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Implement if-expressions

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This commit is contained in:
David Peter
2024-12-18 11:32:56 +01:00
parent c1748f07d6
commit d249801bf2
5 changed files with 88 additions and 57 deletions
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59
crates/red_knot_python_semantic/resources/mdtest/statically_known_branches.md
View File

@@ -41,8 +41,6 @@ if typing.TYPE_CHECKING:
def f(s: SomeType) -> None: ...
```
The rest of this document contains tests for various cases where this feature can be used.
## Common use cases
This section makes sure that we can handle all commonly encountered patterns of static conditions.
@@ -164,6 +162,9 @@ other
## If statements
The rest of this document contains tests for various control flow elements. This section tests `if`
statements.
### Always false
#### If
@@ -349,7 +350,7 @@ else:
reveal_type(x) # revealed: Literal[2, 3, 4]
```
#### `elif` without `else` branch
#### `elif` without `else` branch, always true
```py
def flag() -> bool: ...
@@ -364,6 +365,21 @@ elif True:
reveal_type(x) # revealed: Literal[2, 3]
```
#### `elif` without `else` branch, always false
```py
def flag() -> bool: ...
x = 1
if flag():
x = 2
elif False:
x = 3
reveal_type(x) # revealed: Literal[1, 2]
```
### Nested conditionals
#### `if True` inside `if True`
@@ -769,22 +785,31 @@ reveal_type(x) # revealed: Literal[3, 4]
## If expressions
See also: tests in [expression/if.md](expression/if.md).
Note that the result type of an `if`-expression can be precisely inferred if the condition is
statically known. This is a plain type inference feature that does not need support for statically
known branches. The tests for this feature are in [expression/if.md](expression/if.md).
The tests here make sure that we also handle assignment expressions inside `if`-expressions
correctly.
### Type inference
### Always true
```py
x = 1 if True else 2
x = (y := 1) if True else (y := 2)
reveal_type(x) # revealed: Literal[1]
reveal_type(y) # revealed: Literal[1]
```
### Always false
```py
x = 1 if False else 2
x = (y := 1) if False else (y := 2)
reveal_type(x) # revealed: Literal[2]
reveal_type(y) # revealed: Literal[2]
```
## Boolean expressions
@@ -795,6 +820,10 @@ reveal_type(x) # revealed: Literal[2]
(x := 1) or (x := 2)
reveal_type(x) # revealed: Literal[1]
(y := 1) or (y := 2) or (y := 3) or (y := 4)
reveal_type(y) # revealed: Literal[1]
```
### Always true, `and`
@@ -803,22 +832,34 @@ reveal_type(x) # revealed: Literal[1]
(x := 1) and (x := 2)
reveal_type(x) # revealed: Literal[2]
(y := 1) and (y := 2) and (y := 3) and (y := 4)
reveal_type(y) # revealed: Literal[4]
```
### Always false, `or`
```py
(x := 0) or (x := 2)
(x := 0) or (x := 1)
reveal_type(x) # revealed: Literal[2]
reveal_type(x) # revealed: Literal[1]
(y := 0) or (y := 0) or (y := 1) or (y := 2)
reveal_type(y) # revealed: Literal[1]
```
### Always false, `and`
```py
(x := 0) and (x := 2)
(x := 0) and (x := 1)
reveal_type(x) # revealed: Literal[0]
(y := 0) and (y := 1) and (y := 2) and (y := 3)
reveal_type(y) # revealed: Literal[0]
```
## While loops

