1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 pub fn glb(v1: ty::Variance, v2: ty::Variance) -> ty::Variance {
14 // Greatest lower bound of the variance lattice as
15 // defined in The Paper:
22 (_, ty::Invariant) => ty::Invariant,
24 (ty::Covariant, ty::Contravariant) => ty::Invariant,
25 (ty::Contravariant, ty::Covariant) => ty::Invariant,
27 (ty::Covariant, ty::Covariant) => ty::Covariant,
29 (ty::Contravariant, ty::Contravariant) => ty::Contravariant,
32 (ty::Bivariant, x) => x,