emacs-28 21397cc: Improve documentation string for 'compilation-error-regexp-alist'.

[Philipp Stephani]

branch: emacs-28
commit 21397cce51dc3f9b6e9b0e7a5cc877b63efa8dd4
Author: Philipp Stephani <phst@google.com>
Commit: Philipp Stephani <phst@google.com>

    Improve documentation string for 'compilation-error-regexp-alist'.
    
    * lisp/progmodes/compile.el (compilation-error-regexp-alist): Clarify
    behavior when TYPE is a cons cell.
---
 lisp/progmodes/compile.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index 73f9806..ac26f5e 100644
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -662,7 +662,8 @@ has just been matched, and should correspondingly preserve 
this match data.
 TYPE is 2 or nil for a real error or 1 for warning or 0 for info.
 TYPE can also be of the form (WARNING . INFO).  In that case this
 will be equivalent to 1 if the WARNING'th subexpression matched
-or else equivalent to 0 if the INFO'th subexpression matched.
+or else equivalent to 0 if the INFO'th subexpression matched,
+or else equivalent to 2 if neither of them matched.
 See `compilation-error-face', `compilation-warning-face',
 `compilation-info-face' and `compilation-skip-threshold'.