Auto merge of rust-lang#111035 - Nilstrieb:layout-err, r=wesleywiser

Shrink error variants for layout and fn_abi

The errors are bigger than the result, so let's put them behind a reference. Since query results have to be `Copy`, we use a reference into the arena instead of a `Box<T>`.

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -72,7 +72,7 @@ pub(crate) fn eval_nullary_intrinsic<'tcx>(
         }
         sym::pref_align_of => {
             // Correctly handles non-monomorphic calls, so there is no need for ensure_monomorphic_enough.
-            let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(e)))?;
+            let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(*e)))?;
             ConstValue::from_target_usize(layout.align.pref.bytes(), &tcx)
         }
         sym::type_id => {

compiler/rustc_const_eval/src/util/check_validity_requirement.rs

@@ -21,7 +21,7 @@ pub fn check_validity_requirement<'tcx>(
     tcx: TyCtxt<'tcx>,
     kind: ValidityRequirement,
     param_env_and_ty: ParamEnvAnd<'tcx, Ty<'tcx>>,
-) -> Result<bool, LayoutError<'tcx>> {
+) -> Result<bool, &'tcx LayoutError<'tcx>> {
     let layout = tcx.layout_of(param_env_and_ty)?;
 
     // There is nothing strict or lax about inhabitedness.
@@ -43,7 +43,7 @@ fn might_permit_raw_init_strict<'tcx>(
     ty: TyAndLayout<'tcx>,
     tcx: TyCtxt<'tcx>,
     kind: ValidityRequirement,
-) -> Result<bool, LayoutError<'tcx>> {
+) -> Result<bool, &'tcx LayoutError<'tcx>> {
     let machine = CompileTimeInterpreter::new(CanAccessStatics::No, CheckAlignment::Error);
 
     let mut cx = InterpCx::new(tcx, rustc_span::DUMMY_SP, ParamEnv::reveal_all(), machine);
@@ -75,7 +75,7 @@ fn might_permit_raw_init_lax<'tcx>(
     this: TyAndLayout<'tcx>,
     cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
     init_kind: ValidityRequirement,
-) -> Result<bool, LayoutError<'tcx>> {
+) -> Result<bool, &'tcx LayoutError<'tcx>> {
     let scalar_allows_raw_init = move |s: Scalar| -> bool {
         match init_kind {
             ValidityRequirement::Inhabited => {

compiler/rustc_hir_typeck/src/intrinsicck.rs

@@ -81,7 +81,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         // Try to display a sensible error with as much information as possible.
-        let skeleton_string = |ty: Ty<'tcx>, sk| match sk {
+        let skeleton_string = |ty: Ty<'tcx>, sk: Result<_, &_>| match sk {
             Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
             Ok(SizeSkeleton::Known(size)) => {
                 if let Some(v) = u128::from(size.bytes()).checked_mul(8) {
@@ -101,7 +101,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
             Err(LayoutError::Unknown(bad)) => {
-                if bad == ty {
+                if *bad == ty {
                     "this type does not have a fixed size".to_owned()
                 } else {
                     format!("size can vary because of {bad}")

compiler/rustc_middle/src/query/erase.rs

@@ -71,8 +71,8 @@ impl<T> EraseType for Result<&'_ T, traits::CodegenObligationError> {
     type Result = [u8; size_of::<Result<&'static (), traits::CodegenObligationError>>()];
 }
 
-impl<T> EraseType for Result<&'_ T, ty::layout::FnAbiError<'_>> {
-    type Result = [u8; size_of::<Result<&'static (), ty::layout::FnAbiError<'static>>>()];
+impl<T> EraseType for Result<&'_ T, &'_ ty::layout::FnAbiError<'_>> {
+    type Result = [u8; size_of::<Result<&'static (), &'static ty::layout::FnAbiError<'static>>>()];
 }
 
 impl<T> EraseType for Result<(&'_ T, rustc_middle::thir::ExprId), rustc_errors::ErrorGuaranteed> {
@@ -96,15 +96,17 @@ impl EraseType for Result<ty::GenericArg<'_>, traits::query::NoSolution> {
     type Result = [u8; size_of::<Result<ty::GenericArg<'static>, traits::query::NoSolution>>()];
 }
 
-impl EraseType for Result<bool, ty::layout::LayoutError<'_>> {
-    type Result = [u8; size_of::<Result<bool, ty::layout::LayoutError<'static>>>()];
+impl EraseType for Result<bool, &ty::layout::LayoutError<'_>> {
+    type Result = [u8; size_of::<Result<bool, &'static ty::layout::LayoutError<'static>>>()];
 }
 
