Add a helper for replacing the self type in trait refs

2 files changed, 8 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index b4779655252..8bac76d559f 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -852,6 +852,10 @@ impl<'tcx> TraitPredicate<'tcx> {
         }
     }
 
+    pub fn with_self_type(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
+        Self { trait_ref: self.trait_ref.with_self_type(tcx, self_ty), ..self }
+    }
+
     pub fn def_id(self) -> DefId {
         self.trait_ref.def_id
     }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index b9717f2b37e..47cdabb5f81 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -811,6 +811,10 @@ impl<'tcx> TraitRef<'tcx> {
         TraitRef { def_id, substs }
     }
 
+    pub fn with_self_type(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
+        tcx.mk_trait_ref(self.def_id, self_ty, &self.substs[1..])
+    }
+
     /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
     /// are the parameters defined on trait.
     pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> Binder<'tcx, TraitRef<'tcx>> {