ty::layout: implement layout_of automatically as a default method.

Author: eddyb

compiler/rustc_codegen_cranelift/src/common.rs

@@ -1,4 +1,5 @@
 use rustc_index::vec::IndexVec;
+use rustc_middle::ty::layout::LayoutError;
 use rustc_middle::ty::SymbolName;
 use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::{Integer, Primitive};
@@ -259,8 +260,9 @@ pub(crate) struct FunctionCx<'m, 'clif, 'tcx: 'm> {
 impl<'tcx> LayoutOf<'tcx> for FunctionCx<'_, '_, 'tcx> {
     type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> TyAndLayout<'tcx> {
-        RevealAllLayoutCx(self.tcx).layout_of(ty)
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
+        RevealAllLayoutCx(self.tcx).handle_layout_err(err, span, ty)
     }
 }
 
@@ -366,15 +368,13 @@ pub(crate) struct RevealAllLayoutCx<'tcx>(pub(crate) TyCtxt<'tcx>);
 impl<'tcx> LayoutOf<'tcx> for RevealAllLayoutCx<'tcx> {
     type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> TyAndLayout<'tcx> {
-        assert!(!ty.still_further_specializable());
-        self.0.layout_of(ParamEnv::reveal_all().and(&ty)).unwrap_or_else(|e| {
-            if let layout::LayoutError::SizeOverflow(_) = e {
-                self.0.sess.fatal(&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 layout::LayoutError::SizeOverflow(_) = err {
+            self.0.sess.span_fatal(span, &err.to_string())
+        } else {
+            span_bug!(span, "failed to get layout for `{}`: {}", ty, err)
+        }
     }
 }
 

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::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{LayoutError, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
 use rustc_target::abi::{self, Align, Size};
@@ -91,8 +91,9 @@ impl HasTargetSpec for Builder<'_, '_, 'tcx> {
 impl LayoutOf<'tcx> for Builder<'_, '_, 'tcx> {
     type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        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/context.rs

@@ -14,13 +14,13 @@ 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, LayoutOf, 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, PointeeInfo, Size, TargetDataLayout, VariantIdx};
 use rustc_target::spec::{HasTargetSpec, RelocModel, Target, TlsModel};
@@ -838,18 +838,13 @@ impl ty::layout::HasTyCtxt<'tcx> for CodegenCx<'ll, 'tcx> {
 impl LayoutOf<'tcx> for CodegenCx<'ll, 'tcx> {
     type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.spanned_layout_of(ty, DUMMY_SP)
-    }
-
-    fn spanned_layout_of(&self, ty: Ty<'tcx>, span: Span) -> Self::LayoutOfResult {
-        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_lint/src/context.rs

@@ -1083,8 +1083,9 @@ impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
 impl<'tcx> LayoutOf<'tcx> for LateContext<'tcx> {
     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.tcx.layout_of(self.param_env.and(ty))
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
+        err
     }
 }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -2095,35 +2095,74 @@ pub type TyAndLayout<'tcx> = rustc_target::abi::TyAndLayout<'tcx, Ty<'tcx>>;
 
 /// Trait for contexts that can compute layouts of types.
 pub trait LayoutOf<'tcx>: HasDataLayout + HasTyCtxt<'tcx> + HasParamEnv<'tcx> {
+    /// The `TyAndLayout`-wrapping type (or `TyAndLayout` itself), which will be
+    /// returned from `layout_of` (see also `handle_layout_err`).
     type LayoutOfResult: MaybeResult<TyAndLayout<'tcx>>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult;
+    /// `Span` to use for `tcx.at(span)`, from `layout_of`.
+    // FIXME(eddyb) perhaps make this mandatory to get contexts to track it better?
+    #[inline]
+    fn layout_tcx_at_span(&self) -> Span {
+        DUMMY_SP
+    }
+
+    /// Helper used for `layout_of`, to adapt `tcx.layout_of(...)` into a
+    /// `Self::LayoutOfResult` (which does not need to be a `Result<...>`).
+    ///
+    /// Most `impl`s, which propagate `LayoutError`s, should simply return `err`,
+    /// but this hook allows e.g. codegen to return only `TyAndLayout` from its
+    /// `cx.layout_of(...)`, without any `Result<...>` around it to deal with
+    /// (and any `LayoutError`s are turned into fatal errors or ICEs).
+    fn handle_layout_err(
+        &self,
+        err: LayoutError<'tcx>,
+        span: Span,
+        ty: Ty<'tcx>,
+    ) -> <Self::LayoutOfResult as MaybeResult<TyAndLayout<'tcx>>>::Error;
+
+    /// Computes the layout of a type. Note that this implicitly
+    /// executes in "reveal all" mode, and will normalize the input type.
+    #[inline]
+    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
+        self.spanned_layout_of(ty, DUMMY_SP)
+    }
+
+    /// Computes the layout of a type, at `span`. Note that this implicitly
+    /// executes in "reveal all" mode, and will normalize the input type.
     // FIXME(eddyb) avoid passing information like this, and instead add more
     // `TyCtxt::at`-like APIs to be able to do e.g. `cx.at(span).layout_of(ty)`.
-    fn spanned_layout_of(&self, ty: Ty<'tcx>, _span: Span) -> Self::LayoutOfResult {
-        self.layout_of(ty)
+    #[inline]
+    fn spanned_layout_of(&self, ty: Ty<'tcx>, span: Span) -> Self::LayoutOfResult {
+        let span = if !span.is_dummy() { span } else { self.layout_tcx_at_span() };
+        MaybeResult::from(
+            self.tcx()
+                .at(span)
+                .layout_of(self.param_env().and(ty))
+                .map_err(|err| self.handle_layout_err(err, span, ty)),
+        )
     }
 }
 
