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Carl Meyer c32234cf0d
[ty] support subscripting typing.Literal with a type alias (#21207) 
Fixes https://github.com/astral-sh/ty/issues/1368

## Summary

Add support for patterns like this, where a type alias to a literal type
(or union of literal types) is used to subscript `typing.Literal`:

```py
type MyAlias = Literal[1]
def _(x: Literal[MyAlias]): ...
```

This shows up in the ecosystem report for PEP 613 type alias support.

One interesting case is an alias to `bool` or an enum type. `bool` is an
equivalent type to `Literal[True, False]`, which is a union of literal
types. Similarly an enum type `E` is also equivalent to a union of its
member literal types. Since (for explicit type aliases) we infer the RHS
directly as a type expression, this makes it difficult for us to
distinguish between `bool` and `Literal[True, False]`, so we allow
either one to (or an alias to either one) to appear inside `Literal`,
where other type checkers allow only the latter.

I think for implicit type aliases it may be simpler to support only
types derived from actually subscripting `typing.Literal`, though, so I
didn't make a TODO-comment commitment here.

## Test Plan

Added mdtests, including TODO-filled tests for PEP 613 and implicit type
aliases.

### Conformance suite

All changes here are positive -- we now emit errors on lines that should
be errors. This is a side effect of the new implementation, not the
primary purpose of this PR, but it's still a positive change.

