Rollup merge of #100483 - compiler-errors:point-to-projection-too, r=jyn514

Point to generic or arg if it's the self type of unsatisfied projection predicate

We do this for `TraitPredicate`s in `point_at_type_arg_instead_of_call_if_possible` and `point_at_arg_instead_of_call_if_possible`, so also do it for `ProjectionPredicate`.

Improves spans for a lot of unit tests.

1 files changed, 27 insertions, 23 deletions

diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
index 1177113ad8a..296fdf504ce 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
@@ -1664,12 +1664,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     ObligationCauseCode::ImplDerivedObligation(code) => {
                         code.derived.parent_trait_pred.self_ty().skip_binder().into()
                     }
-                    _ if let ty::PredicateKind::Trait(predicate) =
-                        error.obligation.predicate.kind().skip_binder() =>
-                    {
-                        predicate.self_ty().into()
-                    }
-                    _ => continue,
+                    _ => match error.obligation.predicate.kind().skip_binder() {
+                        ty::PredicateKind::Trait(predicate) => predicate.self_ty().into(),
+                        ty::PredicateKind::Projection(predicate) => {
+                            predicate.projection_ty.self_ty().into()
+                        }
+                        _ => continue,
+                    },
                 };
             let self_ = self.resolve_vars_if_possible(self_);
             let ty_matches_self = |ty: Ty<'tcx>| ty.walk().any(|arg| arg == self_);
@@ -1759,25 +1760,28 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let hir::ExprKind::Call(path, _) = &call_expr.kind {
             if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = &path.kind {
                 for error in errors {
-                    if let ty::PredicateKind::Trait(predicate) =
-                        error.obligation.predicate.kind().skip_binder()
+                    let self_ty = match error.obligation.predicate.kind().skip_binder() {
+                        ty::PredicateKind::Trait(predicate) => predicate.self_ty(),
+                        ty::PredicateKind::Projection(predicate) => {
+                            predicate.projection_ty.self_ty()
+                        }
+                        _ => continue,
+                    };
+                    // If any of the type arguments in this path segment caused the
+                    // `FulfillmentError`, point at its span (#61860).
+                    for arg in path
+                        .segments
+                        .iter()
+                        .filter_map(|seg| seg.args.as_ref())
+                        .flat_map(|a| a.args.iter())
                     {
-                        // If any of the type arguments in this path segment caused the
-                        // `FulfillmentError`, point at its span (#61860).
-                        for arg in path
-                            .segments
-                            .iter()
-                            .filter_map(|seg| seg.args.as_ref())
-                            .flat_map(|a| a.args.iter())
+                        if let hir::GenericArg::Type(hir_ty) = &arg
+                            && let Some(ty) =
+                                self.typeck_results.borrow().node_type_opt(hir_ty.hir_id)
+                            && self.resolve_vars_if_possible(ty) == self_ty
                         {
-                            if let hir::GenericArg::Type(hir_ty) = &arg
-                                && let Some(ty) =
-                                    self.typeck_results.borrow().node_type_opt(hir_ty.hir_id)
-                                && self.resolve_vars_if_possible(ty) == predicate.self_ty()
-                            {
-                                error.obligation.cause.span = hir_ty.span;
-                                break;
-                            }
+                            error.obligation.cause.span = hir_ty.span;
+                            break;
                         }
                     }
                 }