Refactor the way we emit no such method handlers so it's easier to optimize it later.

lib/compiler/implementation/world.dart

Index: lib/compiler/implementation/world.dart
diff --git a/lib/compiler/implementation/world.dart b/lib/compiler/implementation/world.dart
index f616c5aa4c892251aa2f5984e0c03e6980e8324a..37fff42988ce3a6fbd4e9addec32e2cbbb974638 100644
--- a/lib/compiler/implementation/world.dart
+++ b/lib/compiler/implementation/world.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 class World {
+  Compiler compiler;  // Set in populate().
   final Map<ClassElement, Set<ClassElement>> subtypes;
 
   World() : subtypes = new Map<ClassElement, Set<ClassElement>>();
@@ -28,6 +29,10 @@ class World {
         addSubtypes(cls);
       }
     });
+
+    // Mark the world as populated.
+    assert(compiler !== null);
+    this.compiler = compiler;
   }
 
   /**
@@ -35,6 +40,7 @@ class World {
    * selector named [member] on a receiver whose type is [type].
    */
   MemberSet _memberSetFor(Type type, SourceString member) {
+    assert(compiler !== null);
     ClassElement cls = type.element;
     MemberSet result = new MemberSet(member);
     Element element = cls.lookupMember(member);
@@ -69,6 +75,17 @@ class World {
     });
     return (fieldCount == 1 && nonFieldCount == 0) ? field : null;
   }
+
+  bool mayHaveUserDefinedNoSuchMethod(Type type) {

[ahe, 2012/08/02 17:15:05]

We should consider this class as "delete-only" as it should be superseded by
Enqueuer :-)

[kasperl, 2012/08/03 05:21:00]

Yeah, that's probably better.

+    MemberSet memberSet = _memberSetFor(type, Compiler.NO_SUCH_METHOD);
+    // TODO(kasperl): Only return true if the set contains an instance
+    // method with the right signature. Remember to disregard the
+    // implementation in Object.
+    for (Element element in memberSet.elements) {
+      if (element.getEnclosingClass() !== compiler.objectClass) return true;
+    }
+    return false;
+  }
 }
 
 /**