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[ty] Fix incorrect diagnostic when calling __setitem__ (#19645)

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## Summary

Resolves https://github.com/astral-sh/ty/issues/862 by not emitting a
diagnostic.

## Test Plan

Add test to show we don't emit the diagnostic
This commit is contained in:
Matthew Mckee 2025-07-30 19:34:52 +01:00 • committed by GitHub
parent 7b4103bcb6
commit 4739bc8d14
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GPG key ID: B5690EEEBB952194
3 changed files with 35 additions and 19 deletions
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1
crates/ty_python_semantic/resources/mdtest/narrow/assignment.md
View file

@ -253,7 +253,6 @@ does["not"]["exist"] = 0
reveal_type(does["not"]["exist"]) # revealed: Unknown
non_subscriptable = 1
# error: [non-subscriptable]
non_subscriptable[0] = 0
# error: [non-subscriptable]
reveal_type(non_subscriptable[0]) # revealed: Unknown

19
crates/ty_python_semantic/resources/mdtest/subscript/instance.md
View file

@ -1,6 +1,6 @@
# Instance subscript
## Getitem unbound
## `__getitem__` unbound
```py
class NotSubscriptable: ...
@ -8,7 +8,7 @@ class NotSubscriptable: ...
a = NotSubscriptable()[0] # error: "Cannot subscript object of type `NotSubscriptable` with no `__getitem__` method"
```
## Getitem not callable
## `__getitem__` not callable
```py
class NotSubscriptable:
@ -18,7 +18,7 @@ class NotSubscriptable:
a = NotSubscriptable()[0]
```
## Valid getitem
## Valid `__getitem__`
```py
class Identity:
@ -28,7 +28,7 @@ class Identity:
reveal_type(Identity()[0]) # revealed: int
```
## Getitem union
## `__getitem__` union
```py
def _(flag: bool):
@ -42,3 +42,14 @@ def _(flag: bool):
reveal_type(Identity()[0]) # revealed: int | str
```
## `__setitem__` with no `__getitem__`
```py
class NoGetitem:
def __setitem__(self, index: int, value: int) -> None:
pass
a = NoGetitem()
a[0] = 0
```

34
crates/ty_python_semantic/src/types/infer.rs
View file

@ -1900,13 +1900,14 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
} else if let AnyNodeRef::ExprSubscript(ast::ExprSubscript {
value,
slice,
ctx,
..
}) = node
{
let value_ty = self.infer_expression(value);
let slice_ty = self.infer_expression(slice);
let result_ty =
self.infer_subscript_expression_types(value, value_ty, slice_ty);
let result_ty = self
.infer_subscript_expression_types(value, value_ty, slice_ty, *ctx);
return (result_ty, is_modifiable);
}
}
@ -8291,7 +8292,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
ExprContext::Store => {
let value_ty = self.infer_expression(value);
let slice_ty = self.infer_expression(slice);
self.infer_subscript_expression_types(value, value_ty, slice_ty);
self.infer_subscript_expression_types(value, value_ty, slice_ty, *ctx);
Type::Never
}
ExprContext::Del => {
@ -8301,7 +8302,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
ExprContext::Invalid => {
let value_ty = self.infer_expression(value);
let slice_ty = self.infer_expression(slice);
self.infer_subscript_expression_types(value, value_ty, slice_ty);
self.infer_subscript_expression_types(value, value_ty, slice_ty, *ctx);
Type::unknown()
}
}
@ -8313,7 +8314,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
node_index: _,
value,
slice,
ctx: _,
ctx,
} = subscript;
let value_ty = self.infer_expression(value);
let mut constraint_keys = vec![];
@ -8330,7 +8331,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
// Even if we can obtain the subscript type based on the assignments, we still perform default type inference
// (to store the expression type and to report errors).
let slice_ty = self.infer_expression(slice);
self.infer_subscript_expression_types(value, value_ty, slice_ty);
self.infer_subscript_expression_types(value, value_ty, slice_ty, *ctx);
return ty;
}
}
@ -8364,7 +8365,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
}
let slice_ty = self.infer_expression(slice);
let result_ty = self.infer_subscript_expression_types(value, value_ty, slice_ty);
let result_ty = self.infer_subscript_expression_types(value, value_ty, slice_ty, *ctx);
self.narrow_expr_with_applicable_constraints(subscript, result_ty, &constraint_keys)
}
@ -8418,6 +8419,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
value_node: &ast::Expr,
value_ty: Type<'db>,
slice_ty: Type<'db>,
expr_context: ExprContext,
) -> Type<'db> {
match (value_ty, slice_ty, slice_ty.slice_literal(self.db())) {
(Type::NominalInstance(instance), _, _)
@ -8427,11 +8429,12 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
value_node,
Type::version_info_tuple(self.db()),
slice_ty,
expr_context,
)
}
(Type::Union(union), _, _) => union.map(self.db(), |element| {
self.infer_subscript_expression_types(value_node, *element, slice_ty)
self.infer_subscript_expression_types(value_node, *element, slice_ty, expr_context)
}),
// TODO: we can map over the intersection and fold the results back into an intersection,
@ -8562,6 +8565,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
value_node,
value_ty,
Type::IntLiteral(i64::from(bool)),
expr_context,
),
(Type::SpecialForm(SpecialFormType::Protocol), Type::Tuple(typevars), _) => {
@ -8754,12 +8758,14 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
);
}
} else {
report_non_subscriptable(
&self.context,
value_node.into(),
value_ty,
"__getitem__",
);
if expr_context != ExprContext::Store {
report_non_subscriptable(
&self.context,
value_node.into(),
value_ty,
"__getitem__",
);
}
}
Type::unknown()