Auto merge of #126569 - jieyouxu:rollup-1uvkb2y, r=jieyouxu

Rollup of 8 pull requests

Successful merges:

 - #125258 (Resolve elided lifetimes in assoc const to static if no other lifetimes are in scope)
 - #126250 (docs(change): Don't mention a Cargo 2024 edition change for 1.79)
 - #126288 (doc: Added commas where needed)
 - #126346 (export std::os::fd module on HermitOS)
 - #126468 (div_euclid, rem_euclid: clarify/extend documentation)
 - #126531 (Add codegen test for `Request::provide_*`)
 - #126535 (coverage: Arrange span extraction/refinement as a series of passes)
 - #126538 (coverage: Several small improvements to graph code)

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

RELEASES.md

@@ -97,7 +97,6 @@ Cargo
 - [Prevent dashes in `lib.name`, always normalizing to `_`.](https://github.com/rust-lang/cargo/pull/12783/)
 - [Stabilize MSRV-aware version requirement selection in `cargo add`.](https://github.com/rust-lang/cargo/pull/13608/)
 - [Switch to using `gitoxide` by default for listing files.](https://github.com/rust-lang/cargo/pull/13696/)
-- [Error on `[project]` in Edition 2024; `cargo fix --edition` will change it to `[package]`.](https://github.com/rust-lang/cargo/pull/13747/)
 
 <a id="1.79.0-Rustdoc"></a>
 

compiler/rustc_lint/messages.ftl

@@ -14,6 +14,7 @@ lint_associated_const_elided_lifetime = {$elided ->
         *[false] `'_` cannot be used here
     }
     .suggestion = use the `'static` lifetime
+    .note = cannot automatically infer `'static` because of other lifetimes in scope
 
 lint_async_fn_in_trait = use of `async fn` in public traits is discouraged as auto trait bounds cannot be specified
     .note = you can suppress this lint if you plan to use the trait only in your own code, or do not care about auto traits like `Send` on the `Future`

compiler/rustc_lint/src/context/diagnostics.rs

@@ -319,11 +319,20 @@ pub(super) fn decorate_lint(sess: &Session, diagnostic: BuiltinLintDiag, diag: &
         BuiltinLintDiag::UnusedQualifications { removal_span } => {
             lints::UnusedQualifications { removal_span }.decorate_lint(diag);
         }
-        BuiltinLintDiag::AssociatedConstElidedLifetime { elided, span: lt_span } => {
+        BuiltinLintDiag::AssociatedConstElidedLifetime {
+            elided,
+            span: lt_span,
+            lifetimes_in_scope,
+        } => {
             let lt_span = if elided { lt_span.shrink_to_hi() } else { lt_span };
             let code = if elided { "'static " } else { "'static" };
-            lints::AssociatedConstElidedLifetime { span: lt_span, code, elided }
+            lints::AssociatedConstElidedLifetime {
-                .decorate_lint(diag);
+                span: lt_span,
+                code,
+                elided,
+                lifetimes_in_scope,
+            }
+            .decorate_lint(diag);
         }
         BuiltinLintDiag::RedundantImportVisibility { max_vis, span: vis_span, import_vis } => {
             lints::RedundantImportVisibility { span: vis_span, help: (), max_vis, import_vis }

compiler/rustc_lint/src/lints.rs

@@ -2873,6 +2873,8 @@ pub struct AssociatedConstElidedLifetime {
 
     pub code: &'static str,
     pub elided: bool,
+    #[note]
+    pub lifetimes_in_scope: MultiSpan,
 }
 
 #[derive(LintDiagnostic)]

compiler/rustc_lint_defs/src/builtin.rs

@@ -4593,16 +4593,18 @@ declare_lint! {
 
 declare_lint! {
     /// The `elided_lifetimes_in_associated_constant` lint detects elided lifetimes
-    /// that were erroneously allowed in associated constants.
+    /// in associated constants when there are other lifetimes in scope. This was
+    /// accidentally supported, and this lint was later relaxed to allow eliding
+    /// lifetimes to `'static` when there are no lifetimes in scope.
     ///
     /// ### Example
     ///
     /// ```rust,compile_fail
     /// #![deny(elided_lifetimes_in_associated_constant)]
     ///
-    /// struct Foo;
+    /// struct Foo<'a>(&'a ());
     ///
-    /// impl Foo {
+    /// impl<'a> Foo<'a> {
     ///     const STR: &str = "hello, world";
     /// }
     /// ```

compiler/rustc_lint_defs/src/lib.rs

@@ -696,6 +696,7 @@ pub enum BuiltinLintDiag {
     AssociatedConstElidedLifetime {
         elided: bool,
         span: Span,
+        lifetimes_in_scope: MultiSpan,
     },
     RedundantImportVisibility {
         span: Span,

compiler/rustc_mir_transform/src/coverage/counters.rs

@@ -168,11 +168,6 @@ impl CoverageCounters {
         self.counter_increment_sites.len()
     }
 
-    #[cfg(test)]
-    pub(super) fn num_expressions(&self) -> usize {
-        self.expressions.len()
-    }
-
     fn set_bcb_counter(&mut self, bcb: BasicCoverageBlock, counter_kind: BcbCounter) -> BcbCounter {
         if let Some(replaced) = self.bcb_counters[bcb].replace(counter_kind) {
             bug!(

compiler/rustc_mir_transform/src/coverage/graph.rs

@@ -14,16 +14,16 @@ use std::ops::{Index, IndexMut};
 /// A coverage-specific simplification of the MIR control flow graph (CFG). The `CoverageGraph`s
 /// nodes are `BasicCoverageBlock`s, which encompass one or more MIR `BasicBlock`s.
 #[derive(Debug)]
-pub(super) struct CoverageGraph {
+pub(crate) struct CoverageGraph {
     bcbs: IndexVec<BasicCoverageBlock, BasicCoverageBlockData>,
     bb_to_bcb: IndexVec<BasicBlock, Option<BasicCoverageBlock>>,
-    pub successors: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
+    pub(crate) successors: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
-    pub predecessors: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
+    pub(crate) predecessors: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
     dominators: Option<Dominators<BasicCoverageBlock>>,
 }
 
 impl CoverageGraph {
-    pub fn from_mir(mir_body: &mir::Body<'_>) -> Self {
+    pub(crate) fn from_mir(mir_body: &mir::Body<'_>) -> Self {
         let (bcbs, bb_to_bcb) = Self::compute_basic_coverage_blocks(mir_body);
 
         // Pre-transform MIR `BasicBlock` successors and predecessors into the BasicCoverageBlock
@@ -135,24 +135,28 @@ impl CoverageGraph {
     }
 
     #[inline(always)]
-    pub fn iter_enumerated(
+    pub(crate) fn iter_enumerated(
         &self,
     ) -> impl Iterator<Item = (BasicCoverageBlock, &BasicCoverageBlockData)> {
         self.bcbs.iter_enumerated()
     }
 
     #[inline(always)]
-    pub fn bcb_from_bb(&self, bb: BasicBlock) -> Option<BasicCoverageBlock> {
+    pub(crate) fn bcb_from_bb(&self, bb: BasicBlock) -> Option<BasicCoverageBlock> {
         if bb.index() < self.bb_to_bcb.len() { self.bb_to_bcb[bb] } else { None }
     }
 
     #[inline(always)]
-    pub fn dominates(&self, dom: BasicCoverageBlock, node: BasicCoverageBlock) -> bool {
+    pub(crate) fn dominates(&self, dom: BasicCoverageBlock, node: BasicCoverageBlock) -> bool {
         self.dominators.as_ref().unwrap().dominates(dom, node)
     }
 
     #[inline(always)]
-    pub fn cmp_in_dominator_order(&self, a: BasicCoverageBlock, b: BasicCoverageBlock) -> Ordering {
+    pub(crate) fn cmp_in_dominator_order(
+        &self,
+        a: BasicCoverageBlock,
+        b: BasicCoverageBlock,
+    ) -> Ordering {
         self.dominators.as_ref().unwrap().cmp_in_dominator_order(a, b)
     }
 
@@ -166,7 +170,7 @@ impl CoverageGraph {
     ///
     /// FIXME: That assumption might not be true for [`TerminatorKind::Yield`]?
     #[inline(always)]
-    pub(super) fn bcb_has_multiple_in_edges(&self, bcb: BasicCoverageBlock) -> bool {
+    pub(crate) fn bcb_has_multiple_in_edges(&self, bcb: BasicCoverageBlock) -> bool {
         // Even though bcb0 conceptually has an extra virtual in-edge due to
         // being the entry point, we've already asserted that it has no _other_
         // in-edges, so there's no possibility of it having _multiple_ in-edges.
@@ -212,7 +216,7 @@ impl graph::StartNode for CoverageGraph {
 impl graph::Successors for CoverageGraph {
     #[inline]
     fn successors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node> {
-        self.successors[node].iter().cloned()
+        self.successors[node].iter().copied()
     }
 }
 
