Mark native methods as external.

lib/kernel.dart

 // Copyright (c) 2016, 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.md file.
 
 library rasta.kernel;
 
 import 'dart:async' show
     Future;
 
 import 'dart:collection' show
@@ skipping 31 matching lines @@
 
 import 'package:compiler/src/diagnostics/spannable.dart' show
     Spannable;
 
 import 'package:compiler/src/diagnostics/messages.dart' show
     MessageKind;
 
 import 'package:compiler/src/constants/expressions.dart' show
     TypeConstantExpression;
 
+import 'package:compiler/src/tree/tree.dart' show
+    FunctionExpression,
+    Node;
+
 import 'custom_compiler.dart' show
     CustomCompiler;
 
 import 'kernel_visitor.dart' show
     IrFunction,
     KernelVisitor;
 
 typedef void WorkAction();
 
 class WorkItem {
@@ skipping 261 matching lines @@
       member.parent = elementToIr(element.enclosingElement);
     } else if (element.isTopLevel) {
       member.parent = elementToIr(element.library);
     } else if (element.isClassMember) {
       member.parent = elementToIr(element.enclosingClass);
     } else {
       member.parent = elementToIr(element.enclosingElement);
     }
   }
 
+  bool isNativeMethod(FunctionElement element) {
+    // This method is a (modified) copy of the same method in
+    // `pkg/compiler/lib/src/native/enqueue.dart`.
+    if (!compiler.backend.canLibraryUseNative(element.library)) return false;
+    return compiler.reporter.withCurrentElement(element, () {
+      FunctionExpression functionExpression =
+          element.node?.asFunctionExpression();
+      if (functionExpression == null) return false;
+      Node body = functionExpression.body;
+      if (body == null) return false;
+      if (identical(body.getBeginToken().stringValue, 'native')) return true;
+      return false;
+    });
+  }
+
   ir.Member functionToIr(FunctionElement function) {
     if (function.isDeferredLoaderGetter) {
       internalError(function, "Deferred loader.");
     }
     if (function.isLocal) {
       internalError(function, "Local function.");
     }
     if (isSyntheticError(function)) {
       internalError(function, "Synthetic error function: $function.");
     }
     function = function.declaration;
     return functions.putIfAbsent(function, () {
       compiler.analyzeElement(function);
       compiler.enqueuer.resolution.emptyDeferredTaskQueue();
       function = function.implementation;
       ir.Member member;
       ir.Constructor constructor;
       ir.Procedure procedure;
       ir.Name name = irName(function.name, function);
+      bool isNative = isNativeMethod(function);
       if (function.isGenerativeConstructor) {
         member = constructor = new ir.Constructor(
             null, name: name, isConst: function.isConst,
-            isExternal: function.isExternal, initializers: null);
+            isExternal: isNative || function.isExternal, initializers: null);
       } else {
         member = procedure = new ir.Procedure(
             name, null, null, isAbstract: function.isAbstract,
             isStatic: function.isStatic || function.isTopLevel
                 || function.isFactoryConstructor,
-            isExternal: function.isExternal,
+            isExternal: isNative || function.isExternal,
             isConst: false); // TODO(ahe): When is this true?
       }
       addWork(function, () {
         setParent(member, function);
         KernelVisitor visitor =
             new KernelVisitor(function, function.treeElements, this);
         beginFactoryScope(function);
         IrFunction irFunction = visitor.buildFunction();
         // TODO(ahe): Add addFunction/set function to [ir.Procedure].
         irFunction.node.parent = member;
@@ skipping 293 matching lines @@
 }
 
 class ConstructorTarget {
   final ConstructorElement element;
   final DartType type;
 
   ConstructorTarget(this.element, this.type);
 
   String toString() => "ConstructorTarget($element, $type)";
 }