Remove most manual LayoutData creations and move them to `rustc_abi`

...either as:
- methods on LayoutCalculator, for faillible operations;
- constructors on LayoutData, for infaillible ones.

6 files changed, 228 insertions, 267 deletions

diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs
index d3ae6a29f10..42ecbce8117 100644
--- a/compiler/rustc_abi/src/layout.rs
+++ b/compiler/rustc_abi/src/layout.rs
@@ -12,6 +12,8 @@ use crate::{
     Variants, WrappingRange,
 };
 
+mod simple;
+
 #[cfg(feature = "nightly")]
 mod ty;
 
@@ -102,41 +104,27 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         Self { cx }
     }
 
-    pub fn scalar_pair<FieldIdx: Idx, VariantIdx: Idx>(
+    pub fn array_like<FieldIdx: Idx, VariantIdx: Idx, F>(
         &self,
-        a: Scalar,
-        b: Scalar,
-    ) -> LayoutData<FieldIdx, VariantIdx> {
-        let dl = self.cx.data_layout();
-        let b_align = b.align(dl);
-        let align = a.align(dl).max(b_align).max(dl.aggregate_align);
-        let b_offset = a.size(dl).align_to(b_align.abi);
-        let size = (b_offset + b.size(dl)).align_to(align.abi);
-
-        // HACK(nox): We iter on `b` and then `a` because `max_by_key`
-        // returns the last maximum.
-        let largest_niche = Niche::from_scalar(dl, b_offset, b)
-            .into_iter()
-            .chain(Niche::from_scalar(dl, Size::ZERO, a))
-            .max_by_key(|niche| niche.available(dl));
-
-        let combined_seed = a.size(&self.cx).bytes().wrapping_add(b.size(&self.cx).bytes());
+        element: &LayoutData<FieldIdx, VariantIdx>,
+        count_if_sized: Option<u64>, // None for slices
+    ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
+        let count = count_if_sized.unwrap_or(0);
+        let size =
+            element.size.checked_mul(count, &self.cx).ok_or(LayoutCalculatorError::SizeOverflow)?;
 
-        LayoutData {
+        Ok(LayoutData {
             variants: Variants::Single { index: VariantIdx::new(0) },
-            fields: FieldsShape::Arbitrary {
-                offsets: [Size::ZERO, b_offset].into(),
-                memory_index: [0, 1].into(),
-            },
-            backend_repr: BackendRepr::ScalarPair(a, b),
-            largest_niche,
-            uninhabited: false,
-            align,
+            fields: FieldsShape::Array { stride: element.size, count },
+            backend_repr: BackendRepr::Memory { sized: count_if_sized.is_some() },
+            largest_niche: element.largest_niche.filter(|_| count != 0),
+            uninhabited: element.uninhabited && count != 0,
+            align: element.align,
             size,
             max_repr_align: None,
-            unadjusted_abi_align: align.abi,
-            randomization_seed: Hash64::new(combined_seed),
-        }
+            unadjusted_abi_align: element.align.abi,
+            randomization_seed: element.randomization_seed.wrapping_add(Hash64::new(count)),
+        })
     }
 
     pub fn univariant<
@@ -214,25 +202,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         layout
     }
 
