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[red-knot] Do not panic if named expressions show up in assignment position #13711

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Oct 16, 2024
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Original file line number Diff line number Diff line change
@@ -6,3 +6,35 @@
x = []
reveal_type(x) # revealed: list
```

## Indexing into lists

A list can be indexed into with:

- numbers
- slices

```py
x = [1, 2, 3]
reveal_type(x) # revealed: list
# TODO reveal int
reveal_type(x[0]) # revealed: @Todo
# TODO reveal list
reveal_type(x[0:1]) # revealed: @Todo
# TODO error
reveal_type(x["a"]) # revealed: @Todo
```

## Assignments within list assignment

In assignment, we might also have a named assignment.
This should also get type checked.

```py
x = [1, 2, 3]
x[0 if (y := 2) else 1] = 5
# TODO error? (indeterminite index type)
x["a" if (y := 2) else 1] = 6
# TODO error (can't index via string)
x["a" if (y := 2) else "b"] = 6
```
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73 changes: 45 additions & 28 deletions crates/red_knot_python_semantic/src/semantic_index/builder.rs
Original file line number Diff line number Diff line change
@@ -38,8 +38,9 @@ pub(super) struct SemanticIndexBuilder<'db> {
file: File,
module: &'db ParsedModule,
scope_stack: Vec<FileScopeId>,
/// The assignment we're currently visiting.
current_assignment: Option<CurrentAssignment<'db>>,
/// The assignments we're currently visiting, with
/// the most recent visit at the end of the Vec
current_assignments: Vec<CurrentAssignment<'db>>,
/// The match case we're currently visiting.
current_match_case: Option<CurrentMatchCase<'db>>,
/// Flow states at each `break` in the current loop.
@@ -67,7 +68,7 @@ impl<'db> SemanticIndexBuilder<'db> {
file,
module: parsed,
scope_stack: Vec::new(),
current_assignment: None,
current_assignments: vec![],
current_match_case: None,
loop_break_states: vec![],

@@ -238,6 +239,19 @@ impl<'db> SemanticIndexBuilder<'db> {
expression
}

fn push_assignment(&mut self, assignment: CurrentAssignment<'db>) {
self.current_assignments.push(assignment);
}

fn pop_assignment(&mut self) {
let popped_assignment = self.current_assignments.pop();
debug_assert!(popped_assignment.is_some());
}

fn current_assignment(&self) -> Option<&CurrentAssignment<'db>> {
self.current_assignments.last()
}

fn add_pattern_constraint(
&mut self,
subject: &ast::Expr,
@@ -359,12 +373,12 @@ impl<'db> SemanticIndexBuilder<'db> {
self.visit_expr(&generator.iter);
self.push_scope(scope);

self.current_assignment = Some(CurrentAssignment::Comprehension {
self.push_assignment(CurrentAssignment::Comprehension {
node: generator,
first: true,
});
self.visit_expr(&generator.target);
self.current_assignment = None;
self.pop_assignment();

for expr in &generator.ifs {
self.visit_expr(expr);
@@ -374,12 +388,12 @@ impl<'db> SemanticIndexBuilder<'db> {
self.add_standalone_expression(&generator.iter);
self.visit_expr(&generator.iter);

self.current_assignment = Some(CurrentAssignment::Comprehension {
self.push_assignment(CurrentAssignment::Comprehension {
node: generator,
first: false,
});
self.visit_expr(&generator.target);
self.current_assignment = None;
self.pop_assignment();

for expr in &generator.ifs {
self.visit_expr(expr);
@@ -415,7 +429,7 @@ impl<'db> SemanticIndexBuilder<'db> {
self.pop_scope();
assert!(self.scope_stack.is_empty());

assert!(self.current_assignment.is_none());
assert_eq!(&self.current_assignments, &[]);

let mut symbol_tables: IndexVec<_, _> = self
.symbol_tables
@@ -563,7 +577,7 @@ where
}
}
ast::Stmt::Assign(node) => {
debug_assert!(self.current_assignment.is_none());
