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[red-knot] Trust module-level undeclared symbols in stubs #17577

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Merged
sharkdp merged 1 commit into from
Apr 23, 2025
Merged

[red-knot] Trust module-level undeclared symbols in stubs #17577

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2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/scopes/eager.md
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Original file line number Diff line number Diff line change
Expand Up @@ -404,7 +404,7 @@ x = int
class C:
var: ClassVar[x]

reveal_type(C.var) # revealed: Unknown | str
reveal_type(C.var) # revealed: str

x = str
```
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2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/subscript/lists.md
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Expand Up @@ -12,7 +12,7 @@ x = [1, 2, 3]
reveal_type(x) # revealed: list

# TODO reveal int
reveal_type(x[0]) # revealed: Unknown
reveal_type(x[0]) # revealed: @Todo(Support for `typing.TypeVar` instances in type expressions)

# TODO reveal list
reveal_type(x[0:1]) # revealed: @Todo(specialized non-generic class)
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5 changes: 1 addition & 4 deletions crates/red_knot_python_semantic/resources/mdtest/type_properties/is_singleton.md
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Expand Up @@ -128,10 +128,7 @@ python-version = "3.10"
import types
from knot_extensions import static_assert, is_singleton

# TODO: types.NotImplementedType is a TypeAlias of builtins._NotImplementedType
# Once TypeAlias support is added, it should satisfy `is_singleton`
reveal_type(types.NotImplementedType) # revealed: Unknown | Literal[_NotImplementedType]
static_assert(not is_singleton(types.NotImplementedType))
static_assert(is_singleton(types.NotImplementedType))
```

### Callables
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8 changes: 8 additions & 0 deletions crates/red_knot_python_semantic/src/semantic_index/symbol.rs
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Expand Up @@ -115,6 +115,10 @@ impl<'db> ScopeId<'db> {
self.node(db).scope_kind().is_function_like()
}

pub(crate) fn is_module_scope(self, db: &'db dyn Db) -> bool {
self.node(db).scope_kind().is_module()
}

pub(crate) fn is_type_parameter(self, db: &'db dyn Db) -> bool {
self.node(db).scope_kind().is_type_parameter()
}
Expand Down Expand Up @@ -263,6 +267,10 @@ impl ScopeKind {
matches!(self, ScopeKind::Class)
}

pub(crate) fn is_module(self) -> bool {
matches!(self, ScopeKind::Module)
}

pub(crate) fn is_type_parameter(self) -> bool {
matches!(self, ScopeKind::Annotation | ScopeKind::TypeAlias)
}
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14 changes: 12 additions & 2 deletions crates/red_knot_python_semantic/src/symbol.rs
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Expand Up @@ -593,8 +593,18 @@ fn symbol_by_id<'db>(
"__slots__" | "TYPE_CHECKING"
);

widen_type_for_undeclared_public_symbol(db, inferred, is_considered_non_modifiable)
.into()
if scope.is_module_scope(db) && scope.file(db).is_stub(db.upcast()) {
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@AlexWaygood AlexWaygood Apr 23, 2025

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why only at the module level? Typeshed does things like this as well, and I think there's an argument to be made that the public type for DeprecatedNameForThing should also not be unioned with Unknown here:

class Foo:
    THING: Final = 42
    DeprecatedNameForThing = THING

it feels consistent with the idea behind this PR.

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@sharkdp sharkdp Apr 23, 2025

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I didn't have this restriction initially, but then added it because Carl suggested this as a rule here: #17032 (comment). What was your reasoning @carljm?

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@sharkdp sharkdp Apr 23, 2025

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I'm going to do the following: I'm going to merge this as-is, and then re-open another PR with that restriction lifted. This should allow us to see the impact in a better way.

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@AlexWaygood AlexWaygood Apr 23, 2025

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Sounds good!

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@carljm carljm Apr 23, 2025 •
edited
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I do think the same rationale applies; I don't think I carefully thought through the class-scope case as even a thing that would happen in stub files.

// We generally trust module-level undeclared symbols in stubs and do not union
// with `Unknown`. If we don't do this, simple aliases like `IOError = OSError` in
// stubs would result in `IOError` being a union of `OSError` and `Unknown`, which
// leads to all sorts of downstream problems. Similarly, type variables are often
// defined as `_T = TypeVar("_T")`, without being declared.

inferred.into()
} else {
widen_type_for_undeclared_public_symbol(db, inferred, is_considered_non_modifiable)
.into()
}
}
// Symbol has conflicting declared types
Err((declared, _)) => {
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5 changes: 1 addition & 4 deletions crates/red_knot_python_semantic/src/types/signatures.rs
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Expand Up @@ -1631,10 +1631,7 @@ mod tests {
assert_eq!(a_name, "a");
assert_eq!(b_name, "b");
// Parameter resolution deferred; we should see B
assert_eq!(
a_annotated_ty.unwrap().display(&db).to_string(),
"Unknown | B"
);
assert_eq!(a_annotated_ty.unwrap().display(&db).to_string(), "B");
assert_eq!(b_annotated_ty.unwrap().display(&db).to_string(), "T");
}

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