Rollup merge of #138776 - Zalathar:unexpand, r=oli-obk

coverage: Separate span-extraction from unexpansion

Historically, coverage instrumentation has relied on eagerly “unexpanding” MIR spans back to ancestor spans that have the same context as the function body, and lie within that body. Doing so makes several subsequent operations more straightforward.

In order to support expansion regions, we need to stop doing that, and handle layers of macro-expansion more explicitly. This PR takes a step in that direction, by deferring some of the unexpansion steps, and concentrating them in one place (`spans::extract_refined_covspans`).

Unexpansion still takes place as before, but these changes will make it easier to experiment with expansion-aware coverage instrumentation.

1 files changed, 7 insertions, 14 deletions

diff --git a/compiler/rustc_mir_transform/src/coverage/mod.rs b/compiler/rustc_mir_transform/src/coverage/mod.rs
index 572dbae8fd2..aa4c0ef1e1f 100644
--- a/compiler/rustc_mir_transform/src/coverage/mod.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mod.rs
@@ -273,8 +273,9 @@ struct ExtractedHirInfo {
     /// Must have the same context and filename as the body span.
     fn_sig_span_extended: Option<Span>,
     body_span: Span,
-    /// "Holes" are regions within the body span that should not be included in
-    /// coverage spans for this function (e.g. closures and nested items).
+    /// "Holes" are regions within the function body (or its expansions) that
+    /// should not be included in coverage spans for this function
+    /// (e.g. closures and nested items).
     hole_spans: Vec<Span>,
 }
 
@@ -323,7 +324,7 @@ fn extract_hir_info<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> ExtractedHir
 
     let function_source_hash = hash_mir_source(tcx, hir_body);
 
-    let hole_spans = extract_hole_spans_from_hir(tcx, body_span, hir_body);
+    let hole_spans = extract_hole_spans_from_hir(tcx, hir_body);
 
     ExtractedHirInfo {
         function_source_hash,
@@ -340,14 +341,9 @@ fn hash_mir_source<'tcx>(tcx: TyCtxt<'tcx>, hir_body: &'tcx hir::Body<'tcx>) ->
     tcx.hir_owner_nodes(owner).opt_hash_including_bodies.unwrap().to_smaller_hash().as_u64()
 }
 
-fn extract_hole_spans_from_hir<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    body_span: Span, // Usually `hir_body.value.span`, but not always
-    hir_body: &hir::Body<'tcx>,
-) -> Vec<Span> {
+fn extract_hole_spans_from_hir<'tcx>(tcx: TyCtxt<'tcx>, hir_body: &hir::Body<'tcx>) -> Vec<Span> {
     struct HolesVisitor<'tcx> {
         tcx: TyCtxt<'tcx>,
-        body_span: Span,
         hole_spans: Vec<Span>,
     }
 
@@ -387,14 +383,11 @@ fn extract_hole_spans_from_hir<'tcx>(
     }
     impl HolesVisitor<'_> {
         fn visit_hole_span(&mut self, hole_span: Span) {
-            // Discard any holes that aren't directly visible within the body span.
-            if self.body_span.contains(hole_span) && self.body_span.eq_ctxt(hole_span) {
-                self.hole_spans.push(hole_span);
-            }
+            self.hole_spans.push(hole_span);
         }
     }
 
-    let mut visitor = HolesVisitor { tcx, body_span, hole_spans: vec![] };
+    let mut visitor = HolesVisitor { tcx, hole_spans: vec![] };
 
     visitor.visit_body(hir_body);
     visitor.hole_spans