bug#35119: 26.1; narrow-to-region loses word-start/symbol-start information at end

[Sam Halliday <sam.halliday@gmail.com>]

If the function `narrow-to-region' (as it is in `looking-back') is used
to restrict the region prior to an invocation of re-search-forward or
looking-at, then zero length regexp patterns are lost at the boundaries.

It is unclear if this is a bug or an undocumented feature, but it has
consequences for lexers that must operate backwards (such as those used
by SMIE).


In GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.7)
 of 2019-03-17 built on juergen
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description:	Arch Linux

Recent messages:

Mark set
You did not specify a variable
Type "q" to restore previous buffer. [2 times]
C-x <down> is undefined
funcall-interactively: Beginning of buffer [2 times]
Quit

Mark set
Quit

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-- 
Best regards,
Sam