An invalid combination of tests was encountered in a stream type test.
#2126 Compile-time error
An invalid combination of tests was encountered in a stream type test.
Additional Information
For stream 'X', current keyword is 'Y'.
where X is the name of the stream in the test, and Y is the current
keyword which conflicts with keywords already present in the test.
Explanation
Certain tests make no sense, such as "WHEN STREAM <name> IS (OPEN AND
CLOSED)" or "(FILE AND SOURCE-BUFFER)" or "(READER-FUNCTION AND
REFERENT AND OPEN)". The compiler does not complain about redundant
tests, such as "(OPEN AND OPEN)" or "(FILE AND SINK)".