From e0cd8057c85260e827e417cfcf3c6c861d2c8426 Mon Sep 17 00:00:00 2001 From: Zalathar Date: Wed, 6 Dec 2023 18:40:06 +1100 Subject: [PATCH] coverage: Simplify the heuristic for ignoring `async fn` return spans --- .../rustc_mir_transform/src/coverage/spans.rs | 21 ++++--------------- .../src/coverage/spans/from_mir.rs | 10 +++++++++ 2 files changed, 14 insertions(+), 17 deletions(-) diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs index c415a832994..0124bb7337c 100644 --- a/compiler/rustc_mir_transform/src/coverage/spans.rs +++ b/compiler/rustc_mir_transform/src/coverage/spans.rs @@ -319,29 +319,16 @@ fn to_refined_spans(mut self) -> Vec { } } - let prev = self.take_prev(); - debug!(" AT END, adding last prev={prev:?}"); - // Drain any remaining dups into the output. for dup in self.pending_dups.drain(..) { debug!(" ...adding at least one pending dup={:?}", dup); self.refined_spans.push(dup); } - // Async functions wrap a closure that implements the body to be executed. The enclosing - // function is called and returns an `impl Future` without initially executing any of the - // body. To avoid showing the return from the enclosing function as a "covered" return from - // the closure, the enclosing function's `TerminatorKind::Return`s `CoverageSpan` is - // excluded. The closure's `Return` is the only one that will be counted. This provides - // adequate coverage, and more intuitive counts. (Avoids double-counting the closing brace - // of the function body.) - let body_ends_with_closure = if let Some(last_covspan) = self.refined_spans.last() { - last_covspan.is_closure && last_covspan.span.hi() == self.body_span.hi() - } else { - false - }; - - if !body_ends_with_closure { + // There is usually a final span remaining in `prev` after the loop ends, + // so add it to the output as well. + if let Some(prev) = self.some_prev.take() { + debug!(" AT END, adding last prev={prev:?}"); self.refined_spans.push(prev); } diff --git a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs index e1531f2c239..b850b3374ba 100644 --- a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs +++ b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs @@ -44,6 +44,16 @@ 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 }