Macro rustc_middle::TrivialTypeFoldableImpls

macro_rules! TrivialTypeFoldableImpls {
    (for < $tcx : lifetime > { $($ty : ty,) + }) => { ... };
    ($($ty : ty,) +) => { ... };
}

Used for types that are Copy and which do not care arena allocated data (i.e., don’t need to be folded).