Rollup of 12 pull requests

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs

@@ -437,6 +437,12 @@ fn build_enum_variant_member_di_node<'ll, 'tcx>(
         .source_info
         .unwrap_or_else(|| (unknown_file_metadata(cx), UNKNOWN_LINE_NUMBER));
 
+    let discr = discr_value.opt_single_val().map(|value| {
+        let tag_base_type = tag_base_type(cx.tcx, enum_type_and_layout);
+        let size = cx.size_of(tag_base_type);
+        cx.const_uint_big(cx.type_ix(size.bits()), value)
+    });
+
     unsafe {
         llvm::LLVMRustDIBuilderCreateVariantMemberType(
             DIB(cx),
@@ -448,7 +454,7 @@ fn build_enum_variant_member_di_node<'ll, 'tcx>(
             enum_type_and_layout.size.bits(),
             enum_type_and_layout.align.abi.bits() as u32,
             Size::ZERO.bits(),
-            discr_value.opt_single_val().map(|value| cx.const_u128(value)),
+            discr,
             DIFlags::FlagZero,
             variant_member_info.variant_struct_type_di_node,
         )

compiler/rustc_errors/src/emitter.rs

@@ -1976,13 +1976,16 @@ impl HumanEmitter {
             Some(Style::HeaderMsg),
         );
 
+        let other_suggestions = suggestions.len().saturating_sub(MAX_SUGGESTIONS);
+
         let mut row_num = 2;
         for (i, (complete, parts, highlights, _)) in
-            suggestions.iter().enumerate().take(MAX_SUGGESTIONS)
+            suggestions.into_iter().enumerate().take(MAX_SUGGESTIONS)
         {
             debug!(?complete, ?parts, ?highlights);
 
-            let has_deletion = parts.iter().any(|p| p.is_deletion(sm) || p.is_replacement(sm));
+            let has_deletion =
+                parts.iter().any(|p| p.is_deletion(sm) || p.is_destructive_replacement(sm));
             let is_multiline = complete.lines().count() > 1;
 
             if i == 0 {
@@ -2167,7 +2170,7 @@ impl HumanEmitter {
                 self.draw_code_line(
                     &mut buffer,
                     &mut row_num,
-                    highlight_parts,
+                    &highlight_parts,
                     line_pos + line_start,
                     line,
                     show_code_change,
@@ -2213,7 +2216,12 @@ impl HumanEmitter {
             if let DisplaySuggestion::Diff | DisplaySuggestion::Underline | DisplaySuggestion::Add =
                 show_code_change
             {
-                for part in parts {
+                for mut part in parts {
+                    // If this is a replacement of, e.g. `"a"` into `"ab"`, adjust the
+                    // suggestion and snippet to look as if we just suggested to add
+                    // `"b"`, which is typically much easier for the user to understand.
+                    part.trim_trivial_replacements(sm);
+
                     let snippet = if let Ok(snippet) = sm.span_to_snippet(part.span) {
                         snippet
                     } else {
@@ -2376,9 +2384,12 @@ impl HumanEmitter {
                 row_num = row + 1;
             }
         }
-        if suggestions.len() > MAX_SUGGESTIONS {
-            let others = suggestions.len() - MAX_SUGGESTIONS;
-            let msg = format!("and {} other candidate{}", others, pluralize!(others));
+        if other_suggestions > 0 {
+            let msg = format!(
+                "and {} other candidate{}",
+                other_suggestions,
+                pluralize!(other_suggestions)
+            );
             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
         }
 

compiler/rustc_errors/src/lib.rs

@@ -230,10 +230,40 @@ impl SubstitutionPart {
         !self.snippet.is_empty() && self.replaces_meaningful_content(sm)
     }
 
+    /// Whether this is a replacement that overwrites source with a snippet
+    /// in a way that isn't a superset of the original string. For example,
+    /// replacing "abc" with "abcde" is not destructive, but replacing it
+    /// it with "abx" is, since the "c" character is lost.
+    pub fn is_destructive_replacement(&self, sm: &SourceMap) -> bool {
+        self.is_replacement(sm)
+            && !sm.span_to_snippet(self.span).is_ok_and(|snippet| {
+                self.snippet.trim_start().starts_with(snippet.trim_start())
+                    || self.snippet.trim_end().ends_with(snippet.trim_end())
+            })
+    }
+
     fn replaces_meaningful_content(&self, sm: &SourceMap) -> bool {
         sm.span_to_snippet(self.span)
             .map_or(!self.span.is_empty(), |snippet| !snippet.trim().is_empty())
     }
+
+    /// Try to turn a replacement into an addition when the span that is being
+    /// overwritten matches either the prefix or suffix of the replacement.
+    fn trim_trivial_replacements(&mut self, sm: &SourceMap) {
+        if self.snippet.is_empty() {
+            return;
+        }
+        let Ok(snippet) = sm.span_to_snippet(self.span) else {
+            return;
+        };
+        if self.snippet.starts_with(&snippet) {
+            self.span = self.span.shrink_to_hi();
+            self.snippet = self.snippet[snippet.len()..].to_string();
+        } else if self.snippet.ends_with(&snippet) {
+            self.span = self.span.shrink_to_lo();
+            self.snippet = self.snippet[..self.snippet.len() - snippet.len()].to_string();
+        }
+    }
 }
 
