Rollup of 8 pull requests

compiler/rustc/build.rs

@@ -5,6 +5,9 @@ fn main() {
     let target_env = env::var("CARGO_CFG_TARGET_ENV");
     if Ok("windows") == target_os.as_deref() && Ok("msvc") == target_env.as_deref() {
         set_windows_exe_options();
+    } else {
+        // Avoid rerunning the build script every time.
+        println!("cargo:rerun-if-changed=build.rs");
     }
 }
 

compiler/rustc_errors/src/diagnostic.rs

@@ -614,6 +614,14 @@ impl Diagnostic {
         self
     }
 
+    /// Clear any existing suggestions.
+    pub fn clear_suggestions(&mut self) -> &mut Self {
+        if let Ok(suggestions) = &mut self.suggestions {
+            suggestions.clear();
+        }
+        self
+    }
+
     /// Helper for pushing to `self.suggestions`, if available (not disable).
     fn push_suggestion(&mut self, suggestion: CodeSuggestion) {
         if let Ok(suggestions) = &mut self.suggestions {

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -461,6 +461,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 
     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
+    forward!(pub fn clear_suggestions(&mut self,) -> &mut Self);
 
     forward!(pub fn multipart_suggestion(
         &mut self,

compiler/rustc_lint_defs/src/builtin.rs

@@ -3132,6 +3132,56 @@ declare_lint! {
     "detects unexpected names and values in `#[cfg]` conditions",
 }
 
+declare_lint! {
+    /// The `repr_transparent_external_private_fields` lint
+    /// detects types marked #[repr(trasparent)] that (transitively)
+    /// contain an external ZST type marked #[non_exhaustive]
+    ///
+    /// ### Example
+    ///
+    /// ```rust,ignore (needs external crate)
+    /// #![deny(repr_transparent_external_private_fields)]
+    /// use foo::NonExhaustiveZst;
+    ///
+    /// #[repr(transparent)]
+    /// struct Bar(u32, ([u32; 0], NonExhaustiveZst));
+    /// ```
+    ///
+    /// This will produce:
+    ///
+    /// ```text
+    /// error: deprecated `#[macro_use]` attribute used to import macros should be replaced at use sites with a `use` item to import the macro instead
+    ///  --> src/main.rs:3:1
+    ///   |
+    /// 3 | #[macro_use]
+    ///   | ^^^^^^^^^^^^
+    ///   |
+    /// note: the lint level is defined here
+    ///  --> src/main.rs:1:9
+    ///   |
+    /// 1 | #![deny(repr_transparent_external_private_fields)]
+    ///   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    /// ```
+    ///
+    /// ### Explanation
+    ///
+    /// Previous, Rust accepted fields that contain external private zero-sized types,
+    /// even though it should not be a breaking change to add a non-zero-sized field to
+    /// that private type.
+    ///
+    /// This is a [future-incompatible] lint to transition this
+    /// to a hard error in the future. See [issue #78586] for more details.
+    ///
+    /// [issue #78586]: https://github.com/rust-lang/rust/issues/78586
+    /// [future-incompatible]: ../index.md#future-incompatible-lints
+    pub REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
+    Warn,
+    "tranparent type contains an external ZST that is marked #[non_exhaustive] or contains private fields",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #78586 <https://github.com/rust-lang/rust/issues/78586>",
+    };
+}
+
 declare_lint_pass! {
     /// Does nothing as a lint pass, but registers some `Lint`s
     /// that are used by other parts of the compiler.
@@ -3237,6 +3287,7 @@ declare_lint_pass! {
         DEPRECATED_WHERE_CLAUSE_LOCATION,
         TEST_UNSTABLE_LINT,
         FFI_UNWIND_CALLS,
+        REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
     ]
 }
 

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -2094,6 +2094,9 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                         //    |
                         //    = note: cannot satisfy `_: Tt`
 
+                        // Clear any more general suggestions in favor of our specific one
+                        err.clear_suggestions();
+
                         err.span_suggestion_verbose(
                             span.shrink_to_hi(),
                             &format!(

compiler/rustc_typeck/src/check/check.rs

@@ -17,6 +17,7 @@ use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::Obligation;
+use rustc_lint::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
 use rustc_middle::ty::subst::GenericArgKind;
@@ -1318,7 +1319,8 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: ty::AdtD
         }
     }
 
