Auto merge of #126049 - compiler-errors:rework-use, r=oli-obk

Rework `feature(precise_capturing)` to represent `use<...>` as a syntactical bound

Reworks `precise_capturing` for a recent lang-team consensus.

Specifically:

> The conclusion of the team is that we'll make use<..> a bound. That is, we'll support impl use<..> + Trait, impl Trait + use<..>, etc.

> For now, we will support at most one such bound in a list of bounds, and semantically we'll only support these bounds in the item bounds of RPIT-like impl Trait opaque types (i.e., in the places discussed in the RFC).

Lang decision in favor of this approach:

- https://github.com/rust-lang/rust/issues/125836#issuecomment-2151351849

Tracking:

- https://github.com/rust-lang/rust/issues/123432

1 files changed, 5 insertions, 2 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 72e5995e892..3b53c253195 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -481,9 +481,12 @@ fn sanity_check_found_hidden_type<'tcx>(
 /// 2. Checking that all lifetimes that are implicitly captured are mentioned.
 /// 3. Asserting that all parameters mentioned in the captures list are invariant.
 fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDefId) {
-    let hir::OpaqueTy { precise_capturing_args, .. } =
+    let hir::OpaqueTy { bounds, .. } =
         *tcx.hir_node_by_def_id(opaque_def_id).expect_item().expect_opaque_ty();
-    let Some((precise_capturing_args, _)) = precise_capturing_args else {
+    let Some(precise_capturing_args) = bounds.iter().find_map(|bound| match *bound {
+        hir::GenericBound::Use(bounds, ..) => Some(bounds),
+        _ => None,
+    }) else {
         // No precise capturing args; nothing to validate
         return;
     };