 impl CodeSuggestion {

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -798,13 +798,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 bug!("`resolve_ty_and_res_fully_qualified_call` called on `LangItem`")
             }
         };
+
+        self.register_wf_obligation(
+            ty.raw.into(),
+            qself.span,
+            ObligationCauseCode::WellFormed(None),
+        );
+        self.select_obligations_where_possible(|_| {});
+
         if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id)
         {
-            self.register_wf_obligation(
-                ty.raw.into(),
-                qself.span,
-                ObligationCauseCode::WellFormed(None),
-            );
             // Return directly on cache hit. This is useful to avoid doubly reporting
             // errors with default match binding modes. See #44614.
             let def = cached_result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id));
@@ -824,18 +827,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let trait_missing_method =
                     matches!(error, method::MethodError::NoMatch(_)) && ty.normalized.is_trait();
-                // If we have a path like `MyTrait::missing_method`, then don't register
-                // a WF obligation for `dyn MyTrait` when method lookup fails. Otherwise,
-                // register a WF obligation so that we can detect any additional
-                // errors in the self type.
-                if !trait_missing_method {
-                    self.register_wf_obligation(
-                        ty.raw.into(),
-                        qself.span,
-                        ObligationCauseCode::WellFormed(None),
-                    );
-                }
-
                 if item_name.name != kw::Empty {
                     self.report_method_error(
                         hir_id,
@@ -849,14 +840,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 result
             });
 
-        if result.is_ok() {
-            self.register_wf_obligation(
-                ty.raw.into(),
-                qself.span,
-                ObligationCauseCode::WellFormed(None),
-            );
-        }
-
         // Write back the new resolution.
         self.write_resolution(hir_id, result);
         (

compiler/rustc_mir_transform/src/coverage/counters.rs

@@ -114,12 +114,8 @@ pub(crate) fn transcribe_counters(
         let mut new_counters_for_sites = |sites: Vec<BasicCoverageBlock>| {
             sites.into_iter().map(|node| new.ensure_phys_counter(node)).collect::<Vec<_>>()
         };
-        let mut pos = new_counters_for_sites(pos);
-        let mut neg = new_counters_for_sites(neg);
-
-        // These sorts are also not strictly necessary; see above.
-        pos.sort();
-        neg.sort();
+        let pos = new_counters_for_sites(pos);
+        let neg = new_counters_for_sites(neg);
 
         let pos_counter = new.make_sum(&pos).unwrap_or(CovTerm::Zero);
         let new_counter = new.make_subtracted_sum(pos_counter, &neg);

compiler/rustc_mir_transform/src/coverage/query.rs

@@ -123,11 +123,20 @@ fn coverage_ids_info<'tcx>(
         }
     }
 
-    // FIXME(Zalathar): It should be possible to sort `priority_list[1..]` by
-    // `!bcbs_seen.contains(bcb)` to simplify the mappings even further, at the
-    // expense of some churn in the tests. When doing so, also consider removing
-    // the sorts in `transcribe_counters`.
-    let node_counters = make_node_counters(&fn_cov_info.node_flow_data, &fn_cov_info.priority_list);
+    // Clone the priority list so that we can re-sort it.
+    let mut priority_list = fn_cov_info.priority_list.clone();
+    // The first ID in the priority list represents the synthetic "sink" node,
+    // and must remain first so that it _never_ gets a physical counter.
+    debug_assert_eq!(priority_list[0], priority_list.iter().copied().max().unwrap());
+    assert!(!bcbs_seen.contains(priority_list[0]));
+    // Partition the priority list, so that unreachable nodes (removed by MIR opts)
+    // are sorted later and therefore are _more_ likely to get a physical counter.
+    // This is counter-intuitive, but it means that `transcribe_counters` can
+    // easily skip those unused physical counters and replace them with zero.
+    // (The original ordering remains in effect within both partitions.)
+    priority_list[1..].sort_by_key(|&bcb| !bcbs_seen.contains(bcb));
+
+    let node_counters = make_node_counters(&fn_cov_info.node_flow_data, &priority_list);
     let coverage_counters = transcribe_counters(&node_counters, &bcb_needs_counter, &bcbs_seen);
 
