Resolve to Instance::VtableShim when necessary.

Author: qnighy

src/librustc_codegen_llvm/callee.rs

@@ -220,3 +220,19 @@ pub fn resolve_and_get_fn(
         ).unwrap()
     )
 }
+
+pub fn resolve_and_get_fn_for_vtable(
+    cx: &CodegenCx<'ll, 'tcx>,
+    def_id: DefId,
+    substs: &'tcx Substs<'tcx>,
+) -> &'ll Value {
+    get_fn(
+        cx,
+        ty::Instance::resolve_for_vtable(
+            cx.tcx,
+            ty::ParamEnv::reveal_all(),
+            def_id,
+            substs
+        ).unwrap()
+    )
+}

src/librustc_codegen_llvm/meth.rs

@@ -89,7 +89,7 @@ pub fn get_vtable(
     let methods = tcx.vtable_methods(trait_ref.with_self_ty(tcx, ty));
     let methods = methods.iter().cloned().map(|opt_mth| {
         opt_mth.map_or(nullptr, |(def_id, substs)| {
-            callee::resolve_and_get_fn(cx, def_id, substs)
+            callee::resolve_and_get_fn_for_vtable(cx, def_id, substs)
         })
     });
 

src/librustc_mir/monomorphize/collector.rs

@@ -915,7 +915,7 @@ fn create_mono_items_for_vtable_methods<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // Walk all methods of the trait, including those of its supertraits
         let methods = tcx.vtable_methods(poly_trait_ref);
         let methods = methods.iter().cloned().filter_map(|method| method)
-            .map(|(def_id, substs)| ty::Instance::resolve(
+            .map(|(def_id, substs)| ty::Instance::resolve_for_vtable(
                     tcx,
                     ty::ParamEnv::reveal_all(),
                     def_id,