Macro field

macro_rules! field {
    { $id:tt : $ty:expr } => { ... };
}

Construct a field type, which can be used in TypeInner::Record and TypeInner::Variant.

field!{ a: TypeInner::Nat.into() } expands to Field { id: Label::Named("a"), ty: ... } field!{ 0: Nat::ty() } expands to Field { id: Label::Id(0), ty: ... }