@@ -227,7 +231,7 @@ rustc_index::newtype_index! {
     /// A node in the control-flow graph of CoverageGraph.
     #[orderable]
     #[debug_format = "bcb{}"]
-    pub(super) struct BasicCoverageBlock {
+    pub(crate) struct BasicCoverageBlock {
         const START_BCB = 0;
     }
 }
@@ -259,23 +263,23 @@ rustc_index::newtype_index! {
 /// queries (`dominates()`, `predecessors`, `successors`, etc.) have branch (control flow)
 /// significance.
 #[derive(Debug, Clone)]
-pub(super) struct BasicCoverageBlockData {
+pub(crate) struct BasicCoverageBlockData {
-    pub basic_blocks: Vec<BasicBlock>,
+    pub(crate) basic_blocks: Vec<BasicBlock>,
 }
 
 impl BasicCoverageBlockData {
-    pub fn from(basic_blocks: Vec<BasicBlock>) -> Self {
+    fn from(basic_blocks: Vec<BasicBlock>) -> Self {
         assert!(basic_blocks.len() > 0);
         Self { basic_blocks }
     }
 
     #[inline(always)]
-    pub fn leader_bb(&self) -> BasicBlock {
+    pub(crate) fn leader_bb(&self) -> BasicBlock {
         self.basic_blocks[0]
     }
 
     #[inline(always)]
-    pub fn last_bb(&self) -> BasicBlock {
+    pub(crate) fn last_bb(&self) -> BasicBlock {
         *self.basic_blocks.last().unwrap()
     }
 }
@@ -364,7 +368,7 @@ fn bcb_filtered_successors<'a, 'tcx>(terminator: &'a Terminator<'tcx>) -> Covera
 /// CoverageGraph outside all loops. This supports traversing the BCB CFG in a way that
 /// ensures a loop is completely traversed before processing Blocks after the end of the loop.
 #[derive(Debug)]
-pub(super) struct TraversalContext {
+struct TraversalContext {
     /// BCB with one or more incoming loop backedges, indicating which loop
     /// this context is for.
     ///
@@ -375,7 +379,7 @@ pub(super) struct TraversalContext {
     worklist: VecDeque<BasicCoverageBlock>,
 }
 
-pub(super) struct TraverseCoverageGraphWithLoops<'a> {
+pub(crate) struct TraverseCoverageGraphWithLoops<'a> {
     basic_coverage_blocks: &'a CoverageGraph,
 
     backedges: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
@@ -384,7 +388,7 @@ pub(super) struct TraverseCoverageGraphWithLoops<'a> {
 }
 
 impl<'a> TraverseCoverageGraphWithLoops<'a> {
-    pub(super) fn new(basic_coverage_blocks: &'a CoverageGraph) -> Self {
+    pub(crate) fn new(basic_coverage_blocks: &'a CoverageGraph) -> Self {
         let backedges = find_loop_backedges(basic_coverage_blocks);
 
         let worklist = VecDeque::from([basic_coverage_blocks.start_node()]);
@@ -400,7 +404,7 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
 
     /// For each loop on the loop context stack (top-down), yields a list of BCBs
     /// within that loop that have an outgoing edge back to the loop header.
-    pub(super) fn reloop_bcbs_per_loop(&self) -> impl Iterator<Item = &[BasicCoverageBlock]> {
+    pub(crate) fn reloop_bcbs_per_loop(&self) -> impl Iterator<Item = &[BasicCoverageBlock]> {
         self.context_stack
             .iter()
             .rev()
@@ -408,39 +412,38 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
             .map(|header_bcb| self.backedges[header_bcb].as_slice())
     }
 
-    pub(super) fn next(&mut self) -> Option<BasicCoverageBlock> {
+    pub(crate) fn next(&mut self) -> Option<BasicCoverageBlock> {
         debug!(
             "TraverseCoverageGraphWithLoops::next - context_stack: {:?}",
             self.context_stack.iter().rev().collect::<Vec<_>>()
         );
 
         while let Some(context) = self.context_stack.last_mut() {
-            if let Some(bcb) = context.worklist.pop_front() {
+            let Some(bcb) = context.worklist.pop_front() else {
-                if !self.visited.insert(bcb) {
+                // This stack level is exhausted; pop it and try the next one.
-                    debug!("Already visited: {bcb:?}");
-                    continue;
-                }
-                debug!("Visiting {bcb:?}");
-
-                if self.backedges[bcb].len() > 0 {
-                    debug!("{bcb:?} is a loop header! Start a new TraversalContext...");
-                    self.context_stack.push(TraversalContext {
-                        loop_header: Some(bcb),
-                        worklist: VecDeque::new(),
-                    });
-                }
-                self.add_successors_to_worklists(bcb);
-                return Some(bcb);
-            } else {
-                // Strip contexts with empty worklists from the top of the stack
                 self.context_stack.pop();
+                continue;
+            };
+
+            if !self.visited.insert(bcb) {
+                debug!("Already visited: {bcb:?}");
+                continue;
             }
+            debug!("Visiting {bcb:?}");
+
+            if self.backedges[bcb].len() > 0 {
+                debug!("{bcb:?} is a loop header! Start a new TraversalContext...");
+                self.context_stack
+                    .push(TraversalContext { loop_header: Some(bcb), worklist: VecDeque::new() });
+            }
+            self.add_successors_to_worklists(bcb);
+            return Some(bcb);
         }
 
         None
     }
 
-    pub fn add_successors_to_worklists(&mut self, bcb: BasicCoverageBlock) {
+    fn add_successors_to_worklists(&mut self, bcb: BasicCoverageBlock) {
         let successors = &self.basic_coverage_blocks.successors[bcb];
         debug!("{:?} has {} successors:", bcb, successors.len());
 
@@ -494,11 +497,11 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
         }
     }
 
-    pub fn is_complete(&self) -> bool {
+    pub(crate) fn is_complete(&self) -> bool {
         self.visited.count() == self.visited.domain_size()
     }
 
-    pub fn unvisited(&self) -> Vec<BasicCoverageBlock> {
+    pub(crate) fn unvisited(&self) -> Vec<BasicCoverageBlock> {
         let mut unvisited_set: BitSet<BasicCoverageBlock> =
             BitSet::new_filled(self.visited.domain_size());
         unvisited_set.subtract(&self.visited);
@@ -506,7 +509,7 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
     }
 }
 
-pub(super) fn find_loop_backedges(
+fn find_loop_backedges(
     basic_coverage_blocks: &CoverageGraph,
 ) -> IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>> {
     let num_bcbs = basic_coverage_blocks.num_nodes();

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -1,9 +1,15 @@
+use std::collections::VecDeque;
+
+use rustc_data_structures::captures::Captures;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::mir;
 use rustc_span::Span;
 
 use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
 use crate::coverage::mappings;
-use crate::coverage::spans::from_mir::SpanFromMir;
+use crate::coverage::spans::from_mir::{
+    extract_covspans_and_holes_from_mir, ExtractedCovspans, Hole, SpanFromMir,
+};
 use crate::coverage::ExtractedHirInfo;
 
 mod from_mir;
@@ -19,50 +25,181 @@ pub(super) fn extract_refined_covspans(
     basic_coverage_blocks: &CoverageGraph,
     code_mappings: &mut impl Extend<mappings::CodeMapping>,
 ) {
-    let sorted_span_buckets =
+    let ExtractedCovspans { mut covspans, mut holes } =
-        from_mir::mir_to_initial_sorted_coverage_spans(mir_body, hir_info, basic_coverage_blocks);
+        extract_covspans_and_holes_from_mir(mir_body, hir_info, basic_coverage_blocks);
-    for bucket in sorted_span_buckets {
+
-        let refined_spans = refine_sorted_spans(bucket);
+    // First, perform the passes that need macro information.
-        code_mappings.extend(refined_spans.into_iter().map(|RefinedCovspan { span, bcb }| {
+    covspans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
+    remove_unwanted_macro_spans(&mut covspans);
+    split_visible_macro_spans(&mut covspans);
+
+    // We no longer need the extra information in `SpanFromMir`, so convert to `Covspan`.
+    let mut covspans = covspans.into_iter().map(SpanFromMir::into_covspan).collect::<Vec<_>>();
+
+    let compare_covspans = |a: &Covspan, b: &Covspan| {
+        compare_spans(a.span, b.span)
+            // After deduplication, we want to keep only the most-dominated BCB.
+            .then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
+    };
+    covspans.sort_by(compare_covspans);
+
+    // Among covspans with the same span, keep only one,
+    // preferring the one with the most-dominated BCB.
+    // (Ideally we should try to preserve _all_ non-dominating BCBs, but that
+    // requires a lot more complexity in the span refiner, for little benefit.)
+    covspans.dedup_by(|b, a| a.span.source_equal(b.span));
+
+    // Sort the holes, and merge overlapping/adjacent holes.
+    holes.sort_by(|a, b| compare_spans(a.span, b.span));
+    holes.dedup_by(|b, a| a.merge_if_overlapping_or_adjacent(b));
+
+    // Split the covspans into separate buckets that don't overlap any holes.
+    let buckets = divide_spans_into_buckets(covspans, &holes);
+
+    for mut covspans in buckets {
+        // Make sure each individual bucket is internally sorted.
+        covspans.sort_by(compare_covspans);
+        let _span = debug_span!("processing bucket", ?covspans).entered();
+
+        let mut covspans = remove_unwanted_overlapping_spans(covspans);
+        debug!(?covspans, "after removing overlaps");
+
+        // Do one last merge pass, to simplify the output.
+        covspans.dedup_by(|b, a| a.merge_if_eligible(b));
+        debug!(?covspans, "after merge");
+
+        code_mappings.extend(covspans.into_iter().map(|Covspan { span, bcb }| {
             // Each span produced by the refiner represents an ordinary code region.
             mappings::CodeMapping { span, bcb }
         }));
     }
 }
 
