Auto merge of rust-lang#119634 - matthiaskrgr:rollup-v2xt7et, r=matth…

…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#119151 (Hide foreign `#[doc(hidden)]` paths in import suggestions)
 - rust-lang#119350 (Imply outlives-bounds on lazy type aliases)
 - rust-lang#119354 (Make `negative_bounds` internal & fix some of its issues)
 - rust-lang#119506 (Use `resolutions(()).effective_visiblities` to avoid cycle errors in `report_object_error`)
 - rust-lang#119554 (Fix scoping for let chains in match guards)
 - rust-lang#119563 (Check yield terminator's resume type in borrowck)
 - rust-lang#119589 (cstore: Remove unnecessary locking from `CrateMetadata`)
 - rust-lang#119622 (never patterns: Document behavior of never patterns with macros-by-example)

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

compiler/rustc_ast_lowering/src/expr.rs

@@ -546,20 +546,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_arm(&mut self, arm: &Arm) -> hir::Arm<'hir> {
         let pat = self.lower_pat(&arm.pat);
-        let guard = arm.guard.as_ref().map(|cond| {
-            if let ExprKind::Let(pat, scrutinee, span, is_recovered) = &cond.kind {
-                hir::Guard::IfLet(self.arena.alloc(hir::Let {
-                    hir_id: self.next_id(),
-                    span: self.lower_span(*span),
-                    pat: self.lower_pat(pat),
-                    ty: None,
-                    init: self.lower_expr(scrutinee),
-                    is_recovered: *is_recovered,
-                }))
-            } else {
-                hir::Guard::If(self.lower_expr(cond))
-            }
-        });
+        let guard = arm.guard.as_ref().map(|cond| self.lower_expr(cond));
         let hir_id = self.next_id();
         let span = self.lower_span(arm.span);
         self.lower_attrs(hir_id, &arm.attrs);

compiler/rustc_ast_passes/messages.ftl

@@ -188,6 +188,9 @@ ast_passes_module_nonascii = trying to load file for module `{$name}` with non-a
 ast_passes_negative_bound_not_supported =
     negative bounds are not supported
 
+ast_passes_negative_bound_with_parenthetical_notation =
+    parenthetical notation may not be used for negative bounds
+
 ast_passes_nested_impl_trait = nested `impl Trait` is not allowed
     .outer = outer `impl Trait`
     .inner = nested `impl Trait` here

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1312,13 +1312,24 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         if let GenericBound::Trait(trait_ref, modifiers) = bound
             && let BoundPolarity::Negative(_) = modifiers.polarity
             && let Some(segment) = trait_ref.trait_ref.path.segments.last()
-            && let Some(ast::GenericArgs::AngleBracketed(args)) = segment.args.as_deref()
         {
-            for arg in &args.args {
-                if let ast::AngleBracketedArg::Constraint(constraint) = arg {
-                    self.dcx()
-                        .emit_err(errors::ConstraintOnNegativeBound { span: constraint.span });
+            match segment.args.as_deref() {
+                Some(ast::GenericArgs::AngleBracketed(args)) => {
+                    for arg in &args.args {
+                        if let ast::AngleBracketedArg::Constraint(constraint) = arg {
+                            self.dcx().emit_err(errors::ConstraintOnNegativeBound {
+                                span: constraint.span,
+                            });
+                        }
+                    }
+                }
+                // The lowered form of parenthesized generic args contains a type binding.
+                Some(ast::GenericArgs::Parenthesized(args)) => {
+                    self.dcx().emit_err(errors::NegativeBoundWithParentheticalNotation {
+                        span: args.span,
+                    });
                 }
+                None => {}
             }
         }
 

compiler/rustc_ast_passes/src/errors.rs

@@ -763,6 +763,13 @@ pub struct ConstraintOnNegativeBound {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(ast_passes_negative_bound_with_parenthetical_notation)]
+pub struct NegativeBoundWithParentheticalNotation {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(ast_passes_invalid_unnamed_field_ty)]
 pub struct InvalidUnnamedFieldTy {