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debug_assert_eq!(&self.current_assignments, &[]);
self.visit_expr(&node.value);
self.add_standalone_expression(&node.value);
for (target_index, target) in node.targets.iter().enumerate() {
@@ -573,25 +587,28 @@ where
_ => None,
};
if let Some(kind) = kind {
self.current_assignment = Some(CurrentAssignment::Assign {
self.push_assignment(CurrentAssignment::Assign {
assignment: node,
target_index,
kind,
});
}
self.visit_expr(target);
self.current_assignment = None;
if kind.is_some() {
// only need to pop in the case where we pushed something
self.pop_assignment();
}
}
}
ast::Stmt::AnnAssign(node) => {
debug_assert!(self.current_assignment.is_none());
debug_assert_eq!(&self.current_assignments, &[]);
self.visit_expr(&node.annotation);
if let Some(value) = &node.value {
self.visit_expr(value);
}
self.current_assignment = Some(node.into());
self.push_assignment(node.into());
self.visit_expr(&node.target);
self.current_assignment = None;
self.pop_assignment();
}
ast::Stmt::AugAssign(
aug_assign @ ast::StmtAugAssign {
@@ -601,11 +618,11 @@ where
value,
},
) => {
debug_assert!(self.current_assignment.is_none());
debug_assert_eq!(&self.current_assignments, &[]);
self.visit_expr(value);
self.current_assignment = Some(aug_assign.into());
self.push_assignment(aug_assign.into());
self.visit_expr(target);
self.current_assignment = None;
self.pop_assignment();
}
ast::Stmt::If(node) => {
self.visit_expr(&node.test);
@@ -673,9 +690,9 @@ where
self.visit_expr(&item.context_expr);
if let Some(optional_vars) = item.optional_vars.as_deref() {
self.add_standalone_expression(&item.context_expr);
self.current_assignment = Some(item.into());
self.push_assignment(item.into());
self.visit_expr(optional_vars);
self.current_assignment = None;
self.pop_assignment();
}
}
self.visit_body(body);
@@ -700,10 +717,10 @@ where
let pre_loop = self.flow_snapshot();
let saved_break_states = std::mem::take(&mut self.loop_break_states);

debug_assert!(self.current_assignment.is_none());
self.current_assignment = Some(for_stmt.into());
debug_assert_eq!(&self.current_assignments, &[]);
self.push_assignment(for_stmt.into());
self.visit_expr(target);
self.current_assignment = None;
self.pop_assignment();

// TODO: Definitions created by loop variables
// (and definitions created inside the body)
@@ -813,7 +830,7 @@ where

match expr {
ast::Expr::Name(name_node @ ast::ExprName { id, ctx, .. }) => {
let (is_use, is_definition) = match (ctx, self.current_assignment) {
let (is_use, is_definition) = match (ctx, self.current_assignment()) {
(ast::ExprContext::Store, Some(CurrentAssignment::AugAssign(_))) => {
// For augmented assignment, the target expression is also used.
(true, true)
@@ -824,8 +841,9 @@ where
(ast::ExprContext::Invalid, _) => (false, false),
};
let symbol = self.add_symbol(id.clone());

if is_definition {
match self.current_assignment {
match self.current_assignment().copied() {
Some(CurrentAssignment::Assign {
assignment,
target_index,
@@ -896,12 +914,11 @@ where
walk_expr(self, expr);
}
ast::Expr::Named(node) => {
debug_assert!(self.current_assignment.is_none());
// TODO walrus in comprehensions is implicitly nonlocal
self.visit_expr(&node.value);
self.current_assignment = Some(node.into());
self.push_assignment(node.into());
self.visit_expr(&node.target);
self.current_assignment = None;
self.pop_assignment();
}
ast::Expr::Lambda(lambda) => {
if let Some(parameters) = &lambda.parameters {
@@ -1060,7 +1077,7 @@ where
}
}

#[derive(Copy, Clone, Debug)]
#[derive(Copy, Clone, Debug, PartialEq)]
enum CurrentAssignment<'a> {
Assign {
assignment: &'a ast::StmtAssign,