From fb5002d68aa22f23ced3e2b5265f622264e4840a Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Tue, 27 Sep 2022 15:21:31 -0700 Subject: [PATCH] Manually order `DefId` on 64-bit big-endian `DefId` uses different field orders on 64-bit big-endian vs. others, in order to optimize its `Hash` implementation. However, that also made it derive different lexical ordering for `PartialOrd` and `Ord`. That caused spurious differences wherever `DefId`s are sorted, like the candidate sources list in `report_method_error`. Now we manually implement `PartialOrd` and `Ord` on 64-bit big-endian to match the same lexical ordering as other targets, fixing at least one test, `src/test/ui/methods/method-ambig-two-traits-cross-crate.rs`. --- compiler/rustc_span/src/def_id.rs | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/compiler/rustc_span/src/def_id.rs b/compiler/rustc_span/src/def_id.rs index 37b8371a8fe28..bbeabdb55a72a 100644 --- a/compiler/rustc_span/src/def_id.rs +++ b/compiler/rustc_span/src/def_id.rs @@ -218,7 +218,9 @@ impl Decodable for DefIndex { /// index and a def index. /// /// You can create a `DefId` from a `LocalDefId` using `local_def_id.to_def_id()`. -#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Copy)] +#[derive(Clone, PartialEq, Eq, Copy)] +// Don't derive order on 64-bit big-endian, so we can be consistent regardless of field order. +#[cfg_attr(not(all(target_pointer_width = "64", target_endian = "big")), derive(PartialOrd, Ord))] // On below-64 bit systems we can simply use the derived `Hash` impl #[cfg_attr(not(target_pointer_width = "64"), derive(Hash))] #[repr(C)] @@ -260,6 +262,22 @@ impl Hash for DefId { } } +// Implement the same comparison as derived with the other field order. +#[cfg(all(target_pointer_width = "64", target_endian = "big"))] +impl Ord for DefId { + #[inline] + fn cmp(&self, other: &DefId) -> std::cmp::Ordering { + Ord::cmp(&(self.index, self.krate), &(other.index, other.krate)) + } +} +#[cfg(all(target_pointer_width = "64", target_endian = "big"))] +impl PartialOrd for DefId { + #[inline] + fn partial_cmp(&self, other: &DefId) -> Option { + Some(Ord::cmp(self, other)) + } +} + impl DefId { /// Makes a local `DefId` from the given `DefIndex`. #[inline]