31
crates/red_knot_python_semantic/src/semantic_index/builder.rs
View File

@@ -296,14 +296,6 @@ impl<'db> SemanticIndexBuilder<'db> {
self.current_use_def_map_mut().record_constraint(constraint)
}
fn add_visibility_constraint(
&mut self,
constraint: ScopedConstraintId,
) -> ScopedVisibilityConstraintId {
self.current_use_def_map_mut()
.add_visibility_constraint(VisibilityConstraint::VisibleIf(constraint))
}
fn record_visibility_constraint(
&mut self,
constraint: ScopedConstraintId,
@@ -1325,14 +1317,17 @@ where
}) => {
self.visit_expr(test);
let pre_if = self.flow_snapshot();
let (_, constraint) = self.record_expression_constraint(test);
let (constraint_id, constraint) = self.record_expression_constraint(test);
self.visit_expr(body);
let visibility_constraint = self.record_visibility_constraint(constraint_id);
let post_body = self.flow_snapshot();
self.flow_restore(pre_if);
self.flow_restore(pre_if.clone());
self.record_negated_constraint(constraint);
self.visit_expr(orelse);
self.record_negated_visibility_constraint(visibility_constraint);
self.flow_merge(post_body);
self.reset_visibility_constraints(pre_if);
}
ast::Expr::ListComp(
list_comprehension @ ast::ExprListComp {
@@ -1392,12 +1387,13 @@ where
let pre_op = self.flow_snapshot();
let mut snapshots = vec![];
let mut constraints = vec![];
let mut visibility_constraints = vec![];
let mut last_constraint = None;
for (index, value) in values.iter().enumerate() {
self.visit_expr(value);
if let Some(last_constraint_id) = constraints.last() {
self.record_visibility_constraint(*last_constraint_id);
if let Some(id) = last_constraint {
visibility_constraints.push(self.record_visibility_constraint(id));
}
// Snapshot is taken after visiting the expression but before adding the constraint.
snapshots.push(self.flow_snapshot());
@@ -1408,7 +1404,7 @@ where
BoolOp::And => self.record_constraint(constraint),
BoolOp::Or => self.record_negated_constraint(constraint),
};
constraints.push(id);
last_constraint = Some(id);
}
}
@@ -1416,9 +1412,10 @@ where
let first = snapshots.next().expect("at least one value");
self.flow_restore(first);
for id in constraints {
let vid = self.add_visibility_constraint(id);
self.record_negated_visibility_constraint(vid);
// debug_assert(constraints.len() == snapshots.len());
for id in visibility_constraints {
self.record_negated_visibility_constraint(id);
}
for snapshot in snapshots {

11
crates/red_knot_python_semantic/src/semantic_index/use_def.rs
View File

@@ -472,7 +472,7 @@ impl<'db> UseDefMapBuilder<'db> {
all_definitions: IndexVec::from_iter([None]),
all_constraints: IndexVec::new(),
visibility_constraints: VisibilityConstraints::new(),
unbound_visibility: ScopedVisibilityConstraintId::ALWAYS_VISIBLE,
unbound_visibility: ScopedVisibilityConstraintId::ALWAYS_TRUE,
bindings_by_use: IndexVec::new(),
definitions_by_definition: FxHashMap::default(),
symbol_states: IndexVec::new(),
@@ -504,18 +504,11 @@ impl<'db> UseDefMapBuilder<'db> {
constraint_id
}
pub(super) fn add_visibility_constraint(
&mut self,
constraint: VisibilityConstraint,
) -> ScopedVisibilityConstraintId {
self.visibility_constraints.add(constraint)
}
pub(super) fn record_visibility_constraint(
&mut self,
constraint: VisibilityConstraint,
) -> ScopedVisibilityConstraintId {
let new_constraint_id = self.add_visibility_constraint(constraint);
let new_constraint_id = self.visibility_constraints.add(constraint);
for state in &mut self.symbol_states {
state.record_visibility_constraint(&mut self.visibility_constraints, new_constraint_id);
}

38
crates/red_knot_python_semantic/src/semantic_index/use_def/symbol_state.rs
View File

