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Rollup merge of #137251 - Zalathar:holes-visitor, r=jieyouxu

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coverage: Get hole spans from nested items without fully visiting them

This is a small simplification to the code that collects the spans of nested items within a function, so that those spans can be treated as “holes” to be avoided by the current function's coverage mappings.

The old code was using `nested_filter::All` to ensure that the visitor would see nested items. But we don't need the actual items themselves; we just need their spans, which we can obtain via a custom implementation of `visit_nested_item`.

This avoids the more expansive queries required by `nested_filter::All`.
This commit is contained in:
Matthias Krüger 2025-02-19 18:52:10 +01:00 • committed by GitHub
commit 3fc6dfd5ed
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4 changed files with 114 additions and 42 deletions
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51
compiler/rustc_mir_transform/src/coverage/mod.rs
View file

@ -346,35 +346,37 @@ fn extract_hole_spans_from_hir<'tcx>(
body_span: Span, // Usually `hir_body.value.span`, but not always
hir_body: &hir::Body<'tcx>,
) -> Vec<Span> {
struct HolesVisitor<'hir, F> {
tcx: TyCtxt<'hir>,
visit_hole_span: F,
struct HolesVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
body_span: Span,
hole_spans: Vec<Span>,
}
impl<'hir, F: FnMut(Span)> Visitor<'hir> for HolesVisitor<'hir, F> {
/// - We need `NestedFilter::INTRA = true` so that `visit_item` will be called.
/// - Bodies of nested items don't actually get visited, because of the
/// `visit_item` override.
/// - For nested bodies that are not part of an item, we do want to visit any
/// items contained within them.
type NestedFilter = nested_filter::All;
impl<'tcx> Visitor<'tcx> for HolesVisitor<'tcx> {
/// We have special handling for nested items, but we still want to
/// traverse into nested bodies of things that are not considered items,
/// such as "anon consts" (e.g. array lengths).
type NestedFilter = nested_filter::OnlyBodies;
fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
fn maybe_tcx(&mut self) -> TyCtxt<'tcx> {
self.tcx
}
fn visit_item(&mut self, item: &'hir hir::Item<'hir>) {
(self.visit_hole_span)(item.span);
/// We override `visit_nested_item` instead of `visit_item` because we
/// only need the item's span, not the item itself.
fn visit_nested_item(&mut self, id: hir::ItemId) -> Self::Result {
let span = self.tcx.def_span(id.owner_id.def_id);
self.visit_hole_span(span);
// Having visited this item, we don't care about its children,
// so don't call `walk_item`.
}
// We override `visit_expr` instead of the more specific expression
// visitors, so that we have direct access to the expression span.
fn visit_expr(&mut self, expr: &'hir hir::Expr<'hir>) {
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
match expr.kind {
hir::ExprKind::Closure(_) | hir::ExprKind::ConstBlock(_) => {
(self.visit_hole_span)(expr.span);
self.visit_hole_span(expr.span);
// Having visited this expression, we don't care about its
// children, so don't call `walk_expr`.
}
@ -384,18 +386,17 @@ fn extract_hole_spans_from_hir<'tcx>(
}
}
}
let mut hole_spans = vec![];
let mut visitor = HolesVisitor {
tcx,
visit_hole_span: |hole_span| {
impl HolesVisitor<'_> {
fn visit_hole_span(&mut self, hole_span: Span) {
// Discard any holes that aren't directly visible within the body span.
if body_span.contains(hole_span) && body_span.eq_ctxt(hole_span) {
hole_spans.push(hole_span);
if self.body_span.contains(hole_span) && self.body_span.eq_ctxt(hole_span) {
self.hole_spans.push(hole_span);
}
},
};
}
}
let mut visitor = HolesVisitor { tcx, body_span, hole_spans: vec![] };
visitor.visit_body(hir_body);
hole_spans
visitor.hole_spans
}