-#[derive(Debug)]
+/// Macros that expand into branches (e.g. `assert!`, `trace!`) tend to generate
-struct RefinedCovspan {
+/// multiple condition/consequent blocks that have the span of the whole macro
-    span: Span,
+/// invocation, which is unhelpful. Keeping only the first such span seems to
-    bcb: BasicCoverageBlock,
+/// 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(covspans: &mut Vec<SpanFromMir>) {
+    let mut seen_macro_spans = FxHashSet::default();
+    covspans.retain(|covspan| {
+        // Ignore (retain) non-macro-expansion spans.
+        if covspan.visible_macro.is_none() {
+            return true;
+        }
+
+        // Retain only the first macro-expanded covspan with this span.
+        seen_macro_spans.insert(covspan.span)
+    });
 }
 
-impl RefinedCovspan {
+/// When a span corresponds to a macro invocation that is visible from the
-    fn is_mergeable(&self, other: &Self) -> bool {
+/// function body, split it into two parts. The first part covers just the
-        self.bcb == other.bcb
+/// 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(covspans: &mut Vec<SpanFromMir>) {
+    let mut extra_spans = vec![];
+
+    covspans.retain(|covspan| {
+        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;
+        }
+
+        extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb));
+        extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb));
+        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.
+    covspans.extend(extra_spans);
+}
+
+/// Uses the holes to divide the given covspans into buckets, such that:
+/// - No span in any hole overlaps a bucket (truncating the spans if necessary).
+/// - The spans in each bucket are strictly after all spans in previous buckets,
+///   and strictly before all spans in subsequent buckets.
+///
+/// The resulting buckets are sorted relative to each other, but might not be
+/// internally sorted.
+#[instrument(level = "debug")]
+fn divide_spans_into_buckets(input_covspans: Vec<Covspan>, holes: &[Hole]) -> Vec<Vec<Covspan>> {
+    debug_assert!(input_covspans.is_sorted_by(|a, b| compare_spans(a.span, b.span).is_le()));
+    debug_assert!(holes.is_sorted_by(|a, b| compare_spans(a.span, b.span).is_le()));
+
+    // Now we're ready to start carving holes out of the initial coverage spans,
+    // and grouping them in buckets separated by the holes.
+
+    let mut input_covspans = VecDeque::from(input_covspans);
+    let mut fragments = vec![];
+
+    // For each hole:
+    // - Identify the spans that are entirely or partly before the hole.
+    // - Put those spans in a corresponding bucket, truncated to the start of the hole.
+    // - If one of those spans also extends after the hole, put the rest of it
+    //   in a "fragments" vector that is processed by the next hole.
+    let mut buckets = (0..holes.len()).map(|_| vec![]).collect::<Vec<_>>();
+    for (hole, bucket) in holes.iter().zip(&mut buckets) {
+        let fragments_from_prev = std::mem::take(&mut fragments);
+
+        // Only inspect spans that precede or overlap this hole,
+        // leaving the rest to be inspected by later holes.
+        // (This relies on the spans and holes both being sorted.)
+        let relevant_input_covspans =
+            drain_front_while(&mut input_covspans, |c| c.span.lo() < hole.span.hi());
+
+        for covspan in fragments_from_prev.into_iter().chain(relevant_input_covspans) {
+            let (before, after) = covspan.split_around_hole_span(hole.span);
+            bucket.extend(before);
+            fragments.extend(after);
+        }
     }
 
-    fn merge_from(&mut self, other: &Self) {
+    // After finding the spans before each hole, any remaining fragments/spans
-        debug_assert!(self.is_mergeable(other));
+    // form their own final bucket, after the final hole.
-        self.span = self.span.to(other.span);
+    // (If there were no holes, this will just be all of the initial spans.)
-    }
+    fragments.extend(input_covspans);
+    buckets.push(fragments);
+
+    buckets
+}
+
+/// Similar to `.drain(..)`, but stops just before it would remove an item not
+/// satisfying the predicate.
+fn drain_front_while<'a, T>(
+    queue: &'a mut VecDeque<T>,
+    mut pred_fn: impl FnMut(&T) -> bool,
+) -> impl Iterator<Item = T> + Captures<'a> {
+    std::iter::from_fn(move || if pred_fn(queue.front()?) { queue.pop_front() } else { None })
 }
 
 /// Takes one of the buckets of (sorted) spans extracted from MIR, and "refines"
-/// those spans by removing spans that overlap in unwanted ways, and by merging
+/// those spans by removing spans that overlap in unwanted ways.
-/// compatible adjacent spans.
 #[instrument(level = "debug")]
-fn refine_sorted_spans(sorted_spans: Vec<SpanFromMir>) -> Vec<RefinedCovspan> {
+fn remove_unwanted_overlapping_spans(sorted_spans: Vec<Covspan>) -> Vec<Covspan> {
+    debug_assert!(sorted_spans.is_sorted_by(|a, b| compare_spans(a.span, b.span).is_le()));
+
     // Holds spans that have been read from the input vector, but haven't yet
     // been committed to the output vector.
     let mut pending = vec![];
     let mut refined = vec![];
 
     for curr in sorted_spans {
-        pending.retain(|prev: &SpanFromMir| {
+        pending.retain(|prev: &Covspan| {
             if prev.span.hi() <= curr.span.lo() {
                 // There's no overlap between the previous/current covspans,
                 // so move the previous one into the refined list.
-                refined.push(RefinedCovspan { span: prev.span, bcb: prev.bcb });
+                refined.push(prev.clone());
                 false
             } else {
                 // Otherwise, retain the previous covspan only if it has the
@@ -75,22 +212,57 @@ fn refine_sorted_spans(sorted_spans: Vec<SpanFromMir>) -> Vec<RefinedCovspan> {
     }
 
     // Drain the rest of the pending list into the refined list.
-    for prev in pending {
+    refined.extend(pending);
-        refined.push(RefinedCovspan { span: prev.span, bcb: prev.bcb });
-    }
-
-    // Do one last merge pass, to simplify the output.
-    debug!(?refined, "before merge");
-    refined.dedup_by(|b, a| {
-        if a.is_mergeable(b) {
-            debug!(?a, ?b, "merging list-adjacent refined spans");
-            a.merge_from(b);
-            true
-        } else {
-            false
-        }
-    });
-    debug!(?refined, "after merge");
-
     refined
 }
+
+#[derive(Clone, Debug)]
+struct Covspan {
+    span: Span,
+    bcb: BasicCoverageBlock,
+}
+
+impl Covspan {
+    /// Splits this covspan into 0-2 parts:
+    /// - The part that is strictly before the hole span, if any.
+    /// - The part that is strictly after the hole span, if any.
+    fn split_around_hole_span(&self, hole_span: Span) -> (Option<Self>, Option<Self>) {
+        let before = try {
+            let span = self.span.trim_end(hole_span)?;
+            Self { span, ..*self }
+        };
+        let after = try {
+            let span = self.span.trim_start(hole_span)?;
+            Self { span, ..*self }
+        };
+
+        (before, after)
+    }
+
+    /// If `self` and `other` can be merged (i.e. they have the same BCB),
+    /// mutates `self.span` to also include `other.span` and returns true.
+    ///
+    /// Note that compatible covspans can be merged even if their underlying
+    /// spans are not overlapping/adjacent; any space between them will also be
+    /// part of the merged covspan.
+    fn merge_if_eligible(&mut self, other: &Self) -> bool {
+        if self.bcb != other.bcb {
+            return false;
+        }
+
+        self.span = self.span.to(other.span);
+        true
+    }
+}
+
+/// Compares two spans in (lo ascending, hi descending) order.
+fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering {
+    // First sort by span start.
+    Ord::cmp(&a.lo(), &b.lo())
+        // If span starts are the same, sort by span end in reverse order.
+        // This ensures that if spans A and B are adjacent in the list,
+        // and they overlap but are not equal, then either:
+        // - Span A extends further left, or
+        // - Both have the same start and span A extends further right
+        .then_with(|| Ord::cmp(&a.hi(), &b.hi()).reverse())
+}

compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs

@@ -1,7 +1,3 @@
-use std::collections::VecDeque;
-
-use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::bug;
 use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::mir::{
@@ -13,25 +9,25 @@ use rustc_span::{ExpnKind, MacroKind, Span, Symbol};
 use crate::coverage::graph::{
     BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB,
 };
+use crate::coverage::spans::Covspan;
 use crate::coverage::ExtractedHirInfo;
 
