diff --git a/compiler/rustc_codegen_cranelift/src/constant.rs b/compiler/rustc_codegen_cranelift/src/constant.rs index 3a62cd52a9d94..864a836bf89d8 100644 --- a/compiler/rustc_codegen_cranelift/src/constant.rs +++ b/compiler/rustc_codegen_cranelift/src/constant.rs @@ -175,6 +175,13 @@ pub(crate) fn codegen_const_value<'tcx>( fx.module.declare_data_in_func(data_id, &mut fx.bcx.func); fx.bcx.ins().global_value(fx.pointer_type, local_data_id) } + GlobalAlloc::Type { .. } => { + return CValue::const_val( + fx, + layout, + ScalarInt::try_from_target_usize(offset.bytes(), fx.tcx).unwrap(), + ); + } GlobalAlloc::Static(def_id) => { assert!(fx.tcx.is_static(def_id)); let data_id = data_id_for_static( @@ -360,6 +367,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant GlobalAlloc::Memory(alloc) => alloc, GlobalAlloc::Function { .. } | GlobalAlloc::Static(_) + | GlobalAlloc::Type { .. } | GlobalAlloc::VTable(..) => { unreachable!() } @@ -471,6 +479,11 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant .principal() .map(|principal| tcx.instantiate_bound_regions_with_erased(principal)), ), + GlobalAlloc::Type { .. } => { + // Nothing to do, the bytes/offset of this pointer have already been written together with all other bytes, + // so we just need to drop this provenance. + continue; + } GlobalAlloc::Static(def_id) => { if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) { diff --git a/compiler/rustc_codegen_gcc/src/common.rs b/compiler/rustc_codegen_gcc/src/common.rs index fdd47821b515b..394f69a24245f 100644 --- a/compiler/rustc_codegen_gcc/src/common.rs +++ b/compiler/rustc_codegen_gcc/src/common.rs @@ -1,7 +1,6 @@ use gccjit::{LValue, RValue, ToRValue, Type}; -use rustc_abi as abi; -use rustc_abi::HasDataLayout; use rustc_abi::Primitive::Pointer; +use rustc_abi::{self as abi, HasDataLayout}; use rustc_codegen_ssa::traits::{ BaseTypeCodegenMethods, ConstCodegenMethods, MiscCodegenMethods, StaticCodegenMethods, }; @@ -290,6 +289,10 @@ impl<'gcc, 'tcx> ConstCodegenMethods for CodegenCx<'gcc, 'tcx> { let init = self.const_data_from_alloc(alloc); self.static_addr_of(init, alloc.inner().align, None) } + GlobalAlloc::Type { .. } => { + let val = self.const_usize(offset.bytes()); + return self.context.new_cast(None, val, ty); + } GlobalAlloc::Static(def_id) => { assert!(self.tcx.is_static(def_id)); self.get_static(def_id).get_address(None) diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs index ae5add59322fe..605b136ebd51f 100644 --- a/compiler/rustc_codegen_llvm/src/common.rs +++ b/compiler/rustc_codegen_llvm/src/common.rs @@ -3,9 +3,8 @@ use std::borrow::Borrow; use libc::{c_char, c_uint}; -use rustc_abi as abi; -use rustc_abi::HasDataLayout; use rustc_abi::Primitive::Pointer; +use rustc_abi::{self as abi, HasDataLayout as _}; use rustc_ast::Mutability; use rustc_codegen_ssa::common::TypeKind; use rustc_codegen_ssa::traits::*; @@ -284,7 +283,8 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> { self.const_bitcast(llval, llty) }; } else { - let init = const_alloc_to_llvm(self, alloc, /*static*/ false); + let init = + const_alloc_to_llvm(self, alloc.inner(), /*static*/ false); let alloc = alloc.inner(); let value = match alloc.mutability { Mutability::Mut => self.static_addr_of_mut(init, alloc.align, None), @@ -316,15 +316,19 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> { }), ))) .unwrap_memory(); - let init = const_alloc_to_llvm(self, alloc, /*static*/ false); - let value = self.static_addr_of_impl(init, alloc.inner().align, None); - value + let init = const_alloc_to_llvm(self, alloc.inner(), /*static*/ false); + self.static_addr_of_impl(init, alloc.inner().align, None) } GlobalAlloc::Static(def_id) => { assert!