To whom do I report error "LSP: unable to edit document because not previously opened"?

Question

I have this repeatable error running Neovim 0.8 with dartls.

It occurs if I :-

1. open a dart file
2. make a change, eg add a blank line
3. :w to save it
4. immediately :e!
5. on the next change attempt, I get the above error message and the dartls process terminates

Looking at the lsp.log file with debug set, I can see the :e! causes LSP didOpen with version=0 and then, when I make the change, at step 5, I see didChange with version=nnn where nnn is a positive integer.

At a guess, it's the disparity between the file open with version=0 and then an edit with version=nnn which causes dartls to respond with the error and then terminate. Is this a Dart issue or Neovim LSP issue?

For anybody else with this problem, the workaround is to do a fresh :e! which restarts the dartls process.