Stop requiring ctxts in inline and outline spans being synchronized

Author: petrochenkov

compiler/rustc_span/src/span_encoding.rs

@@ -136,13 +136,13 @@ impl Span {
         }
 
         // Partially-interned or fully-interned format.
-        let index =
-            with_span_interner(|interner| interner.intern(&SpanData { lo, hi, ctxt, parent }));
-        let ctxt_or_parent_or_marker = if ctxt2 <= MAX_CTXT {
-            ctxt2 as u16 // partially-interned
+        let (ctxt_or_parent_or_marker, ctxt) = if ctxt2 <= MAX_CTXT {
+            (ctxt2 as u16, SyntaxContext::from_u32(u32::MAX)) // partially-interned
         } else {
-            CTXT_INTERNED_MARKER // fully-interned
+            (CTXT_INTERNED_MARKER, ctxt) // fully-interned
         };
+        let index =
+            with_span_interner(|interner| interner.intern(&SpanData { lo, hi, ctxt, parent }));
         Span {
             lo_or_index: index,
             len_with_tag_or_marker: BASE_LEN_INTERNED_MARKER,
@@ -193,7 +193,11 @@ impl Span {
             // the interned value contains all the data, so we don't need to
             // distinguish them.
             let index = self.lo_or_index;
-            with_span_interner(|interner| interner.spans[index as usize])
+            let mut data = with_span_interner(|interner| interner.spans[index as usize]);
+            if data.ctxt.as_u32() == u32::MAX {
+                data.ctxt = SyntaxContext::from_u32(u32::from(self.ctxt_or_parent_or_marker));
+            }
+            data
         }
     }