Rollup of 8 pull requests

compiler/rustc_ast_lowering/src/lib.rs

@@ -1636,7 +1636,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     if let Some(old_def_id) = self.orig_opt_local_def_id(param) {
                         old_def_id
                     } else {
-                        self.dcx().span_bug(lifetime.ident.span, "no def-id for fresh lifetime");
+                        self.dcx()
+                            .span_delayed_bug(lifetime.ident.span, "no def-id for fresh lifetime");
+                        continue;
                     }
                 }
 

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -123,7 +123,11 @@ impl<'me, 'bccx, 'tcx> NllTypeRelating<'me, 'bccx, 'tcx> {
         // `handle_opaque_type` cannot handle subtyping, so to support subtyping
         // we instead eagerly generalize here. This is a bit of a mess but will go
         // away once we're using the new solver.
-        let mut enable_subtyping = |ty, ty_is_expected| {
+        //
+        // Given `opaque rel B`, we create a new infer var `ty_vid` constrain it
+        // by using `ty_vid rel B` and then finally and end by equating `ty_vid` to
+        // the opaque.
+        let mut enable_subtyping = |ty, opaque_is_expected| {
             let ty_vid = infcx.next_ty_var_id_in_universe(
                 TypeVariableOrigin {
                     kind: TypeVariableOriginKind::MiscVariable,
@@ -132,15 +136,15 @@ impl<'me, 'bccx, 'tcx> NllTypeRelating<'me, 'bccx, 'tcx> {
                 ty::UniverseIndex::ROOT,
             );
 
-            let variance = if ty_is_expected {
+            let variance = if opaque_is_expected {
                 self.ambient_variance
             } else {
                 self.ambient_variance.xform(ty::Contravariant)
             };
 
             self.type_checker.infcx.instantiate_ty_var(
                 self,
-                ty_is_expected,
+                opaque_is_expected,
                 ty_vid,
                 variance,
                 ty,
@@ -149,8 +153,8 @@ impl<'me, 'bccx, 'tcx> NllTypeRelating<'me, 'bccx, 'tcx> {
         };
 
         let (a, b) = match (a.kind(), b.kind()) {
-            (&ty::Alias(ty::Opaque, ..), _) => (a, enable_subtyping(b, false)?),
-            (_, &ty::Alias(ty::Opaque, ..)) => (enable_subtyping(a, true)?, b),
+            (&ty::Alias(ty::Opaque, ..), _) => (a, enable_subtyping(b, true)?),
+            (_, &ty::Alias(ty::Opaque, ..)) => (enable_subtyping(a, false)?, b),
             _ => unreachable!(
                 "expected at least one opaque type in `relate_opaques`, got {a} and {b}."
             ),

compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs

@@ -154,21 +154,17 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         trait_m_sig.inputs_and_output,
     ));
     if !ocx.select_all_or_error().is_empty() {
-        // This code path is not reached in any tests, but may be reachable. If
-        // this is triggered, it should be converted to `delayed_bug` and the
-        // triggering case turned into a test.
-        tcx.dcx().bug("encountered errors when checking RPITIT refinement (selection)");
+        tcx.dcx().delayed_bug("encountered errors when checking RPITIT refinement (selection)");
+        return;
     }
     let outlives_env = OutlivesEnvironment::with_bounds(
         param_env,
         infcx.implied_bounds_tys(param_env, impl_m.def_id.expect_local(), &implied_wf_types),
     );
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
-        // This code path is not reached in any tests, but may be reachable. If
-        // this is triggered, it should be converted to `delayed_bug` and the
-        // triggering case turned into a test.
-        tcx.dcx().bug("encountered errors when checking RPITIT refinement (regions)");
+        tcx.dcx().delayed_bug("encountered errors when checking RPITIT refinement (regions)");
+        return;
     }
     // Resolve any lifetime variables that may have been introduced during normalization.
     let Ok((trait_bounds, impl_bounds)) = infcx.fully_resolve((trait_bounds, impl_bounds)) else {

