fn open_problem<'a, MS: STeXModuleStore, Err: FnMut(String, SourceRange<LSPLineCol>, DiagnosticLevel)>(
sub: bool,
p: &mut LaTeXParser<'a, ParseStr<'a, LSPLineCol>, STeXToken<LSPLineCol>, Err, STeXParseState<'a, LSPLineCol, MS>>,
env: &mut Environment<'a, LSPLineCol, &'a str, STeXToken<LSPLineCol>>,
)