Avoid inlining of external functions

Change-Id: I43aed9e484c55d40a9fa7d5db029e0d11a698b3e
Reviewed-on: https://dart-review.googlesource.com/28562
Reviewed-by: Sigmund Cherem <sigmund@google.com>

pkg/compiler/lib/src/ssa/builder_kernel.dart

@@ -922,6 +922,8 @@ class KernelSsaGraphBuilder extends ir.Visitor
 
   /// Builds a SSA graph for FunctionNodes of external methods.
   void buildExternalFunctionNode(ir.FunctionNode functionNode) {
+    // TODO(johnniwinther): Non-js-interop external functions should
+    // throw a runtime error.
     assert(functionNode.body == null);
     openFunction(functionNode);
     ir.TreeNode parent = functionNode.parent;
@@ -4270,7 +4272,6 @@ class KernelSsaGraphBuilder extends ir.Visitor
    * Try to inline [element] within the correct context of the builder. The
    * insertion point is the state of the builder.
    */
-  // TODO(redemption): Use this.
   bool _tryInlineMethod(
       FunctionEntity function,
       Selector selector,
@@ -4284,6 +4285,10 @@ class KernelSsaGraphBuilder extends ir.Visitor
       // Temporarily disable inlining of platform libraries.
       return false;
     }
+    if (function.isExternal) {
+      // Don't inline external methods; these should just fail at runtime.
+      return false;
+    }
 
     if (nativeData.isJsInteropMember(function) &&
         !(function is ConstructorEntity && function.isFactoryConstructor)) {

tests/compiler/dart2js/inlining/data/external.dart

@@ -0,0 +1,20 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// ignore: IMPORT_INTERNAL_LIBRARY
+import 'dart:_js_helper';
+
+/*element: main:[]*/
+main() {
+  externalFunction();
+}
+
+/*element: externalFunction:[]*/
+@NoInline()
+externalFunction() {
+  _externalFunction();
+}
+
+/*element: _externalFunction:[]*/
+external _externalFunction();

tests/compiler/dart2js/inlining/inlining_test.dart

@@ -28,7 +28,7 @@ main(List<String> args) {
     Directory dataDir = new Directory.fromUri(Platform.script.resolve('data'));
     await checkTests(
         dataDir, computeMemberAstInlinings, computeMemberIrInlinings,
-        args: args, skipForKernel: []);
+        args: args, skipforAst: ['external.dart'], skipForKernel: []);
   });
 }