+pub(crate) struct ExtractedCovspans {
+    pub(crate) covspans: Vec<SpanFromMir>,
+    pub(crate) holes: Vec<Hole>,
+}
+
 /// Traverses the MIR body to produce an initial collection of coverage-relevant
 /// spans, each associated with a node in the coverage graph (BCB) and possibly
 /// other metadata.
-///
+pub(crate) fn extract_covspans_and_holes_from_mir(
-/// The returned spans are divided into one or more buckets, such that:
-/// - The spans in each bucket are strictly after all spans in previous buckets,
-///   and strictly before all spans in subsequent buckets.
-/// - The contents of each bucket are also sorted, in a specific order that is
-///   expected by the subsequent span-refinement step.
-pub(super) fn mir_to_initial_sorted_coverage_spans(
     mir_body: &mir::Body<'_>,
     hir_info: &ExtractedHirInfo,
     basic_coverage_blocks: &CoverageGraph,
-) -> Vec<Vec<SpanFromMir>> {
+) -> ExtractedCovspans {
     let &ExtractedHirInfo { body_span, .. } = hir_info;
 
-    let mut initial_spans = vec![];
+    let mut covspans = vec![];
     let mut holes = vec![];
 
     for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
@@ -40,150 +36,21 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
             body_span,
             bcb,
             bcb_data,
-            &mut initial_spans,
+            &mut covspans,
             &mut holes,
         );
     }
 
     // Only add the signature span if we found at least one span in the body.
-    if !initial_spans.is_empty() || !holes.is_empty() {
+    if !covspans.is_empty() || !holes.is_empty() {
         // If there is no usable signature span, add a fake one (before refinement)
         // to avoid an ugly gap between the body start and the first real span.
         // FIXME: Find a more principled way to solve this problem.
         let fn_sig_span = hir_info.fn_sig_span_extended.unwrap_or_else(|| body_span.shrink_to_lo());
-        initial_spans.push(SpanFromMir::for_fn_sig(fn_sig_span));
+        covspans.push(SpanFromMir::for_fn_sig(fn_sig_span));
     }
 
-    initial_spans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
+    ExtractedCovspans { covspans, holes }
-    remove_unwanted_macro_spans(&mut initial_spans);
-    split_visible_macro_spans(&mut initial_spans);
-
-    let compare_covspans = |a: &SpanFromMir, b: &SpanFromMir| {
-        compare_spans(a.span, b.span)
-            // After deduplication, we want to keep only the most-dominated BCB.
-            .then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
-    };
-    initial_spans.sort_by(compare_covspans);
-
-    // Among covspans with the same span, keep only one,
-    // preferring the one with the most-dominated BCB.
-    // (Ideally we should try to preserve _all_ non-dominating BCBs, but that
-    // requires a lot more complexity in the span refiner, for little benefit.)
-    initial_spans.dedup_by(|b, a| a.span.source_equal(b.span));
-
-    // Sort the holes, and merge overlapping/adjacent holes.
-    holes.sort_by(|a, b| compare_spans(a.span, b.span));
-    holes.dedup_by(|b, a| a.merge_if_overlapping_or_adjacent(b));
-
-    // Now we're ready to start carving holes out of the initial coverage spans,
-    // and grouping them in buckets separated by the holes.
-
-    let mut initial_spans = VecDeque::from(initial_spans);
-    let mut fragments: Vec<SpanFromMir> = vec![];
-
-    // For each hole:
-    // - Identify the spans that are entirely or partly before the hole.
-    // - Put those spans in a corresponding bucket, truncated to the start of the hole.
-    // - If one of those spans also extends after the hole, put the rest of it
-    //   in a "fragments" vector that is processed by the next hole.
-    let mut buckets = (0..holes.len()).map(|_| vec![]).collect::<Vec<_>>();
-    for (hole, bucket) in holes.iter().zip(&mut buckets) {
-        let fragments_from_prev = std::mem::take(&mut fragments);
-
-        // Only inspect spans that precede or overlap this hole,
-        // leaving the rest to be inspected by later holes.
-        // (This relies on the spans and holes both being sorted.)
-        let relevant_initial_spans =
-            drain_front_while(&mut initial_spans, |c| c.span.lo() < hole.span.hi());
-
-        for covspan in fragments_from_prev.into_iter().chain(relevant_initial_spans) {
-            let (before, after) = covspan.split_around_hole_span(hole.span);
-            bucket.extend(before);
-            fragments.extend(after);
-        }
-    }
-
-    // After finding the spans before each hole, any remaining fragments/spans
-    // form their own final bucket, after the final hole.
-    // (If there were no holes, this will just be all of the initial spans.)
-    fragments.extend(initial_spans);
-    buckets.push(fragments);
-
-    // Make sure each individual bucket is still internally sorted.
-    for bucket in &mut buckets {
-        bucket.sort_by(compare_covspans);
-    }
-    buckets
-}
-
-fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering {
-    // First sort by span start.
-    Ord::cmp(&a.lo(), &b.lo())
-        // If span starts are the same, sort by span end in reverse order.
-        // This ensures that if spans A and B are adjacent in the list,
-        // and they overlap but are not equal, then either:
-        // - Span A extends further left, or
-        // - Both have the same start and span A extends further right
-        .then_with(|| Ord::cmp(&a.hi(), &b.hi()).reverse())
-}
-
-/// Similar to `.drain(..)`, but stops just before it would remove an item not
-/// satisfying the predicate.
-fn drain_front_while<'a, T>(
-    queue: &'a mut VecDeque<T>,
-    mut pred_fn: impl FnMut(&T) -> bool,
-) -> impl Iterator<Item = T> + Captures<'a> {
-    std::iter::from_fn(move || if pred_fn(queue.front()?) { queue.pop_front() } else { None })
-}
-
-/// 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) non-macro-expansion spans.
-        if 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| {
-        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;
-        }
-
-        extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb));
-        extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb));
-        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 coverage spans from the filtered set of `Statement`s and `Terminator`s of
@@ -402,12 +269,12 @@ fn unexpand_into_body_span_with_prev(
 }
 
 #[derive(Debug)]
-struct Hole {
+pub(crate) struct Hole {
-    span: Span,
+    pub(crate) span: Span,
 }
 
 impl Hole {
-    fn merge_if_overlapping_or_adjacent(&mut self, other: &mut Self) -> bool {
+    pub(crate) fn merge_if_overlapping_or_adjacent(&mut self, other: &mut Self) -> bool {
         if !self.span.overlaps_or_adjacent(other.span) {
             return false;
         }
@@ -418,7 +285,7 @@ impl Hole {
 }
 
 #[derive(Debug)]
-pub(super) struct SpanFromMir {
+pub(crate) 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
@@ -426,9 +293,9 @@ pub(super) struct SpanFromMir {
     ///
     /// With the exception of `fn_sig_span`, this should always be contained
     /// within `body_span`.
-    pub(super) span: Span,
+    pub(crate) span: Span,
-    visible_macro: Option<Symbol>,
+    pub(crate) visible_macro: Option<Symbol>,
-    pub(super) bcb: BasicCoverageBlock,
+    pub(crate) bcb: BasicCoverageBlock,
 }
 
 impl SpanFromMir {
@@ -436,23 +303,12 @@ impl SpanFromMir {
         Self::new(fn_sig_span, None, START_BCB)
     }
 
-    fn new(span: Span, visible_macro: Option<Symbol>, bcb: BasicCoverageBlock) -> Self {
+    pub(crate) fn new(span: Span, visible_macro: Option<Symbol>, bcb: BasicCoverageBlock) -> Self {
         Self { span, visible_macro, bcb }
     }
 
-    /// Splits this span into 0-2 parts:
+    pub(crate) fn into_covspan(self) -> Covspan {
-    /// - The part that is strictly before the hole span, if any.
+        let Self { span, visible_macro: _, bcb } = self;
-    /// - The part that is strictly after the hole span, if any.
+        Covspan { span, bcb }
-    fn split_around_hole_span(&self, hole_span: Span) -> (Option<Self>, Option<Self>) {
-        let before = try {
-            let span = self.span.trim_end(hole_span)?;
-            Self { span, ..*self }
-        };
-        let after = try {
-            let span = self.span.trim_start(hole_span)?;
-            Self { span, ..*self }
-        };
-
-        (before, after)
     }
 }

compiler/rustc_mir_transform/src/coverage/tests.rs

@@ -24,7 +24,6 @@
 //! globals is comparatively simpler. The easiest way is to wrap the test in a closure argument
 //! to: `rustc_span::create_default_session_globals_then(|| { test_here(); })`.
 