-    pub fn layout_of_never_type<FieldIdx: Idx, VariantIdx: Idx>(
-        &self,
-    ) -> LayoutData<FieldIdx, VariantIdx> {
-        let dl = self.cx.data_layout();
-        // This is also used for uninhabited enums, so we use `Variants::Empty`.
-        LayoutData {
-            variants: Variants::Empty,
-            fields: FieldsShape::Primitive,
-            backend_repr: BackendRepr::Memory { sized: true },
-            largest_niche: None,
-            uninhabited: true,
-            align: dl.i8_align,
-            size: Size::ZERO,
-            max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
-            randomization_seed: Hash64::ZERO,
-        }
-    }
-
     pub fn layout_of_struct_or_enum<
         'a,
         FieldIdx: Idx,
@@ -260,7 +229,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             Some(present_first) => present_first,
             // Uninhabited because it has no variants, or only absent ones.
             None if is_enum => {
-                return Ok(self.layout_of_never_type());
+                return Ok(LayoutData::never_type(&self.cx));
             }
             // If it's a struct, still compute a layout so that we can still compute the
             // field offsets.
@@ -949,7 +918,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     // Common prim might be uninit.
                     Scalar::Union { value: prim }
                 };
-                let pair = self.scalar_pair::<FieldIdx, VariantIdx>(tag, prim_scalar);
+                let pair =
+                    LayoutData::<FieldIdx, VariantIdx>::scalar_pair(&self.cx, tag, prim_scalar);
                 let pair_offsets = match pair.fields {
                     FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
                         assert_eq!(memory_index.raw, [0, 1]);
@@ -1341,7 +1311,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                             } else {
                                 ((j, b), (i, a))
                             };
-                            let pair = self.scalar_pair::<FieldIdx, VariantIdx>(a, b);
+                            let pair =
+                                LayoutData::<FieldIdx, VariantIdx>::scalar_pair(&self.cx, a, b);
                             let pair_offsets = match pair.fields {
                                 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
                                     assert_eq!(memory_index.raw, [0, 1]);
diff --git a/compiler/rustc_abi/src/layout/simple.rs b/compiler/rustc_abi/src/layout/simple.rs
new file mode 100644
index 00000000000..0d0706defc2
--- /dev/null
+++ b/compiler/rustc_abi/src/layout/simple.rs
@@ -0,0 +1,148 @@
+use std::num::NonZero;
+
+use rustc_hashes::Hash64;
+use rustc_index::{Idx, IndexVec};
+
+use crate::{
+    BackendRepr, FieldsShape, HasDataLayout, LayoutData, Niche, Primitive, Scalar, Size, Variants,
+};
+
+/// "Simple" layout constructors that cannot fail.
+impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
+    pub fn unit<C: HasDataLayout>(cx: &C, sized: bool) -> Self {
+        let dl = cx.data_layout();
+        LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Arbitrary {
+                offsets: IndexVec::new(),
+                memory_index: IndexVec::new(),
+            },
+            backend_repr: BackendRepr::Memory { sized },
+            largest_niche: None,
+            uninhabited: false,
+            align: dl.i8_align,
+            size: Size::ZERO,
+            max_repr_align: None,
+            unadjusted_abi_align: dl.i8_align.abi,
+            randomization_seed: Hash64::new(0),
+        }
+    }
+
+    pub fn never_type<C: HasDataLayout>(cx: &C) -> Self {
+        let dl = cx.data_layout();
+        // This is also used for uninhabited enums, so we use `Variants::Empty`.
+        LayoutData {
+            variants: Variants::Empty,
+            fields: FieldsShape::Primitive,
+            backend_repr: BackendRepr::Memory { sized: true },
+            largest_niche: None,
+            uninhabited: true,
+            align: dl.i8_align,
+            size: Size::ZERO,
+            max_repr_align: None,
+            unadjusted_abi_align: dl.i8_align.abi,
+            randomization_seed: Hash64::ZERO,
+        }
+    }
+
+    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);
+        let align = scalar.align(cx);
+
+        let range = scalar.valid_range(cx);
+
+        // All primitive types for which we don't have subtype coercions should get a distinct seed,
+        // so that types wrapping them can use randomization to arrive at distinct layouts.
+        //
+        // Some type information is already lost at this point, so as an approximation we derive
+        // the seed from what remains. For example on 64-bit targets usize and u64 can no longer
+        // be distinguished.
+        let randomization_seed = size
+            .bytes()
+            .wrapping_add(
+                match scalar.primitive() {
+                    Primitive::Int(_, true) => 1,