@@ -98,7 +98,7 @@ type ConstraintsIntoIterator = smallvec::IntoIter<InlineConstraintArray>;
pub(crate) struct ScopedVisibilityConstraintId;
impl ScopedVisibilityConstraintId {
pub(crate) const ALWAYS_VISIBLE: ScopedVisibilityConstraintId =
pub(crate) const ALWAYS_TRUE: ScopedVisibilityConstraintId =
ScopedVisibilityConstraintId::from_u32(0);
}
@@ -135,7 +135,7 @@ impl SymbolDeclarations {
self.visibility_constraints = VisibilityConstraintPerBinding::with_capacity(1);
self.visibility_constraints
.push(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
.push(ScopedVisibilityConstraintId::ALWAYS_TRUE);
}
/// Add given visibility constraint to all live bindings.
@@ -199,7 +199,7 @@ impl SymbolBindings {
self.visibility_constraints = VisibilityConstraintPerBinding::with_capacity(1);
self.visibility_constraints
.push(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
.push(ScopedVisibilityConstraintId::ALWAYS_TRUE);
}
/// Add given constraint to all live bindings.
@@ -655,7 +655,7 @@ mod tests {
fn unbound() {
let constraints = AllConstraints::new();
let visibility_constraints = VisibilityConstraints::new();
let sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
assert_bindings(&constraints, &visibility_constraints, &sym, &["unbound<>"]);
}
@@ -664,7 +664,7 @@ mod tests {
fn with() {
let constraints = AllConstraints::new();
let visibility_constraints = VisibilityConstraints::new();
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.record_binding(ScopedDefinitionId::from_u32(1));
assert_bindings(&constraints, &visibility_constraints, &sym, &["1<>"]);
@@ -674,7 +674,7 @@ mod tests {
fn record_constraint() {
let constraints = AllConstraints::new();
let visibility_constraints = VisibilityConstraints::new();
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.record_binding(ScopedDefinitionId::from_u32(1));
sym.record_constraint(ScopedConstraintId::from_u32(0));
@@ -687,11 +687,11 @@ mod tests {
let mut visibility_constraints = VisibilityConstraints::new();
// merging the same definition with the same constraint keeps the constraint
let mut sym1a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym1a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym1a.record_binding(ScopedDefinitionId::from_u32(1));
sym1a.record_constraint(ScopedConstraintId::from_u32(0));
let mut sym1b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym1b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym1b.record_binding(ScopedDefinitionId::from_u32(1));
sym1b.record_constraint(ScopedConstraintId::from_u32(0));
@@ -700,11 +700,11 @@ mod tests {
assert_bindings(&constraints, &visibility_constraints, &sym1, &["1<0>"]);
// merging the same definition with differing constraints drops all constraints
let mut sym2a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym2a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym2a.record_binding(ScopedDefinitionId::from_u32(2));
sym2a.record_constraint(ScopedConstraintId::from_u32(1));
let mut sym1b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym1b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym1b.record_binding(ScopedDefinitionId::from_u32(2));
sym1b.record_constraint(ScopedConstraintId::from_u32(2));
@@ -713,11 +713,11 @@ mod tests {
assert_bindings(&constraints, &visibility_constraints, &sym2, &["2<>"]);
// merging a constrained definition with unbound keeps both
let mut sym3a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym3a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym3a.record_binding(ScopedDefinitionId::from_u32(3));
sym3a.record_constraint(ScopedConstraintId::from_u32(3));
let sym2b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let sym2b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym3a.merge(sym2b, &mut visibility_constraints);
let sym3 = sym3a;
@@ -743,7 +743,7 @@ mod tests {
fn no_declaration() {
let constraints = AllConstraints::new();
let visibility_constraints = VisibilityConstraints::new();
let sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
assert_declarations(&constraints, &visibility_constraints, &sym, &["undeclared"]);
}
@@ -752,7 +752,7 @@ mod tests {
fn record_declaration() {
let constraints = AllConstraints::new();
let visibility_constraints = VisibilityConstraints::new();
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.record_declaration(ScopedDefinitionId::from_u32(1));
assert_declarations(&constraints, &visibility_constraints, &sym, &["1"]);
@@ -762,7 +762,7 @@ mod tests {
fn record_declaration_override() {
let constraints = AllConstraints::new();
let visibility_constraints = VisibilityConstraints::new();
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.record_declaration(ScopedDefinitionId::from_u32(1));
sym.record_declaration(ScopedDefinitionId::from_u32(2));
@@ -773,10 +773,10 @@ mod tests {
fn record_declaration_merge() {
let constraints = AllConstraints::new();
let mut visibility_constraints = VisibilityConstraints::new();
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.record_declaration(ScopedDefinitionId::from_u32(1));
let mut sym2 = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym2 = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym2.record_declaration(ScopedDefinitionId::from_u32(2));
sym.merge(sym2, &mut visibility_constraints);
@@ -788,10 +788,10 @@ mod tests {
fn record_declaration_merge_partial_undeclared() {
let constraints = AllConstraints::new();
let mut visibility_constraints = VisibilityConstraints::new();
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.record_declaration(ScopedDefinitionId::from_u32(1));
let sym2 = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_VISIBLE);
let sym2 = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
sym.merge(sym2, &mut visibility_constraints);

6
crates/red_knot_python_semantic/src/visibility_constraints.rs
View File

@@ -43,10 +43,10 @@ impl VisibilityConstraints {
) -> ScopedVisibilityConstraintId {
match (&self.constraints[a], &self.constraints[b]) {
(_, VisibilityConstraint::VisibleIfNot(id)) if a == *id => {
ScopedVisibilityConstraintId::ALWAYS_VISIBLE
ScopedVisibilityConstraintId::ALWAYS_TRUE
}
(VisibilityConstraint::VisibleIfNot(id), _) if *id == b => {
ScopedVisibilityConstraintId::ALWAYS_VISIBLE
ScopedVisibilityConstraintId::ALWAYS_TRUE
}
_ => self.add(VisibilityConstraint::Merged(a, b)),
}
@@ -57,7 +57,7 @@ impl VisibilityConstraints {
a: ScopedVisibilityConstraintId,
b: ScopedVisibilityConstraintId,
) -> ScopedVisibilityConstraintId {
if a == ScopedVisibilityConstraintId::ALWAYS_VISIBLE {
if a == ScopedVisibilityConstraintId::ALWAYS_TRUE {
b
} else {
self.add(VisibilityConstraint::Sequence(a, b))