bug#33516: Should the docstring for flymake-diag-region mention behavior with narrowing?

[Matthew Bregg <bregg@google.com>]

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Currently it can be confusing when developing a flymake checker that
flymake-diag-region does not handle narrowing.

Updating the comment to mention this seems useful to me.

Thanks!

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From 0b4712c8553b918227bd58a2071a0dbdecaa04c0 Mon Sep 17 00:00:00 2001
From: Matthew Bregg <bregg@google.com>
Date: Fri, 16 Nov 2018 15:01:14 -0500
Subject: [PATCH] Update documentation for flymake.

Flymake flymake-diag-region does not mention behavior with narrowing, which can be confusing.
---
 lisp/progmodes/flymake.el | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
index f0f93f1087..58bbbd500e 100644
--- a/lisp/progmodes/flymake.el
+++ b/lisp/progmodes/flymake.el
@@ -384,7 +384,9 @@ verify FILTER, a function, and sort them by COMPARE (using KEY)."
 (defun flymake-diag-region (buffer line &optional col)
   "Compute BUFFER's region (BEG . END) corresponding to LINE and COL.
 If COL is nil, return a region just for LINE.  Return nil if the
-region is invalid."
+region is invalid.
+If the BUFFER has been narrowed,
+the region returned will correspond to the BUFFER's narrowed state."
   (condition-case-unless-debug _err
       (with-current-buffer buffer
         (let ((line (min (max line 1)
-- 
2.19.1.1215.g8438c0b245-goog