Macro fungi_lang::fgi_kind

macro_rules! fgi_kind {
    { fromast $ast:expr } => { ... };
    { ($($kind:tt)+) } => { ... };
    { type } => { ... };
    { type => $($kinds:tt)+ } => { ... };
    { $g:tt => $($kinds:tt)+ } => { ... };
    { $($any:tt)* } => { ... };
}

Parser for Kinds

K ::=
    fromast ast (inject ast nodes)
    (K)         (parens)
    type        (kind of value types)
    type => K   (type argument)
    g => K      (index argument)