bug#50766: Regexp paren pairs in query-replace-regexp prompt should be highlighted

[ndame]

>
> I think that it would help users a lot when constructing regexps, so it
> would be very welcome.

I wonder if it could be a generic feature which besides working in the
minibuffer for regexps would also work when typing escaped parens in
in strings, e.g. when using a string regexp in a program:

   "stuff ( \\(  ) "

Here it could indicate the mismatching parens.