Auto merge of #119648 - compiler-errors:rollup-42inxd8, r=compiler-errors

Rollup of 9 pull requests

Successful merges:

 - #119208 (coverage: Hoist some complex code out of the main span refinement loop)
 - #119216 (Use diagnostic namespace in stdlib)
 - #119414 (bootstrap: Move -Clto= setting from Rustc::run to rustc_cargo)
 - #119420 (Handle ForeignItem as TAIT scope.)
 - #119468 (rustdoc-search: tighter encoding for f index)
 - #119628 (remove duplicate test)
 - #119638 (fix cyle error when suggesting to use associated function instead of constructor)
 - #119640 (library: Fix warnings in rtstartup)
 - #119642 (library: Fix a symlink test failing on Windows)

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

2 files changed, 175 insertions, 154 deletions

diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs
index ed091752187..5983189984d 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans.rs
@@ -1,11 +1,9 @@
-use std::cell::OnceCell;
-
 use rustc_data_structures::graph::WithNumNodes;
 use rustc_index::IndexVec;
 use rustc_middle::mir;
-use rustc_span::{BytePos, ExpnKind, MacroKind, Span, Symbol, DUMMY_SP};
+use rustc_span::{BytePos, Span, DUMMY_SP};
 
-use super::graph::{BasicCoverageBlock, CoverageGraph, START_BCB};
+use super::graph::{BasicCoverageBlock, CoverageGraph};
 use crate::coverage::ExtractedHirInfo;
 
 mod from_mir;
@@ -70,35 +68,17 @@ impl CoverageSpans {
 /// `dominates()` the `BasicBlock`s in this `CoverageSpan`.
 #[derive(Debug, Clone)]
 struct CoverageSpan {
-    pub span: Span,
-    pub expn_span: Span,
-    pub current_macro_or_none: OnceCell<Option<Symbol>>,
-    pub bcb: BasicCoverageBlock,
+    span: Span,
+    bcb: BasicCoverageBlock,
     /// List of all the original spans from MIR that have been merged into this
     /// span. Mainly used to precisely skip over gaps when truncating a span.
-    pub merged_spans: Vec<Span>,
-    pub is_closure: bool,
+    merged_spans: Vec<Span>,
+    is_closure: bool,
 }
 
 impl CoverageSpan {
-    pub fn for_fn_sig(fn_sig_span: Span) -> Self {
-        Self::new(fn_sig_span, fn_sig_span, START_BCB, false)
-    }
-
-    pub(super) fn new(
-        span: Span,
-        expn_span: Span,
-        bcb: BasicCoverageBlock,
-        is_closure: bool,
-    ) -> Self {
-        Self {
-            span,
-            expn_span,
-            current_macro_or_none: Default::default(),
-            bcb,
-            merged_spans: vec![span],
-            is_closure,
-        }
+    fn new(span: Span, bcb: BasicCoverageBlock, is_closure: bool) -> Self {
+        Self { span, bcb, merged_spans: vec![span], is_closure }
     }
 
     pub fn merge_from(&mut self, other: &Self) {
@@ -123,37 +103,6 @@ impl CoverageSpan {
     pub fn is_in_same_bcb(&self, other: &Self) -> bool {
         self.bcb == other.bcb
     }
-
-    /// If the span is part of a macro, returns the macro name symbol.
-    pub fn current_macro(&self) -> Option<Symbol> {
-        self.current_macro_or_none
-            .get_or_init(|| {
-                if let ExpnKind::Macro(MacroKind::Bang, current_macro) =
-                    self.expn_span.ctxt().outer_expn_data().kind
-                {
-                    return Some(current_macro);
-                }
-                None
-            })
-            .map(|symbol| symbol)
-    }
-
-    /// If the span is part of a macro, and the macro is visible (expands directly to the given
-    /// body_span), returns the macro name symbol.
-    pub fn visible_macro(&self, body_span: Span) -> Option<Symbol> {
-        let current_macro = self.current_macro()?;
-        let parent_callsite = self.expn_span.parent_callsite()?;
-
-        // In addition to matching the context of the body span, the parent callsite
-        // must also be the source callsite, i.e. the parent must have no parent.
-        let is_visible_macro =
-            parent_callsite.parent_callsite().is_none() && parent_callsite.eq_ctxt(body_span);
-        is_visible_macro.then_some(current_macro)
-    }
-
-    pub fn is_macro_expansion(&self) -> bool {
-        self.current_macro().is_some()
-    }
 }
 
