That is one of the error messages emitted by the Macintosh Programmer's Workshop C compiler. So are:
This label is the target of a goto from outside of the block containing this label AND this block has an automatic variable with an initializer AND your window wasn't wide enough to read this whole error messageand:
You can't modify a constant, float upstream, win an argument with the IRS, or satisfy this compiler
I found these in Tony Cunningham's C Compiler Errors (For Real)., from the Best of RHF: Computer, Science and Math Jokes. Which is itself from a certain newsgroup set up in 1987 by Brad Templeton, one rec.humor.funny. Tony was bored one afternoon and decompiled the MPW compiler's String resources. He believes there may be other messages...