[ty] Don't confuse multiple occurrences of typing.Self when binding bound methods by dcreager · Pull Request #21754 · astral-sh/ruff (original) (raw)

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December 2, 2025 10:48

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Multi-file analysis & type inference

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Dec 2, 2025

dcreager added a commit that referenced this pull request

Dec 2, 2025

• origin/main: (67 commits) Move Token, TokenKind and Tokens to ruff-python-ast (#21760) [ty] Don't confuse multiple occurrences of typing.Self when binding bound methods (#21754) Use our org-wide Renovate preset (#21759) Delete my-script.py (#21751) [ty] Move all_members, and related types/routines, out of ide_support.rs (#21695) [ty] Fix find-references for import aliases (#21736) [ty] add tests for workspaces (#21741) [ty] Stop testing the (brittle) constraint set display implementation (#21743) [ty] Use generator over list comprehension to avoid cast (#21748) [ty] Add a diagnostic for prohibited NamedTuple attribute overrides (#21717) [ty] Fix subtyping with type[T] and unions (#21740) Use npm ci --ignore-scripts everywhere (#21742) [flake8-simplify] Fix truthiness assumption for non-iterable arguments in tuple/list/set calls (SIM222, SIM223) (#21479) [flake8-use-pathlib] Mark fixes unsafe for return type changes (PTH104, PTH105, PTH109, PTH115) (#21440) [ty] Fix auto-import code action to handle pre-existing import Enable PEP 740 attestations when publishing to PyPI (#21735) [ty] Fix find references for type defined in stub (#21732) Use OIDC instead of codspeed token (#21719) [ty] Exclude typing_extensions from completions unless it's really available [ty] Fix false positives for class F(Generic[*Ts]): ... (#21723) ...

AlexWaygood pushed a commit that referenced this pull request

Dec 2, 2025

… bound methods (#21754)

In the following example, there are two occurrences of typing.Self, one for Foo.foo and one for Bar.bar:

from typing import Self, reveal_type

class Foo[T]:
    def foo(self: Self) -> T:
        raise NotImplementedError

class Bar:
    def bar(self: Self, x: Foo[Self]):
        # SHOULD BE: bound method Foo[Self@bar].foo() -> Self@bar
        # revealed: bound method Foo[Self@bar].foo() -> Foo[Self@bar]
        reveal_type(x.foo)

def f[U: Bar](x: Foo[U]):
    # revealed: bound method Foo[U@f].foo() -> U@f
    reveal_type(x.foo)

When accessing a bound method, we replace any occurrences of Self with the bound self type.

We were doing this correctly for the second reveal. We would first apply the specialization, getting (self: Self@foo) -> U@F as the signature of x.foo. We would then bind the self parameter, substituting Self@foo with Foo[U@F] as part of that. The return type was already specialized to U@F, so that substitution had no further affect on the type that we revealed.

In the first reveal, we would follow the same process, but we confused the two occurrences of Self. We would first apply the specialization, getting (self: Self@foo) -> Self@bar as the method signature. We would then try to bind the self parameter, substituting Self@foo with Foo[Self@bar]. However, because we didn't distinguish the two separate Selfs, and applied the substitution to the return type as well as to the self parameter.

The fix is to track which particular Self we're trying to substitute when applying the type mapping.

Fixes astral-sh/ty#1713

dcreager added a commit that referenced this pull request

Dec 3, 2025

• origin/main: [ty] Improve @override, @final and Liskov checks in cases where there are multiple reachable definitions (#21767) [ty] Extend invalid-explicit-override to also cover properties decorated with @override that do not override anything (#21756) [ty] Enable LRU collection for parsed module (#21749) [ty] Support typevar-specialized dynamic types in generic type aliases (#21730) Add token based parenthesized_ranges implementation (#21738) [ty] Default-specialization of generic type aliases (#21765) [ty] Suppress false positives when dataclasses.dataclass(...)(cls) is called imperatively (#21729) [syntax-error] Default type parameter followed by non-default type parameter (#21657) new module for parsing ranged suppressions (#21441) [ty] type[T] is assignable to an inferable typevar (#21766) Fix syntax error false positives for await outside functions (#21763) [ty] Improve diagnostics for unsupported comparison operations (#21737) Move Token, TokenKind and Tokens to ruff-python-ast (#21760) [ty] Don't confuse multiple occurrences of typing.Self when binding bound methods (#21754) Use our org-wide Renovate preset (#21759) Delete my-script.py (#21751) [ty] Move all_members, and related types/routines, out of ide_support.rs (#21695)

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