 impl LayoutOf<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 
-    /// Computes the layout of a type. Note that this implicitly
-    /// executes in "reveal all" mode, and will normalize the input type.
     #[inline]
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.tcx.layout_of(self.param_env.and(ty))
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
+        err
     }
 }
 
 impl LayoutOf<'tcx> for LayoutCx<'tcx, ty::query::TyCtxtAt<'tcx>> {
     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 
-    /// Computes the layout of a type. Note that this implicitly
-    /// executes in "reveal all" mode, and will normalize the input type.
     #[inline]
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.tcx.layout_of(self.param_env.and(ty))
+    fn layout_tcx_at_span(&self) -> Span {
+        self.tcx.span
+    }
+
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
+        err
     }
 }
 

compiler/rustc_mir/src/interpret/eval_context.rs

@@ -8,7 +8,7 @@ use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use rustc_middle::ich::StableHashingContext;
 use rustc_middle::mir;
-use rustc_middle::ty::layout::{self, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{self, LayoutError, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{
     self, query::TyCtxtAt, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable,
 };
@@ -17,9 +17,9 @@ use rustc_span::{Pos, Span};
 use rustc_target::abi::{Align, HasDataLayout, Size, TargetDataLayout};
 
 use super::{
-    AllocId, GlobalId, Immediate, InterpResult, MPlaceTy, Machine, MemPlace, MemPlaceMeta, Memory,
-    MemoryKind, Operand, Place, PlaceTy, Pointer, Provenance, Scalar, ScalarMaybeUninit,
-    StackPopJump,
+    AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine, MemPlace,
+    MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, Pointer, Provenance, Scalar,
+    ScalarMaybeUninit, StackPopJump,
 };
 use crate::transform::validate::equal_up_to_regions;
 use crate::util::storage::AlwaysLiveLocals;
@@ -316,10 +316,18 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> LayoutOf<'tcx> for InterpCx<'mir,
     type LayoutOfResult = InterpResult<'tcx, TyAndLayout<'tcx>>;
 
     #[inline]
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.tcx
-            .layout_of(self.param_env.and(ty))
-            .map_err(|layout| err_inval!(Layout(layout)).into())
+    fn layout_tcx_at_span(&self) -> Span {
+        self.tcx.span
+    }
+
+    #[inline]
+    fn handle_layout_err(
+        &self,
+        err: LayoutError<'tcx>,
+        _: Span,
+        _: Ty<'tcx>,
+    ) -> InterpErrorInfo<'tcx> {
+        err_inval!(Layout(err)).into()
     }
 }
 

compiler/rustc_mir/src/transform/const_prop.rs

@@ -333,8 +333,9 @@ struct ConstPropagator<'mir, 'tcx> {
 impl<'mir, 'tcx> LayoutOf<'tcx> for ConstPropagator<'mir, 'tcx> {
     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.tcx.layout_of(self.param_env.and(ty))
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
+        err
     }
 }
 

compiler/rustc_passes/src/layout_test.rs

@@ -3,9 +3,10 @@ use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_hir::ItemKind;
-use rustc_middle::ty::layout::{HasParamEnv, HasTyCtxt, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{HasParamEnv, HasTyCtxt, LayoutError, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
 use rustc_span::symbol::sym;
+use rustc_span::Span;
 use rustc_target::abi::{HasDataLayout, TargetDataLayout};
 
 pub fn test_layout(tcx: TyCtxt<'_>) {
@@ -116,8 +117,13 @@ struct UnwrapLayoutCx<'tcx> {
 impl LayoutOf<'tcx> for UnwrapLayoutCx<'tcx> {
     type LayoutOfResult = TyAndLayout<'tcx>;
 
-    fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
-        self.tcx.layout_of(self.param_env.and(ty)).unwrap()
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
+        span_bug!(
+            span,
+            "`#[rustc_layout(..)]` test resulted in `layout_of({}) = Err({})`",
+            ty,
+            err
+        );
     }
 }