Highlight active parameter with face eldoc-highlight-function-argument

[MaskRay]

int foo(int a, int b, int c = 7) {
  return a+ b + c;
}

int main() {
  foo(1, 2<point>, 3);
}

In ccls, this was rendered as foo(int a, int b, int c = 7) -> int before, and now foo(int a, <strong>int b</strong>, int c = 7) -> int.

Similar approaches are used by

LanguageClient-neovim src/languageclient.rs

eglot (but it trims the signature label (propertize (replace-regexp-in-string "(.*$" "(" label) which will remove -> return_type)

[MaskRay]

BTW, (defun lsp--text-document-signature-help () ...) only takes effect when (symbol-at-point)is notnil. This does not work well for foo(arg0, ` (when there is no symbol in the argument position)

[vibhavp]

Thanks.