Rollup of 10 pull requests

compiler/rustc_ast/src/ast.rs

@@ -2902,6 +2902,17 @@ pub struct AttrItem {
     pub tokens: Option<LazyAttrTokenStream>,
 }
 
+impl AttrItem {
+    pub fn is_valid_for_outer_style(&self) -> bool {
+        self.path == sym::cfg_attr
+            || self.path == sym::cfg
+            || self.path == sym::forbid
+            || self.path == sym::warn
+            || self.path == sym::allow
+            || self.path == sym::deny
+    }
+}
+
 /// `TraitRef`s appear in impls.
 ///
 /// Resolution maps each `TraitRef`'s `ref_id` to its defining trait; that's all

compiler/rustc_hir_analysis/src/variance/dump.rs

@@ -1,18 +1,36 @@
+use std::fmt::Write;
+
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::CRATE_DEF_ID;
-use rustc_middle::ty::TyCtxt;
+use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
+use rustc_middle::ty::{GenericArgs, TyCtxt};
 use rustc_span::symbol::sym;
 
+fn format_variances(tcx: TyCtxt<'_>, def_id: LocalDefId) -> String {
+    let variances = tcx.variances_of(def_id);
+    let generics = GenericArgs::identity_for_item(tcx, def_id);
+    // 7 = 2-letter parameter + ": " + 1-letter variance + ", "
+    let mut ret = String::with_capacity(2 + 7 * variances.len());
+    ret.push('[');
+    for (arg, variance) in generics.iter().zip(variances.iter()) {
+        write!(ret, "{arg}: {variance:?}, ").unwrap();
+    }
+    // Remove trailing `, `.
+    if !variances.is_empty() {
+        ret.pop();
+        ret.pop();
+    }
+    ret.push(']');
+    ret
+}
+
 pub(crate) fn variances(tcx: TyCtxt<'_>) {
     if tcx.has_attr(CRATE_DEF_ID, sym::rustc_variance_of_opaques) {
         for id in tcx.hir().items() {
             let DefKind::OpaqueTy = tcx.def_kind(id.owner_id) else { continue };
 
-            let variances = tcx.variances_of(id.owner_id);
-
             tcx.dcx().emit_err(crate::errors::VariancesOf {
                 span: tcx.def_span(id.owner_id),
-                variances: format!("{variances:?}"),
+                variances: format_variances(tcx, id.owner_id.def_id),
             });
         }
     }
@@ -22,11 +40,9 @@ pub(crate) fn variances(tcx: TyCtxt<'_>) {
             continue;
         }
 
-        let variances = tcx.variances_of(id.owner_id);
-
         tcx.dcx().emit_err(crate::errors::VariancesOf {
             span: tcx.def_span(id.owner_id),
-            variances: format!("{variances:?}"),
+            variances: format_variances(tcx, id.owner_id.def_id),
         });
     }
 }

compiler/rustc_hir_typeck/src/expr.rs

@@ -841,13 +841,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let ret_ty = ret_coercion.borrow().expected_ty();
         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
         let mut span = return_expr.span;
+        let mut hir_id = return_expr.hir_id;
         // Use the span of the trailing expression for our cause,
         // not the span of the entire function
         if !explicit_return
             && let ExprKind::Block(body, _) = return_expr.kind
             && let Some(last_expr) = body.expr
         {
             span = last_expr.span;
+            hir_id = last_expr.hir_id;
         }
         ret_coercion.borrow_mut().coerce(
             self,
@@ -864,6 +866,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.select_obligations_where_possible(|errors| {
                 self.point_at_return_for_opaque_ty_error(
                     errors,
+                    hir_id,
                     span,
                     return_expr_ty,
                     return_expr.span,
@@ -921,6 +924,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn point_at_return_for_opaque_ty_error(
         &self,
         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
+        hir_id: HirId,
         span: Span,
         return_expr_ty: Ty<'tcx>,
         return_span: Span,
@@ -935,7 +939,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let new_cause = ObligationCause::new(
                     cause.span,
                     cause.body_id,
-                    ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
+                    ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, hir_id))),
                 );
                 *cause = new_cause;
             }