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -315,7 +315,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
 
             if is_host_effect {
                 if let Some(idx) = host_effect_index {
-                    tcx.dcx().span_bug(
+                    tcx.dcx().span_delayed_bug(
                         param.span,
                         format!("parent also has host effect param? index: {idx}, def: {def_id:?}"),
                     );

compiler/rustc_hir_typeck/src/expr.rs

@@ -77,8 +77,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // coercions from ! to `expected`.
         if ty.is_never() {
             if let Some(_) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
-                self.dcx()
-                    .span_bug(expr.span, "expression with never type wound up being adjusted");
+                let reported = self.dcx().span_delayed_bug(
+                    expr.span,
+                    "expression with never type wound up being adjusted",
+                );
+                return Ty::new_error(self.tcx(), reported);
             }
 
             let adj_ty = self.next_ty_var(TypeVariableOrigin {

compiler/rustc_hir_typeck/src/mem_categorization.rs

@@ -582,7 +582,8 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
         match ty.kind() {
             ty::Tuple(args) => Ok(args.len()),
             _ => {
-                self.tcx().dcx().span_bug(span, "tuple pattern not applied to a tuple");
+                self.tcx().dcx().span_delayed_bug(span, "tuple pattern not applied to a tuple");
+                Err(())
             }
         }
     }

compiler/rustc_infer/src/infer/relate/generalize.rs

@@ -26,13 +26,13 @@ impl<'tcx> InferCtxt<'tcx> {
     /// This is *not* expected to be used anywhere except for an implementation of
     /// `TypeRelation`. Do not use this, and instead please use `At::eq`, for all
     /// other usecases (i.e. setting the value of a type var).
-    #[instrument(level = "debug", skip(self, relation, target_is_expected))]
+    #[instrument(level = "debug", skip(self, relation))]
     pub fn instantiate_ty_var<R: ObligationEmittingRelation<'tcx>>(
         &self,
         relation: &mut R,
         target_is_expected: bool,
         target_vid: ty::TyVid,
-        ambient_variance: ty::Variance,
+        instantiation_variance: ty::Variance,
         source_ty: Ty<'tcx>,
     ) -> RelateResult<'tcx, ()> {
         debug_assert!(self.inner.borrow_mut().type_variables().probe(target_vid).is_unknown());
@@ -46,7 +46,7 @@ impl<'tcx> InferCtxt<'tcx> {
         //
         // We then relate `generalized_ty <: source_ty`,adding constraints like `'x: '?2` and `?1 <: ?3`.
         let Generalization { value_may_be_infer: generalized_ty, has_unconstrained_ty_var } =
-            self.generalize(relation.span(), target_vid, ambient_variance, source_ty)?;
+            self.generalize(relation.span(), target_vid, instantiation_variance, source_ty)?;
 
         // Constrain `b_vid` to the generalized type `generalized_ty`.
         if let &ty::Infer(ty::TyVar(generalized_vid)) = generalized_ty.kind() {
@@ -73,7 +73,7 @@ impl<'tcx> InferCtxt<'tcx> {
             // the alias can be normalized to something which does not
             // mention `?0`.
             if self.next_trait_solver() {
-                let (lhs, rhs, direction) = match ambient_variance {
+                let (lhs, rhs, direction) = match instantiation_variance {
                     ty::Variance::Invariant => {
                         (generalized_ty.into(), source_ty.into(), AliasRelationDirection::Equate)
                     }
@@ -106,22 +106,28 @@ impl<'tcx> InferCtxt<'tcx> {
                 }
             }
         } else {
-            // HACK: make sure that we `a_is_expected` continues to be
-            // correct when relating the generalized type with the source.
+            // NOTE: The `instantiation_variance` is not the same variance as
+            // used by the relation. When instantiating `b`, `target_is_expected`
+            // is flipped and the `instantion_variance` is also flipped. To
+            // constrain the `generalized_ty` while using the original relation,
+            // we therefore only have to flip the arguments.
+            //
+            // ```ignore (not code)
+            // ?a rel B
+            // instantiate_ty_var(?a, B) # expected and variance not flipped
+            // B' rel B
+            // ```
+            // or
+            // ```ignore (not code)
+            // A rel ?b
+            // instantiate_ty_var(?b, A) # expected and variance flipped
+            // A rel A'
+            // ```
             if target_is_expected == relation.a_is_expected() {
-                relation.relate_with_variance(
-                    ambient_variance,
-                    ty::VarianceDiagInfo::default(),
-                    generalized_ty,
-                    source_ty,
-                )?;
+                relation.relate(generalized_ty, source_ty)?;
             } else {
-                relation.relate_with_variance(
-                    ambient_variance.xform(ty::Contravariant),
-                    ty::VarianceDiagInfo::default(),
-                    source_ty,
-                    generalized_ty,
-                )?;
+                debug!("flip relation");
+                relation.relate(source_ty, generalized_ty)?;
             }
         }
 