-impl EraseType for Result<rustc_target::abi::TyAndLayout<'_, Ty<'_>>, ty::layout::LayoutError<'_>> {
+impl EraseType
+    for Result<rustc_target::abi::TyAndLayout<'_, Ty<'_>>, &ty::layout::LayoutError<'_>>
+{
     type Result = [u8; size_of::<
         Result<
             rustc_target::abi::TyAndLayout<'static, Ty<'static>>,
-            ty::layout::LayoutError<'static>,
+            &'static ty::layout::LayoutError<'static>,
         >,
     >()];
 }

compiler/rustc_middle/src/query/mod.rs

@@ -1383,7 +1383,7 @@ rustc_queries! {
     /// executes in "reveal all" mode, and will normalize the input type.
     query layout_of(
         key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>
-    ) -> Result<ty::layout::TyAndLayout<'tcx>, ty::layout::LayoutError<'tcx>> {
+    ) -> Result<ty::layout::TyAndLayout<'tcx>, &'tcx ty::layout::LayoutError<'tcx>> {
         depth_limit
         desc { "computing layout of `{}`", key.value }
     }
@@ -1394,7 +1394,7 @@ rustc_queries! {
     /// instead, where the instance is an `InstanceDef::Virtual`.
     query fn_abi_of_fn_ptr(
         key: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>
-    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, ty::layout::FnAbiError<'tcx>> {
+    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, &'tcx ty::layout::FnAbiError<'tcx>> {
         desc { "computing call ABI of `{}` function pointers", key.value.0 }
     }
 
@@ -1405,7 +1405,7 @@ rustc_queries! {
     /// to an `InstanceDef::Virtual` instance (of `<dyn Trait as Trait>::fn`).
     query fn_abi_of_instance(
         key: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>
-    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, ty::layout::FnAbiError<'tcx>> {
+    ) -> Result<&'tcx abi::call::FnAbi<'tcx, Ty<'tcx>>, &'tcx ty::layout::FnAbiError<'tcx>> {
         desc { "computing call ABI of `{}`", key.value.0 }
     }
 
@@ -2164,7 +2164,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query check_validity_requirement(key: (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>)) -> Result<bool, ty::layout::LayoutError<'tcx>> {
+    query check_validity_requirement(key: (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>)) -> Result<bool, &'tcx ty::layout::LayoutError<'tcx>> {
         desc { "checking validity requirement for `{}`: {}", key.1.value, key.0 }
     }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -310,7 +310,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
         ty: Ty<'tcx>,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-    ) -> Result<SizeSkeleton<'tcx>, LayoutError<'tcx>> {
+    ) -> Result<SizeSkeleton<'tcx>, &'tcx LayoutError<'tcx>> {
         debug_assert!(!ty.has_non_region_infer());
 
         // First try computing a static layout.
@@ -353,21 +353,21 @@ impl<'tcx> SizeSkeleton<'tcx> {
                             let size = s
                                 .bytes()
                                 .checked_mul(c)
-                                .ok_or_else(|| LayoutError::SizeOverflow(ty))?;
+                                .ok_or_else(|| &*tcx.arena.alloc(LayoutError::SizeOverflow(ty)))?;
                             return Ok(SizeSkeleton::Known(Size::from_bytes(size)));
                         }
                         let len = tcx.expand_abstract_consts(len);
                         let prev = ty::Const::from_target_usize(tcx, s.bytes());
                         let Some(gen_size) = mul_sorted_consts(tcx, param_env, len, prev) else {
-                            return Err(LayoutError::SizeOverflow(ty));
+                            return Err(tcx.arena.alloc(LayoutError::SizeOverflow(ty)));
                         };
                         Ok(SizeSkeleton::Generic(gen_size))
                     }
                     SizeSkeleton::Pointer { .. } => Err(err),
                     SizeSkeleton::Generic(g) => {
                         let len = tcx.expand_abstract_consts(len);
                         let Some(gen_size) = mul_sorted_consts(tcx, param_env, len, g) else {
-                            return Err(LayoutError::SizeOverflow(ty));
+                            return Err(tcx.arena.alloc(LayoutError::SizeOverflow(ty)));
                         };
                         Ok(SizeSkeleton::Generic(gen_size))
                     }
@@ -672,33 +672,43 @@ pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
 
