3 pub fn glb(v1: ty::Variance, v2: ty::Variance) -> ty::Variance {
4 // Greatest lower bound of the variance lattice as
5 // defined in The Paper:
11 (ty::Invariant, _) | (_, ty::Invariant) => ty::Invariant,
13 (ty::Covariant, ty::Contravariant) => ty::Invariant,
14 (ty::Contravariant, ty::Covariant) => ty::Invariant,
16 (ty::Covariant, ty::Covariant) => ty::Covariant,
18 (ty::Contravariant, ty::Contravariant) => ty::Contravariant,
20 (x, ty::Bivariant) | (ty::Bivariant, x) => x,