Stop sorting Spans' SyntaxContext, as that is incompatible with incremental

compiler/rustc_span/src/lib.rs

@@ -469,46 +469,23 @@ impl FileName {
 /// `SpanData` is public because `Span` uses a thread-local interner and can't be
 /// sent to other threads, but some pieces of performance infra run in a separate thread.
 /// Using `Span` is generally preferred.
-#[derive(Clone, Copy, Hash, PartialEq, Eq)]
+#[derive(Clone, Copy, Hash, PartialEq, Eq, derivative::Derivative)]
+#[derivative(PartialOrd, Ord)]
 pub struct SpanData {
     pub lo: BytePos,
     pub hi: BytePos,
     /// Information about where the macro came from, if this piece of
     /// code was created by a macro expansion.
+    #[derivative(PartialOrd = "ignore", Ord = "ignore")]
+    // `SyntaxContext` does not implement `Ord`.
+    // The other fields are enough to determine in-file order.
     pub ctxt: SyntaxContext,
+    #[derivative(PartialOrd = "ignore", Ord = "ignore")]
+    // `LocalDefId` does not implement `Ord`.
+    // The other fields are enough to determine in-file order.
     pub parent: Option<LocalDefId>,
 }
 
-// Order spans by position in the file.
-impl Ord for SpanData {
-    fn cmp(&self, other: &Self) -> Ordering {
-        let SpanData {
-            lo: s_lo,
-            hi: s_hi,
-            ctxt: s_ctxt,
-            // `LocalDefId` does not implement `Ord`.
-            // The other fields are enough to determine in-file order.
-            parent: _,
-        } = self;
-        let SpanData {
-            lo: o_lo,
-            hi: o_hi,
-            ctxt: o_ctxt,
-            // `LocalDefId` does not implement `Ord`.
-            // The other fields are enough to determine in-file order.
-            parent: _,
-        } = other;
-
-        (s_lo, s_hi, s_ctxt).cmp(&(o_lo, o_hi, o_ctxt))
-    }
-}
-
-impl PartialOrd for SpanData {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
 impl SpanData {
     #[inline]
     pub fn span(&self) -> Span {