Macro declare_types

macro_rules! declare_types {
    (   type Sort = $sort:ty;
        type KVar = $kvar:ty;
        type Var = $var:ty;

        type Numeral = $int:ty;
        type Decimal = $real:ty;
        type String = $str:ty;

        type Tag = $tag:ty;
    ) => { ... };
}