Rollup merge of #144560 - Zalathar:auto-derived, r=compiler-errors

coverage: Treat `#[automatically_derived]` as `#[coverage(off)]`

One of the contributing factors behind https://github.com/rust-lang/rust/issues/141577#issuecomment-3120667286 was the presence of derive-macro-generated code containing nested closures.

Coverage instrumentation already has a heuristic for skipping code marked with `#[automatically_derived]` (rust-lang/rust#120185), because derived code is usually not worth instrumenting, and also has a tendency to trigger vexing edge-case bugs in coverage instrumentation or coverage codegen.

However, the existing heuristic only applied to the associated items directly within an auto-derived impl block, and had no effect on closures or nested items within those associated items.

This PR therefore extends the search for `#[coverage(..)]` attributes to also treat `#[automatically_derived]` as an implied `#[coverage(off)]` for the purposes of coverage instrumentation.

---

This change doesn’t rule out an entire category of bugs, because it only affects code that actually uses the auto-derived attribute. But it should reduce the overall chance of edge-case macro span bugs being observed in the wild.

1 files changed, 6 insertions, 14 deletions

diff --git a/compiler/rustc_attr_data_structures/src/attributes.rs b/compiler/rustc_attr_data_structures/src/attributes.rs
index 610c93a253c..55019cd57a7 100644
--- a/compiler/rustc_attr_data_structures/src/attributes.rs
+++ b/compiler/rustc_attr_data_structures/src/attributes.rs
@@ -110,18 +110,10 @@ pub enum DeprecatedSince {
     Err,
 }
 
-#[derive(
-    Copy,
-    Debug,
-    Eq,
-    PartialEq,
-    Encodable,
-    Decodable,
-    Clone,
-    HashStable_Generic,
-    PrintAttribute
-)]
-pub enum CoverageStatus {
+/// Successfully-parsed value of a `#[coverage(..)]` attribute.
+#[derive(Copy, Debug, Eq, PartialEq, Encodable, Decodable, Clone)]
+#[derive(HashStable_Generic, PrintAttribute)]
+pub enum CoverageAttrKind {
     On,
     Off,
 }
@@ -304,8 +296,8 @@ pub enum AttributeKind {
     /// Represents `#[const_trait]`.
     ConstTrait(Span),
 
-    /// Represents `#[coverage]`.
-    Coverage(Span, CoverageStatus),
+    /// Represents `#[coverage(..)]`.
+    Coverage(Span, CoverageAttrKind),
 
     ///Represents `#[rustc_deny_explicit_impl]`.
     DenyExplicitImpl(Span),