Skip to content

Resolve Self to the TypeVar when subscripting a class-bounded TypeVar #5258

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
kinto0 wants to merge 2 commits into
base: main
Choose a base branch
from
+103 −21
Open

Resolve Self to the TypeVar when subscripting a class-bounded TypeVar #5258

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
1de9af0
Add test for subscripting a TypeVar bounded by a class whose `__getit…
kinto0 Oct 17, 2026
4e58de2
Resolve `Self` to the TypeVar when subscripting a class-bounded TypeVar
kinto0 Oct 17, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
67 changes: 46 additions & 21 deletions pyrefly/lib/alt/expr.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3420,6 +3420,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
let mut aliases = SmallSet::new();
self.subscript_infer_for_type_with_key_present_inner(
base,
None,
slice,
range,
errors,
Expand All @@ -3429,9 +3430,13 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
)
}

/// `receiver`, when set, is the restricted TypeVar whose bound or constraint `base` is.
/// `__getitem__` is then called on the TypeVar, so that `Self` in its signature binds to
/// the TypeVar, while `base` still selects any builtin subscript handling.
fn subscript_infer_for_type_with_key_present_inner(
&self,
base: &Type,
receiver: Option<&Type>,
slice: &Expr,
range: TextRange,
errors: &ErrorCollector,
Expand Down Expand Up @@ -3467,6 +3472,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
let mut aliases = aliases.clone();
self.subscript_infer_for_type_with_key_present_inner(
branch,
receiver,
slice,
range,
errors,
Expand Down Expand Up @@ -3760,15 +3766,18 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
self.infer_shaped_array_index(shaped_array_type, slice, range, errors)
}
// Shaped arrays that opt out of built-in indexing use their declared method.
Type::ShapedArray(_) => self.call_method_or_error(
&base,
&dunder::GETITEM,
range,
&[CallArg::expr(slice)],
&[],
errors,
Some(&|| ErrorContext::Index(self.for_display(base.clone()))),
),
Type::ShapedArray(_) => {
let receiver = receiver.unwrap_or(&base);
self.call_method_or_error(
receiver,
&dunder::GETITEM,
range,
&[CallArg::expr(slice)],
&[],
errors,
Some(&|| ErrorContext::Index(self.for_display(receiver.clone()))),
)
}
// Shaped arrays that have not gone through annotation
// canonicalization still use tensor indexing logic.
Type::ClassType(ref cls)
Expand All @@ -3792,32 +3801,42 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
}
// Special handling for nn.ModuleDict with TypedDict type argument
Type::ClassType(ref cls) if is_nn_module_dict(cls) => {
self.try_nn_module_dict_index(cls, &base, slice, range, errors)
self.try_nn_module_dict_index(
cls,
receiver.unwrap_or(&base),
slice,
range,
errors,
)
}
Type::ClassType(ref cls) | Type::SelfType(ref cls) if cls.is_builtin("list") => {
let index_arg = match builtin_sequence_slice_ty {
Some(ty) => CallArg::ty(ty, slice.range()),
None => CallArg::expr(slice),
};
let receiver = receiver.unwrap_or(&base);
self.call_method_or_error(
&base,
receiver,
&dunder::GETITEM,
range,
&[index_arg],
&[],
errors,
Some(&|| ErrorContext::Index(self.for_display(base.clone()))),
Some(&|| ErrorContext::Index(self.for_display(receiver.clone()))),
)
}
Type::ClassType(_) | Type::SelfType(_) => {
let receiver = receiver.unwrap_or(&base);
self.call_method_or_error(
receiver,
&dunder::GETITEM,
range,
&[CallArg::expr(slice)],
&[],
errors,
Some(&|| ErrorContext::Index(self.for_display(receiver.clone()))),
)
}
Type::ClassType(_) | Type::SelfType(_) => self.call_method_or_error(
&base,
&dunder::GETITEM,
range,
&[CallArg::expr(slice)],
&[],
errors,
Some(&|| ErrorContext::Index(self.for_display(base.clone()))),
),
Type::DataFrame(schema) => {
if let Expr::List(ExprList { elts, .. }) = slice
&& schema.kind == DataFrameKind::Polars
Expand Down Expand Up @@ -3853,6 +3872,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
}
let result = self.subscript_infer_for_type_with_key_present_inner(
&schema.underlying_type(),
receiver,
slice,
range,
errors,
Expand All @@ -3876,6 +3896,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
}
Type::Series(schema) => self.subscript_infer_for_type_with_key_present_inner(
&schema.underlying_type(),
receiver,
slice,
range,
errors,
Expand All @@ -3888,6 +3909,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
Restriction::Bound(bound) => self
.subscript_infer_for_type_with_key_present_inner(
bound,
Some(&base),
slice,
range,
errors,
Expand All @@ -3899,6 +3921,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
self.unions(constraints.map(|constraint| {
self.subscript_infer_for_type_with_key_present_inner(
constraint,
Some(&base),
slice,
range,
errors,
Expand All @@ -3911,6 +3934,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
Restriction::ShapeExtension(extension) => self
.subscript_infer_for_type_with_key_present_inner(
&extension.upper_bound(self.stdlib, self.heap),
Some(&base),
slice,
range,
errors,
Expand Down Expand Up @@ -4014,6 +4038,7 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
} else {
let result = self.subscript_infer_for_type_with_key_present_inner(
&self.untype_alias(&ta),
receiver,
slice,
range,
errors,
Expand Down
57 changes: 57 additions & 0 deletions pyrefly/lib/test/generic_restrictions.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -755,6 +755,63 @@ def foo[T: (A, B)](x: T) -> T:
"#,
);

testcase!(
test_bounded_typevar_subscript_return_self,
r#"
from typing import Protocol, Self, assert_type

class SupportsSlice(Protocol):
def __getitem__(self, index: slice) -> Self: ...

class Concrete:
def __getitem__(self, index: slice) -> Self:
return self

def protocol_bound[S: SupportsSlice](seq: S) -> None:
assert_type(seq[0:1], S)

def class_bound[S: Concrete](seq: S) -> None:
assert_type(seq[0:1], S)

def tuple_bound[S: tuple[int, str]](seq: S) -> None:
assert_type(seq[0], int)
"#,
);

testcase!(
test_restricted_typevar_subscript_return_self,
r#"
from typing import NamedTuple, Self, assert_type

class A:
def __getitem__(self, index: slice) -> Self:
return self

class B:
def __getitem__(self, index: slice) -> Self:
return self

class NT(NamedTuple):
x: int
y: str

def union_bound[S: A | B](seq: S) -> None:
assert_type(seq[0:1], S)

def constrained[S: (A, B)](seq: S) -> None:
assert_type(seq[0:1], S)

def named_tuple_bound[S: NT](seq: S) -> None:
assert_type(seq[0], int)

def list_bound[S: list[int]](seq: S) -> None:
assert_type(seq[0:1], list[int])

def not_subscriptable[S: int](x: S) -> None:
x[0] # E: Cannot index into `S`
"#,
);

testcase!(
test_typevar_single_constraint_is_error,
r#"
Expand Down
Loading