Auto merge of #122832 - oli-obk:no_ord_def_id3, r=michaelwoerister

Remove `DefId`'s `Partial/Ord` impls

work towards https://github.com/rust-lang/rust/issues/90317

based on https://github.com/rust-lang/rust/pull/122824 and https://github.com/rust-lang/rust/pull/122820

r? `@michaelwoerister`

1 files changed, 6 insertions, 18 deletions

diff --git a/compiler/rustc_span/src/def_id.rs b/compiler/rustc_span/src/def_id.rs
index 0c811d7dff1..8f721bac951 100644
--- a/compiler/rustc_span/src/def_id.rs
+++ b/compiler/rustc_span/src/def_id.rs
@@ -218,8 +218,6 @@ rustc_index::newtype_index! {
 ///
 /// You can create a `DefId` from a `LocalDefId` using `local_def_id.to_def_id()`.
 #[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)]
@@ -236,6 +234,12 @@ pub struct DefId {
     pub index: DefIndex,
 }
 
+// To ensure correctness of incremental compilation,
+// `DefId` must not implement `Ord` or `PartialOrd`.
+// See https://github.com/rust-lang/rust/issues/90317.
+impl !Ord for DefId {}
+impl !PartialOrd for DefId {}
+
 // On 64-bit systems, we can hash the whole `DefId` as one `u64` instead of two `u32`s. This
 // improves performance without impairing `FxHash` quality. So the below code gets compiled to a
 // noop on little endian systems because the memory layout of `DefId` is as follows:
@@ -261,22 +265,6 @@ 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<std::cmp::Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
 impl DefId {
     /// Makes a local `DefId` from the given `DefIndex`.
     #[inline]