 /// Converts the initial set of `CoverageSpan`s (one per MIR `Statement` or `Terminator`) into a
@@ -164,10 +113,6 @@ impl CoverageSpan {
 ///    execution
 ///  * Carve out (leave uncovered) any span that will be counted by another MIR (notably, closures)
 struct CoverageSpansGenerator<'a> {
-    /// A `Span` covering the function body of the MIR (typically from left curly brace to right
-    /// curly brace).
-    body_span: Span,
-
     /// The BasicCoverageBlock Control Flow Graph (BCB CFG).
     basic_coverage_blocks: &'a CoverageGraph,
 
@@ -244,7 +189,6 @@ impl<'a> CoverageSpansGenerator<'a> {
         );
 
         let coverage_spans = Self {
-            body_span: hir_info.body_span,
             basic_coverage_blocks,
             sorted_spans_iter: sorted_spans.into_iter(),
             some_curr: None,
@@ -266,7 +210,6 @@ impl<'a> CoverageSpansGenerator<'a> {
             // span-processing steps don't make sense yet.
             if self.some_prev.is_none() {
                 debug!("  initial span");
-                self.maybe_push_macro_name_span();
                 continue;
             }
 
@@ -278,7 +221,6 @@ impl<'a> CoverageSpansGenerator<'a> {
                 debug!("  same bcb (and neither is a closure), merge with prev={prev:?}");
                 let prev = self.take_prev();
                 self.curr_mut().merge_from(&prev);
-                self.maybe_push_macro_name_span();
             // Note that curr.span may now differ from curr_original_span
             } else if prev.span.hi() <= curr.span.lo() {
                 debug!(
@@ -286,7 +228,6 @@ impl<'a> CoverageSpansGenerator<'a> {
                 );
                 let prev = self.take_prev();
                 self.refined_spans.push(prev);
-                self.maybe_push_macro_name_span();
             } else if prev.is_closure {
                 // drop any equal or overlapping span (`curr`) and keep `prev` to test again in the
                 // next iter
@@ -297,35 +238,11 @@ impl<'a> CoverageSpansGenerator<'a> {
             } else if curr.is_closure {
                 self.carve_out_span_for_closure();
             } else if self.prev_original_span == curr.span {
-                // Note that this compares the new (`curr`) span to `prev_original_span`.
-                // In this branch, the actual span byte range of `prev_original_span` is not
-                // important. What is important is knowing whether the new `curr` span was
-                // **originally** the same as the original span of `prev()`. The original spans
-                // reflect their original sort order, and for equal spans, conveys a partial
-                // ordering based on CFG dominator priority.
-                if prev.is_macro_expansion() && curr.is_macro_expansion() {
-                    // Macros that expand to include branching (such as
-                    // `assert_eq!()`, `assert_ne!()`, `info!()`, `debug!()`, or
-                    // `trace!()`) typically generate callee spans with identical
-                    // ranges (typically the full span of the macro) for all
-                    // `BasicBlocks`. This makes it impossible to distinguish
-                    // the condition (`if val1 != val2`) from the optional
-                    // branched statements (such as the call to `panic!()` on
-                    // assert failure). In this case it is better (or less
-                    // worse) to drop the optional branch bcbs and keep the
-                    // non-conditional statements, to count when reached.
-                    debug!(
-                        "  curr and prev are part of a macro expansion, and curr has the same span \
-                        as prev, but is in a different bcb. Drop curr and keep prev for next iter. \
-                        prev={prev:?}",
-                    );
-                    self.take_curr(); // Discards curr.
-                } else {
-                    self.update_pending_dups();
-                }
+                // `prev` and `curr` have the same span, or would have had the
+                // same span before `prev` was modified by other spans.
+                self.update_pending_dups();
             } else {
                 self.cutoff_prev_at_overlapping_curr();
-                self.maybe_push_macro_name_span();
             }
         }
 