         MaybeResult::from(
             tcx.layout_of(self.param_env().and(ty))
-                .map_err(|err| self.handle_layout_err(err, span, ty)),
+                .map_err(|err| self.handle_layout_err(*err, span, ty)),
         )
     }
 }
 
 impl<'tcx, C: LayoutOfHelpers<'tcx>> LayoutOf<'tcx> for C {}
 
 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
-    type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
+    type LayoutOfResult = Result<TyAndLayout<'tcx>, &'tcx LayoutError<'tcx>>;
 
     #[inline]
-    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
-        err
+    fn handle_layout_err(
+        &self,
+        err: LayoutError<'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>, LayoutError<'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>) -> LayoutError<'tcx> {
-        err
+    fn handle_layout_err(
+        &self,
+        err: LayoutError<'tcx>,
+        _: Span,
+        _: Ty<'tcx>,
+    ) -> &'tcx LayoutError<'tcx> {
+        self.tcx.arena.alloc(err)
     }
 }
 
@@ -1250,18 +1260,6 @@ pub enum FnAbiError<'tcx> {
     AdjustForForeignAbi(call::AdjustForForeignAbiError),
 }
 
-impl<'tcx> From<LayoutError<'tcx>> for FnAbiError<'tcx> {
-    fn from(err: LayoutError<'tcx>) -> Self {
-        Self::Layout(err)
-    }
-}
-
-impl From<call::AdjustForForeignAbiError> for FnAbiError<'_> {
-    fn from(err: call::AdjustForForeignAbiError) -> Self {
-        Self::AdjustForForeignAbi(err)
-    }
-}
-
 impl<'a, 'b> IntoDiagnostic<'a, !> for FnAbiError<'b> {
     fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, !> {
         match self {
@@ -1321,7 +1319,7 @@ pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
         let tcx = self.tcx().at(span);
 
         MaybeResult::from(tcx.fn_abi_of_fn_ptr(self.param_env().and((sig, extra_args))).map_err(
-            |err| self.handle_fn_abi_err(err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
+            |err| self.handle_fn_abi_err(*err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
         ))
     }
 
@@ -1348,7 +1346,11 @@ pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
                 // However, we don't do this early in order to avoid calling
                 // `def_span` unconditionally (which may have a perf penalty).
                 let span = if !span.is_dummy() { span } else { tcx.def_span(instance.def_id()) };
-                self.handle_fn_abi_err(err, span, FnAbiRequest::OfInstance { instance, extra_args })
+                self.handle_fn_abi_err(
+                    *err,
+                    span,
+                    FnAbiRequest::OfInstance { instance, extra_args },
+                )
             }),
         )
     }

compiler/rustc_middle/src/values.rs

@@ -106,9 +106,12 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::EarlyBinder<ty::Binder<'_, ty::F
     }
 }
 
-impl<'tcx, T> Value<TyCtxt<'tcx>, DepKind> for Result<T, ty::layout::LayoutError<'_>> {
+impl<'tcx, T> Value<TyCtxt<'tcx>, DepKind> for Result<T, &'_ ty::layout::LayoutError<'_>> {
     fn from_cycle_error(_tcx: TyCtxt<'tcx>, _cycle: &[QueryInfo<DepKind>]) -> Self {
-        Err(ty::layout::LayoutError::Cycle)
+        // tcx.arena.alloc cannot be used because we are not allowed to use &'tcx LayoutError under
+        // min_specialization. Since this is an error path anyways, leaking doesn't matter (and really,
+        // tcx.arena.alloc is pretty much equal to leaking).
+        Err(Box::leak(Box::new(ty::layout::LayoutError::Cycle)))
     }
 }
 

compiler/rustc_passes/src/layout_test.rs

@@ -94,6 +94,7 @@ fn dump_layout_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
         Err(layout_error) => {
             tcx.sess.emit_fatal(Spanned {
                 node: layout_error.into_diagnostic(),
+
                 span: tcx.def_span(item_def_id.to_def_id()),
             });
         }

compiler/rustc_transmute/src/layout/tree.rs

@@ -192,8 +192,8 @@ pub(crate) mod rustc {
         TypeError(ErrorGuaranteed),
     }
 