compiler/rustc_lint/messages.ftl

@@ -429,6 +429,7 @@ lint_non_upper_case_global = {$sort} `{$name}` should have an upper case name
 lint_noop_method_call = call to `.{$method}()` on a reference in this situation does nothing
     .suggestion = remove this redundant call
     .note = the type `{$orig_ty}` does not implement `{$trait_}`, so calling `{$method}` on `&{$orig_ty}` copies the reference, which does not do anything and can be removed
+    .derive_suggestion = if you meant to clone `{$orig_ty}`, implement `Clone` for it
 
 lint_only_cast_u8_to_char = only `u8` can be cast into `char`
     .suggestion = use a `char` literal instead

compiler/rustc_lint/src/lints.rs

@@ -1314,6 +1314,12 @@ pub struct NoopMethodCallDiag<'a> {
     pub trait_: Symbol,
     #[suggestion(code = "", applicability = "machine-applicable")]
     pub label: Span,
+    #[suggestion(
+        lint_derive_suggestion,
+        code = "#[derive(Clone)]\n",
+        applicability = "maybe-incorrect"
+    )]
+    pub suggest_derive: Option<Span>,
 }
 
 #[derive(LintDiagnostic)]

compiler/rustc_lint/src/noop_method_call.rs

@@ -121,10 +121,20 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
         let orig_ty = expr_ty.peel_refs();
 
         if receiver_ty == expr_ty {
+            let suggest_derive = match orig_ty.kind() {
+                ty::Adt(def, _) => Some(cx.tcx.def_span(def.did()).shrink_to_lo()),
+                _ => None,
+            };
             cx.emit_span_lint(
                 NOOP_METHOD_CALL,
                 span,
-                NoopMethodCallDiag { method: call.ident.name, orig_ty, trait_, label: span },
+                NoopMethodCallDiag {
+                    method: call.ident.name,
+                    orig_ty,
+                    trait_,
+                    label: span,
+                    suggest_derive,
+                },
             );
         } else {
             match name {

compiler/rustc_mir_transform/src/coverage/graph.rs

@@ -52,19 +52,18 @@ impl CoverageGraph {
             }
         }
 
-        let mut basic_coverage_blocks =
-            Self { bcbs, bb_to_bcb, successors, predecessors, dominators: None };
-        let dominators = dominators::dominators(&basic_coverage_blocks);
-        basic_coverage_blocks.dominators = Some(dominators);
+        let mut this = Self { bcbs, bb_to_bcb, successors, predecessors, dominators: None };
+
+        this.dominators = Some(dominators::dominators(&this));
 
         // The coverage graph's entry-point node (bcb0) always starts with bb0,
         // which never has predecessors. Any other blocks merged into bcb0 can't
         // have multiple (coverage-relevant) predecessors, so bcb0 always has
         // zero in-edges.
-        assert!(basic_coverage_blocks[START_BCB].leader_bb() == mir::START_BLOCK);
-        assert!(basic_coverage_blocks.predecessors[START_BCB].is_empty());
+        assert!(this[START_BCB].leader_bb() == mir::START_BLOCK);
+        assert!(this.predecessors[START_BCB].is_empty());
 
-        basic_coverage_blocks
+        this
     }
 
     fn compute_basic_coverage_blocks(

compiler/rustc_privacy/src/lib.rs

@@ -988,7 +988,10 @@ impl<'tcx> Visitor<'tcx> for NamePrivacyVisitor<'tcx> {
     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
         if let hir::ExprKind::Struct(qpath, fields, ref base) = expr.kind {
             let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
-            let adt = self.typeck_results().expr_ty(expr).ty_adt_def().unwrap();
+            let Some(adt) = self.typeck_results().expr_ty(expr).ty_adt_def() else {
+                self.tcx.dcx().span_delayed_bug(expr.span, "no adt_def for expression");
+                return;
+            };
             let variant = adt.variant_of_res(res);
             if let Some(base) = *base {
                 // If the expression uses FRU we need to make sure all the unmentioned fields

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -172,9 +172,7 @@ fn do_normalize_predicates<'tcx>(
     // the normalized predicates.
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
-        // @lcnr: Let's still ICE here for now. I want a test case
-        // for that.
-        tcx.dcx().span_bug(
+        tcx.dcx().span_delayed_bug(
             span,
             format!("failed region resolution while normalizing {elaborated_env:?}: {errors:?}"),
         );

src/bootstrap/defaults/config.compiler.toml

@@ -19,9 +19,9 @@ lto = "off"
 frame-pointers = true
 
 [llvm]
-# This enables debug-assertions in LLVM,
-# catching logic errors in codegen much earlier in the process.
-assertions = true
+# Having this set to true disrupts compiler development workflows for people who use `llvm.download-ci-llvm = true`
+# because we don't provide ci-llvm on the `rustc-alt-builds` server. Therefore, it is kept off by default.
+assertions = false
 # Enable warnings during the LLVM compilation (when LLVM is changed, causing a compilation)
 enable-warnings = true
 # Will download LLVM from CI if available on your platform.