-use super::counters;
 use super::graph::{self, BasicCoverageBlock};
 
 use itertools::Itertools;
@@ -551,108 +550,3 @@ fn test_covgraph_switchint_loop_then_inner_loop_else_break() {
     assert_successors(&basic_coverage_blocks, bcb(5), &[bcb(1)]);
     assert_successors(&basic_coverage_blocks, bcb(6), &[bcb(4)]);
 }
-
-#[test]
-fn test_find_loop_backedges_none() {
-    let mir_body = goto_switchint();
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-    if false {
-        eprintln!(
-            "basic_coverage_blocks = {:?}",
-            basic_coverage_blocks.iter_enumerated().collect::<Vec<_>>()
-        );
-        eprintln!("successors = {:?}", basic_coverage_blocks.successors);
-    }
-    let backedges = graph::find_loop_backedges(&basic_coverage_blocks);
-    assert_eq!(
-        backedges.iter_enumerated().map(|(_bcb, backedges)| backedges.len()).sum::<usize>(),
-        0,
-        "backedges: {:?}",
-        backedges
-    );
-}
-
-#[test]
-fn test_find_loop_backedges_one() {
-    let mir_body = switchint_then_loop_else_return();
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-    let backedges = graph::find_loop_backedges(&basic_coverage_blocks);
-    assert_eq!(
-        backedges.iter_enumerated().map(|(_bcb, backedges)| backedges.len()).sum::<usize>(),
-        1,
-        "backedges: {:?}",
-        backedges
-    );
-
-    assert_eq!(backedges[bcb(1)], &[bcb(3)]);
-}
-
-#[test]
-fn test_find_loop_backedges_two() {
-    let mir_body = switchint_loop_then_inner_loop_else_break();
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-    let backedges = graph::find_loop_backedges(&basic_coverage_blocks);
-    assert_eq!(
-        backedges.iter_enumerated().map(|(_bcb, backedges)| backedges.len()).sum::<usize>(),
-        2,
-        "backedges: {:?}",
-        backedges
-    );
-
-    assert_eq!(backedges[bcb(1)], &[bcb(5)]);
-    assert_eq!(backedges[bcb(4)], &[bcb(6)]);
-}
-
-#[test]
-fn test_traverse_coverage_with_loops() {
-    let mir_body = switchint_loop_then_inner_loop_else_break();
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-    let mut traversed_in_order = Vec::new();
-    let mut traversal = graph::TraverseCoverageGraphWithLoops::new(&basic_coverage_blocks);
-    while let Some(bcb) = traversal.next() {
-        traversed_in_order.push(bcb);
-    }
-
-    // bcb0 is visited first. Then bcb1 starts the first loop, and all remaining nodes, *except*
-    // bcb6 are inside the first loop.
-    assert_eq!(
-        *traversed_in_order.last().expect("should have elements"),
-        bcb(6),
-        "bcb6 should not be visited until all nodes inside the first loop have been visited"
-    );
-}
-
-#[test]
-fn test_make_bcb_counters() {
-    rustc_span::create_default_session_globals_then(|| {
-        let mir_body = goto_switchint();
-        let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-        // Historically this test would use `spans` internals to set up fake
-        // coverage spans for BCBs 1 and 2. Now we skip that step and just tell
-        // BCB counter construction that those BCBs have spans.
-        let bcb_has_coverage_spans = |bcb: BasicCoverageBlock| (1..=2).contains(&bcb.as_usize());
-        let coverage_counters = counters::CoverageCounters::make_bcb_counters(
-            &basic_coverage_blocks,
-            bcb_has_coverage_spans,
-        );
-        assert_eq!(coverage_counters.num_expressions(), 0);
-
-        assert_eq!(
-            0, // bcb1 has a `Counter` with id = 0
-            match coverage_counters.bcb_counter(bcb(1)).expect("should have a counter") {
-                counters::BcbCounter::Counter { id, .. } => id,
-                _ => panic!("expected a Counter"),
-            }
-            .as_u32()
-        );
-
-        assert_eq!(
-            1, // bcb2 has a `Counter` with id = 1
-            match coverage_counters.bcb_counter(bcb(2)).expect("should have a counter") {
-                counters::BcbCounter::Counter { id, .. } => id,
-                _ => panic!("expected a Counter"),
-            }
-            .as_u32()
-        );
-    });
-}

compiler/rustc_resolve/src/late.rs

@@ -310,9 +310,10 @@ enum LifetimeRibKind {
     /// error on default object bounds (e.g., `Box<dyn Foo>`).
     AnonymousReportError,
 
-    /// Resolves elided lifetimes to `'static`, but gives a warning that this behavior
+    /// Resolves elided lifetimes to `'static` if there are no other lifetimes in scope,
-    /// is a bug and will be reverted soon.
+    /// otherwise give a warning that the previous behavior of introducing a new early-bound
-    AnonymousWarn(NodeId),
+    /// lifetime is a bug and will be removed (if `emit_lint` is enabled).
+    StaticIfNoLifetimeInScope { lint_id: NodeId, emit_lint: bool },
 
     /// Signal we cannot find which should be the anonymous lifetime.
     ElisionFailure,
@@ -1212,7 +1213,7 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
                             }
                             LifetimeRibKind::AnonymousCreateParameter { .. }
                             | LifetimeRibKind::AnonymousReportError
-                            | LifetimeRibKind::AnonymousWarn(_)
+                            | LifetimeRibKind::StaticIfNoLifetimeInScope { .. }
                             | LifetimeRibKind::Elided(_)
                             | LifetimeRibKind::ElisionFailure
                             | LifetimeRibKind::ConcreteAnonConst(_)
@@ -1580,7 +1581,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                                     // lifetime would be illegal.
                                     LifetimeRibKind::Item
                                     | LifetimeRibKind::AnonymousReportError
-                                    | LifetimeRibKind::AnonymousWarn(_)
+                                    | LifetimeRibKind::StaticIfNoLifetimeInScope { .. }
                                     | LifetimeRibKind::ElisionFailure => Some(LifetimeUseSet::Many),
                                     // An anonymous lifetime is legal here, and bound to the right
                                     // place, go ahead.
@@ -1643,7 +1644,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 | LifetimeRibKind::Generics { .. }
                 | LifetimeRibKind::ElisionFailure
                 | LifetimeRibKind::AnonymousReportError
-                | LifetimeRibKind::AnonymousWarn(_) => {}
+                | LifetimeRibKind::StaticIfNoLifetimeInScope { .. } => {}
             }
         }
 
@@ -1677,16 +1678,36 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                     self.record_lifetime_res(lifetime.id, res, elision_candidate);
                     return;
                 }
-                LifetimeRibKind::AnonymousWarn(node_id) => {
+                LifetimeRibKind::StaticIfNoLifetimeInScope { lint_id: node_id, emit_lint } => {
-                    self.r.lint_buffer.buffer_lint(
+                    let mut lifetimes_in_scope = vec![];
-                        lint::builtin::ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT,
+                    for rib in &self.lifetime_ribs[..i] {
-                        node_id,
+                        lifetimes_in_scope.extend(rib.bindings.iter().map(|(ident, _)| ident.span));
-                        lifetime.ident.span,
+                        // Consider any anonymous lifetimes, too
-                        lint::BuiltinLintDiag::AssociatedConstElidedLifetime {
+                        if let LifetimeRibKind::AnonymousCreateParameter { binder, .. } = rib.kind
-                            elided,
+                            && let Some(extra) = self.r.extra_lifetime_params_map.get(&binder)
-                            span: lifetime.ident.span,
+                        {
-                        },
+                            lifetimes_in_scope.extend(extra.iter().map(|(ident, _, _)| ident.span));
-                    );
+                        }
+                    }
+                    if lifetimes_in_scope.is_empty() {
+                        self.record_lifetime_res(
+                            lifetime.id,
+                            LifetimeRes::Static,
+                            elision_candidate,
+                        );
+                        return;
+                    } else if emit_lint {
+                        self.r.lint_buffer.buffer_lint(
+                            lint::builtin::ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT,
+                            node_id,
+                            lifetime.ident.span,
+                            lint::BuiltinLintDiag::AssociatedConstElidedLifetime {
+                                elided,
+                                span: lifetime.ident.span,
+                                lifetimes_in_scope: lifetimes_in_scope.into(),
+                            },
+                        );
+                    }
                 }
                 LifetimeRibKind::AnonymousReportError => {
                     if elided {
@@ -1904,7 +1925,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                     //     impl Foo for std::cell::Ref<u32> // note lack of '_
                     //     async fn foo(_: std::cell::Ref<u32>) { ... }
                     LifetimeRibKind::AnonymousCreateParameter { report_in_path: true, .. }
-                    | LifetimeRibKind::AnonymousWarn(_) => {
+                    | LifetimeRibKind::StaticIfNoLifetimeInScope { .. } => {
                         let sess = self.r.tcx.sess;
                         let subdiag = rustc_errors::elided_lifetime_in_path_suggestion(
                             sess.source_map(),
@@ -2838,19 +2859,27 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                             kind: LifetimeBinderKind::ConstItem,
                         },
                         |this| {
-                            this.visit_generics(generics);
+                            this.with_lifetime_rib(
-                            this.visit_ty(ty);
+                                LifetimeRibKind::StaticIfNoLifetimeInScope {
+                                    lint_id: item.id,
+                                    emit_lint: false,
+                                },
+                                |this| {
+                                    this.visit_generics(generics);
+                                    this.visit_ty(ty);
 
