X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=compiler%2Frustc_infer%2Fsrc%2Ftraits%2Futil.rs;h=18a966449aa72f2e9432ab3c833d8bdc1ba22bae;hb=e45984b7746737feeef1dffe403475b2cc4e68cd;hp=cd5bde2a791309c6c0f6d5aa6d73a55e412e0e36;hpb=ad48c109815a2e9441a7ad7796e55b8771fe01a5;p=rust.git

diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index cd5bde2a791..18a966449aa 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -145,30 +145,32 @@ fn elaborate(&mut self, obligation: &PredicateObligation<'tcx>) {
                 // Get predicates declared on the trait.
                 let predicates = tcx.super_predicates_of(data.def_id());
 
-                let obligations = predicates.predicates.iter().map(|&(mut pred, span)| {
-                    // when parent predicate is non-const, elaborate it to non-const predicates.
-                    if data.constness == ty::BoundConstness::NotConst {
-                        pred = pred.without_const(tcx);
-                    }
-
-                    let cause = obligation.cause.clone().derived_cause(
-                        bound_predicate.rebind(data),
-                        |derived| {
-                            traits::ImplDerivedObligation(Box::new(
-                                traits::ImplDerivedObligationCause {
-                                    derived,
-                                    impl_def_id: data.def_id(),
-                                    span,
-                                },
-                            ))
-                        },
-                    );
-                    predicate_obligation(
-                        pred.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref)),
-                        obligation.param_env,
-                        cause,
-                    )
-                });
+                let obligations =
+                    predicates.predicates.iter().enumerate().map(|(index, &(mut pred, span))| {
+                        // when parent predicate is non-const, elaborate it to non-const predicates.
+                        if data.constness == ty::BoundConstness::NotConst {
+                            pred = pred.without_const(tcx);
+                        }
+
+                        let cause = obligation.cause.clone().derived_cause(
+                            bound_predicate.rebind(data),
+                            |derived| {
+                                traits::ImplDerivedObligation(Box::new(
+                                    traits::ImplDerivedObligationCause {
+                                        derived,
+                                        impl_def_id: data.def_id(),
+                                        impl_def_predicate_index: Some(index),
+                                        span,
+                                    },
+                                ))
+                            },
+                        );
+                        predicate_obligation(
+                            pred.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref)),
+                            obligation.param_env,
+                            cause,
+                        )
+                    });
                 debug!(?data, ?obligations, "super_predicates");
 
                 // Only keep those bounds that we haven't already seen.