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -3590,7 +3590,7 @@ impl<'b, 'v> Visitor<'v> for ConditionVisitor<'b> {
                                 ));
                             } else if let Some(guard) = &arm.guard {
                                 self.errors.push((
-                                    arm.pat.span.to(guard.body().span),
+                                    arm.pat.span.to(guard.span),
                                     format!(
                                         "if this pattern and condition are matched, {} is not \
                                          initialized",

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -94,31 +94,22 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             );
         }
 
-        debug!(
-            "equate_inputs_and_outputs: body.yield_ty {:?}, universal_regions.yield_ty {:?}",
-            body.yield_ty(),
-            universal_regions.yield_ty
-        );
-
-        // We will not have a universal_regions.yield_ty if we yield (by accident)
-        // outside of a coroutine and return an `impl Trait`, so emit a span_delayed_bug
-        // because we don't want to panic in an assert here if we've already got errors.
-        if body.yield_ty().is_some() != universal_regions.yield_ty.is_some() {
-            self.tcx().dcx().span_delayed_bug(
-                body.span,
-                format!(
-                    "Expected body to have yield_ty ({:?}) iff we have a UR yield_ty ({:?})",
-                    body.yield_ty(),
-                    universal_regions.yield_ty,
-                ),
+        if let Some(mir_yield_ty) = body.yield_ty() {
+            let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
+            self.equate_normalized_input_or_output(
+                universal_regions.yield_ty.unwrap(),
+                mir_yield_ty,
+                yield_span,
             );
         }
 
-        if let (Some(mir_yield_ty), Some(ur_yield_ty)) =
-            (body.yield_ty(), universal_regions.yield_ty)
-        {
+        if let Some(mir_resume_ty) = body.resume_ty() {
             let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
-            self.equate_normalized_input_or_output(ur_yield_ty, mir_yield_ty, yield_span);
+            self.equate_normalized_input_or_output(
+                universal_regions.resume_ty.unwrap(),
+                mir_resume_ty,
+                yield_span,
+            );
         }
 
         // Return types are a bit more complex. They may contain opaque `impl Trait` types.

compiler/rustc_borrowck/src/type_check/liveness/mod.rs

@@ -183,6 +183,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for LiveVariablesVisitor<'cx, 'tcx> {
         match ty_context {
             TyContext::ReturnTy(SourceInfo { span, .. })
             | TyContext::YieldTy(SourceInfo { span, .. })
+            | TyContext::ResumeTy(SourceInfo { span, .. })
             | TyContext::UserTy(span)
             | TyContext::LocalDecl { source_info: SourceInfo { span, .. }, .. } => {
                 span_bug!(span, "should not be visiting outside of the CFG: {:?}", ty_context);

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1450,13 +1450,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
                 }
             }
-            TerminatorKind::Yield { value, .. } => {
+            TerminatorKind::Yield { value, resume_arg, .. } => {
                 self.check_operand(value, term_location);
 
-                let value_ty = value.ty(body, tcx);
                 match body.yield_ty() {
                     None => span_mirbug!(self, term, "yield in non-coroutine"),
                     Some(ty) => {
+                        let value_ty = value.ty(body, tcx);
                         if let Err(terr) = self.sub_types(
                             value_ty,
                             ty,
@@ -1474,6 +1474,28 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                 }
+
+                match body.resume_ty() {
+                    None => span_mirbug!(self, term, "yield in non-coroutine"),
+                    Some(ty) => {
+                        let resume_ty = resume_arg.ty(body, tcx);
+                        if let Err(terr) = self.sub_types(
+                            ty,
+                            resume_ty.ty,
+                            term_location.to_locations(),
+                            ConstraintCategory::Yield,
+                        ) {
+                            span_mirbug!(
+                                self,
+                                term,
+                                "type of resume place is {:?}, but the resume type is {:?}: {:?}",
+                                resume_ty,
+                                ty,
+                                terr
+                            );
+                        }
+                    }
+                }
             }
         }
     }

compiler/rustc_borrowck/src/universal_regions.rs

@@ -76,6 +76,8 @@ pub struct UniversalRegions<'tcx> {
     pub unnormalized_input_tys: &'tcx [Ty<'tcx>],
 
     pub yield_ty: Option<Ty<'tcx>>,
+
+    pub resume_ty: Option<Ty<'tcx>>,
 }
 
 /// The "defining type" for this MIR. The key feature of the "defining
@@ -525,9 +527,12 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         debug!("build: extern regions = {}..{}", first_extern_index, first_local_index);
         debug!("build: local regions  = {}..{}", first_local_index, num_universals);
 
