Register iterate-protocol helper if there is for-in.

lib/compiler/implementation/resolver.dart

 // Copyright (c) 2012, 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.
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   DartType getType(TypeAnnotation annotation);
   bool isParameterChecked(Element element);
 }
@@ skipping 1733 matching lines @@
 
   visitConditional(Conditional node) {
     node.visitChildren(this);
   }
 
   visitStringInterpolation(StringInterpolation node) {
     node.visitChildren(this);
   }
 
   visitStringInterpolationPart(StringInterpolationPart node) {
-    SourceString name = const SourceString('toString');
-    LibraryElement library = enclosingElement.getLibrary();
-    Selector selector = new Selector.call(name, library, 0);
-    world.registerDynamicInvocation(name, selector);
+    registerImplicitInvocation(const SourceString('toString'), 0);
     node.visitChildren(this);
   }
 
   visitBreakStatement(BreakStatement node) {
     TargetElement target;
     if (node.target === null) {
       target = statementScope.currentBreakTarget();
       if (target === null) {
         error(node, MessageKind.NO_BREAK_TARGET);
         return;
@@ skipping 40 matching lines @@
       // TODO(lrn): Handle continues to switch cases.
       if (target.statement is SwitchCase) {
         unimplemented(node, "continue to switch case");
       }
       label.setContinueTarget();
       mapping[node.target] = label;
     }
     mapping[node] = target;
   }
 
+  registerImplicitInvocation(SourceString name, int arity) {
+    Selector selector = new Selector.call(name, null, arity);
+    world.registerDynamicInvocation(name, selector);
+  }
+
   visitForIn(ForIn node) {
+    for (final name in const [
+        const SourceString('iterator'),
+        const SourceString('next'),
+        const SourceString('hasNext')]) {
+      registerImplicitInvocation(name, 0);
+    }
     visit(node.expression);
     Scope blockScope = new BlockScope(scope);
     Node declaration = node.declaredIdentifier;
     visitIn(declaration, blockScope);
     visitLoopBodyIn(node, node.body, blockScope);
 
     // TODO(lrn): Also allow a single identifier.
     if ((declaration is !Send || declaration.asSend().selector is !Identifier)
         && (declaration is !VariableDefinitions ||
         !declaration.asVariableDefinitions().definitions.nodes.tail.isEmpty()))
@@ skipping 988 matching lines @@
 
   Element localLookup(SourceString name) => library.find(name);
   Element lookup(SourceString name) => localLookup(name);
   Element lexicalLookup(SourceString name) => localLookup(name);
 
   Element add(Element newElement) {
     throw "Cannot add an element in the top scope";
   }
   String toString() => '$element';
 }