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[red-knot] detect unreachable attribute assignments (#16852)

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## Summary

This PR closes #15967.

Attribute assignments that are statically known to be unreachable are
excluded from consideration for implicit instance attribute type
inference. If none of the assignments are found to be reachable, an
`unresolved-attribute` error is reported.

## Test Plan

[A test
case](https://github.com/astral-sh/ruff/blob/main/crates/red_knot_python_semantic/resources/mdtest/attributes.md#attributes-defined-in-statically-known-to-be-false-branches)
marked as TODO now work as intended, and new test cases have been added.

---------

Co-authored-by: David Peter <mail@david-peter.de>
This commit is contained in:
Shunsuke Shibayama 2025-04-14 16:23:20 +09:00 • committed by GitHub
parent 3aa3ee8b89
commit dfd8eaeb32
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GPG key ID: B5690EEEBB952194
10 changed files with 764 additions and 328 deletions
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39
crates/red_knot_python_semantic/src/semantic_index.rs
View file

@ -13,7 +13,6 @@ use crate::module_name::ModuleName;
use crate::node_key::NodeKey;
use crate::semantic_index::ast_ids::node_key::ExpressionNodeKey;
use crate::semantic_index::ast_ids::AstIds;
use crate::semantic_index::attribute_assignment::AttributeAssignments;
use crate::semantic_index::builder::SemanticIndexBuilder;
use crate::semantic_index::definition::{Definition, DefinitionNodeKey, Definitions};
use crate::semantic_index::expression::Expression;
@ -24,7 +23,6 @@ use crate::semantic_index::use_def::{EagerBindingsKey, ScopedEagerBindingsId, Us
use crate::Db;
pub mod ast_ids;
pub mod attribute_assignment;
mod builder;
pub mod definition;
pub mod expression;
@ -98,23 +96,25 @@ pub(crate) fn use_def_map<'db>(db: &'db dyn Db, scope: ScopeId<'db>) -> Arc<UseD
index.use_def_map(scope.file_scope_id(db))
}
/// Returns all attribute assignments for a specific class body scope.
///
/// Using [`attribute_assignments`] over [`semantic_index`] has the advantage that
/// Salsa can avoid invalidating dependent queries if this scope's instance attributes
/// are unchanged.
#[salsa::tracked]
pub(crate) fn attribute_assignments<'db>(
/// Returns all attribute assignments (and their method scope IDs) for a specific class body scope.
/// Only call this when doing type inference on the same file as `class_body_scope`, otherwise it
/// introduces a direct dependency on that file's AST.
pub(crate) fn attribute_assignments<'db, 's>(
db: &'db dyn Db,
class_body_scope: ScopeId<'db>,
) -> Option<Arc<AttributeAssignments<'db>>> {
name: &'s str,
) -> impl Iterator<Item = (BindingWithConstraintsIterator<'db, 'db>, FileScopeId)> + use<'s, 'db> {
let file = class_body_scope.file(db);
let index = semantic_index(db, file);
let class_scope_id = class_body_scope.file_scope_id(db);
index
.attribute_assignments
.get(&class_body_scope.file_scope_id(db))
.cloned()
ChildrenIter::new(index, class_scope_id).filter_map(|(file_scope_id, maybe_method)| {
maybe_method.node().as_function()?;
let attribute_table = index.instance_attribute_table(file_scope_id);
let symbol = attribute_table.symbol_id_by_name(name)?;
let use_def = &index.use_def_maps[file_scope_id];
Some((use_def.instance_attribute_bindings(symbol), file_scope_id))
})
}
/// Returns the module global scope of `file`.
@ -137,6 +137,9 @@ pub(crate) struct SemanticIndex<'db> {
/// List of all symbol tables in this file, indexed by scope.
symbol_tables: IndexVec<FileScopeId, Arc<SymbolTable>>,
/// List of all instance attribute tables in this file, indexed by scope.
instance_attribute_tables: IndexVec<FileScopeId, SymbolTable>,
/// List of all scopes in this file.
scopes: IndexVec<FileScopeId, Scope>,
@ -170,10 +173,6 @@ pub(crate) struct SemanticIndex<'db> {
/// Flags about the global scope (code usage impacting inference)
has_future_annotations: bool,
/// Maps from class body scopes to attribute assignments that were found
/// in methods of that class.
attribute_assignments: FxHashMap<FileScopeId, Arc<AttributeAssignments<'db>>>,
/// Map of all of the eager bindings that appear in this file.
eager_bindings: FxHashMap<EagerBindingsKey, ScopedEagerBindingsId>,
}
@ -188,6 +187,10 @@ impl<'db> SemanticIndex<'db> {
self.symbol_tables[scope_id].clone()
}
pub(super) fn instance_attribute_table(&self, scope_id: FileScopeId) -> &SymbolTable {
&self.instance_attribute_tables[scope_id]
}
/// Returns the use-def map for a specific scope.
///
/// Use the Salsa cached [`use_def_map()`] query if you only need the