Rollup merge of rust-lang#132255 - workingjubilee:layout-is-🏚️, r=compiler-errors

Add `LayoutS::is_uninhabited` and use it

Use accessors for the things that accessors are good at: reducing everyone's need to be nosy and peek at the internals of every data structure.

Author: workingjubilee

Cargo.lock

@@ -4100,6 +4100,7 @@ version = "0.0.0"
 dependencies = [
  "either",
  "itertools",
+ "rustc_abi",
  "rustc_arena",
  "rustc_ast",
  "rustc_attr",

compiler/rustc_abi/src/layout.rs

@@ -28,7 +28,7 @@ where
     VariantIdx: Idx,
     F: Deref<Target = &'a LayoutData<FieldIdx, VariantIdx>> + fmt::Debug,
 {
-    let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
+    let uninhabited = fields.iter().any(|f| f.is_uninhabited());
     // We cannot ignore alignment; that might lead us to entirely discard a variant and
     // produce an enum that is less aligned than it should be!
     let is_1zst = fields.iter().all(|f| f.is_1zst());
@@ -681,7 +681,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         let discr_type = repr.discr_type();
         let bits = Integer::from_attr(dl, discr_type).size().bits();
         for (i, mut val) in discriminants {
-            if !repr.c() && variants[i].iter().any(|f| f.abi.is_uninhabited()) {
+            if !repr.c() && variants[i].iter().any(|f| f.is_uninhabited()) {
                 continue;
             }
             if discr_type.is_signed() {

compiler/rustc_abi/src/lib.rs

@@ -1652,6 +1652,11 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
         }
     }
 
+    /// Returns `true` if this is an uninhabited type
+    pub fn is_uninhabited(&self) -> bool {
+        self.abi.is_uninhabited()
+    }
+
     pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
         let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
         let size = scalar.size(cx);

compiler/rustc_codegen_llvm/src/abi.rs

@@ -415,7 +415,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         instance: Option<ty::Instance<'tcx>>,
     ) {
         let mut func_attrs = SmallVec::<[_; 3]>::new();
-        if self.ret.layout.abi.is_uninhabited() {
+        if self.ret.layout.is_uninhabited() {
             func_attrs.push(llvm::AttributeKind::NoReturn.create_attr(cx.llcx));
         }
         if !self.can_unwind {
@@ -532,7 +532,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
 
     fn apply_attrs_callsite(&self, bx: &mut Builder<'_, 'll, 'tcx>, callsite: &'ll Value) {
         let mut func_attrs = SmallVec::<[_; 2]>::new();
-        if self.ret.layout.abi.is_uninhabited() {
+        if self.ret.layout.is_uninhabited() {
             func_attrs.push(llvm::AttributeKind::NoReturn.create_attr(bx.cx.llcx));
         }
         if !self.can_unwind {

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -364,7 +364,7 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         let mut flags = DIFlags::FlagPrototyped;
 
-        if fn_abi.ret.layout.abi.is_uninhabited() {
+        if fn_abi.ret.layout.is_uninhabited() {
             flags |= DIFlags::FlagNoReturn;
         }
 

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -438,7 +438,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 _ => bug!("C-variadic function must have a `VaList` place"),
             }
         }
-        if self.fn_abi.ret.layout.abi.is_uninhabited() {
+        if self.fn_abi.ret.layout.is_uninhabited() {
             // Functions with uninhabited return values are marked `noreturn`,
             // so we should make sure that we never actually do.
             // We play it safe by using a well-defined `abort`, but we could go for immediate UB
@@ -774,7 +774,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             Some(if do_panic {
                 let msg_str = with_no_visible_paths!({
                     with_no_trimmed_paths!({
-                        if layout.abi.is_uninhabited() {
+                        if layout.is_uninhabited() {
                             // Use this error even for the other intrinsics as it is more precise.
                             format!("attempted to instantiate uninhabited type `{ty}`")
                         } else if requirement == ValidityRequirement::Zero {