-                            // Only impose the restrictions of `ConstRibKind` for an
+                                    // Only impose the restrictions of `ConstRibKind` for an
-                            // actual constant expression in a provided default.
+                                    // actual constant expression in a provided default.
-                            if let Some(expr) = expr {
+                                    if let Some(expr) = expr {
-                                // We allow arbitrary const expressions inside of associated consts,
+                                        // We allow arbitrary const expressions inside of associated consts,
-                                // even if they are potentially not const evaluatable.
+                                        // even if they are potentially not const evaluatable.
-                                //
+                                        //
-                                // Type parameters can already be used and as associated consts are
+                                        // Type parameters can already be used and as associated consts are
-                                // not used as part of the type system, this is far less surprising.
+                                        // not used as part of the type system, this is far less surprising.
-                                this.resolve_const_body(expr, None);
+                                        this.resolve_const_body(expr, None);
-                            }
+                                    }
+                                },
+                            )
                         },
                     );
                 }
@@ -3030,30 +3059,37 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                         kind: LifetimeBinderKind::ConstItem,
                     },
                     |this| {
-                        this.with_lifetime_rib(LifetimeRibKind::AnonymousWarn(item.id), |this| {
+                        this.with_lifetime_rib(
-                            // If this is a trait impl, ensure the const
+                            LifetimeRibKind::StaticIfNoLifetimeInScope {
-                            // exists in trait
+                                lint_id: item.id,
-                            this.check_trait_item(
+                                // In impls, it's not a hard error yet due to backcompat.
-                                item.id,
+                                emit_lint: true,
-                                item.ident,
+                            },
-                                &item.kind,
+                            |this| {
-                                ValueNS,
+                                // If this is a trait impl, ensure the const
-                                item.span,
+                                // exists in trait
-                                seen_trait_items,
+                                this.check_trait_item(
-                                |i, s, c| ConstNotMemberOfTrait(i, s, c),
+                                    item.id,
-                            );
+                                    item.ident,
+                                    &item.kind,
+                                    ValueNS,
+                                    item.span,
+                                    seen_trait_items,
+                                    |i, s, c| ConstNotMemberOfTrait(i, s, c),
+                                );
 
-                            this.visit_generics(generics);
+                                this.visit_generics(generics);
-                            this.visit_ty(ty);
+                                this.visit_ty(ty);
-                            if let Some(expr) = expr {
+                                if let Some(expr) = expr {
-                                // We allow arbitrary const expressions inside of associated consts,
+                                    // We allow arbitrary const expressions inside of associated consts,
-                                // even if they are potentially not const evaluatable.
+                                    // even if they are potentially not const evaluatable.
-                                //
+                                    //
-                                // Type parameters can already be used and as associated consts are
+                                    // Type parameters can already be used and as associated consts are
-                                // not used as part of the type system, this is far less surprising.
+                                    // not used as part of the type system, this is far less surprising.
-                                this.resolve_const_body(expr, None);
+                                    this.resolve_const_body(expr, None);
-                            }
+                                }
-                        });
+                            },
+                        );
                     },
                 );
             }

library/core/src/error.rs

@@ -928,7 +928,7 @@ pub(crate) mod tags {
 /// An `Option` with a type tag `I`.
 ///
 /// Since this struct implements `Erased`, the type can be erased to make a dynamically typed
-/// option. The type can be checked dynamically using `Erased::tag_id` and since this is statically
+/// option. The type can be checked dynamically using `Tagged::tag_id` and since this is statically
 /// checked for the concrete type, there is some degree of type safety.
 #[repr(transparent)]
 pub(crate) struct TaggedOption<'a, I: tags::Type<'a>>(pub Option<I::Reified>);

library/core/src/num/int_macros.rs

@@ -2784,8 +2784,10 @@ macro_rules! int_impl {
         ///
         /// In other words, the result is `self / rhs` rounded to the integer `q`
         /// such that `self >= q * rhs`.
-        /// If `self > 0`, this is equal to round towards zero (the default in Rust);
+        /// If `self > 0`, this is equal to rounding towards zero (the default in Rust);
-        /// if `self < 0`, this is equal to round towards +/- infinity.
+        /// if `self < 0`, this is equal to rounding away from zero (towards +/- infinity).
+        /// If `rhs > 0`, this is equal to rounding towards -infinity;
+        /// if `rhs < 0`, this is equal to rounding towards +infinity.
         ///
         /// # Panics
         ///
@@ -2823,8 +2825,8 @@ macro_rules! int_impl {
         /// Calculates the least nonnegative remainder of `self (mod rhs)`.
         ///
         /// This is done as if by the Euclidean division algorithm -- given
-        /// `r = self.rem_euclid(rhs)`, `self = rhs * self.div_euclid(rhs) + r`, and
+        /// `r = self.rem_euclid(rhs)`, the result satisfies
-        /// `0 <= r < abs(rhs)`.
+        /// `self = rhs * self.div_euclid(rhs) + r` and `0 <= r < abs(rhs)`.
         ///
         /// # Panics
         ///

library/core/src/ptr/mod.rs

@@ -237,7 +237,7 @@
 //! pointer. For code which *does* cast a usize to a pointer, the scope of the change depends
 //! on exactly what you're doing.
 //!
-//! In general you just need to make sure that if you want to convert a usize address to a
+//! In general, you just need to make sure that if you want to convert a usize address to a
 //! pointer and then use that pointer to read/write memory, you need to keep around a pointer
 //! that has sufficient provenance to perform that read/write itself. In this way all of your
 //! casts from an address to a pointer are essentially just applying offsets/indexing.
@@ -309,7 +309,7 @@
 //!   i.e. the usual "ZSTs are fake, do what you want" rules apply *but* this only applies
 //!   for actual forgery (integers cast to pointers). If you borrow some struct's field
 //!   that *happens* to be zero-sized, the resulting pointer will have provenance tied to
-//!   that allocation and it will still get invalidated if the allocation gets deallocated.
+//!   that allocation, and it will still get invalidated if the allocation gets deallocated.
 //!   In the future we may introduce an API to make such a forged allocation explicit.
 //!
 //! * [`wrapping_offset`][] a pointer outside its provenance. This includes pointers
@@ -698,7 +698,7 @@ pub const fn dangling_mut<T>() -> *mut T {
 ///
 /// If there is no 'exposed' provenance that justifies the way this pointer will be used,
 /// the program has undefined behavior. In particular, the aliasing rules still apply: pointers
-/// and references that have been invalidated due to aliasing accesses cannot be used any more,
+/// and references that have been invalidated due to aliasing accesses cannot be used anymore,
 /// even if they have been exposed!
 ///
 /// Note that there is no algorithm that decides which provenance will be used. You can think of this
@@ -1097,7 +1097,7 @@ const unsafe fn swap_nonoverlapping_simple_untyped<T>(x: *mut T, y: *mut T, coun
         // If we end up here, it's because we're using a simple type -- like
         // a small power-of-two-sized thing -- or a special type with particularly
         // large alignment, particularly SIMD types.
-        // Thus we're fine just reading-and-writing it, as either it's small
+        // Thus, we're fine just reading-and-writing it, as either it's small
         // and that works well anyway or it's special and the type's author
         // presumably wanted things to be done in the larger chunk.
 
@@ -1290,7 +1290,7 @@ pub const unsafe fn read<T>(src: *const T) -> T {
     // provides enough information to know that this is a typed operation.
 
     // However, as of March 2023 the compiler was not capable of taking advantage
-    // of that information.  Thus the implementation here switched to an intrinsic,
+    // of that information. Thus, the implementation here switched to an intrinsic,
     // which lowers to `_0 = *src` in MIR, to address a few issues:
     //
     // - Using `MaybeUninit::assume_init` after a `copy_nonoverlapping` was not
@@ -1570,7 +1570,7 @@ pub const unsafe fn write<T>(dst: *mut T, src: T) {
 /// As a result, using `&packed.unaligned as *const FieldType` causes immediate
 /// *undefined behavior* in your program.
 ///
-/// Instead you must use the [`ptr::addr_of_mut!`](addr_of_mut)
+/// Instead, you must use the [`ptr::addr_of_mut!`](addr_of_mut)
 /// macro to create the pointer. You may use that returned pointer together with
 /// this function.
 ///

library/std/src/os/hermit/io/mod.rs

@@ -1,13 +1,4 @@
-#![stable(feature = "os_fd", since = "1.66.0")]
+#![stable(feature = "rust1", since = "1.0.0")]
 
-mod net;
+#[stable(feature = "rust1", since = "1.0.0")]
-#[path = "../../fd/owned.rs"]
+pub use crate::os::fd::*;
-mod owned;
-#[path = "../../fd/raw.rs"]
-mod raw;
-
-// Export the types and traits for the public API.
-#[stable(feature = "os_fd", since = "1.66.0")]
-pub use owned::*;
-#[stable(feature = "os_fd", since = "1.66.0")]
-pub use raw::*;

library/std/src/os/mod.rs

@@ -160,7 +160,7 @@ pub(crate) mod watchos;
 #[cfg(target_os = "xous")]
 pub mod xous;
 
-#[cfg(any(unix, target_os = "wasi", doc))]
+#[cfg(any(unix, target_os = "hermit", target_os = "wasi", doc))]
 pub mod fd;
 