compiler/rustc_lint/messages.ftl

@@ -361,6 +361,11 @@ lint_improper_ctypes_box = box cannot be represented as a single pointer
 lint_improper_ctypes_char_help = consider using `u32` or `libc::wchar_t` instead
 
 lint_improper_ctypes_char_reason = the `char` type has no C equivalent
+
+lint_improper_ctypes_cstr_help =
+    consider passing a `*const std::ffi::c_char` instead, and use `CStr::as_ptr()`
+lint_improper_ctypes_cstr_reason = `CStr`/`CString` do not have a guaranteed layout
+
 lint_improper_ctypes_dyn = trait objects have no C equivalent
 
 lint_improper_ctypes_enum_repr_help =

compiler/rustc_lint/src/types.rs

@@ -985,6 +985,14 @@ struct ImproperCTypesVisitor<'a, 'tcx> {
     mode: CItemKind,
 }
 
+/// Accumulator for recursive ffi type checking
+struct CTypesVisitorState<'tcx> {
+    cache: FxHashSet<Ty<'tcx>>,
+    /// The original type being checked, before we recursed
+    /// to any other types it contains.
+    base_ty: Ty<'tcx>,
+}
+
 enum FfiResult<'tcx> {
     FfiSafe,
     FfiPhantom(Ty<'tcx>),
@@ -1213,7 +1221,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
     /// Checks if the given field's type is "ffi-safe".
     fn check_field_type_for_ffi(
         &self,
-        cache: &mut FxHashSet<Ty<'tcx>>,
+        acc: &mut CTypesVisitorState<'tcx>,
         field: &ty::FieldDef,
         args: GenericArgsRef<'tcx>,
     ) -> FfiResult<'tcx> {
@@ -1223,13 +1231,13 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             .tcx
             .try_normalize_erasing_regions(self.cx.param_env, field_ty)
             .unwrap_or(field_ty);
-        self.check_type_for_ffi(cache, field_ty)
+        self.check_type_for_ffi(acc, field_ty)
     }
 
     /// Checks if the given `VariantDef`'s field types are "ffi-safe".
     fn check_variant_for_ffi(
         &self,
-        cache: &mut FxHashSet<Ty<'tcx>>,
+        acc: &mut CTypesVisitorState<'tcx>,
         ty: Ty<'tcx>,
         def: ty::AdtDef<'tcx>,
         variant: &ty::VariantDef,
@@ -1239,7 +1247,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         let transparent_with_all_zst_fields = if def.repr().transparent() {
             if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
                 // Transparent newtypes have at most one non-ZST field which needs to be checked..
-                match self.check_field_type_for_ffi(cache, field, args) {
+                match self.check_field_type_for_ffi(acc, field, args) {
                     FfiUnsafe { ty, .. } if ty.is_unit() => (),
                     r => return r,
                 }
@@ -1257,7 +1265,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         // We can't completely trust `repr(C)` markings, so make sure the fields are actually safe.
         let mut all_phantom = !variant.fields.is_empty();
         for field in &variant.fields {
-            all_phantom &= match self.check_field_type_for_ffi(cache, field, args) {
+            all_phantom &= match self.check_field_type_for_ffi(acc, field, args) {
                 FfiSafe => false,
                 // `()` fields are FFI-safe!
                 FfiUnsafe { ty, .. } if ty.is_unit() => false,
@@ -1277,7 +1285,11 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
     /// Checks if the given type is "ffi-safe" (has a stable, well-defined
     /// representation which can be exported to C code).
-    fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
+    fn check_type_for_ffi(
+        &self,
+        acc: &mut CTypesVisitorState<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> FfiResult<'tcx> {
         use FfiResult::*;
 
         let tcx = self.cx.tcx;
@@ -1286,7 +1298,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         // `struct S(*mut S);`.
         // FIXME: A recursion limit is necessary as well, for irregular
         // recursive types.
-        if !cache.insert(ty) {
+        if !acc.cache.insert(ty) {
             return FfiSafe;
         }
 