### Ecosystem

Eliminates one ecosystem false positive, where a PEP 695 type alias for
a union of literal types is used to subscript `typing.Literal`.
 		2025-11-02 12:39:55 -05:00
..
annotations [ty] support subscripting typing.Literal with a type alias (#21207) 2025-11-02 12:39:55 -05:00
assignment [ty] support subscripting typing.Literal with a type alias (#21207) 2025-11-02 12:39:55 -05:00
binary [ty] Sync vendored typeshed stubs (#20876) 2025-10-15 11:13:32 +02:00
boolean Revert "[ty] Better control flow for boolean expressions that are inside if (#18010)" (#18150) 2025-05-17 08:27:32 -04:00
boundness_declaredness [ty] Reformulation of public symbol inference test suite (#20667) 2025-10-01 14:26:17 +02:00
call [ty] Use declared attribute types as type context (#21143) 2025-10-31 15:48:28 +00:00
class [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
comparison [ty] detect cycles in binary comparison inference (#20446) 2025-09-17 09:45:25 +02:00
comprehensions [ty] Type inference for comprehensions (#20962) 2025-11-02 14:35:33 +01:00
conditional [ty] Support as-patterns in reachability analysis (#19728) 2025-08-04 20:13:50 +02:00
dataclasses [ty] Fix generic inference for non-dataclass inheriting from generic dataclass (#21159) 2025-10-31 13:55:17 +01:00
declaration [ty] Format conflicting types as an enumeration (#18956) 2025-06-26 14:29:33 +02:00
diagnostics [ty] `continue` and `break` statements outside loops are syntax errors (#20944) 2025-10-17 17:13:40 +00:00
directives [ty] Use annotated parameters as type context (#20635) 2025-10-03 17:14:51 -04:00
doc ty_python_semantic: add union type context to function call type errors 2025-05-09 13:40:51 -04:00
exception [ty] Filter out `revealed-type` and `undefined-reveal` diagnostics from mdtest snapshots (#20820) 2025-10-12 18:39:32 +00:00
expression [ty] Delegate truthiness inference of an enum `Literal` type to its enum-instance supertype (#21060) 2025-10-24 14:34:16 +01:00
function [ty] Improve disambiguation of types via fully qualified names (#20141) 2025-08-29 08:44:18 +00:00
generics [ty] Prefer exact matches when solving constrained type variables (#21165) 2025-10-31 10:58:09 -04:00
ide_support [ty] Filter out `revealed-type` and `undefined-reveal` diagnostics from mdtest snapshots (#20820) 2025-10-12 18:39:32 +00:00
import Consistently wrap tokens in parser diagnostics in `backticks` instead of 'quotes' (#21163) 2025-10-31 11:59:11 -04:00
literal [ty] Type inference for comprehensions (#20962) 2025-11-02 14:35:33 +01:00
loops [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
narrow [ty] Use the top materialization of classes for narrowing in class-patterns for `match` statements (#21150) 2025-10-30 20:44:51 +00:00
regression [ty] Type inference for comprehensions (#20962) 2025-11-02 14:35:33 +01:00
scopes [ty] Improve error messages for unresolved attribute diagnostics (#20963) 2025-10-19 10:58:25 +01:00
shadowing Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
snapshots [ty] don't assume in diagnostic messages that a TypedDict key error is about subscript access (#21166) 2025-10-31 10:49:59 -04:00
stubs [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
subscript [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
suppressions [ty] Add suggestion to unknown rule diagnostics, rename `unknown-rule` lint to `ignore-comment-unknown-rule` (#20948) 2025-10-18 12:44:21 +02:00
type_compendium [ty] Heterogeneous unpacking support for unions (#20377) 2025-10-15 19:30:03 +01:00
type_of [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
type_properties [ty] Add and test when constraint sets are satisfied by their typevars (#21129) 2025-10-31 10:53:37 -04:00
type_qualifiers [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
unary Update class literal display to use `<class 'Foo'>` style (#17889) 2025-05-06 20:11:25 -04:00
with [ty] Use `typing.Self` for the first parameter of instance methods (#20517) 2025-09-29 21:08:08 +02:00
.mdformat.toml Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
async.md [ty] Support `async`/`await`, `async with` and `yield from` (#19595) 2025-07-30 11:51:21 +02:00
attributes.md [ty] Use `range` instead of custom `IntIterable` (#21138) 2025-10-30 15:21:55 +01:00
bidirectional.md [ty] Support type context of union attribute assignments (#21170) 2025-10-31 12:41:14 -04:00
classes.md [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
cycle.md [ty] Avoid ever-growing default types (#20991) 2025-10-21 19:13:36 +02:00
decorators.md ty_python_semantic: add union type context to function call type errors 2025-05-09 13:40:51 -04:00
del.md [ty] No union with `Unknown` for module-global symbols (#20664) 2025-10-01 16:40:30 +02:00
deprecated.md [ty] Consistent use of American english (in rules) (#19488) 2025-07-22 16:10:38 +02:00
descriptor_protocol.md [ty] Infer type for implicit `self` parameters in method bodies (#20922) 2025-10-23 09:34:39 +02:00
enums.md [ty] Enums: allow multiple aliases to point to the same member (#20669) 2025-10-01 15:51:53 +02:00
exhaustiveness_checking.md [ty] Improve exhaustiveness analysis for type variables with bounds or constraints (#21172) 2025-10-31 16:51:11 -04:00
final.md Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
implicit_type_aliases.md [ty] no more diverging query cycles in type expressions (#20359) 2025-09-16 16:44:11 -07:00
instance_layout_conflict.md [ty] initial support for `slots=True` in dataclasses (#20278) 2025-09-07 18:25:35 +01:00
intersection_types.md [ty] Expansion of enums into unions of literals (#19382) 2025-07-21 19:37:55 +02:00
invalid_syntax.md Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
known_constants.md Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
literal_promotion.md [ty] Do not promote literals in contravariant positions of generic specializations (#21171) 2025-10-31 17:48:34 +01:00
mdtest_config.md Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
mdtest_custom_typeshed.md [ty] Remove `Type::Tuple` (#19669) 2025-08-11 22:03:32 +01:00
metaclass.md Update class literal display to use `<class 'Foo'>` style (#17889) 2025-05-06 20:11:25 -04:00
mro.md [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
named_tuple.md [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
overloads.md [ty] Infer type of `self` for decorated methods and properties (#21123) 2025-10-29 21:22:38 +00:00
pep613_type_aliases.md [ty] Fall back to `Divergent` for deeply nested specializations (#20988) 2025-10-22 14:29:10 +02:00
pep695_type_aliases.md [ty] Add cycle handling to `lazy_default` (#20967) 2025-10-23 10:05:08 +02:00
properties.md [ty] `"foo".startswith` is not an instance of `types.MethodWrapperType` (#20317) 2025-09-10 11:14:26 +00:00
protocols.md [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
public_types.md [ty] Disambiguate classes that live in different modules but have the same fully qualified names (#20756) 2025-10-08 18:27:40 +01:00
statically_known_branches.md [ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492) 2025-09-23 14:26:55 +00:00
sys_platform.md Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
sys_version_info.md Rename Red Knot (#17820) 2025-05-03 19:49:15 +02:00
t_strings.md [ty] Add support for PEP 750 t-strings (#20085) 2025-08-25 18:49:49 +00:00
terminal_statements.md [ty] improve lazy scope place lookup (#19321) 2025-07-25 07:11:11 +00:00
ty_extensions.md [ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995) 2025-10-27 11:19:12 +00:00
typed_dict.md [ty] rollback preferring declared type on invalid TypedDict creation (#21169) 2025-10-31 12:06:47 -04:00
union_types.md [ty] Introduce `TypeRelation::Redundancy` (#20602) 2025-10-03 18:35:30 +01:00
unpacking.md [ty] Infer more precise types for collection literals (#20360) 2025-09-17 18:51:50 -04:00
unreachable.md [ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492) 2025-09-23 14:26:55 +00:00