[dart2dart] Cut declaration types by default if we check that it is safe to do so.

lib/compiler/implementation/dart_backend/placeholder_collector.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.
 
 class LocalPlaceholder implements Hashable {
   final String identifier;
   final Set<Node> nodes;
   LocalPlaceholder(this.identifier) : nodes = new Set<Node>();
   int hashCode() => identifier.hashCode();
   String toString() =>
@@ skipping 481 matching lines @@
       } else if (definition is FunctionExpression) {
         // Skip, it will be processed in visitFunctionExpression.
       } else {
         internalError('Unexpected definition structure $definition');
       }
     }
     node.visitChildren(this);
   }
 
   visitFunctionExpression(FunctionExpression node) {
+    bool isKeyword(Identifier id) =>
+        id !== null && Keyword.keywords[id.source.slowToString()] !== null;
+
     Element element = treeElements[node];
     // May get null here in case of A(int this.f());
     if (element !== null) {
       // Rename only local functions.
       if (topmostEnclosingFunction === null) {
         topmostEnclosingFunction = element;
       }
       if (element !== currentElement) {
         if (node.name !== null) {
           assert(node.name is Identifier);
           tryMakeLocalPlaceholder(element, node.name);
         }
       }
     }
     node.visitChildren(this);
-    makeOmitDeclarationTypePlaceholder(node.returnType);
+    // Make sure we don't omit return type of methods which names are
+    // identifiers, because the following works fine:
+    // int interface() => 1;
+    // But omitting 'int' makes VM unhappy.
+    // TODO(smok): Remove it when http://dartbug.com/5278 is fixed.
+    if (node.name === null || !isKeyword(node.name.asIdentifier())) {
+      makeOmitDeclarationTypePlaceholder(node.returnType);
+    }
     collectFunctionParameters(node.parameters);
   }
 
   void collectFunctionParameters(NodeList parameters) {
     if (parameters === null) return;
     for (Node parameter in parameters.nodes) {
       if (parameter is NodeList) {
         // Optional parameter list.
         collectFunctionParameters(parameter);
       } else {
@@ skipping 56 matching lines @@
 
   visitBlock(Block node) {
     for (Node statement in node.statements.nodes) {
       if (statement is VariableDefinitions) {
         makeVarDeclarationTypePlaceholder(statement);
       }
     }
     node.visitChildren(this);
   }
 }