retain_one

This commit is contained in:
Douglas Creager 2025-11-12 15:06:23 -05:00
parent a87c3d9ec8
commit 00fd272b5c

View file

@ -1002,17 +1002,27 @@ impl<'db> Node<'db> {
}
}
fn exists_one_inner(
/// Returns a new BDD that is the _existential abstraction_ of `self` for a set of typevars.
/// All typevars _other_ than the one given will be removed and abstracted away.
fn retain_one(self, db: &'db dyn Db, bound_typevar: BoundTypeVarIdentity<'db>) -> Self {
match self {
Node::AlwaysTrue => Node::AlwaysTrue,
Node::AlwaysFalse => Node::AlwaysFalse,
Node::Interior(interior) => interior.retain_one(db, bound_typevar),
}
}
fn abstract_one_inner(
self,
db: &'db dyn Db,
bound_typevar: BoundTypeVarIdentity<'db>,
should_remove: &mut dyn FnMut(BoundTypeVarInstance) -> bool,
map: &SequentMap<'db>,
path: &mut PathAssignments<'db>,
) -> Self {
match self {
Node::AlwaysTrue => Node::AlwaysTrue,
Node::AlwaysFalse => Node::AlwaysFalse,
Node::Interior(interior) => interior.exists_one_inner(db, bound_typevar, map, path),
Node::Interior(interior) => interior.abstract_one_inner(db, should_remove, map, path),
}
}
@ -1441,91 +1451,93 @@ impl<'db> InteriorNode<'db> {
fn exists_one(self, db: &'db dyn Db, bound_typevar: BoundTypeVarIdentity<'db>) -> Node<'db> {
let map = self.sequent_map(db);
let mut path = PathAssignments::default();
self.exists_one_inner(db, bound_typevar, map, &mut path)
self.abstract_one_inner(
db,
&mut |node_typevar| node_typevar.identity(db) == bound_typevar,
map,
&mut path,
)
}
fn exists_one_inner(
#[salsa::tracked(heap_size=ruff_memory_usage::heap_size)]
fn retain_one(self, db: &'db dyn Db, bound_typevar: BoundTypeVarIdentity<'db>) -> Node<'db> {
let map = self.sequent_map(db);
let mut path = PathAssignments::default();
self.abstract_one_inner(
db,
&mut |node_typevar| node_typevar.identity(db) != bound_typevar,
map,
&mut path,
)
}
fn abstract_one_inner(
self,
db: &'db dyn Db,
bound_typevar: BoundTypeVarIdentity<'db>,
should_remove: &mut dyn FnMut(BoundTypeVarInstance) -> bool,
map: &SequentMap<'db>,
path: &mut PathAssignments<'db>,
) -> Node<'db> {
let self_constraint = self.constraint(db);
let self_typevar = self_constraint.typevar(db);
match bound_typevar.cmp(&self_typevar.identity(db)) {
// If the typevar that this node checks is "later" than the typevar we're abstracting
// over, then we have reached a point in the BDD where the abstraction can no longer
// affect the result, and we can return early.
Ordering::Less => Node::Interior(self),
// If the typevar that this node checks _is_ the typevar we're abstracting over, then
// we replace this node with the OR of its if_false/if_true edges. That is, the result
// is true if there's any assignment of this node's constraint that is true.
if should_remove(self_typevar) {
// If we should remove constraints involving this typevar, then we replace this node
// with the OR of its if_false/if_true edges. That is, the result is true if there's
// any assignment of this node's constraint that is true.
//
// We also have to check if there are any derived facts that depend on the constraint
// we're about to remove. If so, we need to "remember" them by AND-ing them in with the
// corresponding branch.
Ordering::Equal => {
let if_true = path
.walk_edge(map, self_constraint.when_true(), |path, new_range| {
let branch =
self.if_true(db)
.exists_one_inner(db, bound_typevar, map, path);
path.assignments[new_range]
.iter()
.filter(|assignment| {
// Don't add back any derived facts if they reference the typevar
// that we're trying to remove!
!assignment
.constraint()
.typevar(db)
.is_same_typevar_as(db, self_typevar)
})
.fold(branch, |branch, assignment| {
branch.and(db, Node::new_satisfied_constraint(db, *assignment))
})
})
.unwrap_or(Node::AlwaysFalse);
let if_false = path
.walk_edge(map, self_constraint.when_false(), |path, new_range| {
let branch =
self.if_false(db)
.exists_one_inner(db, bound_typevar, map, path);
path.assignments[new_range]
.iter()
.filter(|assignment| {
// Don't add back any derived facts if they reference the typevar
// that we're trying to remove!
!assignment
.constraint()
.typevar(db)
.is_same_typevar_as(db, self_typevar)
})
.fold(branch, |branch, assignment| {
branch.and(db, Node::new_satisfied_constraint(db, *assignment))
})
})
.unwrap_or(Node::AlwaysFalse);
if_true.or(db, if_false)
}
let if_true = path
.walk_edge(map, self_constraint.when_true(), |path, new_range| {
let branch = self
.if_true(db)
.abstract_one_inner(db, should_remove, map, path);
path.assignments[new_range]
.iter()
.filter(|assignment| {
// Don't add back any derived facts if they reference the typevar
// that we're trying to remove!
!should_remove(assignment.constraint().typevar(db))
})
.fold(branch, |branch, assignment| {
branch.and(db, Node::new_satisfied_constraint(db, *assignment))
})
})
.unwrap_or(Node::AlwaysFalse);
let if_false = path
.walk_edge(map, self_constraint.when_false(), |path, new_range| {
let branch = self
.if_false(db)
.abstract_one_inner(db, should_remove, map, path);
path.assignments[new_range]
.iter()
.filter(|assignment| {
// Don't add back any derived facts if they reference the typevar
// that we're trying to remove!
!should_remove(assignment.constraint().typevar(db))
})
.fold(branch, |branch, assignment| {
branch.and(db, Node::new_satisfied_constraint(db, *assignment))
})
})
.unwrap_or(Node::AlwaysFalse);
if_true.or(db, if_false)
} else {
// Otherwise, we abstract the if_false/if_true edges recursively.
Ordering::Greater => {
let if_true = path
.walk_edge(map, self_constraint.when_true(), |path, _| {
self.if_true(db)
.exists_one_inner(db, bound_typevar, map, path)
})
.unwrap_or(Node::AlwaysFalse);
let if_false = path
.walk_edge(map, self_constraint.when_false(), |path, _| {
self.if_false(db)
.exists_one_inner(db, bound_typevar, map, path)
})
.unwrap_or(Node::AlwaysFalse);
Node::new(db, self_constraint, if_true, if_false)
}
let if_true = path
.walk_edge(map, self_constraint.when_true(), |path, _| {
self.if_true(db)
.abstract_one_inner(db, should_remove, map, path)
})
.unwrap_or(Node::AlwaysFalse);
let if_false = path
.walk_edge(map, self_constraint.when_false(), |path, _| {
self.if_false(db)
.abstract_one_inner(db, should_remove, map, path)
})
.unwrap_or(Node::AlwaysFalse);
Node::new(db, self_constraint, if_true, if_false)
}
}