+                    Primitive::Int(_, false) => 2,
+                    Primitive::Float(_) => 3,
+                    Primitive::Pointer(_) => 4,
+                } << 32,
+            )
+            // distinguishes references from pointers
+            .wrapping_add((range.start as u64).rotate_right(16))
+            // distinguishes char from u32 and bool from u8
+            .wrapping_add((range.end as u64).rotate_right(16));
+
+        LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Primitive,
+            backend_repr: BackendRepr::Scalar(scalar),
+            largest_niche,
+            uninhabited: false,
+            size,
+            align,
+            max_repr_align: None,
+            unadjusted_abi_align: align.abi,
+            randomization_seed: Hash64::new(randomization_seed),
+        }
+    }
+
+    pub fn scalar_pair<C: HasDataLayout>(cx: &C, a: Scalar, b: Scalar) -> Self {
+        let dl = cx.data_layout();
+        let b_align = b.align(dl);
+        let align = a.align(dl).max(b_align).max(dl.aggregate_align);
+        let b_offset = a.size(dl).align_to(b_align.abi);
+        let size = (b_offset + b.size(dl)).align_to(align.abi);
+
+        // HACK(nox): We iter on `b` and then `a` because `max_by_key`
+        // returns the last maximum.
+        let largest_niche = Niche::from_scalar(dl, b_offset, b)
+            .into_iter()
+            .chain(Niche::from_scalar(dl, Size::ZERO, a))
+            .max_by_key(|niche| niche.available(dl));
+
+        let combined_seed = a.size(dl).bytes().wrapping_add(b.size(dl).bytes());
+
+        LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Arbitrary {
+                offsets: [Size::ZERO, b_offset].into(),
+                memory_index: [0, 1].into(),
+            },
+            backend_repr: BackendRepr::ScalarPair(a, b),
+            largest_niche,
+            uninhabited: false,
+            align,
+            size,
+            max_repr_align: None,
+            unadjusted_abi_align: align.abi,
+            randomization_seed: Hash64::new(combined_seed),
+        }
+    }
+
+    /// Returns a dummy layout for an uninhabited variant.
+    ///
+    /// Uninhabited variants get pruned as part of the layout calculation,
+    /// so this can be used after the fact to reconstitute a layout.
+    pub fn uninhabited_variant<C: HasDataLayout>(cx: &C, index: VariantIdx, fields: usize) -> Self {
+        let dl = cx.data_layout();
+        LayoutData {
+            variants: Variants::Single { index },
+            fields: match NonZero::new(fields) {
+                Some(fields) => FieldsShape::Union(fields),
+                None => FieldsShape::Arbitrary {
+                    offsets: IndexVec::new(),
+                    memory_index: IndexVec::new(),
+                },
+            },
+            backend_repr: BackendRepr::Memory { sized: true },
+            largest_niche: None,
+            uninhabited: true,
+            align: dl.i8_align,
+            size: Size::ZERO,
+            max_repr_align: None,
+            unadjusted_abi_align: dl.i8_align.abi,
+            randomization_seed: Hash64::ZERO,
+        }
+    }
+}
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index a59dc870aa3..db9a26c3ef7 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -1744,48 +1744,6 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
     pub fn is_uninhabited(&self) -> bool {
         self.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);
-        let align = scalar.align(cx);
-
-        let range = scalar.valid_range(cx);
-
-        // All primitive types for which we don't have subtype coercions should get a distinct seed,
-        // so that types wrapping them can use randomization to arrive at distinct layouts.
-        //
-        // Some type information is already lost at this point, so as an approximation we derive
-        // the seed from what remains. For example on 64-bit targets usize and u64 can no longer
-        // be distinguished.
-        let randomization_seed = size
-            .bytes()
-            .wrapping_add(
-                match scalar.primitive() {
-                    Primitive::Int(_, true) => 1,
-                    Primitive::Int(_, false) => 2,
-                    Primitive::Float(_) => 3,
-                    Primitive::Pointer(_) => 4,
-                } << 32,
-            )
-            // distinguishes references from pointers
-            .wrapping_add((range.start as u64).rotate_right(16))
-            // distinguishes char from u32 and bool from u8
-            .wrapping_add((range.end as u64).rotate_right(16));
-
-        LayoutData {
-            variants: Variants::Single { index: VariantIdx::new(0) },
-            fields: FieldsShape::Primitive,
-            backend_repr: BackendRepr::Scalar(scalar),
-            largest_niche,
-            uninhabited: false,
-            size,
-            align,
-            max_repr_align: None,
-            unadjusted_abi_align: align.abi,
-            randomization_seed: Hash64::new(randomization_seed),
-        }
-    }
 }
 
