resolve: ensure compile failed when has dummy or ambiguous

Author: bvanjoi

compiler/rustc_resolve/src/imports.rs

@@ -989,17 +989,17 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             initial_binding.res()
                         });
                         let res = binding.res();
+                        if res == Res::Err || !this.ambiguity_errors.is_empty() {
+                            this.tcx
+                                .sess
+                                .delay_span_bug(import.span, "some error happened for an import");
+                            return;
+                        }
                         if let Ok(initial_res) = initial_res {
-                            if res != initial_res
-                                && this.ambiguity_errors.is_empty()
-                                && res != Res::Err
-                            {
+                            if res != initial_res {
                                 span_bug!(import.span, "inconsistent resolution for an import");
                             }
-                        } else if res != Res::Err
-                            && this.ambiguity_errors.is_empty()
-                            && this.privacy_errors.is_empty()
-                        {
+                        } else if this.privacy_errors.is_empty() {
                             this.tcx
                                 .sess
                                 .create_err(CannotDetermineImportResolution { span: import.span })