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -55,7 +55,7 @@ impl<V: CodegenObject> PlaceValue<V> {
     /// Creates a `PlaceRef` to this ___location with the given type.
     pub fn with_type<'tcx>(self, layout: TyAndLayout<'tcx>) -> PlaceRef<'tcx, V> {
         assert!(
-            layout.is_unsized() || layout.abi.is_uninhabited() || self.llextra.is_none(),
+            layout.is_unsized() || layout.is_uninhabited() || self.llextra.is_none(),
             "Had pointer metadata {:?} for sized type {layout:?}",
             self.llextra,
         );
@@ -239,7 +239,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
         let dl = &bx.tcx().data_layout;
         let cast_to_layout = bx.cx().layout_of(cast_to);
         let cast_to = bx.cx().immediate_backend_type(cast_to_layout);
-        if self.layout.abi.is_uninhabited() {
+        if self.layout.is_uninhabited() {
             return bx.cx().const_poison(cast_to);
         }
         let (tag_scalar, tag_encoding, tag_field) = match self.layout.variants {
@@ -358,7 +358,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
         bx: &mut Bx,
         variant_index: VariantIdx,
     ) {
-        if self.layout.for_variant(bx.cx(), variant_index).abi.is_uninhabited() {
+        if self.layout.for_variant(bx.cx(), variant_index).is_uninhabited() {
             // We play it safe by using a well-defined `abort`, but we could go for immediate UB
             // if that turns out to be helpful.
             bx.abort();

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -203,10 +203,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> Option<OperandValue<Bx::Value>> {
         // Check for transmutes that are always UB.
         if operand.layout.size != cast.size
-            || operand.layout.abi.is_uninhabited()
-            || cast.abi.is_uninhabited()
+            || operand.layout.is_uninhabited()
+            || cast.is_uninhabited()
         {
-            if !operand.layout.abi.is_uninhabited() {
+            if !operand.layout.is_uninhabited() {
                 // Since this is known statically and the input could have existed
                 // without already having hit UB, might as well trap for it.
                 bx.abort();
@@ -555,7 +555,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
                         assert!(bx.cx().is_backend_immediate(cast));
                         let to_backend_ty = bx.cx().immediate_backend_type(cast);
-                        if operand.layout.abi.is_uninhabited() {
+                        if operand.layout.is_uninhabited() {
                             let val = OperandValue::Immediate(bx.cx().const_poison(to_backend_ty));
                             return OperandRef { val, layout: cast };
                         }

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -395,7 +395,7 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
 
     #[inline(always)]
     fn enforce_validity(ecx: &InterpCx<'tcx, Self>, layout: TyAndLayout<'tcx>) -> bool {
-        ecx.tcx.sess.opts.unstable_opts.extra_const_ub_checks || layout.abi.is_uninhabited()
+        ecx.tcx.sess.opts.unstable_opts.extra_const_ub_checks || layout.is_uninhabited()
     }
 
     fn load_mir(

compiler/rustc_const_eval/src/interpret/discriminant.rs

@@ -27,7 +27,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // discriminant, so we cannot do anything here.
         // When evaluating we will always error before even getting here, but ConstProp 'executes'
         // dead code, so we cannot ICE here.
-        if dest.layout().for_variant(self, variant_index).abi.is_uninhabited() {
+        if dest.layout().for_variant(self, variant_index).is_uninhabited() {
             throw_ub!(UninhabitedEnumVariantWritten(variant_index))
         }
 
@@ -86,7 +86,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     // For consistency with `write_discriminant`, and to make sure that
                     // `project_downcast` cannot fail due to strange layouts, we declare immediate UB
                     // for uninhabited variants.
-                    if op.layout().for_variant(self, index).abi.is_uninhabited() {
+                    if op.layout().for_variant(self, index).is_uninhabited() {
                         throw_ub!(UninhabitedEnumVariantRead(index))
                     }
                 }
@@ -203,7 +203,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // Reading the discriminant of an uninhabited variant is UB. This is the basis for the
         // `uninhabited_enum_branching` MIR pass. It also ensures consistency with
         // `write_discriminant`.
-        if op.layout().for_variant(self, index).abi.is_uninhabited() {
+        if op.layout().for_variant(self, index).is_uninhabited() {
             throw_ub!(UninhabitedEnumVariantRead(index))
         }
         interp_ok(index)