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coverage: Treat #[automatically_derived] as #[coverage(off)] #144560

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merged 3 commits into from
Jul 29, 2025
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coverage: Treat #[automatically_derived] as #[coverage(off)] #144560

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2761034
coverage: Test how `#[automatically_derived]` affects instrumentation
Zalathar Jul 28, 2025
b4d0c91
coverage: Rename `CoverageStatus` to `CoverageAttrKind`
Zalathar Jul 28, 2025
682f744
coverage: Treat `#[automatically_derived]` as `#[coverage(off)]`
Zalathar Jul 28, 2025
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20 changes: 6 additions & 14 deletions compiler/rustc_attr_data_structures/src/attributes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
}
Expand Down Expand Up @@ -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),
Expand Down
10 changes: 5 additions & 5 deletions compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use rustc_attr_data_structures::{AttributeKind, CoverageStatus, OptimizeAttr, UsedBy};
use rustc_attr_data_structures::{AttributeKind, CoverageAttrKind, OptimizeAttr, UsedBy};
use rustc_feature::{AttributeTemplate, template};
use rustc_session::parse::feature_err;
use rustc_span::{Span, Symbol, sym};
Expand Down Expand Up @@ -78,16 +78,16 @@ impl<S: Stage> SingleAttributeParser<S> for CoverageParser {
return None;
};

let status = match arg.path().word_sym() {
Some(sym::off) => CoverageStatus::Off,
Some(sym::on) => CoverageStatus::On,
let kind = match arg.path().word_sym() {
Some(sym::off) => CoverageAttrKind::Off,
Some(sym::on) => CoverageAttrKind::On,
None | Some(_) => {
fail_incorrect_argument(arg.span());
return None;
}
};

Some(AttributeKind::Coverage(cx.attr_span, status))
Some(AttributeKind::Coverage(cx.attr_span, kind))
}
}

Expand Down
48 changes: 25 additions & 23 deletions compiler/rustc_mir_transform/src/coverage/query.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use rustc_attr_data_structures::{AttributeKind, CoverageStatus, find_attr};
use rustc_attr_data_structures::{AttributeKind, CoverageAttrKind, find_attr};
use rustc_index::bit_set::DenseBitSet;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::mir::coverage::{BasicCoverageBlock, CoverageIdsInfo, CoverageKind, MappingKind};
Expand Down Expand Up @@ -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;
Expand All @@ -57,20 +47,32 @@ fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {

/// Query implementation for `coverage_attr_on`.
fn coverage_attr_on(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
// Check for annotations directly on this def.
if let Some(coverage_status) =
find_attr!(tcx.get_all_attrs(def_id), AttributeKind::Coverage(_, status) => status)
// Check for a `#[coverage(..)]` attribute on this def.
if let Some(kind) =
find_attr!(tcx.get_all_attrs(def_id), AttributeKind::Coverage(_sp, kind) => kind)
{
*coverage_status == CoverageStatus::On
} else {
match tcx.opt_local_parent(def_id) {
// Check the parent def (and so on recursively) until we find an
// enclosing attribute or reach the crate root.
Some(parent) => tcx.coverage_attr_on(parent),
// We reached the crate root without seeing a coverage attribute, so
// allow coverage instrumentation by default.
None => true,
match kind {
CoverageAttrKind::On => return true,
CoverageAttrKind::Off => return false,
}
};

// 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) {
Some(parent) => tcx.coverage_attr_on(parent),
// We reached the crate root without seeing a coverage attribute, so
// allow coverage instrumentation by default.
None => true,
}
}

Expand Down
23 changes: 23 additions & 0 deletions tests/coverage/auto-derived.auto.cov-map
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
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
- file 0 => $DIR/auto-derived.rs
Number of expressions: 0
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 31, 9) to (start + 0, 25)
- Code(Counter(0)) at (prev + 1, 13) to (start + 0, 16)
- Code(Counter(0)) at (prev + 0, 17) to (start + 0, 35)
- 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
- file 0 => $DIR/auto-derived.rs
Number of expressions: 0
Number of file 0 mappings: 3
- Code(Counter(0)) at (prev + 51, 1) to (start + 0, 10)
- Code(Counter(0)) at (prev + 1, 5) to (start + 0, 26)
- Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
Highest counter ID seen: c0