 impl<FieldIdx: Idx, VariantIdx: Idx> fmt::Debug for LayoutData<FieldIdx, VariantIdx>
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 272bb0cc915..d32c524a427 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -1,20 +1,17 @@
-use std::num::NonZero;
 use std::ops::Bound;
 use std::{cmp, fmt};
 
 use rustc_abi::{
-    AddressSpace, Align, BackendRepr, ExternAbi, FieldIdx, FieldsShape, HasDataLayout, LayoutData,
-    PointeeInfo, PointerKind, Primitive, ReprOptions, Scalar, Size, TagEncoding, TargetDataLayout,
+    AddressSpace, Align, ExternAbi, FieldIdx, FieldsShape, HasDataLayout, LayoutData, PointeeInfo,
+    PointerKind, Primitive, ReprOptions, Scalar, Size, TagEncoding, TargetDataLayout,
     TyAbiInterface, VariantIdx, Variants,
 };
 use rustc_error_messages::DiagMessage;
 use rustc_errors::{
     Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
 };
-use rustc_hashes::Hash64;
 use rustc_hir::LangItem;
 use rustc_hir::def_id::DefId;
-use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, extension};
 use rustc_session::config::OptLevel;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
@@ -762,11 +759,9 @@ where
         variant_index: VariantIdx,
     ) -> TyAndLayout<'tcx> {
         let layout = match this.variants {
-            Variants::Single { index }
-                // If all variants but one are uninhabited, the variant layout is the enum layout.
-                if index == variant_index =>
-            {
-                this.layout
+            // If all variants but one are uninhabited, the variant layout is the enum layout.
+            Variants::Single { index } if index == variant_index => {
+                return this;
             }
 
             Variants::Single { .. } | Variants::Empty => {
@@ -783,29 +778,18 @@ where
                 }
 
                 let fields = match this.ty.kind() {
-                    ty::Adt(def, _) if def.variants().is_empty() =>
-                        bug!("for_variant called on zero-variant enum {}", this.ty),
+                    ty::Adt(def, _) if def.variants().is_empty() => {
+                        bug!("for_variant called on zero-variant enum {}", this.ty)
+                    }
                     ty::Adt(def, _) => def.variant(variant_index).fields.len(),
                     _ => bug!("`ty_and_layout_for_variant` on unexpected type {}", this.ty),
                 };
-                tcx.mk_layout(LayoutData {
-                    variants: Variants::Single { index: variant_index },
-                    fields: match NonZero::new(fields) {
-                        Some(fields) => FieldsShape::Union(fields),
-                        None => FieldsShape::Arbitrary { offsets: IndexVec::new(), memory_index: IndexVec::new() },
-                    },
-                    backend_repr: BackendRepr::Memory { sized: true },
-                    largest_niche: None,
-                    uninhabited: true,
-                    align: tcx.data_layout.i8_align,
-                    size: Size::ZERO,
-                    max_repr_align: None,
-                    unadjusted_abi_align: tcx.data_layout.i8_align.abi,
-                    randomization_seed: Hash64::ZERO,
-                })
+                tcx.mk_layout(LayoutData::uninhabited_variant(cx, variant_index, fields))
             }
 
-            Variants::Multiple { ref variants, .. } => cx.tcx().mk_layout(variants[variant_index].clone()),
+            Variants::Multiple { ref variants, .. } => {
+                cx.tcx().mk_layout(variants[variant_index].clone())
+            }
         };
 
         assert_eq!(*layout.variants(), Variants::Single { index: variant_index });
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index a53f0538c58..45c2639280f 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -188,6 +188,10 @@ fn layout_of_uncached<'tcx>(
 
     let tcx = cx.tcx();
     let dl = cx.data_layout();
+    let map_layout = |result: Result<_, _>| match result {
+        Ok(layout) => Ok(tcx.mk_layout(layout)),
+        Err(err) => Err(map_error(cx, ty, err)),
+    };
     let scalar_unit = |value: Primitive| {
         let size = value.size(dl);
         assert!(size.bits() <= 128);
@@ -258,7 +262,7 @@ fn layout_of_uncached<'tcx>(
         }
 
         // The never type.
-        ty::Never => tcx.mk_layout(cx.calc.layout_of_never_type()),
+        ty::Never => tcx.mk_layout(LayoutData::never_type(cx)),
 
