Auto merge of #129970 - lukas-code:LayoutCalculator, r=compiler-errors

layout computation: gracefully handle unsized types in unexpected locations

This PR reworks the layout computation to eagerly return an error when encountering an unsized field where a sized field was expected, rather than delaying a bug and attempting to recover a layout. This is required, because with trivially false where clauses like `[T]: Sized`, any field can possible be an unsized type, without causing a compile error.

Since this PR removes the `delayed_bug` method from the `LayoutCalculator` trait, it essentially becomes the same as the `HasDataLayout` trait, so I've also refactored the `LayoutCalculator` to be a simple wrapper struct around a type that implements `HasDataLayout`.

The majority of the diff is whitespace changes, so viewing with whitespace ignored is advised.

implements #123169 (comment)

r? `@compiler-errors` or compiler

fixes #123134
fixes #124182
fixes #126939
fixes #127737

compiler/rustc_abi/src/lib.rs

@@ -26,7 +26,7 @@ mod layout;
 #[cfg(test)]
 mod tests;
 
-pub use layout::LayoutCalculator;
+pub use layout::{LayoutCalculator, LayoutCalculatorError};
 
 /// Requirements for a `StableHashingContext` to be used in this crate.
 /// This is a hack to allow using the `HashStable_Generic` derive macro
@@ -393,6 +393,14 @@ impl HasDataLayout for TargetDataLayout {
     }
 }
 
+// used by rust-analyzer
+impl HasDataLayout for &TargetDataLayout {
+    #[inline]
+    fn data_layout(&self) -> &TargetDataLayout {
+        (**self).data_layout()
+    }
+}
+
 /// Endianness of the target, which must match cfg(target-endian).
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum Endian {

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -319,7 +319,7 @@ pub fn valtree_to_const_value<'tcx>(
                 let branches = valtree.unwrap_branch();
                 // Find the non-ZST field. (There can be aligned ZST!)
                 for (i, &inner_valtree) in branches.iter().enumerate() {
-                    let field = layout.field(&LayoutCx { tcx, param_env }, i);
+                    let field = layout.field(&LayoutCx::new(tcx, param_env), i);
                     if !field.is_zst() {
                         return valtree_to_const_value(tcx, param_env.and(field.ty), inner_valtree);
                     }

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -21,7 +21,7 @@ use rustc_middle::mir::interpret::{
     UnsupportedOpInfo, ValidationErrorInfo,
 };
 use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_target::abi::{
     Abi, FieldIdx, FieldsShape, Scalar as ScalarAbi, Size, VariantIdx, Variants, WrappingRange,
@@ -940,7 +940,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
     ) -> Cow<'e, RangeSet> {
         assert!(layout.ty.is_union());
         assert!(layout.abi.is_sized(), "there are no unsized unions");
-        let layout_cx = LayoutCx { tcx: *ecx.tcx, param_env: ecx.param_env };
+        let layout_cx = LayoutCx::new(*ecx.tcx, ecx.param_env);
         return M::cached_union_data_range(ecx, layout.ty, || {
             let mut out = RangeSet(Vec::new());
             union_data_range_uncached(&layout_cx, layout, Size::ZERO, &mut out);
@@ -949,7 +949,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
 
         /// Helper for recursive traversal: add data ranges of the given type to `out`.
         fn union_data_range_uncached<'tcx>(
-            cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
+            cx: &LayoutCx<'tcx>,
             layout: TyAndLayout<'tcx>,
             base_offset: Size,
             out: &mut RangeSet,

compiler/rustc_const_eval/src/util/check_validity_requirement.rs

@@ -1,5 +1,7 @@
 use rustc_middle::bug;
-use rustc_middle::ty::layout::{LayoutCx, LayoutError, LayoutOf, TyAndLayout, ValidityRequirement};
+use rustc_middle::ty::layout::{
+    HasTyCtxt, LayoutCx, LayoutError, LayoutOf, TyAndLayout, ValidityRequirement,
+};
 use rustc_middle::ty::{ParamEnvAnd, Ty, TyCtxt};
 use rustc_target::abi::{Abi, FieldsShape, Scalar, Variants};
 
@@ -30,7 +32,7 @@ pub fn check_validity_requirement<'tcx>(
         return Ok(!layout.abi.is_uninhabited());
     }
 
