2 files changed, 16 insertions, 14 deletions
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 0ee190302ac..8d6ae142314 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -2820,17 +2820,17 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_trait_ref(
         self,
         trait_def_id: DefId,
-        self_ty: Ty<'tcx>,
-        rest: impl IntoIterator<Item = GenericArg<'tcx>, IntoIter: ExactSizeIterator>,
+        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
     ) -> ty::TraitRef<'tcx> {
-        let rest = rest.into_iter();
+        let substs = substs.into_iter().map(Into::into);
+        let n = self.generics_of(trait_def_id).count();
         debug_assert_eq!(
-            self.generics_of(trait_def_id).count() - 1,
-            rest.len(),
-            "wrong number of generic parameters for {trait_def_id:?} on self type {self_ty:?}: {:?} \nDid you accidentally include the self-type in the params list?",
-            rest.collect::<Vec<_>>(),
+            (n, Some(n)),
+            substs.size_hint(),
+            "wrong number of generic parameters for {trait_def_id:?}: {:?} \nDid you accidentally include the self-type in the params list?",
+            substs.collect::<Vec<_>>(),
         );
-        let substs = self.mk_substs_trait(self_ty, rest);
+        let substs = self.mk_substs(substs);
         ty::TraitRef::new(trait_def_id, substs)
     }
 
@@ -2994,11 +2994,10 @@ impl<'tcx> TyCtxtAt<'tcx> {
     pub fn mk_trait_ref(
         self,
         trait_lang_item: LangItem,
-        self_ty: Ty<'tcx>,
-        rest: impl IntoIterator<Item = ty::GenericArg<'tcx>, IntoIter: ExactSizeIterator>,
+        substs: impl IntoIterator<Item = impl Into<ty::GenericArg<'tcx>>>,
     ) -> ty::TraitRef<'tcx> {
         let trait_def_id = self.require_lang_item(trait_lang_item, Some(self.span));
-        self.tcx.mk_trait_ref(trait_def_id, self_ty, rest)
+        self.tcx.mk_trait_ref(trait_def_id, substs)
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 35ab8b2af6b..db18558e947 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -719,7 +719,7 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
                 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
             }
             ExistentialPredicate::AutoTrait(did) => {
-                let trait_ref = self.rebind(tcx.mk_trait_ref(did, self_ty, []));
+                let trait_ref = self.rebind(tcx.mk_trait_ref(did, [self_ty]));
                 trait_ref.without_const().to_predicate(tcx)
             }
         }
@@ -812,7 +812,10 @@ impl<'tcx> TraitRef<'tcx> {
     }
 
     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.iter().skip(1))
+        tcx.mk_trait_ref(
+            self.def_id,
+            [self_ty.into()].into_iter().chain(self.substs.iter().skip(1)),
+        )
     }
 
     /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
@@ -910,7 +913,7 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
         // otherwise the escaping vars would be captured by the binder
         // debug_assert!(!self_ty.has_escaping_bound_vars());
 
-        tcx.mk_trait_ref(self.def_id, self_ty, self.substs.iter())
+        tcx.mk_trait_ref(self.def_id, [self_ty.into()].into_iter().chain(self.substs.iter()))
     }
 }