bug#38539: char-fold-to-regexp and search-whitespace-regexp
I don't know but bug#35802 removed let-binding of search-spaces-regexp
around the char-fold-to-regexp call in isearch-search-fun-default.
Maybe this is fine, but makes the following slightly more isearch-dependent:
search-whitespace-regexp matches a sequence of whitespace chars
in isearch, i.e. by entering a space it matches any whitespace.
For example, in *scratch* searching with ‘C-s M-s ' 1 2’
will match all these lines:
It would be natural to expect that when char-fold-symmetric
is customized to non-nil, searching for ‘C-s M-s ' 1 2’
will also match the above lines.