         // Potentially-wide pointers.
         ty::Ref(_, pointee, _) | ty::RawPtr(pointee, _) => {
@@ -329,7 +333,7 @@ fn layout_of_uncached<'tcx>(
             };
 
             // Effectively a (ptr, meta) tuple.
-            tcx.mk_layout(cx.calc.scalar_pair(data_ptr, metadata))
+            tcx.mk_layout(LayoutData::scalar_pair(cx, data_ptr, metadata))
         }
 
         ty::Dynamic(_, _, ty::DynStar) => {
@@ -337,7 +341,7 @@ fn layout_of_uncached<'tcx>(
             data.valid_range_mut().start = 0;
             let mut vtable = scalar_unit(Pointer(AddressSpace::DATA));
             vtable.valid_range_mut().start = 1;
-            tcx.mk_layout(cx.calc.scalar_pair(data, vtable))
+            tcx.mk_layout(LayoutData::scalar_pair(cx, data, vtable))
         }
 
         // Arrays and slices.
@@ -347,71 +351,29 @@ fn layout_of_uncached<'tcx>(
                 .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
 
             let element = cx.layout_of(element)?;
-            let size = element
-                .size
-                .checked_mul(count, dl)
-                .ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))?;
-
-            let abi = BackendRepr::Memory { sized: true };
-
-            let largest_niche = if count != 0 { element.largest_niche } else { None };
-            let uninhabited = if count != 0 { element.uninhabited } else { false };
-
-            tcx.mk_layout(LayoutData {
-                variants: Variants::Single { index: FIRST_VARIANT },
-                fields: FieldsShape::Array { stride: element.size, count },
-                backend_repr: abi,
-                largest_niche,
-                uninhabited,
-                align: element.align,
-                size,
-                max_repr_align: None,
-                unadjusted_abi_align: element.align.abi,
-                randomization_seed: element.randomization_seed.wrapping_add(Hash64::new(count)),
-            })
+            map_layout(cx.calc.array_like(&element, Some(count)))?
         }
         ty::Slice(element) => {
             let element = cx.layout_of(element)?;
-            tcx.mk_layout(LayoutData {
-                variants: Variants::Single { index: FIRST_VARIANT },
-                fields: FieldsShape::Array { stride: element.size, count: 0 },
-                backend_repr: BackendRepr::Memory { sized: false },
-                largest_niche: None,
-                uninhabited: false,
-                align: element.align,
-                size: Size::ZERO,
-                max_repr_align: None,
-                unadjusted_abi_align: element.align.abi,
-                // adding a randomly chosen value to distinguish slices
-                randomization_seed: element
-                    .randomization_seed
-                    .wrapping_add(Hash64::new(0x2dcba99c39784102)),
-            })
+            map_layout(cx.calc.array_like(&element, None).map(|mut layout| {
+                // a randomly chosen value to distinguish slices
+                layout.randomization_seed = Hash64::new(0x2dcba99c39784102);
+                layout
+            }))?
+        }
+        ty::Str => {
+            let element = scalar(Int(I8, false));
+            map_layout(cx.calc.array_like(&element, None).map(|mut layout| {
+                // another random value
+                layout.randomization_seed = Hash64::new(0xc1325f37d127be22);
+                layout
+            }))?
         }
-        ty::Str => tcx.mk_layout(LayoutData {
-            variants: Variants::Single { index: FIRST_VARIANT },
-            fields: FieldsShape::Array { stride: Size::from_bytes(1), count: 0 },
-            backend_repr: BackendRepr::Memory { sized: false },
-            largest_niche: None,
-            uninhabited: false,
-            align: dl.i8_align,
-            size: Size::ZERO,
-            max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
-            // another random value
-            randomization_seed: Hash64::new(0xc1325f37d127be22),
-        }),
 
         // Odd unit types.
-        ty::FnDef(..) => univariant(IndexSlice::empty(), StructKind::AlwaysSized)?,
-        ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => {
-            let mut unit =
-                univariant_uninterned(cx, ty, IndexSlice::empty(), StructKind::AlwaysSized)?;
-            match unit.backend_repr {
-                BackendRepr::Memory { ref mut sized } => *sized = false,
-                _ => bug!(),
-            }
-            tcx.mk_layout(unit)
+        ty::FnDef(..) | ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => {
+            let sized = matches!(ty.kind(), ty::FnDef(..));
+            tcx.mk_layout(LayoutData::unit(cx, sized))
         }
 
         ty::Coroutine(def_id, args) => coroutine_layout(cx, ty, def_id, args)?,
@@ -545,11 +507,7 @@ fn layout_of_uncached<'tcx>(
                     return Err(error(cx, LayoutError::ReferencesError(guar)));
                 }
 
