pub fn symdecl<'a, Pos: SourcePos, MS: STeXModuleStore, Err: FnMut(String, SourceRange<Pos>, DiagnosticLevel)>(
symdecl: Macro<'a, Pos, &'a str>,
p: &mut LaTeXParser<'a, ParseStr<'a, Pos>, STeXToken<Pos>, Err, STeXParseState<'a, Pos, MS>>,
) -> MacroResult<'a, Pos, &'a str, STeXToken<Pos>>