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Auto merge of #17924 - ShoyuVanilla:issue-17921, r=Veykril

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fix: Panic when a TAIT exists in a RPIT

Fixes  #17921

When there is a TAIT inside of a RPIT like;

```rust
trait Foo {}
type Bar = impl Foo;
fn foo<A>() -> impl Future<Output = Bar> { .. }
```

while inferencing `fn foo`, `insert_inference_vars_for_impl_trait` tries to substitute impl trait bounds of `Bar`, i.e. `Implemented(Foo)` with RPITs `placeholders`, and this causes panic

fa00326247/crates/hir-ty/src/infer.rs (L903-L905)
This commit is contained in:
bors 2024-08-19 14:17:07 +00:00
commit 644617361d
2 changed files with 85 additions and 11 deletions
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79
crates/hir-ty/src/infer.rs
View file

@ -604,6 +604,11 @@ fn find_continuable(
}
}
enum ImplTraitReplacingMode {
ReturnPosition(FxHashSet<Ty>),
TypeAlias,
}
impl<'a> InferenceContext<'a> {
fn new(
db: &'a dyn HirDatabase,
@ -825,13 +830,19 @@ impl<'a> InferenceContext<'a> {
self.write_binding_ty(self_param, ty);
}
}
let mut params_and_ret_tys = Vec::new();
let mut tait_candidates = FxHashSet::default();
for (ty, pat) in param_tys.zip(&*self.body.params) {
let ty = self.insert_type_vars(ty);
let ty = self.normalize_associated_types_in(ty);
self.infer_top_pat(*pat, &ty);
params_and_ret_tys.push(ty);
if ty
.data(Interner)
.flags
.intersects(TypeFlags::HAS_TY_OPAQUE.union(TypeFlags::HAS_TY_INFER))
{
tait_candidates.insert(ty);
}
}
let return_ty = &*data.ret_type;
@ -844,7 +855,12 @@ impl<'a> InferenceContext<'a> {
let return_ty = if let Some(rpits) = self.db.return_type_impl_traits(func) {
// RPIT opaque types use substitution of their parent function.
let fn_placeholders = TyBuilder::placeholder_subst(self.db, func);
let result = self.insert_inference_vars_for_impl_trait(return_ty, fn_placeholders);
let mut mode = ImplTraitReplacingMode::ReturnPosition(FxHashSet::default());
let result =
self.insert_inference_vars_for_impl_trait(return_ty, fn_placeholders, &mut mode);
if let ImplTraitReplacingMode::ReturnPosition(taits) = mode {
tait_candidates.extend(taits);
}
let rpits = rpits.skip_binders();
for (id, _) in rpits.impl_traits.iter() {
if let Entry::Vacant(e) = self.result.type_of_rpit.entry(id) {
@ -863,11 +879,23 @@ impl<'a> InferenceContext<'a> {
// Functions might be defining usage sites of TAITs.
// To define an TAITs, that TAIT must appear in the function's signatures.
// So, it suffices to check for params and return types.
params_and_ret_tys.push(self.return_ty.clone());
self.make_tait_coercion_table(params_and_ret_tys.iter());
if self
.return_ty
.data(Interner)
.flags
.intersects(TypeFlags::HAS_TY_OPAQUE.union(TypeFlags::HAS_TY_INFER))
{
tait_candidates.insert(self.return_ty.clone());
}
self.make_tait_coercion_table(tait_candidates.iter());
}
fn insert_inference_vars_for_impl_trait<T>(&mut self, t: T, placeholders: Substitution) -> T
fn insert_inference_vars_for_impl_trait<T>(
&mut self,
t: T,
placeholders: Substitution,
mode: &mut ImplTraitReplacingMode,
) -> T
where
T: crate::HasInterner<Interner = Interner> + crate::TypeFoldable<Interner>,
{
@ -880,10 +908,31 @@ impl<'a> InferenceContext<'a> {
};
let (impl_traits, idx) =
match self.db.lookup_intern_impl_trait_id(opaque_ty_id.into()) {
// We don't replace opaque types from other kind with inference vars
// because `insert_inference_vars_for_impl_traits` for each kinds
// and unreplaced opaque types of other kind are resolved while
// inferencing because of `tait_coercion_table`.
// Moreover, calling `insert_inference_vars_for_impl_traits` with same
// `placeholders` for other kind may cause trouble because
// the substs for the bounds of each impl traits do not match
ImplTraitId::ReturnTypeImplTrait(def, idx) => {
if matches!(mode, ImplTraitReplacingMode::TypeAlias) {
// RPITs don't have `tait_coercion_table`, so use inserted inference
// vars for them.
if let Some(ty) = self.result.type_of_rpit.get(idx) {
return ty.clone();
}
return ty;
}
(self.db.return_type_impl_traits(def), idx)
}
ImplTraitId::TypeAliasImplTrait(def, idx) => {
if let ImplTraitReplacingMode::ReturnPosition(taits) = mode {
// Gather TAITs while replacing RPITs because TAITs inside RPITs
// may not visited while replacing TAITs
taits.insert(ty.clone());
return ty;
}
(self.db.type_alias_impl_traits(def), idx)
}
_ => unreachable!(),
@ -892,16 +941,20 @@ impl<'a> InferenceContext<'a> {
return ty;
};
let bounds = (*impl_traits)
.map_ref(|rpits| rpits.impl_traits[idx].bounds.map_ref(|it| it.iter()));
.map_ref(|its| its.impl_traits[idx].bounds.map_ref(|it| it.iter()));
let var = self.table.new_type_var();
let var_subst = Substitution::from1(Interner, var.clone());
for bound in bounds {
let predicate = bound.map(|it| it.cloned()).substitute(Interner, &placeholders);
let predicate = bound.map(|it| it.cloned());
let predicate = predicate.substitute(Interner, &placeholders);
let (var_predicate, binders) =
predicate.substitute(Interner, &var_subst).into_value_and_skipped_binders();
always!(binders.is_empty(Interner)); // quantified where clauses not yet handled
let var_predicate = self
.insert_inference_vars_for_impl_trait(var_predicate, placeholders.clone());
let var_predicate = self.insert_inference_vars_for_impl_trait(
var_predicate,
placeholders.clone(),
mode,
);
self.push_obligation(var_predicate.cast(Interner));
}
self.result.type_of_rpit.insert(idx, var.clone());
@ -1038,7 +1091,11 @@ impl<'a> InferenceContext<'a> {
self.db.lookup_intern_impl_trait_id(id.into())
{
let subst = TyBuilder::placeholder_subst(self.db, alias_id);
let ty = self.insert_inference_vars_for_impl_trait(ty, subst);
let ty = self.insert_inference_vars_for_impl_trait(
ty,
subst,
&mut ImplTraitReplacingMode::TypeAlias,
);
Some((id, ty))
} else {
None

17
crates/hir-ty/src/tests/regression.rs
View file

@ -2211,3 +2211,20 @@ fn f() -> Foo {}
"#]],
);
}
#[test]
fn issue_17921() {
check_infer(
r#"
//- minicore: future
trait Foo {}
type Bar = impl Foo;
async fn f<A, B, C>() -> Bar {}
"#,
expect![[r#"
64..66 '{}': ()
64..66 '{}': impl Future<Output = ()>
"#]],
);
}