Enum Const

pub enum Const<'tcx> {
    Ty(Ty<'tcx>, Const<'tcx>),
    Unevaluated(UnevaluatedConst<'tcx>, Ty<'tcx>),
    Val(ConstValue<'tcx>, Ty<'tcx>),
}

Constants

Variants

Ty(Ty<'tcx>, Const<'tcx>)

This constant came from the type system.

Any way of turning ty::Const into ConstValue should go through valtree_to_const_val; this ensures that we consistently produce “clean” values without data in the padding or anything like that.

FIXME(BoxyUwU): We should remove this Ty and look up the type for params via ParamEnv

Unevaluated(UnevaluatedConst<'tcx>, Ty<'tcx>)

An unevaluated mir constant which is not part of the type system.

Note that Ty(ty::ConstKind::Unevaluated) and this variant are not identical! Ty will always flow through a valtree, so all data not captured in the valtree is lost. This variant directly uses the evaluated result of the given constant, including e.g. data stored in padding.

Val(ConstValue<'tcx>, Ty<'tcx>)

This constant cannot go back into the type system, as it represents something the type system cannot handle (e.g. pointers).