-    impl<'tcx> From<LayoutError<'tcx>> for Err {
-        fn from(err: LayoutError<'tcx>) -> Self {
+    impl<'tcx> From<&LayoutError<'tcx>> for Err {
+        fn from(err: &LayoutError<'tcx>) -> Self {
             match err {
                 LayoutError::Unknown(..) => Self::UnknownLayout,
                 err => unimplemented!("{:?}", err),
@@ -221,7 +221,7 @@ pub(crate) mod rustc {
     }
 
     impl LayoutSummary {
-        fn from_ty<'tcx>(ty: Ty<'tcx>, ctx: TyCtxt<'tcx>) -> Result<Self, LayoutError<'tcx>> {
+        fn from_ty<'tcx>(ty: Ty<'tcx>, ctx: TyCtxt<'tcx>) -> Result<Self, &'tcx LayoutError<'tcx>> {
             use rustc_middle::ty::ParamEnvAnd;
             use rustc_target::abi::{TyAndLayout, Variants};
 
@@ -482,7 +482,7 @@ pub(crate) mod rustc {
     fn layout_of<'tcx>(
         ctx: TyCtxt<'tcx>,
         ty: Ty<'tcx>,
-    ) -> Result<alloc::Layout, LayoutError<'tcx>> {
+    ) -> Result<alloc::Layout, &'tcx LayoutError<'tcx>> {
         use rustc_middle::ty::ParamEnvAnd;
         use rustc_target::abi::TyAndLayout;
 

compiler/rustc_ty_utils/src/abi.rs

@@ -202,7 +202,7 @@ fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: SpecAbi) -> Conv {
 fn fn_abi_of_fn_ptr<'tcx>(
     tcx: TyCtxt<'tcx>,
     query: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
-) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
+) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {
     let (param_env, (sig, extra_args)) = query.into_parts();
 
     let cx = LayoutCx { tcx, param_env };
@@ -212,7 +212,7 @@ fn fn_abi_of_fn_ptr<'tcx>(
 fn fn_abi_of_instance<'tcx>(
     tcx: TyCtxt<'tcx>,
     query: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
-) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
+) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {
     let (param_env, (instance, extra_args)) = query.into_parts();
 
     let sig = fn_sig_for_fn_abi(tcx, instance, param_env);
@@ -331,7 +331,7 @@ fn fn_abi_new_uncached<'tcx>(
     fn_def_id: Option<DefId>,
     // FIXME(eddyb) replace this with something typed, like an `enum`.
     force_thin_self_ptr: bool,
-) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
+) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> {
     let sig = cx.tcx.normalize_erasing_late_bound_regions(cx.param_env, sig);
 
     let conv = conv_from_spec_abi(cx.tcx(), sig.abi);
@@ -376,7 +376,7 @@ fn fn_abi_new_uncached<'tcx>(
     let is_drop_in_place =
         fn_def_id.is_some() && fn_def_id == cx.tcx.lang_items().drop_in_place_fn();
 
-    let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, FnAbiError<'tcx>> {
+    let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, &'tcx FnAbiError<'tcx>> {
         let span = tracing::debug_span!("arg_of");
         let _entered = span.enter();
         let is_return = arg_idx.is_none();
@@ -386,7 +386,8 @@ fn fn_abi_new_uncached<'tcx>(
             _ => bug!("argument to drop_in_place is not a raw ptr: {:?}", ty),
         });
 
-        let layout = cx.layout_of(ty)?;
+        let layout =
+            cx.layout_of(ty).map_err(|err| &*cx.tcx.arena.alloc(FnAbiError::Layout(*err)))?;
         let layout = if force_thin_self_ptr && arg_idx == Some(0) {
             // Don't pass the vtable, it's not an argument of the virtual fn.
             // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`
@@ -454,7 +455,7 @@ fn fn_abi_adjust_for_abi<'tcx>(
     fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,
     abi: SpecAbi,
     fn_def_id: Option<DefId>,
-) -> Result<(), FnAbiError<'tcx>> {
+) -> Result<(), &'tcx FnAbiError<'tcx>> {
     if abi == SpecAbi::Unadjusted {
         return Ok(());
     }
@@ -548,7 +549,9 @@ fn fn_abi_adjust_for_abi<'tcx>(
             fixup(arg, Some(arg_idx));
         }
     } else {
-        fn_abi.adjust_for_foreign_abi(cx, abi)?;
+        fn_abi
+            .adjust_for_foreign_abi(cx, abi)
+            .map_err(|err| &*cx.tcx.arena.alloc(FnAbiError::AdjustForForeignAbi(err)))?;
     }
 
     Ok(())