Implement vtable shim generation.

Author: qnighy

src/librustc_mir/shim.rs

@@ -43,8 +43,14 @@ fn make_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let mut result = match instance {
         ty::InstanceDef::Item(..) =>
             bug!("item {:?} passed to make_shim", instance),
-        ty::InstanceDef::VtableShim(..) => {
-            unimplemented!("make_shim({:?})", instance);
+        ty::InstanceDef::VtableShim(def_id) => {
+            build_call_shim(
+                tcx,
+                def_id,
+                Adjustment::DerefMove,
+                CallKind::Direct(def_id),
+                None,
+            )
         }
         ty::InstanceDef::FnPtrShim(def_id, ty) => {
             let trait_ = tcx.trait_of_item(def_id).unwrap();
@@ -131,6 +137,7 @@ fn make_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 enum Adjustment {
     Identity,
     Deref,
+    DerefMove,
     RefMut,
 }
 
@@ -704,6 +711,14 @@ fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let rcvr = match rcvr_adjustment {
         Adjustment::Identity => Operand::Move(rcvr_l),
         Adjustment::Deref => Operand::Copy(rcvr_l.deref()),
+        Adjustment::DerefMove => {
+            // fn(Self, ...) -> fn(*mut Self, ...)
+            let arg_ty = local_decls[rcvr_arg].ty;
+            assert!(arg_ty.is_self());
+            local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
+
+            Operand::Copy(rcvr_l.deref())
+        }
         Adjustment::RefMut => {
             // let rcvr = &mut rcvr;
             let ref_rcvr = local_decls.push(temp_decl(