Integrated clipboard support fails with “Function name does not match script file name: provider#clipboard#Call”

[Hawk777]

Describe the bug
I set g:GuiInternalClipboard. On startup, I get “Unknown error type: Wait timeout (nvim_command)”. On starting nvim directly with all the same command-line parameters except --embed, I get the error indicated in the bug title.

It seems the documented way to implement a custom clipboard provider is more like this, which seems to work:

let s:lastRegTypes = {'+': 'v', '*': 'v'}

function! s:Copy(regname, lines, regtype)
	let s:lastRegTypes[a:regname] = a:regtype
	call rpcnotify(1, 'Gui', 'Clipboard', 'Set', a:regname, join(a:lines, "\n"))
endfunction

function! s:Paste(regname)
	return [rpcrequest(1, 'Gui', 'Clipboard', 'Get', a:regname), s:lastRegTypes[a:regname]]
endfunction

let g:clipboard = {
			\	'name': 'neovim-gtk-clipboard',
			\	'copy': {
			\		'+': {lines, regtype -> s:Copy('+', lines, regtype)},
			\		'*': {lines, regtype -> s:Copy('*', lines, regtype)},
			\	},
			\	'paste': {
			\		'+': {-> s:Paste('+')},
			\		'*': {-> s:Paste('*')},
			\	},
			\}

Technical information (please complete the following information):

• OS: Gentoo Linux
• Neovim version: 0.4.3
• Neovim-Gtk build version: 0.2.0