-        let yield_ty = match defining_ty {
-            DefiningTy::Coroutine(_, args) => Some(args.as_coroutine().yield_ty()),
-            _ => None,
+        let (resume_ty, yield_ty) = match defining_ty {
+            DefiningTy::Coroutine(_, args) => {
+                let tys = args.as_coroutine();
+                (Some(tys.resume_ty()), Some(tys.yield_ty()))
+            }
+            _ => (None, None),
         };
 
         UniversalRegions {
@@ -541,6 +546,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
             unnormalized_output_ty: *unnormalized_output_ty,
             unnormalized_input_tys,
             yield_ty,
+            resume_ty,
         }
     }
 

compiler/rustc_feature/src/unstable.rs

@@ -210,7 +210,7 @@ declare_features! (
     /// Allows the `multiple_supertrait_upcastable` lint.
     (unstable, multiple_supertrait_upcastable, "1.69.0", None),
     /// Allow negative trait bounds. This is an internal-only feature for testing the trait solver!
-    (incomplete, negative_bounds, "1.71.0", None),
+    (internal, negative_bounds, "1.71.0", None),
     /// Allows using `#[omit_gdb_pretty_printer_section]`.
     (internal, omit_gdb_pretty_printer_section, "1.5.0", None),
     /// Allows using `#[prelude_import]` on glob `use` items.

compiler/rustc_hir/src/hir.rs

@@ -1258,7 +1258,7 @@ pub struct Arm<'hir> {
     /// If this pattern and the optional guard matches, then `body` is evaluated.
     pub pat: &'hir Pat<'hir>,
     /// Optional guard clause.
-    pub guard: Option<Guard<'hir>>,
+    pub guard: Option<&'hir Expr<'hir>>,
     /// The expression the arm evaluates to if this arm matches.
     pub body: &'hir Expr<'hir>,
 }
@@ -1280,26 +1280,6 @@ pub struct Let<'hir> {
     pub is_recovered: Option<ErrorGuaranteed>,
 }
 
-#[derive(Debug, Clone, Copy, HashStable_Generic)]
-pub enum Guard<'hir> {
-    If(&'hir Expr<'hir>),
-    IfLet(&'hir Let<'hir>),
-}
-
-impl<'hir> Guard<'hir> {
-    /// Returns the body of the guard
-    ///
-    /// In other words, returns the e in either of the following:
-    ///
-    /// - `if e`
-    /// - `if let x = e`
-    pub fn body(&self) -> &'hir Expr<'hir> {
-        match self {
-            Guard::If(e) | Guard::IfLet(Let { init: e, .. }) => e,
-        }
-    }
-}
-
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub struct ExprField<'hir> {
     #[stable_hasher(ignore)]

compiler/rustc_hir/src/intravisit.rs

@@ -619,13 +619,8 @@ pub fn walk_stmt<'v, V: Visitor<'v>>(visitor: &mut V, statement: &'v Stmt<'v>) {
 pub fn walk_arm<'v, V: Visitor<'v>>(visitor: &mut V, arm: &'v Arm<'v>) {
     visitor.visit_id(arm.hir_id);
     visitor.visit_pat(arm.pat);
-    if let Some(ref g) = arm.guard {
-        match g {
-            Guard::If(ref e) => visitor.visit_expr(e),
-            Guard::IfLet(ref l) => {
-                visitor.visit_let_expr(l);
-            }
-        }
+    if let Some(ref e) = arm.guard {
+        visitor.visit_expr(e);
     }
     visitor.visit_expr(arm.body);
 }

compiler/rustc_hir_analysis/src/astconv/bounds.rs

@@ -26,23 +26,36 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
         span: Span,
     ) {
         let tcx = self.tcx();
+        let sized_def_id = tcx.lang_items().sized_trait();
+        let mut seen_negative_sized_bound = false;
 
