1 files changed, 8 insertions, 13 deletions

diff --git a/compiler/rustc_codegen_ssa/src/meth.rs b/compiler/rustc_codegen_ssa/src/meth.rs
index 27d791d90..cae46ebd2 100644
--- a/compiler/rustc_codegen_ssa/src/meth.rs
+++ b/compiler/rustc_codegen_ssa/src/meth.rs
@@ -1,6 +1,6 @@
 use crate::traits::*;
 
-use rustc_middle::ty::{self, subst::GenericArgKind, ExistentialPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
 use rustc_session::config::Lto;
 use rustc_symbol_mangling::typeid_for_trait_ref;
 use rustc_target::abi::call::FnAbi;
@@ -29,7 +29,7 @@ impl<'a, 'tcx> VirtualIndex {
             && bx.cx().sess().lto() == Lto::Fat
         {
             let typeid =
-                bx.typeid_metadata(typeid_for_trait_ref(bx.tcx(), get_trait_ref(bx.tcx(), ty)));
+                bx.typeid_metadata(typeid_for_trait_ref(bx.tcx(), expect_dyn_trait_in_self(ty)));
             let vtable_byte_offset = self.0 * bx.data_layout().pointer_size.bytes();
             let type_checked_load = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
             let func = bx.extract_value(type_checked_load, 0);
@@ -64,17 +64,13 @@ impl<'a, 'tcx> VirtualIndex {
     }
 }
 
-fn get_trait_ref<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::PolyExistentialTraitRef<'tcx> {
+/// This takes a valid `self` receiver type and extracts the principal trait
+/// ref of the type.
+fn expect_dyn_trait_in_self<'tcx>(ty: Ty<'tcx>) -> ty::PolyExistentialTraitRef<'tcx> {
     for arg in ty.peel_refs().walk() {
         if let GenericArgKind::Type(ty) = arg.unpack() {
-            if let ty::Dynamic(trait_refs, _) = ty.kind() {
-                return trait_refs[0].map_bound(|trait_ref| match trait_ref {
-                    ExistentialPredicate::Trait(tr) => tr,
-                    ExistentialPredicate::Projection(proj) => proj.trait_ref(tcx),
-                    ExistentialPredicate::AutoTrait(_) => {
-                        bug!("auto traits don't have functions")
-                    }
-                });
+            if let ty::Dynamic(data, _, _) = ty.kind() {
+                return data.principal().expect("expected principal trait object");
             }
         }
     }
@@ -90,6 +86,7 @@ fn get_trait_ref<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::PolyExistentialTr
 /// The `trait_ref` encodes the erased self type. Hence if we are
 /// making an object `Foo<dyn Trait>` from a value of type `Foo<T>`, then
 /// `trait_ref` would map `T: Trait`.
+#[instrument(level = "debug", skip(cx))]
 pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
     cx: &Cx,
     ty: Ty<'tcx>,
@@ -97,8 +94,6 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
 ) -> Cx::Value {
     let tcx = cx.tcx();
 
-    debug!("get_vtable(ty={:?}, trait_ref={:?})", ty, trait_ref);
-
     // Check the cache.
     if let Some(&val) = cx.vtables().borrow().get(&(ty, trait_ref)) {
         return val;