Alex Waygood c91b457044 [ty] Introduce TypeRelation::Redundancy (#20602) ... ## Summary The union `T | U` can be validly simplified to `U` iff: 1. `T` is a subtype of `U` OR 2. `T` is equivalent to `U` OR 3. `U` is a union and contains a type that is equivalent to `T` OR 4. `T` is an intersection and contains a type that is equivalent to `U` (In practice, the only situation in which 2, 3 or 4 would be true when (1) was not true would be if `T` or `U` is a dynamic type.) Currently we achieve these simplifications in the union builder by doing something along the lines of `t.is_subtype_of(db, u) || t.is_equivalent_to_(db, u) || t.into_intersection().is_some_and(|intersection| intersection.positive(db).contains(&u)) || u.into_union().is_some_and(|union| union.elements(db).contains(&t))`. But this is both slow and misses some cases (it doesn't simplify the union `Any | (Unknown & ~None)` to `Any`, for example). We can improve the consistency and performance of our union simplifications by adding a third type relation that sits in between `TypeRelation::Subtyping` and `TypeRelation::Assignability`: `TypeRelation::UnionSimplification`. This change leads to simpler, more user-friendly types due to the more consistent simplification. It also lead to a pretty huge performance improvement! ## Test Plan Existing tests, plus some new ones.		2025-10-03 18:35:30 +01:00
..
annotations	[ty] Use typing.Self for the first parameter of instance methods (#20517)	2025-09-29 21:08:08 +02:00
assignment	[ty] More precise type inference for dictionary literals (#20523)	2025-09-24 18:12:00 -04:00
binary	[ty] Remove special casing for string-literal-in-tuple __contains__ (#19642)	2025-07-31 11:28:03 +01:00
boolean
boundness_declaredness	[ty] Reformulation of public symbol inference test suite (#20667)	2025-10-01 14:26:17 +02:00
call	[ty] Support single-starred argument for overload call (#20223)	2025-10-02 10:41:56 -04:00
class	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
comparison	[ty] detect cycles in binary comparison inference (#20446)	2025-09-17 09:45:25 +02:00
comprehensions	[ty] Async for loops and async iterables (#19634)	2025-07-30 17:40:24 +02:00
conditional	[ty] Support as-patterns in reachability analysis (#19728)	2025-08-04 20:13:50 +02:00
dataclasses	[ty] initial support for slots=True in dataclasses (#20278)	2025-09-07 18:25:35 +01:00
declaration
diagnostics	[ty] Use fully qualified names to distinguish ambiguous protocols in diagnostics (#20627)	2025-09-29 12:02:07 +00:00
directives	[ty] Infer slightly more precise types for comprehensions (#20111)	2025-08-27 13:21:47 +01:00
doc
exception	[ty] Use separate Rust types for bound and unbound type variables (#19796)	2025-08-11 15:29:58 -04:00
expression	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
function	[ty] Improve disambiguation of types via fully qualified names (#20141)	2025-08-29 08:44:18 +00:00
generics	[ty] ~T should never be assignable to T (#20606)	2025-10-02 07:52:47 +01:00
ide_support	[ty] Include NamedTupleFallback members in NamedTuple instance completions (#20356)	2025-09-15 11:00:03 +02:00
import	[ty] No union with Unknown for module-global symbols (#20664)	2025-10-01 16:40:30 +02:00
literal	[ty] More precise type inference for dictionary literals (#20523)	2025-09-24 18:12:00 -04:00
loops	[ty] Add more tests for subtyping/assignability between two protocol types (#20573)	2025-09-26 12:07:57 +01:00
narrow	[ty] No union with Unknown for module-global symbols (#20664)	2025-10-01 16:40:30 +02:00
regression
scopes	[ty] No union with Unknown for module-global symbols (#20664)	2025-10-01 16:40:30 +02:00
shadowing
snapshots	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
stubs
subscript	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
suppressions
type_compendium	[ty] Infer more precise types for collection literals (#20360)	2025-09-17 18:51:50 -04:00
type_of	[ty] Improve the Display for generic type[] types (#19667)	2025-07-31 19:45:01 +01:00
type_properties	[ty] Introduce TypeRelation::Redundancy (#20602)	2025-10-03 18:35:30 +01:00
type_qualifiers	[ty] Allow annotation expressions to be ast::Attribute nodes (#20413)	2025-09-15 12:06:48 +01:00
unary
with	[ty] Use typing.Self for the first parameter of instance methods (#20517)	2025-09-29 21:08:08 +02:00
.mdformat.toml
async.md	[ty] Support async/await, async with and yield from (#19595)	2025-07-30 11:51:21 +02:00
attributes.md	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
classes.md	[ty] don't assume that deferred type inference means deferred name resolution (#20160)	2025-08-29 16:19:45 -07:00
cycle.md
decorators.md
del.md	[ty] No union with Unknown for module-global symbols (#20664)	2025-10-01 16:40:30 +02:00
deprecated.md
descriptor_protocol.md	[ty] Use typing.Self for the first parameter of instance methods (#20517)	2025-09-29 21:08:08 +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] Fix subtyping for dynamic specializations (#20592)	2025-09-26 15:05:03 +02:00
final.md
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
invalid_syntax.md
known_constants.md
mdtest_config.md
mdtest_custom_typeshed.md	[ty] Remove Type::Tuple (#19669)	2025-08-11 22:03:32 +01:00
metaclass.md
mro.md	[ty] Treat Hashable, and similar protocols, equivalently to object for subtyping/assignability (#20284)	2025-09-10 11:38:58 +01:00
named_tuple.md	[ty] Use typing.Self for the first parameter of instance methods (#20517)	2025-09-29 21:08:08 +02:00
overloads.md	[ty] Use C[T] instead of C[Unknown] for the upper bound of Self (#20479)	2025-09-23 14:02:25 +02:00
pep695_type_aliases.md	[ty] Use typing.Self for the first parameter of instance methods (#20517)	2025-09-29 21:08:08 +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] Literal promotion refactor (#20646)	2025-09-30 14:22:36 +02:00
public_types.md	[ty] No union with Unknown for module-global symbols (#20664)	2025-10-01 16:40:30 +02:00
statically_known_branches.md	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
sys_platform.md
sys_version_info.md
t_strings.md	[ty] Add support for PEP 750 t-strings (#20085)	2025-08-25 18:49:49 +00:00
terminal_statements.md
ty_extensions.md	[ty] Fix CallableTypeOf[…] for classmethods (#20345)	2025-09-11 10:14:38 +02:00
typed_dict.md	[ty] Use typing.Self for the first parameter of instance methods (#20517)	2025-09-29 21:08:08 +02:00
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