         // Try to find an unbound in bounds.
         let mut unbounds: SmallVec<[_; 1]> = SmallVec::new();
         let mut search_bounds = |ast_bounds: &'tcx [hir::GenericBound<'tcx>]| {
             for ab in ast_bounds {
-                if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = ab {
-                    unbounds.push(ptr)
+                let hir::GenericBound::Trait(ptr, modifier) = ab else {
+                    continue;
+                };
+                match modifier {
+                    hir::TraitBoundModifier::Maybe => unbounds.push(ptr),
+                    hir::TraitBoundModifier::Negative => {
+                        if let Some(sized_def_id) = sized_def_id
+                            && ptr.trait_ref.path.res == Res::Def(DefKind::Trait, sized_def_id)
+                        {
+                            seen_negative_sized_bound = true;
+                        }
+                    }
+                    _ => {}
                 }
             }
         };
         search_bounds(ast_bounds);
         if let Some((self_ty, where_clause)) = self_ty_where_predicates {
             for clause in where_clause {
-                if let hir::WherePredicate::BoundPredicate(pred) = clause {
-                    if pred.is_param_bound(self_ty.to_def_id()) {
-                        search_bounds(pred.bounds);
-                    }
+                if let hir::WherePredicate::BoundPredicate(pred) = clause
+                    && pred.is_param_bound(self_ty.to_def_id())
+                {
+                    search_bounds(pred.bounds);
                 }
             }
         }
@@ -53,15 +66,13 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
             });
         }
 
-        let sized_def_id = tcx.lang_items().sized_trait();
-
         let mut seen_sized_unbound = false;
         for unbound in unbounds {
-            if let Some(sized_def_id) = sized_def_id {
-                if unbound.trait_ref.path.res == Res::Def(DefKind::Trait, sized_def_id) {
-                    seen_sized_unbound = true;
-                    continue;
-                }
+            if let Some(sized_def_id) = sized_def_id
+                && unbound.trait_ref.path.res == Res::Def(DefKind::Trait, sized_def_id)
+            {
+                seen_sized_unbound = true;
+                continue;
             }
             // There was a `?Trait` bound, but it was not `?Sized`; warn.
             tcx.dcx().span_warn(
@@ -71,15 +82,12 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
             );
         }
 
-        // If the above loop finished there was no `?Sized` bound; add implicitly sized if `Sized` is available.
-        if sized_def_id.is_none() {
-            // No lang item for `Sized`, so we can't add it as a bound.
-            return;
-        }
-        if seen_sized_unbound {
-            // There was in fact a `?Sized` bound, return without doing anything
-        } else {
-            // There was no `?Sized` bound; add implicitly sized if `Sized` is available.
+        if seen_sized_unbound || seen_negative_sized_bound {
+            // There was in fact a `?Sized` or `!Sized` bound;
+            // we don't need to do anything.
+        } else if sized_def_id.is_some() {
+            // There was no `?Sized` or `!Sized` bound;
+            // add `Sized` if it's available.
             bounds.push_sized(tcx, self_ty, span);
         }
     }

compiler/rustc_hir_analysis/src/check/region.rs

@@ -177,14 +177,24 @@ fn resolve_block<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, blk: &'tcx h
 }
 
 fn resolve_arm<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, arm: &'tcx hir::Arm<'tcx>) {
+    fn has_let_expr(expr: &Expr<'_>) -> bool {
+        match &expr.kind {
+            hir::ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs),
+            hir::ExprKind::Let(..) => true,
+            _ => false,
+        }
+    }
+
     let prev_cx = visitor.cx;
 
     visitor.terminating_scopes.insert(arm.hir_id.local_id);
 
     visitor.enter_node_scope_with_dtor(arm.hir_id.local_id);
     visitor.cx.var_parent = visitor.cx.parent;
 
-    if let Some(hir::Guard::If(expr)) = arm.guard {
+    if let Some(expr) = arm.guard
+        && !has_let_expr(expr)
+    {
         visitor.terminating_scopes.insert(expr.hir_id.local_id);
     }