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coverage: Check for async fn explicitly, without needing a heuristic

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The old code used a heuristic to detect async functions and adjust their
coverage spans to produce better output. But there's no need to resort to a
heuristic when we can just check whether the current function is actually an
`async fn`.
This commit is contained in:
Zalathar 2023-12-19 22:05:34 +11:00
parent 2a0290a802
commit cf6dc7adb3
2 changed files with 11 additions and 12 deletions
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4
compiler/rustc_mir_transform/src/coverage/mod.rs
View File

@ -299,6 +299,7 @@ fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
#[derive(Debug)]
struct ExtractedHirInfo {
function_source_hash: u64,
is_async_fn: bool,
fn_sig_span: Span,
body_span: Span,
}
@ -312,6 +313,7 @@ fn extract_hir_info<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> ExtractedHir
hir::map::associated_body(hir_node).expect("HIR node is a function with body");
let hir_body = tcx.hir().body(fn_body_id);
let is_async_fn = hir_node.fn_sig().is_some_and(|fn_sig| fn_sig.header.is_async());
let body_span = get_body_span(tcx, hir_body, def_id);
// The actual signature span is only used if it has the same context and
@ -333,7 +335,7 @@ fn extract_hir_info<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> ExtractedHir
let function_source_hash = hash_mir_source(tcx, hir_body);
ExtractedHirInfo { function_source_hash, fn_sig_span, body_span }
ExtractedHirInfo { function_source_hash, is_async_fn, fn_sig_span, body_span }
}
fn get_body_span<'tcx>(

19
compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
View File

@ -14,7 +14,14 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
hir_info: &ExtractedHirInfo,
basic_coverage_blocks: &CoverageGraph,
) -> Vec<CoverageSpan> {
let &ExtractedHirInfo { fn_sig_span, body_span, .. } = hir_info;
let &ExtractedHirInfo { is_async_fn, fn_sig_span, body_span, .. } = hir_info;
if is_async_fn {
// An async function desugars into a function that returns a future,
// with the user code wrapped in a closure. Any spans in the desugared
// outer function will be unhelpful, so just produce a single span
// associating the function signature with its entry BCB.
return vec![CoverageSpan::for_fn_sig(fn_sig_span)];
}
let mut initial_spans = Vec::with_capacity(mir_body.basic_blocks.len() * 2);
for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
@ -46,16 +53,6 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
.then_with(|| Ord::cmp(&a.is_closure, &b.is_closure).reverse())
});
// The desugaring of an async function includes a closure containing the
// original function body, and a terminator that returns the `impl Future`.
// That terminator will cause a confusing coverage count for the function's
// closing brace, so discard everything after the body closure span.
if let Some(body_closure_index) =
initial_spans.iter().rposition(|covspan| covspan.is_closure && covspan.span == body_span)
{
initial_spans.truncate(body_closure_index + 1);
}
initial_spans
}