     let CoverageCounters {

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -6,7 +6,6 @@ use derive_where::derive_where;
 use rustc_type_ir::fold::TypeFoldable;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
-use rustc_type_ir::solve::inspect;
 use rustc_type_ir::visit::TypeVisitableExt as _;
 use rustc_type_ir::{self as ty, Interner, TypingMode, Upcast as _, elaborate};
 use tracing::{debug, instrument};
@@ -297,25 +296,6 @@ where
         let Ok(normalized_self_ty) =
             self.structurally_normalize_ty(goal.param_env, goal.predicate.self_ty())
         else {
-            // FIXME: We register a fake candidate when normalization fails so that
-            // we can point at the reason for *why*. I'm tempted to say that this
-            // is the wrong way to do this, though.
-            let result =
-                self.probe(|&result| inspect::ProbeKind::RigidAlias { result }).enter(|this| {
-                    let normalized_ty = this.next_ty_infer();
-                    let alias_relate_goal = Goal::new(
-                        this.cx(),
-                        goal.param_env,
-                        ty::PredicateKind::AliasRelate(
-                            goal.predicate.self_ty().into(),
-                            normalized_ty.into(),
-                            ty::AliasRelationDirection::Equate,
-                        ),
-                    );
-                    this.add_goal(GoalSource::AliasWellFormed, alias_relate_goal);
-                    this.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
-                });
-            assert_eq!(result, Err(NoSolution));
             return vec![];
         };
 
@@ -797,11 +777,12 @@ where
     /// treat the alias as rigid.
     ///
     /// See trait-system-refactor-initiative#124 for more details.
-    #[instrument(level = "debug", skip(self), ret)]
+    #[instrument(level = "debug", skip(self, inject_normalize_to_rigid_candidate), ret)]
     pub(super) fn merge_candidates(
         &mut self,
         proven_via: Option<TraitGoalProvenVia>,
         candidates: Vec<Candidate<I>>,
+        inject_normalize_to_rigid_candidate: impl FnOnce(&mut EvalCtxt<'_, D>) -> QueryResult<I>,
     ) -> QueryResult<I> {
         let Some(proven_via) = proven_via else {
             // We don't care about overflow. If proving the trait goal overflowed, then
@@ -818,13 +799,27 @@ where
             // FIXME(const_trait_impl): should this behavior also be used by
             // constness checking. Doing so is *at least theoretically* breaking,
             // see github.com/rust-lang/rust/issues/133044#issuecomment-2500709754
-            TraitGoalProvenVia::ParamEnv | TraitGoalProvenVia::AliasBound => candidates
-                .iter()
-                .filter(|c| {
-                    matches!(c.source, CandidateSource::AliasBound | CandidateSource::ParamEnv(_))
-                })
-                .map(|c| c.result)
-                .collect(),
+            TraitGoalProvenVia::ParamEnv | TraitGoalProvenVia::AliasBound => {
+                let mut candidates_from_env: Vec<_> = candidates
+                    .iter()
+                    .filter(|c| {
+                        matches!(
+                            c.source,
+                            CandidateSource::AliasBound | CandidateSource::ParamEnv(_)
+                        )
+                    })
+                    .map(|c| c.result)
+                    .collect();
+
+                // If the trait goal has been proven by using the environment, we want to treat
+                // aliases as rigid if there are no applicable projection bounds in the environment.
+                if candidates_from_env.is_empty() {
+                    if let Ok(response) = inject_normalize_to_rigid_candidate(self) {
+                        candidates_from_env.push(response);
+                    }
+                }
+                candidates_from_env
+            }
             TraitGoalProvenVia::Misc => candidates.iter().map(|c| c.result).collect(),
         };
 

compiler/rustc_next_trait_solver/src/solve/effect_goals.rs

@@ -405,6 +405,6 @@ where
                 goal.with(ecx.cx(), goal.predicate.trait_ref);
             ecx.compute_trait_goal(trait_goal)
         })?;
-        self.merge_candidates(proven_via, candidates)
+        self.merge_candidates(proven_via, candidates, |_ecx| Err(NoSolution))
     }
 }