-    // For each field, figure out if it's known to be a ZST and align(1)
+    // For each field, figure out if it's known to be a ZST and align(1), with "known"
+    // respecting #[non_exhaustive] attributes.
     let field_infos = adt.all_fields().map(|field| {
         let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
         let param_env = tcx.param_env(field.did);
@@ -1327,16 +1329,56 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: ty::AdtD
         let span = tcx.hir().span_if_local(field.did).unwrap();
         let zst = layout.map_or(false, |layout| layout.is_zst());
         let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1);
-        (span, zst, align1)
+        if !zst {
+            return (span, zst, align1, None);
+        }
+
+        fn check_non_exhaustive<'tcx>(
+            tcx: TyCtxt<'tcx>,
+            t: Ty<'tcx>,
+        ) -> ControlFlow<(&'static str, DefId, SubstsRef<'tcx>, bool)> {
+            match t.kind() {
+                ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)),
+                ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
+                ty::Adt(def, subst) => {
+                    if !def.did().is_local() {
+                        let non_exhaustive = def.is_variant_list_non_exhaustive()
+                            || def
+                                .variants()
+                                .iter()
+                                .any(ty::VariantDef::is_field_list_non_exhaustive);
+                        let has_priv = def.all_fields().any(|f| !f.vis.is_public());
+                        if non_exhaustive || has_priv {
+                            return ControlFlow::Break((
+                                def.descr(),
+                                def.did(),
+                                subst,
+                                non_exhaustive,
+                            ));
+                        }
+                    }
+                    def.all_fields()
+                        .map(|field| field.ty(tcx, subst))
+                        .try_for_each(|t| check_non_exhaustive(tcx, t))
+                }
+                _ => ControlFlow::Continue(()),
+            }
+        }
+
+        (span, zst, align1, check_non_exhaustive(tcx, ty).break_value())
     });
 
-    let non_zst_fields =
-        field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
+    let non_zst_fields = field_infos
+        .clone()
+        .filter_map(|(span, zst, _align1, _non_exhaustive)| if !zst { Some(span) } else { None });
     let non_zst_count = non_zst_fields.clone().count();
     if non_zst_count >= 2 {
         bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
     }
-    for (span, zst, align1) in field_infos {
+    let incompatible_zst_fields =
+        field_infos.clone().filter(|(_, _, _, opt)| opt.is_some()).count();
+    let incompat = incompatible_zst_fields + non_zst_count >= 2 && non_zst_count < 2;
+    for (span, zst, align1, non_exhaustive) in field_infos {
         if zst && !align1 {
             struct_span_err!(
                 tcx.sess,
@@ -1348,6 +1390,25 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: ty::AdtD
             .span_label(span, "has alignment larger than 1")
             .emit();
         }
+        if incompat && let Some((descr, def_id, substs, non_exhaustive)) = non_exhaustive {
+            tcx.struct_span_lint_hir(
+                REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
+                tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()),
+                span,
+                |lint| {
+                    let note = if non_exhaustive {
+                        "is marked with `#[non_exhaustive]`"
+                    } else {
+                        "contains private fields"
+                    };
+                    let field_ty = tcx.def_path_str_with_substs(def_id, substs);
+                    lint.build("zero-sized fields in repr(transparent) cannot contain external non-exhaustive types")
+                        .note(format!("this {descr} contains `{field_ty}`, which {note}, \
+                            and makes it not a breaking change to become non-zero-sized in the future."))
+                        .emit();
+                },
+            )
+        }
     }
 }
 

compiler/rustc_typeck/src/check/intrinsicck.rs

@@ -4,7 +4,7 @@ use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_index::vec::Idx;
 use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
-use rustc_middle::ty::{self, Article, FloatTy, InferTy, IntTy, Ty, TyCtxt, TypeVisitable, UintTy};
+use rustc_middle::ty::{self, Article, FloatTy, IntTy, Ty, TyCtxt, TypeVisitable, UintTy};
 use rustc_session::lint;
 use rustc_span::{Span, Symbol, DUMMY_SP};
 use rustc_target::abi::{Pointer, VariantIdx};
@@ -99,8 +99,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.emit();
     }
 
