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[ty] basic narrowing on attribute and subscript expressions (#17643)

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## Summary

This PR closes astral-sh/ty#164.

This PR introduces a basic type narrowing mechanism for
attribute/subscript expressions.
Member accesses, int literal subscripts, string literal subscripts are
supported (same as mypy and pyright).

## Test Plan

New test cases are added to `mdtest/narrow/complex_target.md`.

---------

Co-authored-by: David Peter <mail@david-peter.de>
This commit is contained in:
Shunsuke Shibayama 2025-06-17 18:07:46 +09:00 • committed by GitHub
parent 390918e790
commit 342b2665db
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GPG key ID: B5690EEEBB952194
15 changed files with 739 additions and 327 deletions
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23
crates/ty_python_semantic/src/semantic_index/builder.rs
View file

@ -33,7 +33,7 @@ use crate::semantic_index::definition::{
use crate::semantic_index::expression::{Expression, ExpressionKind};
use crate::semantic_index::place::{
FileScopeId, NodeWithScopeKey, NodeWithScopeKind, NodeWithScopeRef, PlaceExpr,
PlaceTableBuilder, Scope, ScopeId, ScopeKind, ScopedPlaceId,
PlaceExprWithFlags, PlaceTableBuilder, Scope, ScopeId, ScopeKind, ScopedPlaceId,
};
use crate::semantic_index::predicate::{
PatternPredicate, PatternPredicateKind, Predicate, PredicateNode, ScopedPredicateId,
@ -295,6 +295,15 @@ impl<'db, 'ast> SemanticIndexBuilder<'db, 'ast> {
// If the scope that we just popped off is an eager scope, we need to "lock" our view of
// which bindings reach each of the uses in the scope. Loop through each enclosing scope,
// looking for any that bind each place.
// TODO: Bindings in eager nested scopes also need to be recorded. For example:
// ```python
// class C:
// x: int | None = None
// c = C()
// class _:
// c.x = 1
// reveal_type(c.x) # revealed: Literal[1]
// ```
for enclosing_scope_info in self.scope_stack.iter().rev() {
let enclosing_scope_id = enclosing_scope_info.file_scope_id;
let enclosing_scope_kind = self.scopes[enclosing_scope_id].kind();
@ -306,7 +315,8 @@ impl<'db, 'ast> SemanticIndexBuilder<'db, 'ast> {
// it may refer to the enclosing scope bindings
// so we also need to snapshot the bindings of the enclosing scope.
let Some(enclosing_place_id) = enclosing_place_table.place_id_by_expr(nested_place)
let Some(enclosing_place_id) =
enclosing_place_table.place_id_by_expr(&nested_place.expr)
else {
continue;
};
@ -388,7 +398,7 @@ impl<'db, 'ast> SemanticIndexBuilder<'db, 'ast> {
/// Add a place to the place table and the use-def map.
/// Return the [`ScopedPlaceId`] that uniquely identifies the place in both.
fn add_place(&mut self, place_expr: PlaceExpr) -> ScopedPlaceId {
fn add_place(&mut self, place_expr: PlaceExprWithFlags) -> ScopedPlaceId {
let (place_id, added) = self.current_place_table().add_place(place_expr);
if added {
self.current_use_def_map_mut().add_place(place_id);
@ -1863,7 +1873,7 @@ impl<'ast> Visitor<'ast> for SemanticIndexBuilder<'_, 'ast> {
walk_stmt(self, stmt);
for target in targets {
if let Ok(target) = PlaceExpr::try_from(target) {
let place_id = self.add_place(target);
let place_id = self.add_place(PlaceExprWithFlags::new(target));
self.current_place_table().mark_place_used(place_id);
self.delete_binding(place_id);
}
@ -1898,7 +1908,8 @@ impl<'ast> Visitor<'ast> for SemanticIndexBuilder<'_, 'ast> {
ast::Expr::Name(ast::ExprName { ctx, .. })
| ast::Expr::Attribute(ast::ExprAttribute { ctx, .. })
| ast::Expr::Subscript(ast::ExprSubscript { ctx, .. }) => {
if let Ok(mut place_expr) = PlaceExpr::try_from(expr) {
if let Ok(place_expr) = PlaceExpr::try_from(expr) {
let mut place_expr = PlaceExprWithFlags::new(place_expr);
if self.is_method_of_class().is_some()
&& place_expr.is_instance_attribute_candidate()
{
@ -1906,7 +1917,7 @@ impl<'ast> Visitor<'ast> for SemanticIndexBuilder<'_, 'ast> {
// i.e. typically `self` or `cls`.
let accessed_object_refers_to_first_parameter = self
.current_first_parameter_name
.is_some_and(|fst| place_expr.root_name() == fst);
.is_some_and(|fst| place_expr.expr.root_name() == fst);
if accessed_object_refers_to_first_parameter && place_expr.is_member() {
place_expr.mark_instance_attribute();