bjoernager/rust
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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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19
compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
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@ -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
}