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Traverse types once when relating them invariantly #254

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coord-e merged 1 commit into from
Sep 2, 2026
Merged

Traverse types once when relating them invariantly #254

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203 changes: 110 additions & 93 deletions src/rty/subtyping.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,13 +48,6 @@ pub trait Subtyping {
got: &RefinedType<T>,
expected: &RefinedType<U>,
) -> Vec<chc::Clause>;

#[must_use]
fn relate_equal_refined_type<T: chc::Var, U: chc::Var>(
&self,
got: &RefinedType<T>,
expected: &RefinedType<U>,
) -> Vec<chc::Clause>;
}

impl<C> Subtyping for C
Expand All @@ -66,70 +59,7 @@ where
T: chc::Var,
U: chc::Var,
{
tracing::debug!(got = %got.display(), expected = %expected.display(), "sub_type");

let mut clauses = Vec::new();
match (got, expected) {
(Type::Int, Type::Int)
| (Type::Bool, Type::Bool)
| (Type::String, Type::String)
| (Type::Never, Type::Never) => {}
(Type::Enum(got), Type::Enum(expected)) if got.symbol() == expected.symbol() => {
for (got_ty, expected_ty) in got.args.iter().zip(expected.args.iter()) {
let cs = self.relate_sub_refined_type(got_ty, expected_ty);
clauses.extend(cs);
}
}
(Type::Tuple(got), Type::Tuple(expected))
if got.elems.len() == expected.elems.len() =>
{
for (got_ty, expected_ty) in got.elems.iter().zip(expected.elems.iter()) {
let cs = self.relate_sub_refined_type(got_ty, expected_ty);
clauses.extend(cs);
}
}
(Type::Pointer(got), Type::Pointer(expected)) if got.kind == expected.kind => {
match got.kind {
PointerKind::Ref(RefKind::Immut) => {
let cs = self.relate_sub_refined_type(&got.elem, &expected.elem);
clauses.extend(cs);
}
PointerKind::Own | PointerKind::Ref(RefKind::Mut) => {
let cs = self.relate_equal_refined_type(&got.elem, &expected.elem);
clauses.extend(cs);
}
}
}
(Type::Function(got), Type::Function(expected))
if got.params.len() == expected.params.len() =>
{
let mut builder = chc::ClauseBuilder::default();
for (param_idx, param_rty) in got.params.iter_enumerated() {
let param_sort = param_rty.ty.to_sort();
if !param_sort.is_singleton() {
builder.add_mapped_var(param_idx, param_sort);
}
}
for (got_ty, expected_ty) in got.params.iter().zip(expected.params.iter()) {
let cs = builder.relate_sub_refined_type(expected_ty, got_ty);
clauses.extend(cs);
}
let cs = builder.relate_sub_refined_type(&got.ret, &expected.ret);
clauses.extend(cs);
}
(Type::Array(got), Type::Array(expected)) => {
let cs1 = self.relate_sub_refined_type(&got.index, &expected.index);
clauses.extend(cs1);
let cs2 = self.relate_sub_refined_type(&got.elem, &expected.elem);
clauses.extend(cs2);
}
_ => panic!(
"inconsistent types: got={}, expected={}",
got.display(),
expected.display()
),
}
clauses
relate_type(self, got, expected, Relation::Sub)
}

fn relate_sub_refined_type<T, U>(
Expand All @@ -141,34 +71,121 @@ where
T: chc::Var,
U: chc::Var,
{
tracing::debug!(got = %got.display(), expected = %expected.display(), "sub_refined_type");
relate_refined_type(self, got, expected, Relation::Sub)
}
}

let mut clauses = self.relate_sub_type(&got.ty, &expected.ty);
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum Relation {
Sub,
Equal,
}