src/tools/rustfmt/src/parse/parser.rs

@@ -163,13 +163,21 @@ impl<'a> Parser<'a> {
     fn parse_crate_mod(&mut self) -> Result<ast::Crate, ParserError> {
         let mut parser = AssertUnwindSafe(&mut self.parser);
 
-        match catch_unwind(move || parser.parse_crate_mod()) {
-            Ok(Ok(k)) => Ok(k),
-            Ok(Err(db)) => {
+        // rustfmt doesn't use `run_compiler` like other tools, so it must emit
+        // any stashed diagnostics itself, otherwise the `DiagCtxt` will assert
+        // when dropped. The final result here combines the parsing result and
+        // the `emit_stashed_diagnostics` result.
+        let parse_res = catch_unwind(move || parser.parse_crate_mod());
+        let stashed_res = self.parser.dcx().emit_stashed_diagnostics();
+        let err = Err(ParserError::ParsePanicError);
+        match (parse_res, stashed_res) {
+            (Ok(Ok(k)), None) => Ok(k),
+            (Ok(Ok(_)), Some(_guar)) => err,
+            (Ok(Err(db)), _) => {
                 db.emit();
-                Err(ParserError::ParseError)
+                err
             }
-            Err(_) => Err(ParserError::ParsePanicError),
+            (Err(_), _) => err,
         }
     }
 }

src/tools/rustfmt/src/test/parser.rs

@@ -55,3 +55,10 @@ fn crate_parsing_errors_on_unclosed_delims() {
     let filename = "tests/parser/unclosed-delims/issue_4466.rs";
     assert_parser_error(filename);
 }
+
+#[test]
+fn crate_parsing_stashed_diag() {
+    // See also https://github.com/rust-lang/rust/issues/121450
+    let filename = "tests/parser/stashed-diag.rs";
+    assert_parser_error(filename);
+}

src/tools/rustfmt/tests/parser/stashed-diag.rs

@@ -0,0 +1,3 @@
+#![u={static N;}]
+
+fn main() {}

tests/ui/impl-trait/in-trait/span-bug-issue-121457.rs

@@ -0,0 +1,18 @@
+pub trait Iterable {
+    type Item<'a>
+    where
+        Self: 'a;
+
+    fn iter(&self) -> impl Iterator;
+}
+
+impl<'a, I: 'a + Iterable> Iterable for &'a I {
+    type Item = u32;
+    //~^ ERROR lifetime parameters or bounds on type `Item` do not match the trait declaration
+
+    fn iter(&self) -> impl for<'missing> Iterator<Item = Self::Item<'missing>> {}
+    //~^ ERROR binding for associated type `Item` references lifetime `'missing`
+    //~| ERROR `()` is not an iterator
+}
+
+fn main() {}

tests/ui/impl-trait/in-trait/span-bug-issue-121457.stderr

@@ -0,0 +1,30 @@
+error[E0582]: binding for associated type `Item` references lifetime `'missing`, which does not appear in the trait input types
+  --> $DIR/span-bug-issue-121457.rs:13:51
+   |
+LL |     fn iter(&self) -> impl for<'missing> Iterator<Item = Self::Item<'missing>> {}
+   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0195]: lifetime parameters or bounds on type `Item` do not match the trait declaration
+  --> $DIR/span-bug-issue-121457.rs:10:14
+   |
+LL |     type Item<'a>
+   |              ---- lifetimes in impl do not match this type in trait
+LL |     where
+LL |         Self: 'a;
+   |               -- this bound might be missing in the impl
+...
+LL |     type Item = u32;
+   |              ^ lifetimes do not match type in trait
+
+error[E0277]: `()` is not an iterator
+  --> $DIR/span-bug-issue-121457.rs:13:23
+   |
+LL |     fn iter(&self) -> impl for<'missing> Iterator<Item = Self::Item<'missing>> {}
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not an iterator
+   |
+   = help: the trait `Iterator` is not implemented for `()`
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0195, E0277, E0582.
+For more information about an error, try `rustc --explain E0195`.