@@ -1308,6 +1320,17 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 }
                 match def.adt_kind() {
                     AdtKind::Struct | AdtKind::Union => {
+                        if let Some(sym::cstring_type | sym::cstr_type) =
+                            tcx.get_diagnostic_name(def.did())
+                            && !acc.base_ty.is_mutable_ptr()
+                        {
+                            return FfiUnsafe {
+                                ty,
+                                reason: fluent::lint_improper_ctypes_cstr_reason,
+                                help: Some(fluent::lint_improper_ctypes_cstr_help),
+                            };
+                        }
+
                         if !def.repr().c() && !def.repr().transparent() {
                             return FfiUnsafe {
                                 ty,
@@ -1354,7 +1377,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                             };
                         }
 
-                        self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), args)
+                        self.check_variant_for_ffi(acc, ty, def, def.non_enum_variant(), args)
                     }
                     AdtKind::Enum => {
                         if def.variants().is_empty() {
@@ -1378,7 +1401,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                             if let Some(ty) =
                                 repr_nullable_ptr(self.cx.tcx, self.cx.param_env, ty, self.mode)
                             {
-                                return self.check_type_for_ffi(cache, ty);
+                                return self.check_type_for_ffi(acc, ty);
                             }
 
                             return FfiUnsafe {
@@ -1399,7 +1422,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                                 };
                             }
 
-                            match self.check_variant_for_ffi(cache, ty, def, variant, args) {
+                            match self.check_variant_for_ffi(acc, ty, def, variant, args) {
                                 FfiSafe => (),
                                 r => return r,
                             }
@@ -1469,9 +1492,9 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 FfiSafe
             }
 
-            ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(cache, ty),
+            ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(acc, ty),
 
-            ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
+            ty::Array(inner_ty, _) => self.check_type_for_ffi(acc, inner_ty),
 
             ty::FnPtr(sig_tys, hdr) => {
                 let sig = sig_tys.with(hdr);
@@ -1485,7 +1508,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
                 let sig = tcx.instantiate_bound_regions_with_erased(sig);
                 for arg in sig.inputs() {
-                    match self.check_type_for_ffi(cache, *arg) {
+                    match self.check_type_for_ffi(acc, *arg) {
                         FfiSafe => {}
                         r => return r,
                     }
@@ -1496,7 +1519,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                     return FfiSafe;
                 }
 
-                self.check_type_for_ffi(cache, ret_ty)
+                self.check_type_for_ffi(acc, ret_ty)
             }
 
             ty::Foreign(..) => FfiSafe,
@@ -1619,7 +1642,8 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             return;
         }
 
-        match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
+        let mut acc = CTypesVisitorState { cache: FxHashSet::default(), base_ty: ty };
+        match self.check_type_for_ffi(&mut acc, ty) {
             FfiResult::FfiSafe => {}
             FfiResult::FfiPhantom(ty) => {
                 self.emit_ffi_unsafe_type_lint(

compiler/rustc_middle/src/traits/mod.rs

@@ -353,7 +353,7 @@ pub enum ObligationCauseCode<'tcx> {
     ReturnValue(HirId),
 
     /// Opaque return type of this function
-    OpaqueReturnType(Option<(Ty<'tcx>, Span)>),
+    OpaqueReturnType(Option<(Ty<'tcx>, HirId)>),
 
