Auto merge of #88499 - eddyb:layout-off, r=nagisa

Provide `layout_of` automatically (given tcx + param_env + error handling).

After #88337, there's no longer any uses of `LayoutOf` within `rustc_target` itself, so I realized I could move the trait to `rustc_middle::ty::layout` and redesign it a bit.

This is similar to #88338 (and supersedes it), but at no ergonomic loss, since there's no funky `C: LayoutOf<Ty = Ty>` -> `Ty: TyAbiInterface<C>` generic `impl` chain, and each `LayoutOf` still corresponds to one `impl` (of `LayoutOfHelpers`) for the specific context.

After this PR, this is what's needed to get `trait LayoutOf` (with the `layout_of` method) implemented on some context type:
* `TyCtxt`, via `HasTyCtxt`
* `ParamEnv`, via `HasParamEnv`
* a way to transform `LayoutError`s into the desired error type
  * an error type of `!` can be paired with having `cx.layout_of(...)` return `TyAndLayout` *without* `Result<...>` around it, such as used by codegen
  * this is done through a new `LayoutOfHelpers` trait (and so is specifying the type of `cx.layout_of(...)`)

When going through this path (and not bypassing it with a manual `impl` of `LayoutOf`), the end result is that only the error case can be customized, the query itself and the success paths are guaranteed to be uniform.

(**EDIT**: just noticed that because of the supertrait relationship, you cannot actually implement `LayoutOf` yourself, the blanket `impl` fully covers all possible context types that could ever implement it)

Part of the motivation for this shape of API is that I've been working on querifying `FnAbi::of_*`, and what I want/need to introduce for that looks a lot like the setup in this PR - in particular, it's harder to express the `FnAbi` methods in `rustc_target`, since they're much more tied to `rustc` concepts.

r? `@nagisa` cc `@oli-obk` `@bjorn3`

compiler/rustc_codegen_llvm/src/abi.rs

@@ -11,11 +11,12 @@ use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::MemFlags;
 use rustc_middle::bug;
+use rustc_middle::ty::layout::LayoutOf;
 pub use rustc_middle::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
 use rustc_middle::ty::Ty;
 use rustc_target::abi::call::ArgAbi;
 pub use rustc_target::abi::call::*;
-use rustc_target::abi::{self, HasDataLayout, Int, LayoutOf};
+use rustc_target::abi::{self, HasDataLayout, Int};
 pub use rustc_target::spec::abi::Abi;
 
 use libc::c_uint;

compiler/rustc_codegen_llvm/src/builder.rs

@@ -15,7 +15,7 @@ use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::MemFlags;
 use rustc_data_structures::small_c_str::SmallCStr;
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::layout::TyAndLayout;
+use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
 use rustc_target::abi::{self, Align, Size};
@@ -88,12 +88,12 @@ impl HasTargetSpec for Builder<'_, '_, 'tcx> {
     }
 }
 
-impl abi::LayoutOf<'tcx> for Builder<'_, '_, 'tcx> {
-    type Ty = Ty<'tcx>;
-    type TyAndLayout = TyAndLayout<'tcx>;
+impl LayoutOfHelpers<'tcx> for Builder<'_, '_, 'tcx> {
+    type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyAndLayout {
-        self.cx.layout_of(ty)
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
+        self.cx.handle_layout_err(err, span, ty)
     }
 }
 

compiler/rustc_codegen_llvm/src/common.rs

@@ -12,9 +12,10 @@ use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::bug;
 use rustc_middle::mir::interpret::{Allocation, GlobalAlloc, Scalar};
-use rustc_middle::ty::{layout::TyAndLayout, ScalarInt};
+use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::ScalarInt;
 use rustc_span::symbol::Symbol;
-use rustc_target::abi::{self, AddressSpace, HasDataLayout, LayoutOf, Pointer, Size};
+use rustc_target::abi::{self, AddressSpace, HasDataLayout, Pointer, Size};
 
 use libc::{c_char, c_uint};
 use tracing::debug;

compiler/rustc_codegen_llvm/src/consts.rs

@@ -15,10 +15,11 @@ use rustc_middle::mir::interpret::{
     Scalar as InterpScalar,
 };
 use rustc_middle::mir::mono::MonoItem;
+use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, Instance, Ty};
 use rustc_middle::{bug, span_bug};
 use rustc_target::abi::{
-    AddressSpace, Align, HasDataLayout, LayoutOf, Primitive, Scalar, Size, WrappingRange,
+    AddressSpace, Align, HasDataLayout, Primitive, Scalar, Size, WrappingRange,
 };
 use std::ops::Range;
 use tracing::debug;

compiler/rustc_codegen_llvm/src/context.rs

@@ -14,15 +14,15 @@ use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::base_n;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::small_c_str::SmallCStr;
-use rustc_middle::bug;
 use rustc_middle::mir::mono::CodegenUnit;
-use rustc_middle::ty::layout::{HasParamEnv, LayoutError, TyAndLayout};
+use rustc_middle::ty::layout::{HasParamEnv, LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
+use rustc_middle::{bug, span_bug};
 use rustc_session::config::{CFGuard, CrateType, DebugInfo};
 use rustc_session::Session;
-use rustc_span::source_map::{Span, DUMMY_SP};
+use rustc_span::source_map::Span;
 use rustc_span::symbol::Symbol;
-use rustc_target::abi::{HasDataLayout, LayoutOf, PointeeInfo, Size, TargetDataLayout, VariantIdx};
+use rustc_target::abi::{HasDataLayout, PointeeInfo, Size, TargetDataLayout, VariantIdx};
 use rustc_target::spec::{HasTargetSpec, RelocModel, Target, TlsModel};
 use smallvec::SmallVec;
 
