bug substitution with parenthesis

[jerabaul29]

Writing the following substitution:

:%s/ ))/))/gc

Produces error:

CommandLine: Error executing cmd=%s/ ))/))/gc. err=SyntaxError: Invalid regular expression: / ))/: Unmatched ')'.

while this works fine in Vim.

[J-Fields]

I think this is due to the fact we use javascript's regex engine, not an emulation of vim's. #3996

[J-Fields]

This will work as expected if you enable neovim integration.