Auto merge of #118771 - workingjubilee:rollup-q1p3riz, r=workingjubilee

Rollup of 7 pull requests

Successful merges:

 - #118198 (coverage: Use `SpanMarker` to improve coverage spans for `if !` expressions)
 - #118512 (Add tests related to normalization in implied bounds)
 - #118610 (update target feature following LLVM API change)
 - #118666 (coverage: Simplify the heuristic for ignoring `async fn` return spans)
 - #118737 (Extend tidy alphabetical checking to `tests/`.)
 - #118762 (Some more minor `async gen`-related nits)
 - #118764 (Make async generators fused by default)

r? `@ghost`
`@rustbot` modify labels: rollup

2 files changed, 38 insertions, 34 deletions

diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs
index c415a832994..05ad14f1525 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans.rs
@@ -319,29 +319,16 @@ impl<'a> CoverageSpansGenerator<'a> {
             }
         }
 
-        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);
         }
 
@@ -398,38 +385,36 @@ impl<'a> CoverageSpansGenerator<'a> {
         self.refined_spans.push(macro_name_cov);
     }
 
+    #[track_caller]
     fn curr(&self) -> &CoverageSpan {
-        self.some_curr
-            .as_ref()
-            .unwrap_or_else(|| bug!("invalid attempt to unwrap a None some_curr"))
+        self.some_curr.as_ref().unwrap_or_else(|| bug!("some_curr is None (curr)"))
     }
 
+    #[track_caller]
     fn curr_mut(&mut self) -> &mut CoverageSpan {
-        self.some_curr
-            .as_mut()
-            .unwrap_or_else(|| bug!("invalid attempt to unwrap a None some_curr"))
+        self.some_curr.as_mut().unwrap_or_else(|| bug!("some_curr is None (curr_mut)"))
     }
 
     /// If called, then the next call to `next_coverage_span()` will *not* update `prev` with the
     /// `curr` coverage span.
+    #[track_caller]
     fn take_curr(&mut self) -> CoverageSpan {
-        self.some_curr.take().unwrap_or_else(|| bug!("invalid attempt to unwrap a None some_curr"))
+        self.some_curr.take().unwrap_or_else(|| bug!("some_curr is None (take_curr)"))
     }
 
+    #[track_caller]
     fn prev(&self) -> &CoverageSpan {
-        self.some_prev
-            .as_ref()
-            .unwrap_or_else(|| bug!("invalid attempt to unwrap a None some_prev"))
+        self.some_prev.as_ref().unwrap_or_else(|| bug!("some_prev is None (prev)"))
     }
 
+    #[track_caller]
     fn prev_mut(&mut self) -> &mut CoverageSpan {
-        self.some_prev
-            .as_mut()
-            .unwrap_or_else(|| bug!("invalid attempt to unwrap a None some_prev"))
+        self.some_prev.as_mut().unwrap_or_else(|| bug!("some_prev is None (prev_mut)"))
     }
 
+    #[track_caller]
     fn take_prev(&mut self) -> CoverageSpan {
-        self.some_prev.take().unwrap_or_else(|| bug!("invalid attempt to unwrap a None some_prev"))
+        self.some_prev.take().unwrap_or_else(|| bug!("some_prev is None (take_prev)"))
     }
 
     /// If there are `pending_dups` but `prev` is not a matching dup (`prev.span` doesn't match the
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..eab9a9c98f8 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
 }
 
@@ -92,13 +102,13 @@ fn is_closure(statement: &Statement<'_>) -> bool {
 /// If the MIR `Statement` has a span contributive to computing coverage spans,
 /// return it; otherwise return `None`.
 fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
+    use mir::coverage::CoverageKind;
+
     match statement.kind {
         // These statements have spans that are often outside the scope of the executed source code
         // for their parent `BasicBlock`.
         StatementKind::StorageLive(_)
         | StatementKind::StorageDead(_)
-        // Coverage should not be encountered, but don't inject coverage coverage
-        | StatementKind::Coverage(_)
         // Ignore `ConstEvalCounter`s
         | StatementKind::ConstEvalCounter
         // Ignore `Nop`s
@@ -122,9 +132,13 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
         // If and when the Issue is resolved, remove this special case match pattern:
         StatementKind::FakeRead(box (FakeReadCause::ForGuardBinding, _)) => None,
 
-        // Retain spans from all other statements
+        // Retain spans from most other statements.
         StatementKind::FakeRead(box (_, _)) // Not including `ForGuardBinding`
         | StatementKind::Intrinsic(..)
+        | StatementKind::Coverage(box mir::Coverage {
+            // The purpose of `SpanMarker` is to be matched and accepted here.
+            kind: CoverageKind::SpanMarker
+        })
         | StatementKind::Assign(_)
         | StatementKind::SetDiscriminant { .. }
         | StatementKind::Deinit(..)
@@ -133,6 +147,11 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
         | StatementKind::AscribeUserType(_, _) => {
             Some(statement.source_info.span)
         }
+
+        StatementKind::Coverage(box mir::Coverage {
+            // These coverage statements should not exist prior to coverage instrumentation.
+            kind: CoverageKind::CounterIncrement { .. } | CoverageKind::ExpressionUsed { .. }
+        }) => bug!("Unexpected coverage statement found during coverage instrumentation: {statement:?}"),
     }
 }