After a dynamic call, refine the receiver type by looking at the potential targets of that call.

sdk/lib/_internal/compiler/implementation/universe/full_function_set.dart

Index: sdk/lib/_internal/compiler/implementation/universe/full_function_set.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/universe/full_function_set.dart	(revision 22031)
+++ sdk/lib/_internal/compiler/implementation/universe/full_function_set.dart	(working copy)
@@ -33,14 +33,16 @@
     // TODO(kasperl): Check if any of the found classes may have a
     // non-throwing noSuchMethod implementation in a subclass instead
     // of always disabling the class list computation.
-    if (compiler.enabledNoSuchMethod) return null;
+    if (compiler.enabledNoSuchMethod) {
+      return <ClassElement>[compiler.objectClass];
+    }
     List<ClassElement> classes = <ClassElement>[];
     int budget = MAX_CLASSES_STEPS;
     L: for (Element element in functions) {
       ClassElement enclosing = element.getEnclosingClass();
       for (int i = 0; i < classes.length; i++) {
         if (--budget <= 0) {
-          return null;
+          return <ClassElement>[compiler.objectClass];
         } else if (enclosing.isSubclassOf(classes[i])) {
           continue L;
         } else if (classes[i].isSubclassOf(enclosing)) {
@@ -48,26 +50,28 @@
           continue L;
         }
       }
-      if (classes.length >= MAX_CLASSES) return null;
+      if (classes.length >= MAX_CLASSES) {
+        return <ClassElement>[compiler.objectClass];
+      }
       classes.add(enclosing);
     }
     return classes;
   }
 
   static bool isExactClass(List<ClassElement> classes, Compiler compiler) {
-    if (classes == null || classes.length != 1) return false;
+    if (classes.length != 1) return false;
     ClassElement single = classes[0];
     // Return true if the single class in our list does not have a
     // single instantiated subclass.
-    Set<ClassElement> subtypes = compiler.world.subtypes[single];
-    return subtypes == null
-        || subtypes.every((ClassElement each) => !each.isSubclassOf(single));
+    Set<ClassElement> subclasses = compiler.world.subclasses[single];
+    return subclasses == null || subclasses.isEmpty;
   }
 }
 
 class FullFunctionSetQuery extends FunctionSetQuery {
-  final List<ClassElement> classes;
   final bool isExact;
-  FullFunctionSetQuery(List<Element> functions, this.classes, this.isExact)
-      : super(functions);
+  FullFunctionSetQuery(List<Element> functions,
+                       Iterable<ClassElement> classes,
+                       this.isExact)
+      : super(functions, classes);
 }