@@ -360,41 +277,6 @@ impl<'a> CoverageSpansGenerator<'a> {
         self.refined_spans
     }
 
-    /// If `curr` is part of a new macro expansion, carve out and push a separate
-    /// span that ends just after the macro name and its subsequent `!`.
-    fn maybe_push_macro_name_span(&mut self) {
-        let curr = self.curr();
-
-        let Some(visible_macro) = curr.visible_macro(self.body_span) else { return };
-        if let Some(prev) = &self.some_prev
-            && prev.expn_span.eq_ctxt(curr.expn_span)
-        {
-            return;
-        }
-
-        // The split point is relative to `curr_original_span`,
-        // because `curr.span` may have been merged with preceding spans.
-        let split_point_after_macro_bang = self.curr_original_span.lo()
-            + BytePos(visible_macro.as_str().len() as u32)
-            + BytePos(1); // add 1 for the `!`
-        debug_assert!(split_point_after_macro_bang <= curr.span.hi());
-        if split_point_after_macro_bang > curr.span.hi() {
-            // Something is wrong with the macro name span;
-            // return now to avoid emitting malformed mappings (e.g. #117788).
-            return;
-        }
-
-        let mut macro_name_cov = curr.clone();
-        macro_name_cov.span = macro_name_cov.span.with_hi(split_point_after_macro_bang);
-        self.curr_mut().span = curr.span.with_lo(split_point_after_macro_bang);
-
-        debug!(
-            "  and curr starts a new macro expansion, so add a new span just for \
-            the macro `{visible_macro}!`, new span={macro_name_cov:?}",
-        );
-        self.refined_spans.push(macro_name_cov);
-    }
-
     #[track_caller]
     fn curr(&self) -> &CoverageSpan {
         self.some_curr.as_ref().unwrap_or_else(|| bug!("some_curr is None (curr)"))
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 8f6592afe85..1b6dfccd574 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
@@ -1,11 +1,14 @@
 use rustc_data_structures::captures::Captures;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::mir::{
     self, AggregateKind, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
     TerminatorKind,
 };
-use rustc_span::Span;
+use rustc_span::{ExpnKind, MacroKind, Span, Symbol};
 
-use crate::coverage::graph::{BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph};
+use crate::coverage::graph::{
+    BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB,
+};
 use crate::coverage::spans::CoverageSpan;
 use crate::coverage::ExtractedHirInfo;
 
@@ -15,26 +18,29 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
     basic_coverage_blocks: &CoverageGraph,
 ) -> Vec<CoverageSpan> {
     let &ExtractedHirInfo { is_async_fn, fn_sig_span, body_span, .. } = hir_info;
+
+    let mut initial_spans = vec![SpanFromMir::for_fn_sig(fn_sig_span)];
+
     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() {
-        initial_spans.extend(bcb_to_initial_coverage_spans(mir_body, body_span, bcb, bcb_data));
-    }
+        // outer function will be unhelpful, so just keep the signature span
+        // and ignore all of the spans in the MIR body.
+    } else {
+        for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
+            initial_spans.extend(bcb_to_initial_coverage_spans(mir_body, body_span, bcb, bcb_data));
+        }
 
-    if initial_spans.is_empty() {
-        // This can happen if, for example, the function is unreachable (contains only a
-        // `BasicBlock`(s) with an `Unreachable` terminator).
-        return initial_spans;
+        // If no spans were extracted from the body, discard the signature span.
+        // FIXME: This preserves existing behavior; consider getting rid of it.
+        if initial_spans.len() == 1 {
+            initial_spans.clear();
+        }
     }
 
