[ty] Disallow illegal uses of ClassVar
#19483
Conversation
|
| def __init__(self) -> None: | ||
| # error: [invalid-type-form] "`ClassVar` annotations are not allowed for non-name targets" | ||
| self.x: ClassVar[int] = 1 |
There was a problem hiding this comment.
Does the spec explicitly forbid something like this?
class C:
@classmethod
def f(cls):
cls.x: ClassVar[int] = 1There was a problem hiding this comment.
Does the spec explicitly forbid something like this?
It does not explicitly forbid it. It does say "ClassVar may be used in one of several forms:" and then proceeds to show two examples where ClassVar is used at the class-body level.
Mypy, pyright and pyrefly all reject your example for various reasons (including: "ClassVar" is not allowed in this context).
I also didn't find any references of code like this in the ecosystem.
There was a problem hiding this comment.
I think it would be reasonable to support that, but I also don't think it's high priority at all, especially if no other type checker does.
There was a problem hiding this comment.
By "support that", you mean: "tolerate that"? Because I'm not sure what the intention here would be? When would a cls.x: … = 1 attribute not be a (pure) class variable?
There was a problem hiding this comment.
I guess if it were declared with x: int = 42 in the class body, then that would make it an instance attribute with a class-level default, and cls.x = 56 in a class method would be mutating the default value of the instance attribute? That's a bit suspect, though; I'd consider it at least a code smell.
And I suppose we'd want to emit an error if it were declared as an instance variable in an instance method or the class body, but declared as a class variable in a classmethod
crates/ty_python_semantic/resources/mdtest/type_qualifiers/classvar.md
Outdated
Show resolved
Hide resolved
* main: (76 commits) Move fix suggestion to subdiagnostic (#19464) [ty] Implement non-stdlib stub mapping for classes and functions (#19471) [ty] Disallow illegal uses of `ClassVar` (#19483) [ty] Disallow `Final` in function parameter/return-type annotations (#19480) [ty] Extend `Final` test suite (#19476) [ty] Minor change to diagnostic message for invalid Literal uses (#19482) [ty] Detect illegal non-enum attribute accesses in Literal annotation (#19477) [ty] Reduce size of `TypeInference` (#19435) Run MD tests for Markdown-only changes (#19479) Revert "[ty] Detect illegal non-enum attribute accesses in Literal annotation" [ty] Detect illegal non-enum attribute accesses in Literal annotation [ty] Added semantic token support for more identifiers (#19473) [ty] Make tuple subclass constructors sound (#19469) [ty] Pass down specialization to generic dataclass bases (#19472) [ty] Garbage-collect reachability constraints (#19414) [ty] Implicit instance attributes declared `Final` (#19462) [ty] Expansion of enums into unions of literals (#19382) [ty] Avoid rechecking the entire project when changing the opened files (#19463) [ty] Add warning for unknown `TY_MEMORY_REPORT` value (#19465) [ty] Sync vendored typeshed stubs (#19461) ...
* main: [ty] Use `ThinVec` for sub segments in `PlaceExpr` (#19470) [ty] Splat variadic arguments into parameter list (#18996) [`flake8-pyi`] Skip fix if all `Union` members are `None` (`PYI016`) (#19416) Skip notebook with errors in ecosystem check (#19491) [ty] Consistent use of American english (in rules) (#19488) [ty] Support iterating over enums (#19486) Fix panic for illegal `Literal[…]` annotations with inner subscript expressions (#19489) Move fix suggestion to subdiagnostic (#19464) [ty] Implement non-stdlib stub mapping for classes and functions (#19471) [ty] Disallow illegal uses of `ClassVar` (#19483) [ty] Disallow `Final` in function parameter/return-type annotations (#19480) [ty] Extend `Final` test suite (#19476) [ty] Minor change to diagnostic message for invalid Literal uses (#19482) [ty] Detect illegal non-enum attribute accesses in Literal annotation (#19477) [ty] Reduce size of `TypeInference` (#19435) Run MD tests for Markdown-only changes (#19479) Revert "[ty] Detect illegal non-enum attribute accesses in Literal annotation" [ty] Detect illegal non-enum attribute accesses in Literal annotation [ty] Added semantic token support for more identifiers (#19473) [ty] Make tuple subclass constructors sound (#19469)
* main: (28 commits) [ty] highlight the argument in `static_assert` error messages (astral-sh#19426) [ty] Infer single-valuedness for enums based on `int`/`str` (astral-sh#19510) [ty] Restructure submodule query around `File` dependency [ty] Make `Module` a Salsa ingredient [ty] Reachability analysis for `isinstance(…)` branches (astral-sh#19503) [ty] Normalize single-member enums to their instance type (astral-sh#19502) [ty] Invert `ty_ide` and `ty_project` dependency (astral-sh#19501) [ty] Implement mock language server for testing (astral-sh#19391) [ty] Detect enums if metaclass is a subtype of EnumType/EnumMeta (astral-sh#19481) [ty] perform type narrowing for places marked `global` too (astral-sh#19381) [ty] Use `ThinVec` for sub segments in `PlaceExpr` (astral-sh#19470) [ty] Splat variadic arguments into parameter list (astral-sh#18996) [`flake8-pyi`] Skip fix if all `Union` members are `None` (`PYI016`) (astral-sh#19416) Skip notebook with errors in ecosystem check (astral-sh#19491) [ty] Consistent use of American english (in rules) (astral-sh#19488) [ty] Support iterating over enums (astral-sh#19486) Fix panic for illegal `Literal[…]` annotations with inner subscript expressions (astral-sh#19489) Move fix suggestion to subdiagnostic (astral-sh#19464) [ty] Implement non-stdlib stub mapping for classes and functions (astral-sh#19471) [ty] Disallow illegal uses of `ClassVar` (astral-sh#19483) ... # Conflicts: # crates/ty_ide/src/goto.rs
Summary
It was faster to implement this then to write the ticket: Disallow
ClassVarannotations almost everywhere outside of class body scopes.Test Plan
New Markdown tests