Fix regression introduced in 'Use AbstractValue in most of ssa'

Change-Id: Ie6159eb750ece1748ba1bb0b3c4f4d13a0dff9d6
Reviewed-on: https://dart-review.googlesource.com/58021
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Stephen Adams <sra@google.com>
diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index 4c03def..3c3d569 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -1282,7 +1282,7 @@
       }
       // All intercepted classes extend `Interceptor`, so if the receiver can't
       // be a class extending `Interceptor` then it can be called directly.
-      if (!_abstractValueDomain.canBeInterceptor(toStringType)) {
+      if (!_abstractValueDomain.canBeInterceptor(input.instructionType)) {
         var inputs = <HInstruction>[input, input]; // [interceptor, receiver].
         HInstruction result = new HInvokeDynamicMethod(
             selector,