-    initial_spans.push(CoverageSpan::for_fn_sig(fn_sig_span));
+    initial_spans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
+    remove_unwanted_macro_spans(&mut initial_spans);
+    split_visible_macro_spans(&mut initial_spans);
 
     initial_spans.sort_by(|a, b| {
         // First sort by span start.
@@ -53,7 +59,62 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
             .then_with(|| Ord::cmp(&a.is_closure, &b.is_closure).reverse())
     });
 
-    initial_spans
+    initial_spans.into_iter().map(SpanFromMir::into_coverage_span).collect::<Vec<_>>()
+}
+
+/// Macros that expand into branches (e.g. `assert!`, `trace!`) tend to generate
+/// multiple condition/consequent blocks that have the span of the whole macro
+/// invocation, which is unhelpful. Keeping only the first such span seems to
+/// give better mappings, so remove the others.
+///
+/// (The input spans should be sorted in BCB dominator order, so that the
+/// retained "first" span is likely to dominate the others.)
+fn remove_unwanted_macro_spans(initial_spans: &mut Vec<SpanFromMir>) {
+    let mut seen_macro_spans = FxHashSet::default();
+    initial_spans.retain(|covspan| {
+        // Ignore (retain) closure spans and non-macro-expansion spans.
+        if covspan.is_closure || covspan.visible_macro.is_none() {
+            return true;
+        }
+
+        // Retain only the first macro-expanded covspan with this span.
+        seen_macro_spans.insert(covspan.span)
+    });
+}
+
+/// When a span corresponds to a macro invocation that is visible from the
+/// function body, split it into two parts. The first part covers just the
+/// macro name plus `!`, and the second part covers the rest of the macro
+/// invocation. This seems to give better results for code that uses macros.
+fn split_visible_macro_spans(initial_spans: &mut Vec<SpanFromMir>) {
+    let mut extra_spans = vec![];
+
+    initial_spans.retain(|covspan| {
+        if covspan.is_closure {
+            return true;
+        }
+
+        let Some(visible_macro) = covspan.visible_macro else { return true };
+
+        let split_len = visible_macro.as_str().len() as u32 + 1;
+        let (before, after) = covspan.span.split_at(split_len);
+        if !covspan.span.contains(before) || !covspan.span.contains(after) {
+            // Something is unexpectedly wrong with the split point.
+            // The debug assertion in `split_at` will have already caught this,
+            // but in release builds it's safer to do nothing and maybe get a
+            // bug report for unexpected coverage, rather than risk an ICE.
+            return true;
+        }
+
+        assert!(!covspan.is_closure);
+        extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb, false));
+        extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb, false));
+        false // Discard the original covspan that we just split.
+    });
+
+    // The newly-split spans are added at the end, so any previous sorting
+    // is not preserved.
+    initial_spans.extend(extra_spans);
 }
 
 // Generate a set of `CoverageSpan`s from the filtered set of `Statement`s and `Terminator`s of
@@ -66,22 +127,24 @@ fn bcb_to_initial_coverage_spans<'a, 'tcx>(
     body_span: Span,
     bcb: BasicCoverageBlock,
     bcb_data: &'a BasicCoverageBlockData,
-) -> impl Iterator<Item = CoverageSpan> + Captures<'a> + Captures<'tcx> {
+) -> impl Iterator<Item = SpanFromMir> + Captures<'a> + Captures<'tcx> {
     bcb_data.basic_blocks.iter().flat_map(move |&bb| {
         let data = &mir_body[bb];
 
         let statement_spans = data.statements.iter().filter_map(move |statement| {
             let expn_span = filtered_statement_span(statement)?;
-            let span = unexpand_into_body_span(expn_span, body_span)?;
+            let (span, visible_macro) =
+                unexpand_into_body_span_with_visible_macro(expn_span, body_span)?;
 
