From 5e8c9f4fae106d0ba836a0268ab4e44c19d63f2a Mon Sep 17 00:00:00 2001 From: Matthew Jasper Date: Sat, 13 Jun 2020 17:31:48 +0100 Subject: [PATCH] Explain what the substs we're creating are --- src/librustc_typeck/check/compare_method.rs | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs index 3a292993e39..4c39b2a3b61 100644 --- a/src/librustc_typeck/check/compare_method.rs +++ b/src/librustc_typeck/check/compare_method.rs @@ -1198,6 +1198,15 @@ fn compare_projection_bounds<'tcx>( let param_env = tcx.param_env(impl_ty.def_id); + // Given + // + // impl Foo for (A, B) { + // type Bar =... + // } + // + // - `impl_substs` would be `[A, B, C]` + // - `rebased_substs` would be `[(A, B), u32, C]`, combining the substs from + // the *trait* with the generic associated type parameters. let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id); let rebased_substs = impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);