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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:38 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:13:23 +0000 |
commit | 20431706a863f92cb37dc512fef6e48d192aaf2c (patch) | |
tree | 2867f13f5fd5437ba628c67d7f87309ccadcd286 /compiler/rustc_hir_analysis/src/variance/xform.rs | |
parent | Releasing progress-linux version 1.65.0+dfsg1-2~progress7.99u1. (diff) | |
download | rustc-20431706a863f92cb37dc512fef6e48d192aaf2c.tar.xz rustc-20431706a863f92cb37dc512fef6e48d192aaf2c.zip |
Merging upstream version 1.66.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_hir_analysis/src/variance/xform.rs')
-rw-r--r-- | compiler/rustc_hir_analysis/src/variance/xform.rs | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/compiler/rustc_hir_analysis/src/variance/xform.rs b/compiler/rustc_hir_analysis/src/variance/xform.rs new file mode 100644 index 000000000..027f0859f --- /dev/null +++ b/compiler/rustc_hir_analysis/src/variance/xform.rs @@ -0,0 +1,22 @@ +use rustc_middle::ty; + +pub fn glb(v1: ty::Variance, v2: ty::Variance) -> ty::Variance { + // Greatest lower bound of the variance lattice as + // defined in The Paper: + // + // * + // - + + // o + match (v1, v2) { + (ty::Invariant, _) | (_, ty::Invariant) => ty::Invariant, + + (ty::Covariant, ty::Contravariant) => ty::Invariant, + (ty::Contravariant, ty::Covariant) => ty::Invariant, + + (ty::Covariant, ty::Covariant) => ty::Covariant, + + (ty::Contravariant, ty::Contravariant) => ty::Contravariant, + + (x, ty::Bivariant) | (ty::Bivariant, x) => x, + } +} |