 #[cfg(any(target_os = "linux", target_os = "android", doc))]

tests/codegen/error-provide.rs

@@ -0,0 +1,50 @@
+// Codegen test for #126242
+
+//@ compile-flags: -O
+#![crate_type = "lib"]
+#![feature(error_generic_member_access)]
+use std::error::Request;
+use std::fmt;
+
+#[derive(Debug)]
+struct MyBacktrace1 {}
+
+#[derive(Debug)]
+struct MyBacktrace2 {}
+
+#[derive(Debug)]
+struct MyBacktrace3 {}
+
+#[derive(Debug)]
+struct MyError {
+    backtrace1: MyBacktrace1,
+    backtrace2: MyBacktrace2,
+    backtrace3: MyBacktrace3,
+    other: MyBacktrace3,
+}
+
+impl fmt::Display for MyError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Example Error")
+    }
+}
+
+impl std::error::Error for MyError {
+    // CHECK-LABEL: @provide
+    #[no_mangle]
+    fn provide<'a>(&'a self, request: &mut Request<'a>) {
+        // LLVM should be able to optimize multiple .provide_* calls into a switch table
+        // and eliminate redundant ones, rather than compare one-by-one.
+
+        // CHECK-NEXT: start:
+        // CHECK-NEXT: %[[SCRUTINEE:[^ ]+]] = load i64, ptr
+        // CHECK-NEXT: switch i64 %[[SCRUTINEE]], label %{{.*}} [
+        // CHECK-COUNT-3: i64 {{.*}}, label %{{.*}}
+        // CHECK-NEXT: ]
+        request
+            .provide_ref::<MyBacktrace1>(&self.backtrace1)
+            .provide_ref::<MyBacktrace3>(&self.other)
+            .provide_ref::<MyBacktrace2>(&self.backtrace2)
+            .provide_ref::<MyBacktrace3>(&self.backtrace3);
+    }
+}

tests/ui/associated-consts/double-elided.rs

@@ -1,12 +1,10 @@
+//@ check-pass
+
 struct S;
 
 impl S {
     const C: &&str = &"";
-    //~^ WARN `&` without an explicit lifetime name cannot be used here
+    // Now resolves to `&'static &'static str`.
-    //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-    //~| WARN `&` without an explicit lifetime name cannot be used here
-    //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-    //~| ERROR in type `&&str`, reference has a longer lifetime than the data it references
 }
 
 fn main() {}

tests/ui/associated-consts/double-elided.stderr

@@ -1,47 +0,0 @@
-warning: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/double-elided.rs:4:14
-   |
-LL |     const C: &&str = &"";
-   |              ^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
-   = note: `#[warn(elided_lifetimes_in_associated_constant)]` on by default
-help: use the `'static` lifetime
-   |
-LL |     const C: &'static &str = &"";
-   |               +++++++
-
-warning: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/double-elided.rs:4:15
-   |
-LL |     const C: &&str = &"";
-   |               ^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
-help: use the `'static` lifetime
-   |
-LL |     const C: &&'static str = &"";
-   |                +++++++
-
-error[E0491]: in type `&&str`, reference has a longer lifetime than the data it references
-  --> $DIR/double-elided.rs:4:5
-   |
-LL |     const C: &&str = &"";
-   |     ^^^^^^^^^^^^^^^^^^^^^
-   |
-note: the pointer is valid for the anonymous lifetime as defined here
-  --> $DIR/double-elided.rs:4:14
-   |
-LL |     const C: &&str = &"";
-   |              ^
-note: but the referenced data is only valid for the anonymous lifetime as defined here
-  --> $DIR/double-elided.rs:4:14
-   |
-LL |     const C: &&str = &"";
-   |              ^
-
-error: aborting due to 1 previous error; 2 warnings emitted
-
-For more information about this error, try `rustc --explain E0491`.

tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.rs

@@ -5,8 +5,6 @@ trait Trait {
 impl Trait for () {
     const ASSOC: &dyn Fn(_) = 1i32;
     //~^ ERROR the placeholder `_` is not allowed within types on item signatures for associated constants
-    //~| WARN `&` without an explicit lifetime name cannot be used here
-    //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 }
 
 fn main() {}

tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.stderr

@@ -1,23 +1,9 @@
-warning: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/infer-placeholder-in-non-suggestable-pos.rs:6:18
-   |
-LL |     const ASSOC: &dyn Fn(_) = 1i32;
-   |                  ^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
-   = note: `#[warn(elided_lifetimes_in_associated_constant)]` on by default
-help: use the `'static` lifetime
-   |
-LL |     const ASSOC: &'static dyn Fn(_) = 1i32;
-   |                   +++++++
-
 error[E0121]: the placeholder `_` is not allowed within types on item signatures for associated constants
   --> $DIR/infer-placeholder-in-non-suggestable-pos.rs:6:26
    |
 LL |     const ASSOC: &dyn Fn(_) = 1i32;
    |                          ^ not allowed in type signatures
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0121`.

tests/ui/consts/assoc-const-elided-lifetime.stderr

@@ -6,6 +6,11 @@ LL |     const FOO: Foo<'_> = Foo { x: PhantomData::<&()> };
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
+note: cannot automatically infer `'static` because of other lifetimes in scope
+  --> $DIR/assoc-const-elided-lifetime.rs:9:6
+   |
+LL | impl<'a> Foo<'a> {
+   |      ^^
 note: the lint level is defined here
   --> $DIR/assoc-const-elided-lifetime.rs:1:9
    |
@@ -24,6 +29,13 @@ LL |     const BAR: &() = &();
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
+note: cannot automatically infer `'static` because of other lifetimes in scope
+  --> $DIR/assoc-const-elided-lifetime.rs:9:6
+   |
+LL | impl<'a> Foo<'a> {
+   |      ^^
+LL |     const FOO: Foo<'_> = Foo { x: PhantomData::<&()> };
+   |                    ^^
 help: use the `'static` lifetime
    |
 LL |     const BAR: &'static () = &();

tests/ui/consts/static-default-lifetime/elided-lifetime.rs

@@ -0,0 +1,22 @@
+#![deny(elided_lifetimes_in_associated_constant)]
+
+struct Foo<'a>(&'a ());
+
+impl Foo<'_> {
+    const STATIC: &str = "";
+    //~^ ERROR `&` without an explicit lifetime name cannot be used here
+    //~| WARN this was previously accepted by the compiler but is being phased out
+}
+
+trait Bar {
+    const STATIC: &str;
+}
+
+impl Bar for Foo<'_> {
+    const STATIC: &str = "";
+    //~^ ERROR `&` without an explicit lifetime name cannot be used here
+    //~| WARN this was previously accepted by the compiler but is being phased out
+    //~| ERROR const not compatible with trait
+}
+
+fn main() {}

tests/ui/consts/static-default-lifetime/elided-lifetime.stderr

@@ -0,0 +1,59 @@
+error: `&` without an explicit lifetime name cannot be used here
+  --> $DIR/elided-lifetime.rs:6:19
+   |
+LL |     const STATIC: &str = "";
+   |                   ^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
+note: cannot automatically infer `'static` because of other lifetimes in scope
+  --> $DIR/elided-lifetime.rs:5:10
+   |
+LL | impl Foo<'_> {
+   |          ^^
+note: the lint level is defined here
+  --> $DIR/elided-lifetime.rs:1:9
+   |
+LL | #![deny(elided_lifetimes_in_associated_constant)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: use the `'static` lifetime
+   |
+LL |     const STATIC: &'static str = "";
+   |                    +++++++
+
+error: `&` without an explicit lifetime name cannot be used here
+  --> $DIR/elided-lifetime.rs:16:19
+   |
+LL |     const STATIC: &str = "";
+   |                   ^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
+note: cannot automatically infer `'static` because of other lifetimes in scope
+  --> $DIR/elided-lifetime.rs:15:18
+   |
+LL | impl Bar for Foo<'_> {
+   |                  ^^
+help: use the `'static` lifetime
+   |
+LL |     const STATIC: &'static str = "";
+   |                    +++++++
+
+error[E0308]: const not compatible with trait
+  --> $DIR/elided-lifetime.rs:16:5
+   |
+LL |     const STATIC: &str = "";
+   |     ^^^^^^^^^^^^^^^^^^ lifetime mismatch
+   |
+   = note: expected reference `&'static _`
+              found reference `&_`
+note: the anonymous lifetime as defined here...
+  --> $DIR/elided-lifetime.rs:15:18
+   |
+LL | impl Bar for Foo<'_> {
+   |                  ^^
+   = note: ...does not necessarily outlive the static lifetime
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/consts/static-default-lifetime/generic-associated-const.rs

