x/tools/gopls: add `shadowing` semantic token modifier

[mateusz834]

#75342 made me think that I so often catch shadow bugs early, because i have the shadow analyzer enabled, that it would be nice to have some better way to expose such functionality to users, such that these are not warnings, but as a hint.

This is not only about variable naming bugs, but I often get frustrated that url. does not give any autocomplete only to realize that I have declared an url variable.

It would be nice to have a way to give attention to some parts of code.

My proposition is we add a shadowing semantic token modifier, that is returned to the editor, when an identifier causes other identifier, from outer scope(s), to be shadowed.

Example:

It requires (at least in nvim) some special configuration:

vim.api.nvim_set_hl(0, '@lsp.mod.shadowing', { bold=true, underline=true })

CC @adonovan

[mateusz834]

Initial draft in CL 702555.

[adonovan]

It's a nice idea, but the implementation looks potentially expensive. Also, the modifier should be called "shadowing", if you keep the sense proposed above, which I think makes sense.

[mateusz834]

Also, the modifier should be called "shadowing", if you keep the sense proposed above, which I think makes sense.

Thanks, yes you are right.