-                return Ok(tcx.mk_layout(
-                    cx.calc
-                        .layout_of_union(&def.repr(), &variants)
-                        .map_err(|err| map_error(cx, ty, err))?,
-                ));
+                return map_layout(cx.calc.layout_of_union(&def.repr(), &variants));
             }
 
             let get_discriminant_type =
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/layout.rs b/src/tools/rust-analyzer/crates/hir-ty/src/layout.rs
index 7af31dabe45..05f38cd09e2 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/layout.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/layout.rs
@@ -15,7 +15,7 @@ use hir_def::{
 use la_arena::{Idx, RawIdx};
 use rustc_abi::AddressSpace;
 use rustc_hashes::Hash64;
-use rustc_index::{IndexSlice, IndexVec};
+use rustc_index::IndexVec;
 
 use triomphe::Arc;
 
@@ -190,7 +190,8 @@ pub fn layout_of_ty_query(
     let dl = &*target;
     let cx = LayoutCx::new(dl);
     let ty = normalize(db, trait_env.clone(), ty);
-    let result = match ty.kind(Interner) {
+    let kind = ty.kind(Interner);
+    let result = match kind {
         TyKind::Adt(AdtId(def), subst) => {
             if let hir_def::AdtId::StructId(s) = def {
                 let data = db.struct_data(*s);
@@ -216,7 +217,7 @@ pub fn layout_of_ty_query(
                     valid_range: WrappingRange { start: 0, end: 0x10FFFF },
                 },
             ),
-            chalk_ir::Scalar::Int(i) => scalar(
+            chalk_ir::Scalar::Int(i) => Layout::scalar(dl, scalar_unit(
                 dl,
                 Primitive::Int(
                     match i {
@@ -229,8 +230,8 @@ pub fn layout_of_ty_query(
                     },
                     true,
                 ),
-            ),
-            chalk_ir::Scalar::Uint(i) => scalar(
+            )),
+            chalk_ir::Scalar::Uint(i) => Layout::scalar(dl, scalar_unit(
                 dl,
                 Primitive::Int(
                     match i {
@@ -243,8 +244,8 @@ pub fn layout_of_ty_query(
                     },
                     false,
                 ),
-            ),
-            chalk_ir::Scalar::Float(f) => scalar(
+            )),
+            chalk_ir::Scalar::Float(f) => Layout::scalar(dl, scalar_unit(
                 dl,
                 Primitive::Float(match f {
                     FloatTy::F16 => Float::F16,
@@ -252,7 +253,7 @@ pub fn layout_of_ty_query(
                     FloatTy::F64 => Float::F64,
                     FloatTy::F128 => Float::F128,
                 }),
-            ),
+            )),
         },
         TyKind::Tuple(len, tys) => {
             let kind = if *len == 0 { StructKind::AlwaysSized } else { StructKind::MaybeUnsized };
@@ -268,56 +269,16 @@ pub fn layout_of_ty_query(
         TyKind::Array(element, count) => {
             let count = try_const_usize(db, count).ok_or(LayoutError::HasErrorConst)? as u64;
             let element = db.layout_of_ty(element.clone(), trait_env)?;
-            let size = element
-                .size
-                .checked_mul(count, dl)
-                .ok_or(LayoutError::BadCalc(LayoutCalculatorError::SizeOverflow))?;
-
-            let backend_repr = BackendRepr::Memory { sized: true };
-
-            let largest_niche = if count != 0 { element.largest_niche } else { None };
-            let uninhabited = if count != 0 { element.uninhabited } else { false };
-
-            Layout {
-                variants: Variants::Single { index: struct_variant_idx() },
-                fields: FieldsShape::Array { stride: element.size, count },
-                backend_repr,
-                largest_niche,
-                uninhabited,
-                align: element.align,
-                size,
-                max_repr_align: None,
-                unadjusted_abi_align: element.align.abi,
-                randomization_seed: Hash64::ZERO,
-            }
+            cx.calc.array_like::<_, _, ()>(&element, Some(count))?
         }
         TyKind::Slice(element) => {
             let element = db.layout_of_ty(element.clone(), trait_env)?;
-            Layout {
-                variants: Variants::Single { index: struct_variant_idx() },
-                fields: FieldsShape::Array { stride: element.size, count: 0 },
-                backend_repr: BackendRepr::Memory { sized: false },
-                largest_niche: None,
-                uninhabited: false,
-                align: element.align,
-                size: Size::ZERO,
-                max_repr_align: None,
-                unadjusted_abi_align: element.align.abi,
-                randomization_seed: Hash64::ZERO,
-            }
+            cx.calc.array_like::<_, _, ()>(&element, None)?
+        }
+        TyKind::Str => {
+            let element = scalar_unit(dl, Primitive::Int(Integer::I8, false));
+            cx.calc.array_like::<_, _, ()>(&Layout::scalar(dl, element), None)?
         }
-        TyKind::Str => Layout {
-            variants: Variants::Single { index: struct_variant_idx() },
-            fields: FieldsShape::Array { stride: Size::from_bytes(1), count: 0 },
-            backend_repr: BackendRepr::Memory { sized: false },
-            largest_niche: None,
-            uninhabited: false,
-            align: dl.i8_align,
-            size: Size::ZERO,
-            max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
-            randomization_seed: Hash64::ZERO,
-        },
         // Potentially-wide pointers.
         TyKind::Ref(_, _, pointee) | TyKind::Raw(_, pointee) => {
             let mut data_ptr = scalar_unit(dl, Primitive::Pointer(AddressSpace::DATA));
@@ -355,17 +316,12 @@ pub fn layout_of_ty_query(
             };
 