31
tests/coverage/holes.cov-map
View file

@ -1,52 +1,57 @@
Function name: <holes::main::MyStruct>::_method (unused)
Raw bytes (9): 0x[01, 01, 00, 01, 00, 25, 09, 00, 1d]
Raw bytes (9): 0x[01, 01, 00, 01, 00, 2b, 09, 00, 1d]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Zero) at (prev + 37, 9) to (start + 0, 29)
- Code(Zero) at (prev + 43, 9) to (start + 0, 29)
Highest counter ID seen: (none)
Function name: holes::main
Raw bytes (44): 0x[01, 01, 00, 08, 01, 08, 01, 06, 11, 01, 0f, 05, 00, 12, 01, 04, 05, 00, 12, 01, 07, 05, 00, 12, 01, 06, 05, 00, 12, 01, 06, 05, 03, 0f, 01, 0a, 05, 03, 0f, 01, 0a, 05, 01, 02]
Raw bytes (69): 0x[01, 01, 00, 0d, 01, 08, 01, 01, 12, 01, 05, 05, 00, 12, 01, 07, 09, 00, 11, 01, 09, 05, 00, 12, 01, 04, 05, 00, 12, 01, 07, 05, 00, 12, 01, 06, 05, 00, 12, 01, 04, 05, 00, 12, 01, 04, 05, 00, 12, 01, 06, 05, 03, 0f, 01, 0a, 05, 03, 0f, 01, 0a, 05, 0c, 0d, 01, 0f, 0e, 05, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 8
- Code(Counter(0)) at (prev + 8, 1) to (start + 6, 17)
- Code(Counter(0)) at (prev + 15, 5) to (start + 0, 18)
Number of file 0 mappings: 13
- Code(Counter(0)) at (prev + 8, 1) to (start + 1, 18)
- Code(Counter(0)) at (prev + 5, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 7, 9) to (start + 0, 17)
- Code(Counter(0)) at (prev + 9, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 4, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 7, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 6, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 4, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 4, 5) to (start + 0, 18)
- Code(Counter(0)) at (prev + 6, 5) to (start + 3, 15)
- Code(Counter(0)) at (prev + 10, 5) to (start + 3, 15)
- Code(Counter(0)) at (prev + 10, 5) to (start + 1, 2)
- Code(Counter(0)) at (prev + 10, 5) to (start + 12, 13)
- Code(Counter(0)) at (prev + 15, 14) to (start + 5, 2)
Highest counter ID seen: c0
Function name: holes::main::_unused_fn (unused)
Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 05, 00, 17]
Raw bytes (9): 0x[01, 01, 00, 01, 00, 1f, 05, 00, 17]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Zero) at (prev + 25, 5) to (start + 0, 23)
- Code(Zero) at (prev + 31, 5) to (start + 0, 23)
Highest counter ID seen: (none)
Function name: holes::main::{closure#0} (unused)
Raw bytes (9): 0x[01, 01, 00, 01, 00, 12, 09, 02, 0a]
Raw bytes (9): 0x[01, 01, 00, 01, 00, 18, 09, 02, 0a]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Zero) at (prev + 18, 9) to (start + 2, 10)
- Code(Zero) at (prev + 24, 9) to (start + 2, 10)
Highest counter ID seen: (none)
Function name: holes::main::{closure#1} (unused)
Raw bytes (9): 0x[01, 01, 00, 01, 00, 3d, 09, 02, 0a]
Raw bytes (9): 0x[01, 01, 00, 01, 00, 4b, 09, 02, 0a]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Zero) at (prev + 61, 9) to (start + 2, 10)
- Code(Zero) at (prev + 75, 9) to (start + 2, 10)
Highest counter ID seen: (none)

41
tests/coverage/holes.coverage
View file

@ -7,10 +7,16 @@
LL| |
LL| 1|fn main() {
LL| 1| black_box(());
LL| 1|
LL| 1| // Splitting this across multiple lines makes it easier to see where the
LL| 1| // coverage mapping regions begin and end.
LL| 1| #[rustfmt::skip]
LL| |
LL| | static MY_STATIC: () = ();
LL| |
LL| 1| black_box(());
LL| |
LL| | const MY_CONST: () = ();
LL| |
LL| | // Splitting this across multiple lines makes it easier to see where the
LL| | // coverage mapping regions begin and end.
LL| | #[rustfmt::skip]
LL| 1| let _closure =
LL| | |
LL| | _arg: (),
@ -39,6 +45,14 @@
LL| |
LL| 1| black_box(());
LL| |
LL| | trait MyTrait {}
LL| |
LL| 1| black_box(());
LL| |
LL| | impl MyTrait for MyStruct {}
LL| |
LL| 1| black_box(());
LL| |
LL| | macro_rules! _my_macro {
LL| | () => {};
LL| | }
@ -64,5 +78,24 @@
LL| | ;
LL| |
LL| 1| black_box(());
LL| 1|
LL| 1| // This tests the edge case of a const block nested inside an "anon const",
LL| 1| // such as the length of an array literal. Handling this case requires
LL| 1| // `nested_filter::OnlyBodies` or equivalent.
LL| 1| #[rustfmt::skip]
LL| 1| let _const_block_inside_anon_const =
LL| 1| [
LL| 1| 0
LL| 1| ;
LL| 1| 7
LL| 1| +
LL| 1| const
LL| | {
LL| | 3
LL| 1| }
LL| 1| ]
LL| 1| ;
LL| 1|
LL| 1| black_box(());
LL| 1|}

33
tests/coverage/holes.rs
View file

@ -8,6 +8,12 @@ use core::hint::black_box;
fn main() {
black_box(());
static MY_STATIC: () = ();
black_box(());
const MY_CONST: () = ();
// Splitting this across multiple lines makes it easier to see where the
// coverage mapping regions begin and end.
#[rustfmt::skip]
@ -39,6 +45,14 @@ fn main() {
black_box(());
trait MyTrait {}
black_box(());
impl MyTrait for MyStruct {}
black_box(());
macro_rules! _my_macro {
() => {};
}
@ -64,4 +78,23 @@ fn main() {
;
black_box(());
// This tests the edge case of a const block nested inside an "anon const",
// such as the length of an array literal. Handling this case requires
// `nested_filter::OnlyBodies` or equivalent.
#[rustfmt::skip]
let _const_block_inside_anon_const =
[
0
;
7
+
const
{
3
}
]
;
black_box(());
}