54 changes: 54 additions & 0 deletions tests/coverage/auto-derived.auto.coverage
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Original file line number Diff line number Diff line change
@@ -0,0 +1,54 @@
LL| |#![feature(coverage_attribute)]
LL| |//@ edition: 2024
LL| |//@ revisions: base auto on
LL| |
LL| |// Tests for how `#[automatically_derived]` affects coverage instrumentation.
LL| |//
LL| |// The actual behaviour is an implementation detail, so this test mostly exists
LL| |// to show when that behaviour has been accidentally or deliberately changed.
LL| |//
LL| |// Revision guide:
LL| |// - base: Test baseline instrumentation behaviour without `#[automatically_derived]`
LL| |// - auto: Test how `#[automatically_derived]` affects instrumentation
LL| |// - on: Test interaction between auto-derived and `#[coverage(on)]`
LL| |
LL| |struct MyStruct;
LL| |
LL| |trait MyTrait {
LL| | fn my_assoc_fn();
LL| |}
LL| |
LL| |#[cfg_attr(auto, automatically_derived)]
LL| |#[cfg_attr(on, automatically_derived)]
LL| |#[cfg_attr(on, coverage(on))]
LL| |impl MyTrait for MyStruct {
LL| | fn my_assoc_fn() {
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| | let closure = || {
LL| | say("in closure");
LL| | };
LL| |
LL| | closure();
LL| | inner_fn();
LL| | inner_fn_on();
LL| | }
LL| |}
LL| |
LL| |#[coverage(off)]
LL| |#[inline(never)]
LL| |fn say(s: &str) {
LL| | println!("{s}");
LL| |}
LL| |
LL| 1|fn main() {
LL| 1| MyStruct::my_assoc_fn();
LL| 1|}

61 changes: 61 additions & 0 deletions tests/coverage/auto-derived.base.cov-map
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Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
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
- 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
- file 0 => $DIR/auto-derived.rs
Number of expressions: 0
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 31, 9) to (start + 0, 25)
- Code(Counter(0)) at (prev + 1, 13) to (start + 0, 16)
- Code(Counter(0)) at (prev + 0, 17) to (start + 0, 35)
- 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
- file 0 => $DIR/auto-derived.rs
Number of expressions: 0
Number of file 0 mappings: 3
- Code(Counter(0)) at (prev + 51, 1) to (start + 0, 10)
- Code(Counter(0)) at (prev + 1, 5) to (start + 0, 26)
- Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
Highest counter ID seen: c0

54 changes: 54 additions & 0 deletions tests/coverage/auto-derived.base.coverage
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Original file line number Diff line number Diff line change
@@ -0,0 +1,54 @@
LL| |#![feature(coverage_attribute)]
LL| |//@ edition: 2024
LL| |//@ revisions: base auto on
LL| |
LL| |// Tests for how `#[automatically_derived]` affects coverage instrumentation.
LL| |//
LL| |// The actual behaviour is an implementation detail, so this test mostly exists
LL| |// to show when that behaviour has been accidentally or deliberately changed.
LL| |//
LL| |// Revision guide:
LL| |// - base: Test baseline instrumentation behaviour without `#[automatically_derived]`
LL| |// - auto: Test how `#[automatically_derived]` affects instrumentation
LL| |// - on: Test interaction between auto-derived and `#[coverage(on)]`
LL| |
LL| |struct MyStruct;
LL| |
LL| |trait MyTrait {
LL| | fn my_assoc_fn();
LL| |}
LL| |
LL| |#[cfg_attr(auto, automatically_derived)]
LL| |#[cfg_attr(on, automatically_derived)]
LL| |#[cfg_attr(on, coverage(on))]
LL| |impl MyTrait for MyStruct {
LL| 1| fn my_assoc_fn() {
LL| 1| fn inner_fn() {
LL| 1| say("in inner fn");
LL| 1| }
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| |
LL| 1| closure();
LL| 1| inner_fn();
LL| 1| inner_fn_on();
LL| 1| }
LL| |}
LL| |
LL| |#[coverage(off)]
LL| |#[inline(never)]
LL| |fn say(s: &str) {
LL| | println!("{s}");
LL| |}
LL| |
LL| 1|fn main() {
LL| 1| MyStruct::my_assoc_fn();
LL| 1|}

61 changes: 61 additions & 0 deletions tests/coverage/auto-derived.on.cov-map
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
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
- 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
- file 0 => $DIR/auto-derived.rs
Number of expressions: 0
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 31, 9) to (start + 0, 25)
- Code(Counter(0)) at (prev + 1, 13) to (start + 0, 16)
- Code(Counter(0)) at (prev + 0, 17) to (start + 0, 35)
- 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
- file 0 => $DIR/auto-derived.rs
Number of expressions: 0
Number of file 0 mappings: 3
- Code(Counter(0)) at (prev + 51, 1) to (start + 0, 10)
- Code(Counter(0)) at (prev + 1, 5) to (start + 0, 26)
- Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
Highest counter ID seen: c0

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