
|| obj.downcastable::<PyType>()
Expand All @@ -202,6 +202,36 @@ pub fn is_unionable(obj: PyObjectRef, vm: &VirtualMachine) -> bool {
|| obj.downcast_ref::<TypeAliasType>().is_some()
}

fn type_check(arg: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
// Fast path to avoid calling into typing.py
if is_unionable(arg.clone(), vm) {
return Ok(arg);
}
let message_str: PyObjectRef = vm
.ctx
.new_str("Union[arg, ...]: each arg must be a type.")
.into();
call_typing_func_object(vm, "_type_check", (arg, message_str))
}

fn has_union_operands(a: PyObjectRef, b: PyObjectRef, vm: &VirtualMachine) -> bool {
let union_type = vm.ctx.types.union_type;
a.class().is(union_type) || b.class().is(union_type)
}

pub fn or_op(zelf: PyObjectRef, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
if !has_union_operands(zelf.clone(), other.clone(), vm)
&& (!is_unionable(zelf.clone(), vm) || !is_unionable(other.clone(), vm))
{
return Ok(vm.ctx.not_implemented());
}

let left = type_check(zelf, vm)?;
let right = type_check(other, vm)?;
let tuple = PyTuple::new_ref(vec![left, right], &vm.ctx);
make_union(&tuple, vm)
}

fn make_parameters(args: &Py<PyTuple>, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
let parameters = genericalias::make_parameters(args, vm);
let result = dedup_and_flatten_args(&parameters, vm)?;
Expand Down