let cs = self
.build_clause()
.with_value_var(&got.ty)
.add_body(got.refinement.clone())
.head(expected.refinement.clone());
clauses.extend(cs);
clauses
#[must_use]
fn relate_type<C, T, U>(
scope: &C,
got: &Type<T>,
expected: &Type<U>,
relation: Relation,
) -> Vec<chc::Clause>
where
C: ClauseScope,
T: chc::Var,
U: chc::Var,
{
tracing::debug!(got = %got.display(), expected = %expected.display(), ?relation, "relate_type");

let mut clauses = Vec::new();
match (got, expected) {
(Type::Int, Type::Int)
| (Type::Bool, Type::Bool)
| (Type::String, Type::String)
| (Type::Never, Type::Never) => {}
(Type::Enum(got), Type::Enum(expected)) if got.symbol() == expected.symbol() => {
for (got_ty, expected_ty) in got.args.iter().zip(expected.args.iter()) {
let cs = relate_refined_type(scope, got_ty, expected_ty, relation);
clauses.extend(cs);
}
}
(Type::Tuple(got), Type::Tuple(expected)) if got.elems.len() == expected.elems.len() => {
for (got_ty, expected_ty) in got.elems.iter().zip(expected.elems.iter()) {
let cs = relate_refined_type(scope, got_ty, expected_ty, relation);
clauses.extend(cs);
}
}
(Type::Pointer(got), Type::Pointer(expected)) if got.kind == expected.kind => {
let elem_relation = match got.kind {
PointerKind::Ref(RefKind::Immut) => relation,
PointerKind::Own | PointerKind::Ref(RefKind::Mut) => Relation::Equal,
};
let cs = relate_refined_type(scope, &got.elem, &expected.elem, elem_relation);
clauses.extend(cs);
}
(Type::Function(got), Type::Function(expected))
if got.params.len() == expected.params.len() =>
{
let mut builder = chc::ClauseBuilder::default();
for (param_idx, param_rty) in got.params.iter_enumerated() {
let param_sort = param_rty.ty.to_sort();
if !param_sort.is_singleton() {
builder.add_mapped_var(param_idx, param_sort);
}
}
for (got_ty, expected_ty) in got.params.iter().zip(expected.params.iter()) {
let cs = relate_refined_type(&builder, expected_ty, got_ty, relation);
clauses.extend(cs);
}
let cs = relate_refined_type(&builder, &got.ret, &expected.ret, relation);
clauses.extend(cs);
}
(Type::Array(got), Type::Array(expected)) => {
let cs1 = relate_refined_type(scope, &got.index, &expected.index, relation);
clauses.extend(cs1);
let cs2 = relate_refined_type(scope, &got.elem, &expected.elem, relation);
clauses.extend(cs2);
}
_ => panic!(
"inconsistent types: got={}, expected={}",
got.display(),
expected.display()
),
}
clauses
}

fn relate_equal_refined_type<T, U>(
&self,
got: &RefinedType<T>,
expected: &RefinedType<U>,
) -> Vec<chc::Clause>
where
T: chc::Var,
U: chc::Var,
{
tracing::debug!(got = %got.display(), expected = %expected.display(), "equal_refined_type");
#[must_use]
fn relate_refined_type<C, T, U>(
scope: &C,
got: &RefinedType<T>,
expected: &RefinedType<U>,
relation: Relation,
) -> Vec<chc::Clause>
where
C: ClauseScope,
T: chc::Var,
U: chc::Var,
{
tracing::debug!(got = %got.display(), expected = %expected.display(), ?relation, "relate_refined_type");

let mut clauses = relate_type(scope, &got.ty, &expected.ty, relation);

let mut clauses = self.relate_sub_refined_type(got, expected);
clauses.extend(self.relate_sub_refined_type(expected, got));
clauses
let cs = scope
.build_clause()
.with_value_var(&got.ty)
.add_body(got.refinement.clone())
.head(expected.refinement.clone());
clauses.extend(cs);

if relation == Relation::Equal {
let cs = scope
.build_clause()
.with_value_var(&expected.ty)
.add_body(expected.refinement.clone())
.head(got.refinement.clone());
clauses.extend(cs);
}

clauses
}

#[must_use]
Expand Down