Track span dependency using a callback.

2 files changed, 19 insertions, 2 deletions

diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index de08c5d8a55..60b5ffb1d3e 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -1947,6 +1947,7 @@ pub struct FileLines {
 
 pub static SPAN_DEBUG: AtomicRef<fn(Span, &mut fmt::Formatter<'_>) -> fmt::Result> =
     AtomicRef::new(&(default_span_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+pub static SPAN_TRACK: AtomicRef<fn(LocalDefId)> = AtomicRef::new(&((|_| {}) as fn(_)));
 
 // _____________________________________________________________________________
 // SpanLinesError, SpanSnippetError, DistinctSources, MalformedSourceMapPositions
@@ -2031,7 +2032,7 @@ where
             return;
         }
 
-        let span = self.data();
+        let span = self.decode();
         span.ctxt.hash_stable(ctx, hasher);
         span.parent.hash_stable(ctx, hasher);
 
@@ -2041,7 +2042,7 @@ where
         }
 
         if let Some(parent) = span.parent {
-            let def_span = ctx.def_span(parent).data();
+            let def_span = ctx.def_span(parent).decode();
             if def_span.contains(span) {
                 // This span is enclosed in a definition: only hash the relative position.
                 Hash::hash(&TAG_RELATIVE_SPAN, hasher);
diff --git a/compiler/rustc_span/src/span_encoding.rs b/compiler/rustc_span/src/span_encoding.rs
index 58d639082b0..f74c259d53d 100644
--- a/compiler/rustc_span/src/span_encoding.rs
+++ b/compiler/rustc_span/src/span_encoding.rs
@@ -6,6 +6,7 @@
 
 use crate::def_id::LocalDefId;
 use crate::hygiene::SyntaxContext;
+use crate::SPAN_TRACK;
 use crate::{BytePos, SpanData};
 
 use rustc_data_structures::fx::FxIndexSet;
@@ -55,6 +56,10 @@ use rustc_data_structures::fx::FxIndexSet;
 ///   the code. No crates in `rustc-perf` need more than 15 bits for `ctxt`,
 ///   but larger crates might need more than 16 bits.
 ///
+/// In order to reliably use parented spans in incremental compilation,
+/// the dependency to the parent definition's span. This is performed
+/// using the callback `SPAN_TRACK` to access the query engine.
+///
 #[derive(Clone, Copy, Eq, PartialEq, Hash)]
 pub struct Span {
     base_or_index: u32,
@@ -96,6 +101,17 @@ impl Span {
 
     #[inline]
     pub fn data(self) -> SpanData {
+        let data = self.decode();
+        if let Some(parent) = data.parent {
+            (*SPAN_TRACK)(parent);
+        }
+        data
+    }
+
+    /// Internal function to translate between an encoded span and the expanded representation.
+    /// This function must not be used outside the incremental engine.
+    #[inline]
+    pub fn decode(self) -> SpanData {
         if self.len_or_tag != LEN_TAG {
             // Inline format.
             debug_assert!(self.len_or_tag as u32 <= MAX_LEN);