-    let layout_cx = LayoutCx { tcx, param_env: param_env_and_ty.param_env };
+    let layout_cx = LayoutCx::new(tcx, param_env_and_ty.param_env);
     if kind == ValidityRequirement::Uninit || tcx.sess.opts.unstable_opts.strict_init_checks {
         check_validity_requirement_strict(layout, &layout_cx, kind)
     } else {
@@ -42,12 +44,12 @@ pub fn check_validity_requirement<'tcx>(
 /// for details.
 fn check_validity_requirement_strict<'tcx>(
     ty: TyAndLayout<'tcx>,
-    cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
+    cx: &LayoutCx<'tcx>,
     kind: ValidityRequirement,
 ) -> Result<bool, &'tcx LayoutError<'tcx>> {
     let machine = CompileTimeMachine::new(CanAccessMutGlobal::No, CheckAlignment::Error);
 
-    let mut cx = InterpCx::new(cx.tcx, rustc_span::DUMMY_SP, cx.param_env, machine);
+    let mut cx = InterpCx::new(cx.tcx(), rustc_span::DUMMY_SP, cx.param_env, machine);
 
     let allocated = cx
         .allocate(ty, MemoryKind::Machine(crate::const_eval::MemoryKind::Heap))
@@ -80,7 +82,7 @@ fn check_validity_requirement_strict<'tcx>(
 /// function for details.
 fn check_validity_requirement_lax<'tcx>(
     this: TyAndLayout<'tcx>,
-    cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
+    cx: &LayoutCx<'tcx>,
     init_kind: ValidityRequirement,
 ) -> Result<bool, &'tcx LayoutError<'tcx>> {
     let scalar_allows_raw_init = move |s: Scalar| -> bool {

compiler/rustc_index/src/slice.rs

@@ -20,7 +20,7 @@ pub struct IndexSlice<I: Idx, T> {
 
 impl<I: Idx, T> IndexSlice<I, T> {
     #[inline]
-    pub const fn empty() -> &'static Self {
+    pub const fn empty<'a>() -> &'a Self {
         Self::from_raw(&[])
     }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -1,4 +1,3 @@
-use std::borrow::Cow;
 use std::num::NonZero;
 use std::ops::Bound;
 use std::{cmp, fmt};
@@ -286,20 +285,14 @@ impl<'tcx> IntoDiagArg for LayoutError<'tcx> {
 }
 
 #[derive(Clone, Copy)]
-pub struct LayoutCx<'tcx, C> {
-    pub tcx: C,
+pub struct LayoutCx<'tcx> {
+    pub calc: LayoutCalculator<TyCtxt<'tcx>>,
     pub param_env: ty::ParamEnv<'tcx>,
 }
 
-impl<'tcx> LayoutCalculator for LayoutCx<'tcx, TyCtxt<'tcx>> {
-    type TargetDataLayoutRef = &'tcx TargetDataLayout;
-
-    fn delayed_bug(&self, txt: impl Into<Cow<'static, str>>) {
-        self.tcx.dcx().delayed_bug(txt);
-    }
-
-    fn current_data_layout(&self) -> Self::TargetDataLayoutRef {
-        &self.tcx.data_layout
+impl<'tcx> LayoutCx<'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
+        Self { calc: LayoutCalculator::new(tcx), param_env }
     }
 }
 
@@ -568,33 +561,33 @@ impl<'tcx> HasTyCtxt<'tcx> for TyCtxtAt<'tcx> {
     }
 }
 
-impl<'tcx, C> HasParamEnv<'tcx> for LayoutCx<'tcx, C> {
+impl<'tcx> HasParamEnv<'tcx> for LayoutCx<'tcx> {
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
         self.param_env
     }
 }
 
-impl<'tcx, T: HasDataLayout> HasDataLayout for LayoutCx<'tcx, T> {
+impl<'tcx> HasDataLayout for LayoutCx<'tcx> {
     fn data_layout(&self) -> &TargetDataLayout {
-        self.tcx.data_layout()
+        self.calc.cx.data_layout()
     }
 }
 
-impl<'tcx, T: HasTargetSpec> HasTargetSpec for LayoutCx<'tcx, T> {
+impl<'tcx> HasTargetSpec for LayoutCx<'tcx> {
     fn target_spec(&self) -> &Target {
-        self.tcx.target_spec()
+        self.calc.cx.target_spec()
     }
 }
 
-impl<'tcx, T: HasWasmCAbiOpt> HasWasmCAbiOpt for LayoutCx<'tcx, T> {
+impl<'tcx> HasWasmCAbiOpt for LayoutCx<'tcx> {
     fn wasm_c_abi_opt(&self) -> WasmCAbi {
-        self.tcx.wasm_c_abi_opt()
+        self.calc.cx.wasm_c_abi_opt()
     }
 }
 