             // Effectively a (ptr, meta) tuple.
-            cx.calc.scalar_pair(data_ptr, metadata)
+            LayoutData::scalar_pair(dl, data_ptr, metadata)
         }
-        TyKind::FnDef(_, _) => layout_of_unit(&cx)?,
-        TyKind::Never => cx.calc.layout_of_never_type(),
-        TyKind::Dyn(_) | TyKind::Foreign(_) => {
-            let mut unit = layout_of_unit(&cx)?;
-            match &mut unit.backend_repr {
-                BackendRepr::Memory { sized } => *sized = false,
-                _ => return Err(LayoutError::Unknown),
-            }
-            unit
+        TyKind::Never => LayoutData::never_type(dl),
+        TyKind::FnDef(..) | TyKind::Dyn(_) | TyKind::Foreign(_) => {
+            let sized = matches!(kind, TyKind::FnDef(..));
+            LayoutData::unit(dl, sized)
         }
         TyKind::Function(_) => {
             let mut ptr = scalar_unit(dl, Primitive::Pointer(dl.instruction_address_space));
@@ -434,16 +390,6 @@ pub fn layout_of_ty_recover(
     Err(LayoutError::RecursiveTypeWithoutIndirection)
 }
 
-fn layout_of_unit(cx: &LayoutCx<'_>) -> Result<Layout, LayoutError> {
-    cx.calc
-        .univariant::<RustcFieldIdx, RustcEnumVariantIdx, &&Layout>(
-            IndexSlice::empty(),
-            &ReprOptions::default(),
-            StructKind::AlwaysSized,
-        )
-        .map_err(Into::into)
-}
-
 fn struct_tail_erasing_lifetimes(db: &dyn HirDatabase, pointee: Ty) -> Ty {
     match pointee.kind(Interner) {
         TyKind::Adt(AdtId(hir_def::AdtId::StructId(i)), subst) => {
@@ -474,9 +420,5 @@ fn scalar_unit(dl: &TargetDataLayout, value: Primitive) -> Scalar {
     Scalar::Initialized { value, valid_range: WrappingRange::full(value.size(dl)) }
 }
 
-fn scalar(dl: &TargetDataLayout, value: Primitive) -> Layout {
-    Layout::scalar(dl, scalar_unit(dl, value))
-}
-
 #[cfg(test)]
 mod tests;