+    // FIXME(compiler-errors): This could use `<$ty as Pointee>::Metadata == ()`
     fn is_thin_ptr_ty(&self, ty: Ty<'tcx>) -> bool {
-        if ty.is_sized(self.tcx.at(DUMMY_SP), self.param_env) {
+        // Type still may have region variables, but `Sized` does not depend
+        // on those, so just erase them before querying.
+        if self.tcx.erase_regions(ty).is_sized(self.tcx.at(DUMMY_SP), self.param_env) {
             return true;
         }
         if let ty::Foreign(..) = ty.kind() {
@@ -128,30 +131,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             64 => InlineAsmType::I64,
             _ => unreachable!(),
         };
+
+        // Expect types to be fully resolved, no const or type variables.
+        if ty.has_infer_types_or_consts() {
+            assert!(self.is_tainted_by_errors());
+            return None;
+        }
+
         let asm_ty = match *ty.kind() {
             // `!` is allowed for input but not for output (issue #87802)
             ty::Never if is_input => return None,
             ty::Error(_) => return None,
             ty::Int(IntTy::I8) | ty::Uint(UintTy::U8) => Some(InlineAsmType::I8),
             ty::Int(IntTy::I16) | ty::Uint(UintTy::U16) => Some(InlineAsmType::I16),
-            // Somewhat of a hack: fallback in the presence of errors does not actually
-            // fall back to i32, but to ty::Error. For integer inference variables this
-            // means that they don't get any fallback and stay as `{integer}`.
-            // Since compilation can't succeed anyway, it's fine to use this to avoid printing
-            // "cannot use value of type `{integer}`", even though that would absolutely
-            // work due due i32 fallback if the current function had no other errors.
-            ty::Infer(InferTy::IntVar(_)) => {
-                assert!(self.is_tainted_by_errors());
-                Some(InlineAsmType::I32)
-            }
             ty::Int(IntTy::I32) | ty::Uint(UintTy::U32) => Some(InlineAsmType::I32),
             ty::Int(IntTy::I64) | ty::Uint(UintTy::U64) => Some(InlineAsmType::I64),
             ty::Int(IntTy::I128) | ty::Uint(UintTy::U128) => Some(InlineAsmType::I128),
             ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => Some(asm_ty_isize),
-            ty::Infer(InferTy::FloatVar(_)) => {
-                assert!(self.is_tainted_by_errors());
-                Some(InlineAsmType::F32)
-            }
             ty::Float(FloatTy::F32) => Some(InlineAsmType::F32),
             ty::Float(FloatTy::F64) => Some(InlineAsmType::F64),
             ty::FnPtr(_) => Some(asm_ty_isize),
@@ -191,6 +187,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     _ => None,
                 }
             }
+            ty::Infer(_) => unreachable!(),
             _ => None,
         };
         let Some(asm_ty) = asm_ty else {
@@ -204,11 +201,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return None;
         };
 
-        if ty.has_infer_types_or_consts() {
-            assert!(self.is_tainted_by_errors());
-            return None;
-        }
-
         // Check that the type implements Copy. The only case where this can
         // possibly fail is for SIMD types which don't #[derive(Copy)].
         if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, DUMMY_SP) {

compiler/rustc_typeck/src/check/method/confirm.rs

@@ -81,11 +81,25 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
         let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs);
 
-        debug!("all_substs={:?}", all_substs);
+        debug!("rcvr_substs={rcvr_substs:?}, all_substs={all_substs:?}");
 
         // Create the final signature for the method, replacing late-bound regions.
         let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
 
+        // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
+        // something which derefs to `Self` actually implements the trait and the caller
+        // wanted to make a static dispatch on it but forgot to import the trait.
+        // See test `src/test/ui/issue-35976.rs`.
+        //
+        // In that case, we'll error anyway, but we'll also re-run the search with all traits
+        // in scope, and if we find another method which can be used, we'll output an
+        // appropriate hint suggesting to import the trait.
+        let filler_substs = rcvr_substs
+            .extend_to(self.tcx, pick.item.def_id, |def, _| self.tcx.mk_param_from_def(def));
+        let illegal_sized_bound = self.predicates_require_illegal_sized_bound(
+            &self.tcx.predicates_of(pick.item.def_id).instantiate(self.tcx, filler_substs),
+        );
+
         // Unify the (adjusted) self type with what the method expects.
         //
         // SUBTLE: if we want good error messages, because of "guessing" while matching
@@ -106,16 +120,6 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // Make sure nobody calls `drop()` explicitly.
         self.enforce_illegal_method_limitations(&pick);
 
-        // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
-        // something which derefs to `Self` actually implements the trait and the caller
-        // wanted to make a static dispatch on it but forgot to import the trait.
-        // See test `src/test/ui/issue-35976.rs`.
-        //
-        // In that case, we'll error anyway, but we'll also re-run the search with all traits
-        // in scope, and if we find another method which can be used, we'll output an
-        // appropriate hint suggesting to import the trait.
-        let illegal_sized_bound = self.predicates_require_illegal_sized_bound(&method_predicates);
-
         // Add any trait/regions obligations specified on the method's type parameters.
         // We won't add these if we encountered an illegal sized bound, so that we can use
         // a custom error in that case.

compiler/rustc_typeck/src/check/method/mod.rs

@@ -20,8 +20,8 @@ use rustc_hir::def_id::DefId;
 use rustc_infer::infer::{self, InferOk};
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
-use rustc_middle::ty::GenericParamDefKind;
 use rustc_middle::ty::{self, ToPredicate, Ty, TypeVisitable};
+use rustc_middle::ty::{DefIdTree, GenericParamDefKind};
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 use rustc_trait_selection::traits;
@@ -221,7 +221,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
 
             // We probe again, taking all traits into account (not only those in scope).
-            let candidates = match self.lookup_probe(
+            let mut candidates = match self.lookup_probe(
                 span,
                 segment.ident,
                 self_ty,
@@ -243,6 +243,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .collect(),
                 _ => Vec::new(),
             };
+            candidates.retain(|candidate| *candidate != self.tcx.parent(result.callee.def_id));
 
             return Err(IllegalSizedBound(candidates, needs_mut, span));
         }