-            Some(CoverageSpan::new(span, expn_span, bcb, is_closure_or_coroutine(statement)))
+            Some(SpanFromMir::new(span, visible_macro, bcb, is_closure_or_coroutine(statement)))
         });
 
         let terminator_span = Some(data.terminator()).into_iter().filter_map(move |terminator| {
             let expn_span = filtered_terminator_span(terminator)?;
-            let span = unexpand_into_body_span(expn_span, body_span)?;
+            let (span, visible_macro) =
+                unexpand_into_body_span_with_visible_macro(expn_span, body_span)?;
 
-            Some(CoverageSpan::new(span, expn_span, bcb, false))
+            Some(SpanFromMir::new(span, visible_macro, bcb, false))
         });
 
         statement_spans.chain(terminator_span)
@@ -202,7 +265,83 @@ fn filtered_terminator_span(terminator: &Terminator<'_>) -> Option<Span> {
 ///
 /// [^1]Expansions result from Rust syntax including macros, syntactic sugar,
 /// etc.).
-#[inline]
-fn unexpand_into_body_span(span: Span, body_span: Span) -> Option<Span> {
-    span.find_ancestor_inside_same_ctxt(body_span)
+fn unexpand_into_body_span_with_visible_macro(
+    original_span: Span,
+    body_span: Span,
+) -> Option<(Span, Option<Symbol>)> {
+    let (span, prev) = unexpand_into_body_span_with_prev(original_span, body_span)?;
+
+    let visible_macro = prev
+        .map(|prev| match prev.ctxt().outer_expn_data().kind {
+            ExpnKind::Macro(MacroKind::Bang, name) => Some(name),
+            _ => None,
+        })
+        .flatten();
+
+    Some((span, visible_macro))
+}
+
+/// Walks through the expansion ancestors of `original_span` to find a span that
+/// is contained in `body_span` and has the same [`SyntaxContext`] as `body_span`.
+/// The ancestor that was traversed just before the matching span (if any) is
+/// also returned.
+///
+/// For example, a return value of `Some((ancestor, Some(prev))` means that:
+/// - `ancestor == original_span.find_ancestor_inside_same_ctxt(body_span)`
+/// - `ancestor == prev.parent_callsite()`
+///
+/// [`SyntaxContext`]: rustc_span::SyntaxContext
+fn unexpand_into_body_span_with_prev(
+    original_span: Span,
+    body_span: Span,
+) -> Option<(Span, Option<Span>)> {
+    let mut prev = None;
+    let mut curr = original_span;
+
+    while !body_span.contains(curr) || !curr.eq_ctxt(body_span) {
+        prev = Some(curr);
+        curr = curr.parent_callsite()?;
+    }
+
+    debug_assert_eq!(Some(curr), original_span.find_ancestor_in_same_ctxt(body_span));
+    if let Some(prev) = prev {
+        debug_assert_eq!(Some(curr), prev.parent_callsite());
+    }
+
+    Some((curr, prev))
+}
+
+#[derive(Debug)]
+struct SpanFromMir {
+    /// A span that has been extracted from MIR and then "un-expanded" back to
+    /// within the current function's `body_span`. After various intermediate
+    /// processing steps, this span is emitted as part of the final coverage
+    /// mappings.
+    ///
+    /// With the exception of `fn_sig_span`, this should always be contained
+    /// within `body_span`.
+    span: Span,
+    visible_macro: Option<Symbol>,
+    bcb: BasicCoverageBlock,
+    is_closure: bool,
+}
+
+impl SpanFromMir {
+    fn for_fn_sig(fn_sig_span: Span) -> Self {
+        Self::new(fn_sig_span, None, START_BCB, false)
+    }
+
+    fn new(
+        span: Span,
+        visible_macro: Option<Symbol>,
+        bcb: BasicCoverageBlock,
+        is_closure: bool,
+    ) -> Self {
+        Self { span, visible_macro, bcb, is_closure }
+    }
+
+    fn into_coverage_span(self) -> CoverageSpan {
+        let Self { span, visible_macro: _, bcb, is_closure } = self;
+        CoverageSpan::new(span, bcb, is_closure)
+    }
 }