Possible bug when switching colorschemes

[lifepillar]

As you are probably aware, there is a long-standing issue causing syntax highlighting to be messed up when switching between colorschemes that define highlight groups for syntax items (see, for example, altercation/solarized#102).

Such issue doesn't seem easy to solve, since (see :h hi-default), Vim offers the possibility to override syntax highlight groups in one's own vimrc, and it seems reasonable to assume that such commands should be persistent across colorscheme changes (or should they?), which is at odds with the idea of including such commands in colorschemes (where the reasonable behaviour is that their effects are wiped out when the colorscheme changes). In practice, many colorschemes define highlighting for syntax items, so it would be nice if that didn't cause issues. I don't know whether you consider this something that should or might be addressed by Vim (maybe, your opinion is that people are misusing colorschemes).

However, I'd like to report the following, which does look like a bug to me. Consider this test-vimrc defining three custom highlight groups:

syntax on
hi NormalMode ctermfg=0 ctermbg=15
hi InsertMode ctermfg=0 ctermbg=15
hi Foobar ctermfg=0 ctermbg=15

Execute vim -i NONE -u test-vimrc -N. Then, switch to the default colorscheme and look how the highlight groups are defined:

:hi NormalMode
:hi InsertMode
:hi Foobar

That's the output:

NormalMode     xxx links to StatusLine
InsertMode     xxx links to DiffText
Foobar         xxx cleared

Edit: added missing command.

[lifepillar]

Sorry, I have forgotten a syntax on in the vimrc. I have updated my previous comment.

[lifepillar]

Ah, never mind, syntax on reads inside my .vim folder, that's why I get inconsistent clearing.