     /// Block implicit return
     BlockTailExpression(HirId, hir::MatchSource),

compiler/rustc_parse/src/parser/attr.rs

@@ -76,6 +76,7 @@ impl<'a> Parser<'a> {
                             token::CommentKind::Line => OuterAttributeType::DocComment,
                             token::CommentKind::Block => OuterAttributeType::DocBlockComment,
                         },
+                        true,
                     ) {
                         err.note(fluent::parse_note);
                         err.span_suggestion_verbose(
@@ -139,7 +140,11 @@ impl<'a> Parser<'a> {
 
             // Emit error if inner attribute is encountered and forbidden.
             if style == ast::AttrStyle::Inner {
-                this.error_on_forbidden_inner_attr(attr_sp, inner_parse_policy);
+                this.error_on_forbidden_inner_attr(
+                    attr_sp,
+                    inner_parse_policy,
+                    item.is_valid_for_outer_style(),
+                );
             }
 
             Ok(attr::mk_attr_from_item(&self.psess.attr_id_generator, item, None, style, attr_sp))
@@ -151,6 +156,7 @@ impl<'a> Parser<'a> {
         err: &mut Diag<'_>,
         span: Span,
         attr_type: OuterAttributeType,
+        suggest_to_outer: bool,
     ) -> Option<Span> {
         let mut snapshot = self.create_snapshot_for_diagnostic();
         let lo = span.lo()
@@ -185,16 +191,18 @@ impl<'a> Parser<'a> {
                 // FIXME(#100717)
                 err.arg("item", item.kind.descr());
                 err.span_label(item.span, fluent::parse_label_does_not_annotate_this);
-                err.span_suggestion_verbose(
-                    replacement_span,
-                    fluent::parse_sugg_change_inner_to_outer,
-                    match attr_type {
-                        OuterAttributeType::Attribute => "",
-                        OuterAttributeType::DocBlockComment => "*",
-                        OuterAttributeType::DocComment => "/",
-                    },
-                    rustc_errors::Applicability::MachineApplicable,
-                );
+                if suggest_to_outer {
+                    err.span_suggestion_verbose(
+                        replacement_span,
+                        fluent::parse_sugg_change_inner_to_outer,
+                        match attr_type {
+                            OuterAttributeType::Attribute => "",
+                            OuterAttributeType::DocBlockComment => "*",
+                            OuterAttributeType::DocComment => "/",
+                        },
+                        rustc_errors::Applicability::MachineApplicable,
+                    );
+                }
                 return None;
             }
             Err(item_err) => {
@@ -205,7 +213,12 @@ impl<'a> Parser<'a> {
         Some(replacement_span)
     }
 
-    pub(super) fn error_on_forbidden_inner_attr(&self, attr_sp: Span, policy: InnerAttrPolicy) {
+    pub(super) fn error_on_forbidden_inner_attr(
+        &self,
+        attr_sp: Span,
+        policy: InnerAttrPolicy,
+        suggest_to_outer: bool,
+    ) {
         if let InnerAttrPolicy::Forbidden(reason) = policy {
             let mut diag = match reason.as_ref().copied() {
                 Some(InnerAttrForbiddenReason::AfterOuterDocComment { prev_doc_comment_span }) => {
@@ -239,6 +252,7 @@ impl<'a> Parser<'a> {
                     &mut diag,
                     attr_sp,
                     OuterAttributeType::Attribute,
+                    suggest_to_outer,
                 )
                 .is_some()
             {

compiler/rustc_parse/src/parser/stmt.rs

@@ -459,11 +459,16 @@ impl<'a> Parser<'a> {
     pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
         let (attrs, block) = self.parse_inner_attrs_and_block()?;
         if let [.., last] = &*attrs {
+            let suggest_to_outer = match &last.kind {
+                ast::AttrKind::Normal(attr) => attr.item.is_valid_for_outer_style(),
+                _ => false,
+            };
             self.error_on_forbidden_inner_attr(
                 last.span,
                 super::attr::InnerAttrPolicy::Forbidden(Some(
                     InnerAttrForbiddenReason::InCodeBlock,
                 )),
+                suggest_to_outer,
             );
         }
         Ok(block)