Invalid COPY action encountered.
#2079 Compile-time error
Invalid COPY action encountered.
Additional Information
The shelf "X" cannot be copied to itself.
Explanation
This message is given for an action such as
COPY STREAM buf TO buf.
However, if some shelf X is a variable parameter referring to another
shelf Y while in some function, the compiler will not complain if
shelf X is copied to Y, or vice versa.