Macro all

pub macro all {
    () => { ... },
    ($L:ty $(, $R:ty)*) => { ... },
}

Helper macro to compute whether all of a list of types, all implementing crate::TypeLayout, e.g. [T, U, V], are inhabited.

For instance, a struct is inhabited iff all of its fields are inhabited. The empty list of types is inhabited. This macro resolves into either Inhabited or Uninhabited.