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Nested impl traits trigger opaque_hidden_inferred_bound too much

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This commit is contained in:
Michael Goulet 2023-02-27 20:47:06 +00:00
parent 1c771fec33
commit e5189cc7e4
5 changed files with 18 additions and 39 deletions
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21
compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
View File

@ -27,6 +27,8 @@ declare_lint! {
/// ### Example
///
/// ```rust
/// #![feature(type_alias_impl_trait)]
///
/// trait Duh {}
///
/// impl Duh for i32 {}
@ -41,7 +43,9 @@ declare_lint! {
/// type Assoc = F;
/// }
///
/// fn test() -> impl Trait<Assoc = impl Sized> {
/// type Tait = impl Sized;
///
/// fn test() -> impl Trait<Assoc = Tait> {
/// 42
/// }
/// ```
@ -54,7 +58,7 @@ declare_lint! {
///
/// Although the hidden type, `i32` does satisfy this bound, we do not
/// consider the return type to be well-formed with this lint. It can be
/// fixed by changing `impl Sized` into `impl Sized + Send`.
/// fixed by changing `Tait = impl Sized` into `Tait = impl Sized + Send`.
pub OPAQUE_HIDDEN_INFERRED_BOUND,
Warn,
"detects the use of nested `impl Trait` types in associated type bounds that are not general enough"
@ -64,7 +68,7 @@ declare_lint_pass!(OpaqueHiddenInferredBound => [OPAQUE_HIDDEN_INFERRED_BOUND]);
impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
let hir::ItemKind::OpaqueTy(_) = &item.kind else { return; };
let hir::ItemKind::OpaqueTy(opaque) = &item.kind else { return; };
let def_id = item.owner_id.def_id.to_def_id();
let infcx = &cx.tcx.infer_ctxt().build();
// For every projection predicate in the opaque type's explicit bounds,
@ -81,6 +85,17 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
// have opaques in them anyways.
let Some(proj_term) = proj.term.ty() else { continue };
// HACK: `impl Trait<Assoc = impl Trait2>` from an RPIT is "ok"...
if let ty::Alias(ty::Opaque, opaque_ty) = *proj_term.kind()
&& cx.tcx.parent(opaque_ty.def_id) == def_id
&& matches!(
opaque.origin,
hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_)
)
{
continue;
}
let proj_ty =
cx.tcx.mk_projection(proj.projection_ty.def_id, proj.projection_ty.substs);
// For every instance of the projection type in the bounds,

1
tests/ui/impl-trait/nested-return-type2.rs
View File

@ -26,7 +26,6 @@ impl<R: Duh, F: FnMut() -> R> Trait for F {
// Lazy TAIT would error out, but we inserted a hack to make it work again,
// keeping backwards compatibility.
fn foo() -> impl Trait<Assoc = impl Send> {
//~^ WARN opaque type `impl Trait<Assoc = impl Send>` does not satisfy its associated type bounds
|| 42
}

17
tests/ui/impl-trait/nested-return-type2.stderr
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@ -1,17 +0,0 @@
warning: opaque type `impl Trait<Assoc = impl Send>` does not satisfy its associated type bounds
--> $DIR/nested-return-type2.rs:28:24
|
LL | type Assoc: Duh;
| --- this associated type bound is unsatisfied for `impl Send`
...
LL | fn foo() -> impl Trait<Assoc = impl Send> {
| ^^^^^^^^^^^^^^^^^
|
= note: `#[warn(opaque_hidden_inferred_bound)]` on by default
help: add this bound
|
LL | fn foo() -> impl Trait<Assoc = impl Send + Duh> {
| +++++
warning: 1 warning emitted

1
tests/ui/impl-trait/nested-return-type3.rs
View File

@ -13,7 +13,6 @@ impl<F: Duh> Trait for F {
}
fn foo() -> impl Trait<Assoc = impl Send> {
//~^ WARN opaque type `impl Trait<Assoc = impl Send>` does not satisfy its associated type bounds
42
}

17
tests/ui/impl-trait/nested-return-type3.stderr
View File

@ -1,17 +0,0 @@
warning: opaque type `impl Trait<Assoc = impl Send>` does not satisfy its associated type bounds
--> $DIR/nested-return-type3.rs:15:24
|
LL | type Assoc: Duh;
| --- this associated type bound is unsatisfied for `impl Send`
...
LL | fn foo() -> impl Trait<Assoc = impl Send> {
| ^^^^^^^^^^^^^^^^^
|
= note: `#[warn(opaque_hidden_inferred_bound)]` on by default
help: add this bound
|
LL | fn foo() -> impl Trait<Assoc = impl Send + Duh> {
| +++++
warning: 1 warning emitted