Verify AST instead of constant values.

pkg/analyzer/lib/src/summary/format.dart

Index: pkg/analyzer/lib/src/summary/format.dart
diff --git a/pkg/analyzer/lib/src/summary/format.dart b/pkg/analyzer/lib/src/summary/format.dart
index c46340d592a913c47fc00d28c04aabe875ecebec..f1142481093d14636ea3d24e0bb61a0f9708dde9 100644
--- a/pkg/analyzer/lib/src/summary/format.dart
+++ b/pkg/analyzer/lib/src/summary/format.dart
@@ -223,12 +223,16 @@ enum UnlinkedConstOperation {
   /**
    * Pop the top 2 values from the stack, evaluate `v1 == v2`, and push the
    * result back onto the stack.
-   *
-   * This is also used to represent `v1 != v2`, by composition with [not].
    */
   equal,
 
   /**
+   * Pop the top 2 values from the stack, evaluate `v1 != v2`, and push the
+   * result back onto the stack.
+   */
+  notEqual,
+
+  /**
    * Pop the top value from the stack, compute its boolean negation, and push
    * the result back onto the stack.
    */