[ty] Add precise inference for unpacking a TypeVar if the TypeVar has an upper bound with a precise tuple spec #19985
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
… an upper bound with a precise tuple spec
AlexWaygood
commented
Aug 19, 2025
AlexWaygood
commented
Aug 19, 2025
Comment on lines
472
to
493
| @dataclass | ||
| class Team[T: tuple[int, str]]: | ||
| employees: list[T] | ||
|
|
||
| def x[T: tuple[int, str]](team: Team[T]): | ||
| age, name = team.employees[0] | ||
| reveal_type(age) # revealed: int | ||
| reveal_type(name) # revealed: str | ||
|
|
||
| class Age(int): ... | ||
| class Name(str): ... | ||
|
|
||
| class Employee(NamedTuple): | ||
| age: Age | ||
| name: Name | ||
|
|
||
| EMPLOYEES: Final = (Employee(name=Name("alice"), age=Age(42)),) | ||
| team = Team(employees=list(EMPLOYEES)) | ||
| reveal_type(team.employees) # revealed: list[Employee] | ||
| age, name = team.employees[0] | ||
| reveal_type(age) # revealed: Age | ||
| reveal_type(name) # revealed: Name |
There was a problem hiding this comment.
I enjoyed writing this test. So cool to see the number of features that are coming together here 😃
Diagnostic diff on typing conformance testsNo changes detected when running ty on typing conformance tests ✅ |
|
dcreager
approved these changes
Aug 19, 2025
crates/ty_python_semantic/resources/mdtest/generics/legacy/functions.md
Outdated
Show resolved
Hide resolved
carljm
approved these changes
Aug 19, 2025
crates/ty_python_semantic/resources/mdtest/generics/legacy/functions.md
Outdated
Show resolved
Hide resolved
crates/ty_python_semantic/resources/mdtest/generics/legacy/functions.md
Outdated
Show resolved
Hide resolved
crates/ty_python_semantic/resources/mdtest/generics/pep695/functions.md
Outdated
Show resolved
Hide resolved
AlexWaygood
commented
Aug 19, 2025
crates/ty_python_semantic/resources/mdtest/generics/legacy/functions.md
Outdated
Show resolved
Hide resolved
AlexWaygood
commented
Aug 19, 2025
crates/ty_python_semantic/resources/mdtest/generics/pep695/functions.md
Outdated
Show resolved
Hide resolved
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Summary
If the upper bound of a TypeVar can be unpacked, then so can the TypeVar, because no solutions of the TypeVar exist that would not be assignable to the TypeVar's upper bound.
This is similar in spirit to #19981!
Test Plan
Mdtests