`set iskeyword+=:` breaks highlighting

[KonradHoeffner]

Steps to reproduce

1. Put set iskeyword+=: in ~/.vimrc
2. Save the following file as test.ts and open it in Vim or Neovim:

const x =
{
    onClickFunction: (event) => {
        const body = `${1+1}`;
        console.log("The rest of the file is highlighted incorrectly");
    }
}
x.onClickFunction(null);

Expected behaviour

The line thisFunctionIsShownAsLiteralButItIsntOne(); should be highlighted as a function but it is shown as a literal.

Details and Proposed Change

This issue was originally raised at https://github.com/vim/vim/issues/9772, where @lacygoill proposed a patch to resolve this issue.

[HerringtonDarkholme]

: is not keyword in TypeScript. I wonder why the config is added?

[KonradHoeffner]

To be honest this was only added to get easier word traversal with the 'w' key, mostly for LaTeX, to delete parts of labels more easily, and I probably should make this specific to certain file types, however I thought it better to still raise it here in case this effect is not intended and helps prevent future issues with similar causes.