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

Author: Zalathar

compiler/rustc_mir_transform/src/coverage/query.rs

@@ -32,16 +32,6 @@ fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
         return false;
     }
 
-    // Don't instrument functions with `#[automatically_derived]` on their
-    // enclosing impl block, on the assumption that most users won't care about
-    // coverage for derived impls.
-    if let Some(impl_of) = tcx.impl_of_assoc(def_id.to_def_id())
-        && tcx.is_automatically_derived(impl_of)
-    {
-        trace!("InstrumentCoverage skipped for {def_id:?} (automatically derived)");
-        return false;
-    }
-
     if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::NAKED) {
         trace!("InstrumentCoverage skipped for {def_id:?} (`#[naked]`)");
         return false;
@@ -67,6 +57,15 @@ fn coverage_attr_on(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
         }
     };
 
+    // Treat `#[automatically_derived]` as an implied `#[coverage(off)]`, on
+    // the assumption that most users won't want coverage for derived impls.
+    //
+    // This affects not just the associated items of an impl block, but also
+    // any closures and other nested functions within those associated items.
+    if tcx.is_automatically_derived(def_id.to_def_id()) {
+        return false;
+    }
+
     // Check the parent def (and so on recursively) until we find an
     // enclosing attribute or reach the crate root.
     match tcx.opt_local_parent(def_id) {

tests/coverage/auto-derived.auto.cov-map

@@ -1,15 +1,3 @@
-Function name: <auto_derived::MyStruct as auto_derived::MyTrait>::my_assoc_fn::inner_fn
-Raw bytes (24): 0x[01, 01, 00, 04, 01, 1a, 09, 00, 16, 01, 01, 0d, 00, 10, 01, 00, 11, 00, 1e, 01, 01, 09, 00, 0a]
-Number of files: 1
-- file 0 => $DIR/auto-derived.rs
-Number of expressions: 0
-Number of file 0 mappings: 4
-- Code(Counter(0)) at (prev + 26, 9) to (start + 0, 22)
-- Code(Counter(0)) at (prev + 1, 13) to (start + 0, 16)
-- Code(Counter(0)) at (prev + 0, 17) to (start + 0, 30)
-- Code(Counter(0)) at (prev + 1, 9) to (start + 0, 10)
-Highest counter ID seen: c0
-
 Function name: <auto_derived::MyStruct as auto_derived::MyTrait>::my_assoc_fn::inner_fn_on
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 1f, 09, 00, 19, 01, 01, 0d, 00, 10, 01, 00, 11, 00, 23, 01, 01, 09, 00, 0a]
 Number of files: 1
@@ -22,18 +10,6 @@ Number of file 0 mappings: 4
 - Code(Counter(0)) at (prev + 1, 9) to (start + 0, 10)
 Highest counter ID seen: c0
 
-Function name: <auto_derived::MyStruct as auto_derived::MyTrait>::my_assoc_fn::{closure#0}
-Raw bytes (24): 0x[01, 01, 00, 04, 01, 23, 1a, 00, 1b, 01, 01, 0d, 00, 10, 01, 00, 11, 00, 1d, 01, 01, 09, 00, 0a]
-Number of files: 1
-- file 0 => $DIR/auto-derived.rs
-Number of expressions: 0
-Number of file 0 mappings: 4
-- Code(Counter(0)) at (prev + 35, 26) to (start + 0, 27)
-- Code(Counter(0)) at (prev + 1, 13) to (start + 0, 16)
-- Code(Counter(0)) at (prev + 0, 17) to (start + 0, 29)
-- Code(Counter(0)) at (prev + 1, 9) to (start + 0, 10)
-Highest counter ID seen: c0
-
 Function name: auto_derived::main
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 33, 01, 00, 0a, 01, 01, 05, 00, 1a, 01, 01, 01, 00, 02]
 Number of files: 1

tests/coverage/auto-derived.auto.coverage

@@ -23,18 +23,18 @@
    LL|       |#[cfg_attr(on, coverage(on))]
    LL|       |impl MyTrait for MyStruct {
    LL|       |    fn my_assoc_fn() {
-   LL|      1|        fn inner_fn() {
-   LL|      1|            say("in inner fn");
-   LL|      1|        }
+   LL|       |        fn inner_fn() {
+   LL|       |            say("in inner fn");
+   LL|       |        }
    LL|       |
    LL|       |        #[coverage(on)]
    LL|      1|        fn inner_fn_on() {
    LL|      1|            say("in inner fn (on)");
    LL|      1|        }
    LL|       |
-   LL|      1|        let closure = || {
-   LL|      1|            say("in closure");
-   LL|      1|        };
+   LL|       |        let closure = || {
+   LL|       |            say("in closure");
+   LL|       |        };
    LL|       |
    LL|       |        closure();
    LL|       |        inner_fn();

tests/coverage/auto-derived.on.cov-map

@@ -1,3 +1,17 @@
+Function name: <auto_derived::MyStruct as auto_derived::MyTrait>::my_assoc_fn
+Raw bytes (34): 0x[01, 01, 00, 06, 01, 19, 05, 00, 15, 01, 0a, 0d, 00, 14, 01, 04, 09, 00, 12, 01, 01, 09, 00, 11, 01, 01, 09, 00, 14, 01, 01, 05, 00, 06]
+Number of files: 1
+- file 0 => $DIR/auto-derived.rs
+Number of expressions: 0
+Number of file 0 mappings: 6
+- Code(Counter(0)) at (prev + 25, 5) to (start + 0, 21)
+- Code(Counter(0)) at (prev + 10, 13) to (start + 0, 20)
+- Code(Counter(0)) at (prev + 4, 9) to (start + 0, 18)
+- Code(Counter(0)) at (prev + 1, 9) to (start + 0, 17)
+- Code(Counter(0)) at (prev + 1, 9) to (start + 0, 20)
+- Code(Counter(0)) at (prev + 1, 5) to (start + 0, 6)
+Highest counter ID seen: c0
+
 Function name: <auto_derived::MyStruct as auto_derived::MyTrait>::my_assoc_fn::inner_fn
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 1a, 09, 00, 16, 01, 01, 0d, 00, 10, 01, 00, 11, 00, 1e, 01, 01, 09, 00, 0a]
 Number of files: 1

tests/coverage/auto-derived.on.coverage

@@ -22,7 +22,7 @@
    LL|       |#[cfg_attr(on, automatically_derived)]
    LL|       |#[cfg_attr(on, coverage(on))]
    LL|       |impl MyTrait for MyStruct {
-   LL|       |    fn my_assoc_fn() {
+   LL|      1|    fn my_assoc_fn() {
    LL|      1|        fn inner_fn() {
    LL|      1|            say("in inner fn");
    LL|      1|        }
@@ -36,10 +36,10 @@
    LL|      1|            say("in closure");
    LL|      1|        };
    LL|       |
-   LL|       |        closure();
-   LL|       |        inner_fn();
-   LL|       |        inner_fn_on();
-   LL|       |    }
+   LL|      1|        closure();
+   LL|      1|        inner_fn();
+   LL|      1|        inner_fn_on();
+   LL|      1|    }
    LL|       |}
    LL|       |
    LL|       |#[coverage(off)]