bug#12622: replace-regexp-in-string

[Andreas Röhler]

Hi,

the following question was raised at:

http://stackoverflow.com/questions/12809610/replace-regexp-in-string-with-lookahead-behind

I'd like to replace all occurrences of \w \w with \w\\\w in a string, where the 
\w parts stay the same before and after the replacement, e.g.

[.A foobar] [.B baz]

should result in

[.A\\foobar] [.B\\baz]

;;;;;;;;;;

this might be solved in buffer

by

(while  (re-search-forward "\\_<\\w+\\_>" nil t 1)
  (replace-match (concat "\\\\\\\\" (match-string-no-properties 0) )))

Also would expect a respective form working with replace-regexp-in-string

(setq mystring "[.A foobar] [.B baz]")
(replace-regexp-in-string  "\\_<\\w+\\_>" (concat "\\\\" 
(match-string-no-properties 0) )   mystring)

but it fails.

When commenting "(match-string 0 str)" as follows it subr.el it works

        (setq matches
              (cons (replace-match (if (stringp rep)
                                       rep
                                     (funcall rep
                                              ;; (match-string 0 str)
))
                                   fixedcase literal str subexp)

Which has some plausibility: when receiving a user-specified function, there 
must not be that argument.

Maybe have a look,

Best,

Andreas