-impl<'tcx, T: HasTyCtxt<'tcx>> HasTyCtxt<'tcx> for LayoutCx<'tcx, T> {
+impl<'tcx> HasTyCtxt<'tcx> for LayoutCx<'tcx> {
     fn tcx(&self) -> TyCtxt<'tcx> {
-        self.tcx.tcx()
+        self.calc.cx
     }
 }
 
@@ -685,7 +678,7 @@ pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
 
 impl<'tcx, C: LayoutOfHelpers<'tcx>> LayoutOf<'tcx> for C {}
 
-impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
+impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx> {
     type LayoutOfResult = Result<TyAndLayout<'tcx>, &'tcx LayoutError<'tcx>>;
 
     #[inline]
@@ -695,26 +688,7 @@ impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
         _: Span,
         _: Ty<'tcx>,
     ) -> &'tcx LayoutError<'tcx> {
-        self.tcx.arena.alloc(err)
-    }
-}
-
-impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxtAt<'tcx>> {
-    type LayoutOfResult = Result<TyAndLayout<'tcx>, &'tcx LayoutError<'tcx>>;
-
-    #[inline]
-    fn layout_tcx_at_span(&self) -> Span {
-        self.tcx.span
-    }
-
-    #[inline]
-    fn handle_layout_err(
-        &self,
-        err: LayoutError<'tcx>,
-        _: Span,
-        _: Ty<'tcx>,
-    ) -> &'tcx LayoutError<'tcx> {
-        self.tcx.arena.alloc(err)
+        self.tcx().arena.alloc(err)
     }
 }
 
@@ -1342,7 +1316,7 @@ impl<'tcx> TyCtxt<'tcx> {
     where
         I: Iterator<Item = (VariantIdx, FieldIdx)>,
     {
-        let cx = LayoutCx { tcx: self, param_env };
+        let cx = LayoutCx::new(self, param_env);
         let mut offset = Size::ZERO;
 
         for (variant, field) in indices {

compiler/rustc_passes/src/layout_test.rs

@@ -128,7 +128,7 @@ fn dump_layout_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
         }
 
         Err(layout_error) => {
-            tcx.dcx().emit_fatal(Spanned { node: layout_error.into_diagnostic(), span });
+            tcx.dcx().emit_err(Spanned { node: layout_error.into_diagnostic(), span });
         }
     }
 }

compiler/rustc_transmute/src/layout/mod.rs

@@ -63,8 +63,8 @@ pub mod rustc {
     use std::fmt::{self, Write};
 
     use rustc_middle::mir::Mutability;
-    use rustc_middle::ty::layout::{LayoutCx, LayoutError};
-    use rustc_middle::ty::{self, Ty, TyCtxt};
+    use rustc_middle::ty::layout::{HasTyCtxt, LayoutCx, LayoutError};
+    use rustc_middle::ty::{self, Ty};
     use rustc_target::abi::Layout;
 
     /// A reference in the layout.
@@ -124,11 +124,11 @@ pub mod rustc {
     }
 
     pub(crate) fn layout_of<'tcx>(
-        cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+        cx: LayoutCx<'tcx>,
         ty: Ty<'tcx>,
     ) -> Result<Layout<'tcx>, &'tcx LayoutError<'tcx>> {
         use rustc_middle::ty::layout::LayoutOf;
-        let ty = cx.tcx.erase_regions(ty);
+        let ty = cx.tcx().erase_regions(ty);
         cx.layout_of(ty).map(|tl| tl.layout)
     }
 }

compiler/rustc_transmute/src/layout/tree.rs

@@ -204,15 +204,15 @@ pub(crate) mod rustc {
     }
 
     impl<'tcx> Tree<Def<'tcx>, Ref<'tcx>> {
-        pub(crate) fn from_ty(ty: Ty<'tcx>, cx: LayoutCx<'tcx, TyCtxt<'tcx>>) -> Result<Self, Err> {
+        pub(crate) fn from_ty(ty: Ty<'tcx>, cx: LayoutCx<'tcx>) -> Result<Self, Err> {
             use rustc_target::abi::HasDataLayout;
             let layout = layout_of(cx, ty)?;
 
             if let Err(e) = ty.error_reported() {
                 return Err(Err::TypeError(e));
             }
 
