Allow iterators instead of requiring slices that will get turned into iterators

4 files changed, 15 insertions, 9 deletions

diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
index 458cbfa6e35..b8e6f0258d0 100644
--- a/compiler/rustc_middle/src/ty/adjustment.rs
+++ b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -131,7 +131,7 @@ impl<'tcx> OverloadedDeref<'tcx> {
             .find(|m| m.kind == ty::AssocKind::Fn)
             .unwrap()
             .def_id;
-        tcx.mk_fn_def(method_def_id, tcx.mk_substs_trait(source, &[]))
+        tcx.mk_fn_def(method_def_id, tcx.mk_substs_trait(source, []))
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index cf0d201cbb7..c43447ae05d 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -2809,20 +2809,26 @@ impl<'tcx> TyCtxt<'tcx> {
         iter.intern_with(|xs| self.intern_place_elems(xs))
     }
 
-    pub fn mk_substs_trait(self, self_ty: Ty<'tcx>, rest: &[GenericArg<'tcx>]) -> SubstsRef<'tcx> {
-        self.mk_substs(iter::once(self_ty.into()).chain(rest.iter().cloned()))
+    pub fn mk_substs_trait(
+        self,
+        self_ty: Ty<'tcx>,
+        rest: impl IntoIterator<Item = GenericArg<'tcx>>,
+    ) -> SubstsRef<'tcx> {
+        self.mk_substs(iter::once(self_ty.into()).chain(rest))
     }
 
     pub fn mk_trait_ref(
         self,
         trait_def_id: DefId,
         self_ty: Ty<'tcx>,
-        rest: &[GenericArg<'tcx>],
+        rest: impl IntoIterator<Item = GenericArg<'tcx>, IntoIter: ExactSizeIterator>,
     ) -> ty::TraitRef<'tcx> {
+        let rest = rest.into_iter();
         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:?}: {rest:?} \nDid you accidentally include the self-type in the params list?"
+            "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<_>>(),
         );
         let substs = self.mk_substs_trait(self_ty, rest);
         ty::TraitRef::new(trait_def_id, substs)
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index a792d2694b3..586460986dd 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -551,7 +551,7 @@ impl<'tcx> Instance<'tcx> {
         let sig =
             tcx.try_normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig).ok()?;
         assert_eq!(sig.inputs().len(), 1);
-        let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
+        let substs = tcx.mk_substs_trait(self_ty, [sig.inputs()[0].into()]);
 
         debug!(?self_ty, ?sig);
         Some(Instance { def, substs })
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 47cdabb5f81..35ab8b2af6b 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 +812,7 @@ 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[1..])
+        tcx.mk_trait_ref(self.def_id, self_ty, self.substs.iter().skip(1))
     }
 
     /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
@@ -910,7 +910,7 @@ 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)
+        tcx.mk_trait_ref(self.def_id, self_ty, self.substs.iter())
     }
 }