Take is checks into account when deriving interceptor classes.

sdk/lib/_internal/compiler/implementation/ssa/interceptor_simplifier.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/interceptor_simplifier.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/interceptor_simplifier.dart b/sdk/lib/_internal/compiler/implementation/ssa/interceptor_simplifier.dart
index f2ae1a506763c0fe8b6bb84a2f9a6b61854d3aa7..268380efe2305df43c11deeb6fd0aac95169bfc7 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/interceptor_simplifier.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/interceptor_simplifier.dart
@@ -173,28 +173,34 @@ class SsaSimplifyInterceptors extends HBaseVisitor
     // it with a set of classes it intercepts.
     Set<ClassElement> interceptedClasses;
     JavaScriptBackend backend = compiler.backend;
-    HInstruction dominator =
-        findDominator(node.usedBy.where((i) => i is HInvokeDynamic));
+    HInstruction dominator = findDominator(node.usedBy.where((i) {
+        return i is HInvokeDynamic || i is HIs;

[floitsch, 2014/03/11 17:07:06]

Indent by two and the next line by 0.

+      }));
     // If there is an instruction that dominates all others, we can
     // use only the selector of that instruction.
     if (dominator != null) {
-      interceptedClasses =
-            backend.getInterceptedClassesOn(dominator.selector.name);
-
-      // If we found that we need number, we must still go through all
-      // uses to check if they require int, or double.
-      if (interceptedClasses.contains(backend.jsNumberClass)
-          && !(interceptedClasses.contains(backend.jsDoubleClass)
-               || interceptedClasses.contains(backend.jsIntClass))) {
-        for (HInstruction user in node.usedBy) {
-          if (user is! HInvoke) continue;
-          Set<ClassElement> intercepted =
-              backend.getInterceptedClassesOn(user.selector.name);
-          if (intercepted.contains(backend.jsIntClass)) {
-            interceptedClasses.add(backend.jsIntClass);
-          }
-          if (intercepted.contains(backend.jsDoubleClass)) {
-            interceptedClasses.add(backend.jsDoubleClass);
+      if (dominator is HIs) {
+        // Is checks do not constrain the set of intercepted classes.
+        interceptedClasses = backend.interceptedClasses;
+      } else {
+        interceptedClasses =
+              backend.getInterceptedClassesOn(dominator.selector.name);
+
+        // If we found that we need number, we must still go through all
+        // uses to check if they require int, or double.
+        if (interceptedClasses.contains(backend.jsNumberClass)
+            && !(interceptedClasses.contains(backend.jsDoubleClass)
+                 || interceptedClasses.contains(backend.jsIntClass))) {
+          for (HInstruction user in node.usedBy) {
+            if (user is! HInvoke) continue;
+            Set<ClassElement> intercepted =
+                backend.getInterceptedClassesOn(user.selector.name);
+            if (intercepted.contains(backend.jsIntClass)) {
+              interceptedClasses.add(backend.jsIntClass);
+            }
+            if (intercepted.contains(backend.jsDoubleClass)) {
+              interceptedClasses.add(backend.jsDoubleClass);
+            }
           }
         }
       }