-            let target = cx.tcx.data_layout();
+            let target = cx.data_layout();
             let pointer_size = target.pointer_size;
 
             match ty.kind() {
@@ -274,7 +274,7 @@ pub(crate) mod rustc {
         fn from_tuple(
             (ty, layout): (Ty<'tcx>, Layout<'tcx>),
             members: &'tcx List<Ty<'tcx>>,
-            cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+            cx: LayoutCx<'tcx>,
         ) -> Result<Self, Err> {
             match &layout.fields {
                 FieldsShape::Primitive => {
@@ -299,7 +299,7 @@ pub(crate) mod rustc {
         fn from_struct(
             (ty, layout): (Ty<'tcx>, Layout<'tcx>),
             def: AdtDef<'tcx>,
-            cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+            cx: LayoutCx<'tcx>,
         ) -> Result<Self, Err> {
             assert!(def.is_struct());
             let def = Def::Adt(def);
@@ -314,13 +314,13 @@ pub(crate) mod rustc {
         fn from_enum(
             (ty, layout): (Ty<'tcx>, Layout<'tcx>),
             def: AdtDef<'tcx>,
-            cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+            cx: LayoutCx<'tcx>,
         ) -> Result<Self, Err> {
             assert!(def.is_enum());
 
             // Computes the variant of a given index.
             let layout_of_variant = |index, encoding: Option<TagEncoding<VariantIdx>>| {
-                let tag = cx.tcx.tag_for_variant((cx.tcx.erase_regions(ty), index));
+                let tag = cx.tcx().tag_for_variant((cx.tcx().erase_regions(ty), index));
                 let variant_def = Def::Variant(def.variant(index));
                 let variant_layout = ty_variant(cx, (ty, layout), index);
                 Self::from_variant(
@@ -389,7 +389,7 @@ pub(crate) mod rustc {
             tag: Option<(ScalarInt, VariantIdx, TagEncoding<VariantIdx>)>,
             (ty, layout): (Ty<'tcx>, Layout<'tcx>),
             total_size: Size,
-            cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+            cx: LayoutCx<'tcx>,
         ) -> Result<Self, Err> {
             // This constructor does not support non-`FieldsShape::Arbitrary`
             // layouts.
@@ -417,7 +417,7 @@ pub(crate) mod rustc {
                         }
                     }
                 }
-                struct_tree = struct_tree.then(Self::from_tag(*tag, cx.tcx));
+                struct_tree = struct_tree.then(Self::from_tag(*tag, cx.tcx()));
             }
 
             // Append the fields, in memory order, to the layout.
@@ -470,7 +470,7 @@ pub(crate) mod rustc {
         fn from_union(
             (ty, layout): (Ty<'tcx>, Layout<'tcx>),
             def: AdtDef<'tcx>,
-            cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+            cx: LayoutCx<'tcx>,
         ) -> Result<Self, Err> {
             assert!(def.is_union());
 
@@ -500,7 +500,7 @@ pub(crate) mod rustc {
     }
 
     fn ty_field<'tcx>(
-        cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+        cx: LayoutCx<'tcx>,
         (ty, layout): (Ty<'tcx>, Layout<'tcx>),
         i: FieldIdx,
     ) -> Ty<'tcx> {
@@ -509,12 +509,12 @@ pub(crate) mod rustc {
                 match layout.variants {
                     Variants::Single { index } => {
                         let field = &def.variant(index).fields[i];
-                        field.ty(cx.tcx, args)
+                        field.ty(cx.tcx(), args)
                     }
                     // Discriminant field for enums (where applicable).
                     Variants::Multiple { tag, .. } => {
                         assert_eq!(i.as_usize(), 0);
-                        ty::layout::PrimitiveExt::to_ty(&tag.primitive(), cx.tcx)
+                        ty::layout::PrimitiveExt::to_ty(&tag.primitive(), cx.tcx())
                     }
                 }
             }
@@ -527,11 +527,11 @@ pub(crate) mod rustc {
     }
 
     fn ty_variant<'tcx>(
-        cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+        cx: LayoutCx<'tcx>,
         (ty, layout): (Ty<'tcx>, Layout<'tcx>),
         i: VariantIdx,
     ) -> Layout<'tcx> {
-        let ty = cx.tcx.erase_regions(ty);
+        let ty = cx.tcx().erase_regions(ty);
         TyAndLayout { ty, layout }.for_variant(&cx, i).layout
     }
 }

compiler/rustc_transmute/src/maybe_transmutable/mod.rs

@@ -43,7 +43,7 @@ mod rustc {
         pub fn answer(self) -> Answer<<TyCtxt<'tcx> as QueryContext>::Ref> {
             let Self { src, dst, assume, context } = self;
 
-            let layout_cx = LayoutCx { tcx: context, param_env: ParamEnv::reveal_all() };
+            let layout_cx = LayoutCx::new(context, ParamEnv::reveal_all());
 
             // Convert `src` and `dst` from their rustc representations, to `Tree`-based
             // representations.