Stream test result is invariant.
          #2525   Compile-time warning
          Stream test result is invariant.
Additional Information
The 'IS ATTACHED' test on the STRING SOURCE 'X' is invariantly true; consider removing it.
    or
A stream type test on a VALUE STREAM argument is an invariant; consider removing it.
    or
The 'HAS NAME' test on a VALUE STREAM argument is an invariant; consider removing it.
Recovery
      Compilation continues normally.
    
Explanation
 The result of a stream test is known at compile time.