11.9.5 @error{} (error→): Indicating an Error Message

A piece of code may cause an error when you evaluate it. You can designate the error message with the @error{} command.

The @error{} command is displayed as ‘error→’, either the word ‘error’ in a box in the printed output, the word error followed by an arrow in other formats or (when no arrow is available) ‘error-->’.

Thus,

@lisp
(+ 23 'x)
@error{} Wrong type argument: integer-or-marker-p, x
@end lisp

produces

(+ 23 'x)
error→ Wrong type argument: integer-or-marker-p, x

This indicates that the following error message is printed when you evaluate the expression:

Wrong type argument: integer-or-marker-p, x

The word ‘error→’ itself is not part of the error message.