@@ -835,22 +835,16 @@ impl ty::layout::HasTyCtxt<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 }
 
-impl LayoutOf<'tcx> for CodegenCx<'ll, 'tcx> {
-    type Ty = Ty<'tcx>;
-    type TyAndLayout = TyAndLayout<'tcx>;
+impl LayoutOfHelpers<'tcx> for CodegenCx<'ll, 'tcx> {
+    type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyAndLayout {
-        self.spanned_layout_of(ty, DUMMY_SP)
-    }
-
-    fn spanned_layout_of(&self, ty: Ty<'tcx>, span: Span) -> Self::TyAndLayout {
-        self.tcx.layout_of(ty::ParamEnv::reveal_all().and(ty)).unwrap_or_else(|e| {
-            if let LayoutError::SizeOverflow(_) = e {
-                self.sess().span_fatal(span, &e.to_string())
-            } else {
-                bug!("failed to get layout for `{}`: {}", ty, e)
-            }
-        })
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
+        if let LayoutError::SizeOverflow(_) = err {
+            self.sess().span_fatal(span, &err.to_string())
+        } else {
+            span_bug!(span, "failed to get layout for `{}`: {}", ty, err)
+        }
     }
 }
 

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -28,7 +28,7 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::ich::NodeIdHashingMode;
 use rustc_middle::mir::{self, GeneratorLayout};
-use rustc_middle::ty::layout::{self, IntegerExt, PrimitiveExt, TyAndLayout};
+use rustc_middle::ty::layout::{self, IntegerExt, LayoutOf, PrimitiveExt, TyAndLayout};
 use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::{self, AdtKind, GeneratorSubsts, ParamEnv, Ty, TyCtxt};
@@ -37,7 +37,7 @@ use rustc_session::config::{self, DebugInfo};
 use rustc_span::symbol::{Interner, Symbol};
 use rustc_span::FileNameDisplayPreference;
 use rustc_span::{self, SourceFile, SourceFileHash, Span};
-use rustc_target::abi::{Abi, Align, HasDataLayout, Integer, LayoutOf, TagEncoding};
+use rustc_target::abi::{Abi, Align, HasDataLayout, Integer, TagEncoding};
 use rustc_target::abi::{Int, Pointer, F32, F64};
 use rustc_target::abi::{Primitive, Size, VariantIdx, Variants};
 use tracing::debug;

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -25,14 +25,14 @@ use rustc_data_structures::sync::Lrc;
 use rustc_hir::def_id::{DefId, DefIdMap};
 use rustc_index::vec::IndexVec;
 use rustc_middle::mir;
-use rustc_middle::ty::layout::HasTyCtxt;
+use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::{self, Instance, ParamEnv, Ty, TypeFoldable};
 use rustc_session::config::{self, DebugInfo};
 use rustc_session::Session;
 use rustc_span::symbol::Symbol;
 use rustc_span::{self, BytePos, Pos, SourceFile, SourceFileAndLine, Span};
-use rustc_target::abi::{LayoutOf, Primitive, Size};
+use rustc_target::abi::{Primitive, Size};
 
 use libc::c_uint;
 use smallvec::SmallVec;

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -15,11 +15,11 @@ use rustc_codegen_ssa::mir::operand::OperandRef;
 use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::traits::*;
 use rustc_hir as hir;
-use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
+use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt, LayoutOf};
 use rustc_middle::ty::{self, Ty};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{sym, symbol::kw, Span, Symbol};
-use rustc_target::abi::{self, HasDataLayout, LayoutOf, Primitive};
+use rustc_target::abi::{self, HasDataLayout, Primitive};
 use rustc_target::spec::PanicStrategy;
 
 use std::cmp::Ordering;

compiler/rustc_codegen_llvm/src/mono_item.rs

@@ -8,10 +8,9 @@ use rustc_codegen_ssa::traits::*;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 pub use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::mir::mono::{Linkage, Visibility};
-use rustc_middle::ty::layout::FnAbiExt;
+use rustc_middle::ty::layout::{FnAbiExt, LayoutOf};
 use rustc_middle::ty::{self, Instance, TypeFoldable};
 use rustc_session::config::CrateType;
-use rustc_target::abi::LayoutOf;
 use rustc_target::spec::RelocModel;
 use tracing::debug;
 

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -4,12 +4,12 @@ use crate::context::TypeLowering;
 use crate::type_::Type;
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::bug;
-use rustc_middle::ty::layout::{FnAbiExt, TyAndLayout};
+use rustc_middle::ty::layout::{FnAbiExt, LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, Ty, TypeFoldable};
 use rustc_target::abi::{Abi, AddressSpace, Align, FieldsShape};
 use rustc_target::abi::{Int, Pointer, F32, F64};
-use rustc_target::abi::{LayoutOf, PointeeInfo, Scalar, Size, TyAbiInterface, Variants};
+use rustc_target::abi::{PointeeInfo, Scalar, Size, TyAbiInterface, Variants};
 use smallvec::{smallvec, SmallVec};
 use tracing::debug;
 

compiler/rustc_codegen_llvm/src/va_arg.rs

@@ -7,9 +7,9 @@ use rustc_codegen_ssa::{
     common::IntPredicate,
     traits::{BaseTypeMethods, BuilderMethods, ConstMethods, DerivedTypeMethods},
 };
-use rustc_middle::ty::layout::HasTyCtxt;
+use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::Ty;
-use rustc_target::abi::{Align, Endian, HasDataLayout, LayoutOf, Size};
+use rustc_target::abi::{Align, Endian, HasDataLayout, Size};
 
 fn round_pointer_up_to_alignment(
     bx: &mut Builder<'a, 'll, 'tcx>,