Register toString dynamic invocation in the presence of string interpolation.

tests/compiler/dart2js/resolver_test.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.
 
+#import('dart:uri');
+
 #import("../../../lib/compiler/implementation/leg.dart");
 #import("../../../lib/compiler/implementation/elements/elements.dart");
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 #import("../../../lib/compiler/implementation/util/util.dart");
+#import("compiler_helper.dart");
 #import("mock_compiler.dart");
 #import("parser_helper.dart");
 
 Node buildIdentifier(String name) => new Identifier(scan(name));
 
 Node buildInitialization(String name) =>
   parseBodyCode('$name = 1',
       (parser, tokens) => parser.parseOptionallyInitializedIdentifier(tokens));
 
 createLocals(List variables) {
@@ skipping 43 matching lines @@
   // testOneInterface(); // Generates unexpected error message.
   // testTwoInterfaces(); // Generates unexpected error message.
   testFunctionExpression();
   testNewExpression();
   testTopLevelFields();
   testClassHierarchy();
   testInitializers();
   testThis();
   testSuperCalls();
   testTypeVariables();
+  testToString();
 }
 
 testTypeVariables() {
   matchResolvedTypes(visitor, text, name, expectedElements) {
     VariableDefinitions definition = parseStatement(text);
     visitor.visit(definition.type);
     InterfaceType type = visitor.mapping.getType(definition.type);
     Expect.equals(definition.type.typeArguments.length(),
                   length(type.arguments));
     int index = 0;
@@ skipping 632 matching lines @@
 length(Link link) => link.isEmpty() ? 0 : length(link.tail) + 1;
 
 at(Link link, int index) => (index == 0) ? link.head : at(link.tail, index - 1);
 
 List<String> asSortedStrings(Link link) {
   List<String> result = <String>[];
   for (; !link.isEmpty(); link = link.tail) result.add(link.head.toString());
   result.sort((s1, s2) => s1.compareTo(s2));
   return result;
 }
+
+testToString() {
+  Uri uri = new Uri.fromComponents(scheme: 'source');
+  MockCompiler compiler = compilerFor(
+      @"class C { toString() => 'C'; } main() { '${new C()}'; }",
+      uri);
+  compiler.runCompiler(uri);
+
+  Element toStringMethod = findElement(compiler, 'C')
+      .lookupLocalMember(buildSourceString('toString'));
+  Expect.isNotNull(toStringMethod);
+
+  Expect.isNotNull(
+      compiler.enqueuer.resolution.getCachedElements(toStringMethod));
+}