@@ -0,0 +1,19 @@
+#![deny(elided_lifetimes_in_associated_constant)]
+#![feature(generic_const_items)]
+//~^ WARN the feature `generic_const_items` is incomplete
+
+struct A;
+impl A {
+    const GAC_TYPE<T>: &str = "";
+    const GAC_LIFETIME<'a>: &str = "";
+    //~^ ERROR `&` without an explicit lifetime name cannot be used here
+    //~| WARN this was previously accepted by the compiler but is being phased out
+}
+
+trait Trait {
+    const GAC_TYPE<T>: &str = "";
+    const GAC_LIFETIME<'a>: &str = "";
+    //~^ ERROR missing lifetime specifier
+}
+
+fn main() {}

tests/ui/consts/static-default-lifetime/generic-associated-const.stderr

@@ -0,0 +1,46 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/generic-associated-const.rs:15:29
+   |
+LL |     const GAC_LIFETIME<'a>: &str = "";
+   |                             ^ expected named lifetime parameter
+   |
+help: consider using the `'a` lifetime
+   |
+LL |     const GAC_LIFETIME<'a>: &'a str = "";
+   |                              ++
+
+warning: the feature `generic_const_items` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/generic-associated-const.rs:2:12
+   |
+LL | #![feature(generic_const_items)]
+   |            ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: `&` without an explicit lifetime name cannot be used here
+  --> $DIR/generic-associated-const.rs:8:29
+   |
+LL |     const GAC_LIFETIME<'a>: &str = "";
+   |                             ^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
+note: cannot automatically infer `'static` because of other lifetimes in scope
+  --> $DIR/generic-associated-const.rs:8:24
+   |
+LL |     const GAC_LIFETIME<'a>: &str = "";
+   |                        ^^
+note: the lint level is defined here
+  --> $DIR/generic-associated-const.rs:1:9
+   |
+LL | #![deny(elided_lifetimes_in_associated_constant)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: use the `'static` lifetime
+   |
+LL |     const GAC_LIFETIME<'a>: &'static str = "";
+   |                              +++++++
+
+error: aborting due to 2 previous errors; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0106`.

tests/ui/consts/static-default-lifetime/inner-item.rs

@@ -0,0 +1,21 @@
+//@ check-pass
+
+struct Foo<'a>(&'a ());
+
+impl<'a> Foo<'a> {
+    fn hello(self) {
+        const INNER: &str = "";
+    }
+}
+
+impl Foo<'_> {
+    fn implicit(self) {
+        const INNER: &str = "";
+    }
+
+    fn fn_lifetime(&self) {
+        const INNER: &str = "";
+    }
+}
+
+fn main() {}

tests/ui/consts/static-default-lifetime/static-trait-impl.rs

@@ -0,0 +1,20 @@
+#![deny(elided_lifetimes_in_associated_constant)]
+
+trait Bar<'a> {
+    const STATIC: &'a str;
+}
+
+struct A;
+impl Bar<'_> for A {
+    const STATIC: &str = "";
+    //~^ ERROR `&` without an explicit lifetime name cannot be used here
+    //~| WARN this was previously accepted by the compiler but is being phased out
+    //~| ERROR const not compatible with trait
+}
+
+struct B;
+impl Bar<'static> for B {
+    const STATIC: &str = "";
+}
+
+fn main() {}

tests/ui/consts/static-default-lifetime/static-trait-impl.stderr

@@ -0,0 +1,45 @@
+error: `&` without an explicit lifetime name cannot be used here
+  --> $DIR/static-trait-impl.rs:9:19
+   |
+LL |     const STATIC: &str = "";
+   |                   ^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #115010 <https://github.com/rust-lang/rust/issues/115010>
+note: cannot automatically infer `'static` because of other lifetimes in scope
+  --> $DIR/static-trait-impl.rs:8:10
+   |
+LL | impl Bar<'_> for A {
+   |          ^^
+note: the lint level is defined here
+  --> $DIR/static-trait-impl.rs:1:9
+   |
+LL | #![deny(elided_lifetimes_in_associated_constant)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: use the `'static` lifetime
+   |
+LL |     const STATIC: &'static str = "";
+   |                    +++++++
+
+error[E0308]: const not compatible with trait
+  --> $DIR/static-trait-impl.rs:9:5
+   |
+LL |     const STATIC: &str = "";
+   |     ^^^^^^^^^^^^^^^^^^ lifetime mismatch
+   |
+   = note: expected reference `&_`
+              found reference `&_`
+note: the anonymous lifetime as defined here...
+  --> $DIR/static-trait-impl.rs:8:10
+   |
+LL | impl Bar<'_> for A {
+   |          ^^
+note: ...does not necessarily outlive the anonymous lifetime as defined here
+  --> $DIR/static-trait-impl.rs:8:10
+   |
+LL | impl Bar<'_> for A {
+   |          ^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/suggestions/missing-lifetime-in-assoc-const-type.default.stderr

@@ -1,57 +1,25 @@
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
-  --> $DIR/missing-lifetime-in-assoc-const-type.rs:6:14
-   |
-LL |     const A: &str = "";
-   |              ^ expected named lifetime parameter
-   |
-help: consider introducing a named lifetime parameter
-   |
-LL ~ trait ZstAssert<'a>: Sized {
-LL ~     const A: &'a str = "";
-   |
-
-error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-in-assoc-const-type.rs:7:14
    |
 LL |     const B: S = S { s: &() };
-   |              ^ expected named lifetime parameter
+   |              ^ expected lifetime parameter
    |
-help: consider introducing a named lifetime parameter
+help: indicate the anonymous lifetime
-   |
-LL ~ trait ZstAssert<'a>: Sized {
-LL |     const A: &str = "";
-LL ~     const B: S<'a> = S { s: &() };
    |
+LL |     const B: S<'_> = S { s: &() };
+   |               ++++
 
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
-  --> $DIR/missing-lifetime-in-assoc-const-type.rs:8:15
-   |
-LL |     const C: &'_ str = "";
-   |               ^^ expected named lifetime parameter
-   |
-help: consider introducing a named lifetime parameter
-   |
-LL ~ trait ZstAssert<'a>: Sized {
-LL |     const A: &str = "";
-LL |     const B: S = S { s: &() };
-LL ~     const C: &'a str = "";
-   |
-
-error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-in-assoc-const-type.rs:9:14
    |
 LL |     const D: T = T { a: &(), b: &() };
-   |              ^ expected 2 lifetime parameters
+   |              ^ expected lifetime parameters
    |
-help: consider introducing a named lifetime parameter
+help: indicate the anonymous lifetimes
-   |
-LL ~ trait ZstAssert<'a>: Sized {
-LL |     const A: &str = "";
-LL |     const B: S = S { s: &() };
-LL |     const C: &'_ str = "";
-LL ~     const D: T<'a, 'a> = T { a: &(), b: &() };
    |
+LL |     const D: T<'_, '_> = T { a: &(), b: &() };
+   |               ++++++++
 
-error: aborting due to 4 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0106`.
+For more information about this error, try `rustc --explain E0726`.

tests/ui/suggestions/missing-lifetime-in-assoc-const-type.generic_const_items.stderr

@@ -1,47 +1,25 @@
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
-  --> $DIR/missing-lifetime-in-assoc-const-type.rs:6:14
-   |
-LL |     const A: &str = "";
-   |              ^ expected named lifetime parameter
-   |
-help: consider introducing a named lifetime parameter
-   |
-LL |     const A<'a>: &'a str = "";
-   |            ++++   ++
-
-error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-in-assoc-const-type.rs:7:14
    |
 LL |     const B: S = S { s: &() };
-   |              ^ expected named lifetime parameter
+   |              ^ expected lifetime parameter
    |
-help: consider introducing a named lifetime parameter
+help: indicate the anonymous lifetime
    |
-LL |     const B<'a>: S<'a> = S { s: &() };
+LL |     const B: S<'_> = S { s: &() };
-   |            ++++   ++++
+   |               ++++
 
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
-  --> $DIR/missing-lifetime-in-assoc-const-type.rs:8:15
-   |
-LL |     const C: &'_ str = "";
-   |               ^^ expected named lifetime parameter
-   |
-help: consider introducing a named lifetime parameter
-   |
-LL |     const C<'a>: &'a str = "";
-   |            ++++   ~~
-
-error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-in-assoc-const-type.rs:9:14
    |
 LL |     const D: T = T { a: &(), b: &() };
-   |              ^ expected 2 lifetime parameters
+   |              ^ expected lifetime parameters
    |
-help: consider introducing a named lifetime parameter
+help: indicate the anonymous lifetimes
    |
-LL |     const D<'a>: T<'a, 'a> = T { a: &(), b: &() };
+LL |     const D: T<'_, '_> = T { a: &(), b: &() };
-   |            ++++   ++++++++
+   |               ++++++++
 
-error: aborting due to 4 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0106`.
+For more information about this error, try `rustc --explain E0726`.

tests/ui/suggestions/missing-lifetime-in-assoc-const-type.rs

@@ -3,10 +3,10 @@
 #![cfg_attr(generic_const_items, feature(generic_const_items), allow(incomplete_features))]
 
 trait ZstAssert: Sized {
-    const A: &str = ""; //~ ERROR missing lifetime specifier
+    const A: &str = "";
-    const B: S = S { s: &() }; //~ ERROR missing lifetime specifier
+    const B: S = S { s: &() }; //~ ERROR implicit elided lifetime not allowed here
-    const C: &'_ str = ""; //~ ERROR missing lifetime specifier
+    const C: &'_ str = "";
-    const D: T = T { a: &(), b: &() }; //~ ERROR missing lifetime specifier
+    const D: T = T { a: &(), b: &() }; //~ ERROR implicit elided lifetime not allowed here
 }
 
 struct S<'a> {