(self.tcx.is_static(def_id)); assert!(!self.tcx.is_thread_local_static(def_id)); self.get_static(def_id) } + GlobalAlloc::Type { .. } => { + // Drop the provenance, the offset contains the bytes of the hash + let llval = self.const_usize(offset.bytes()); + return unsafe { llvm::LLVMConstIntToPtr(llval, llty) }; + } }; let base_addr_space = global_alloc.address_space(self); let llval = unsafe { @@ -346,7 +350,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> { } fn const_data_from_alloc(&self, alloc: ConstAllocation<'_>) -> Self::Value { - const_alloc_to_llvm(self, alloc, /*static*/ false) + const_alloc_to_llvm(self, alloc.inner(), /*static*/ false) } fn const_ptr_byte_offset(&self, base_addr: Self::Value, offset: abi::Size) -> Self::Value { diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs index a4492d76c3c59..74a4999d5097b 100644 --- a/compiler/rustc_codegen_llvm/src/consts.rs +++ b/compiler/rustc_codegen_llvm/src/consts.rs @@ -27,10 +27,9 @@ use crate::{base, debuginfo}; pub(crate) fn const_alloc_to_llvm<'ll>( cx: &CodegenCx<'ll, '_>, - alloc: ConstAllocation<'_>, + alloc: &Allocation, is_static: bool, ) -> &'ll Value { - let alloc = alloc.inner(); // We expect that callers of const_alloc_to_llvm will instead directly codegen a pointer or // integer for any &ZST where the ZST is a constant (i.e. not a static). We should never be // producing empty LLVM allocations as they're just adding noise to binaries and forcing less @@ -138,7 +137,7 @@ fn codegen_static_initializer<'ll, 'tcx>( def_id: DefId, ) -> Result<(&'ll Value, ConstAllocation<'tcx>), ErrorHandled> { let alloc = cx.tcx.eval_static_initializer(def_id)?; - Ok((const_alloc_to_llvm(cx, alloc, /*static*/ true), alloc)) + Ok((const_alloc_to_llvm(cx, alloc.inner(), /*static*/ true), alloc)) } fn set_global_alignment<'ll>(cx: &CodegenCx<'ll, '_>, gv: &'ll Value, mut align: Align) { diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs index da615cc9a003d..c05246c1b03d5 100644 --- a/compiler/rustc_codegen_ssa/src/mir/operand.rs +++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs @@ -185,7 +185,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { offset: Size, ) -> Self { let alloc_align = alloc.inner().align; - assert!(alloc_align >= layout.align.abi); + assert!(alloc_align >= layout.align.abi, "{alloc_align:?} < {:?}", layout.align.abi); let read_scalar = |start, size, s: abi::Scalar, ty| { match alloc.0.read_scalar( diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl index 22a1894ee7208..b767ca9a3c251 100644 --- a/compiler/rustc_const_eval/messages.ftl +++ b/compiler/rustc_const_eval/messages.ftl @@ -78,6 +78,8 @@ const_eval_dealloc_kind_mismatch = const_eval_deref_function_pointer = accessing {$allocation} which contains a function +const_eval_deref_typeid_pointer = + accessing {$allocation} which contains a `TypeId` const_eval_deref_vtable_pointer = accessing {$allocation} which contains a vtable const_eval_division_by_zero = diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs index 317b1229a90c1..6c0f22fab6956 100644 --- a/compiler/rustc_const_eval/src/const_eval/machine.rs +++ b/compiler/rustc_const_eval/src/const_eval/machine.rs @@ -2,7 +2,7 @@ use std::borrow::{Borrow, Cow}; use std::fmt; use std::hash::Hash; -use rustc_abi::{Align, Size}; +use rustc_abi::{Align, FieldIdx, Size}; use rustc_ast::Mutability; use rustc_data_structures::fx::{FxHashMap, FxIndexMap, IndexEntry}; use rustc_hir::def_id::{DefId, LocalDefId}; @@ -403,6 +403,24 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> { let cmp = ecx.guaranteed_cmp(a, b)?; ecx.write_scalar(Scalar::from_u8(cmp), dest)?; } + sym::type_id_eq => { + let a = ecx.project_field(&args[0], FieldIdx::ZERO)?; + let b = ecx.project_field(&args[1], FieldIdx::ZERO)?; + + let a = ecx.project_index(&a, 0)?; + let a = ecx.deref_pointer(&a)?; + let (a, offset_a) = a.ptr().into_parts(); + let a = a.unwrap().alloc_id(); + let GlobalAlloc::Type { ty: a } = ecx.tcx.global_alloc(a) else { bug!() }; + + let b = ecx.project_index(&b, 0)?; + let b = ecx.deref_pointer(&b)?; + let (b, offset_b) = b.ptr().into_parts(); + let b = b.unwrap().alloc_id(); + let GlobalAlloc::Type { ty: b } = ecx.tcx.global_alloc(b) else { bug!() }; + + ecx.write_scalar(Scalar::from_bool(a == b && offset_a == offset_b), dest)?; + } sym::const_allocate => { let size = ecx.read_scalar(&args[0])?.to_target_usize(ecx)?; let align = ecx.read_scalar(&args[1])?.to_target_usize(ecx)?; diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs index 14abdd8c98c18..8b58031002876 100644 --- a/compiler/rustc_const_eval/src/errors.rs +++ b/compiler/rustc_const_eval/src/errors.rs @@ -475,6 +475,7 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> { WriteToReadOnly(_) => const_eval_write_to_read_only, DerefFunctionPointer(_) => const_eval_deref_function_pointer, DerefVTablePointer(_) => const_eval_deref_vtable_pointer, + DerefTypeIdPointer(_) => const_eval_deref_typeid_pointer, InvalidBool(_) => const_eval_invalid_bool, InvalidChar(_) => const_eval_invalid_char, InvalidTag(_) => const_eval_invalid_tag, @@ -588,7 +589,10 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> { diag.arg("has", has.bytes()); diag.arg("msg", format!("{msg:?}")); } - WriteToReadOnly(alloc) | DerefFunctionPointer(alloc) | DerefVTablePointer(alloc) => { + WriteToReadOnly(alloc) + | DerefFunctionPointer(alloc) + | DerefVTablePointer(alloc) + | DerefTypeIdPointer(alloc) => { diag.arg("allocation", alloc); } InvalidBool(b) => { diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs index d7cede7129306..68757c93087dc 100644 --- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs +++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs @@ -6,6 +6,8 @@ use std::assert_matches::assert_matches; use rustc_abi::Size; use rustc_apfloat::ieee::{Double, Half, Quad, Single}; +use rustc_ast::Mutability; +use rustc_middle::mir::interpret::{AllocId, AllocInit, alloc_range}; use rustc_middle::mir::{self, BinOp, ConstValue, NonDivergingIntrinsic}; use rustc_middle::ty::layout::{TyAndLayout, ValidityRequirement}; use rustc_middle::ty::{Ty, TyCtxt}; @@ -29,6 +31,37 @@ pub(crate) fn alloc_type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ConstAll tcx.mk_const_alloc(alloc) } +pub(crate) fn alloc_type_id<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> AllocId { + let size = Size::from_bytes(16); + let align = tcx.data_layout.pointer_align; + let mut alloc = Allocation::new(size, *align, AllocInit::Uninit, ()); + let ptr_size = tcx.data_layout.pointer_size; + let type_id_hash = tcx.type_id_hash(ty).as_u128(); + alloc + .write_scalar( + &tcx, + alloc_range(Size::ZERO, Size::from_bytes(16)), + Scalar::from_u128(type_id_hash), + ) + .unwrap(); + + // Give the first pointer-size bytes provenance that knows about the type id + + let alloc_id = tcx.reserve_and_set_type_id_alloc(ty); + let offset = alloc + .read_scalar(&tcx, alloc_range(Size::ZERO, ptr_size), false) + .unwrap() + .to_target_usize(&tcx) + .unwrap(); + let ptr = Pointer::new(alloc_id.into(), Size::from_bytes(offset)); + let val = Scalar::from_pointer(ptr, &tcx); + alloc.write_scalar(&tcx, alloc_range(Size::ZERO, ptr_size), val).unwrap(); + + alloc.mutability = Mutability::Not; + + tcx.reserve_and_set_memory_alloc(tcx.mk_const_alloc(alloc)) +} + impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { /// Returns `true` if emulation happened. /// Here we implement the intrinsics that are common to all Miri instances; individual machines can add their own @@ -63,7 +96,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { sym::type_id => { let tp_ty = instance.args.type_at(0); ensure_monomorphic_enough(tcx, tp_ty)?; - let val = ConstValue::from_u128(tcx.type_id_hash(tp_ty).as_u128()); + let alloc_id = alloc_type_id(tcx, tp_ty); + let val = ConstValue::Indirect { alloc_id, offset: Size::ZERO }; let val = self.const_val_to_op(val, dest.layout.ty, Some(dest.layout))?; self.copy_op(&val, dest)?; } diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs index 69fceb02ff931..2f9104cbed5e2 100644 --- a/compiler/rustc_const_eval/src/interpret/memory.rs +++ b/compiler/rustc_const_eval/src/interpret/memory.rs @@ -346,6 +346,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { kind = "vtable", ) } + Some(GlobalAlloc::Type { .. }) => { + err_ub_custom!( + fluent::const_eval_invalid_dealloc, + alloc_id = alloc_id, + kind = "typeid", + ) + } Some(GlobalAlloc::Static(..) | GlobalAlloc::Memory(..)) => { err_ub_custom!( fluent::const_eval_invalid_dealloc, @@ -615,6 +622,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { } Some(GlobalAlloc::Function { .. }) => throw_ub!(DerefFunctionPointer(id)), Some(GlobalAlloc::VTable(..)) => throw_ub!(DerefVTablePointer(id)), + Some(GlobalAlloc::Type { .. }) => throw_ub!(DerefTypeIdPointer(id)), None => throw_ub!(PointerUseAfterFree(id, CheckInAllocMsg::MemoryAccess)), Some(GlobalAlloc::Static(def_id)) => { assert!(self.tcx.is_static(def_id)); @@ -894,7 +902,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { let (size, align) = global_alloc.size_and_align(*self.tcx, self.typing_env); let mutbl = global_alloc.mutability(*self.tcx, self.typing_env); let kind = match global_alloc { - GlobalAlloc::Static { .. } | GlobalAlloc::Memory { .. } => AllocKind::LiveData, + GlobalAlloc::Type { .. } + | GlobalAlloc::Static { .. } + | GlobalAlloc::Memory { .. } => AllocKind::LiveData, GlobalAlloc::Function { .. } => bug!("We already checked function pointers above"), GlobalAlloc::VTable { .. } => AllocKind::VTable, }; @@ -1204,6 +1214,9 @@ impl<'a, 'tcx, M: Machine<'tcx>> std::fmt::Debug for DumpAllocs<'a, 'tcx, M> { Some(GlobalAlloc::VTable(ty, dyn_ty)) => { write!(fmt, " (vtable: impl {dyn_ty} for {ty})")?; } + Some(GlobalAlloc::Type { ty }) => { + write!(fmt, " (typeid for {ty})")?; + } Some(GlobalAlloc::Static(did)) => { write!(fmt, " (static: {})", self.ecx.tcx.def_path_str(did))?; } diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs index 998ef3729eafe..0a6d341d147ff 100644 --- a/compiler/rustc_const_eval/src/interpret/validity.rs +++ b/compiler/rustc_const_eval/src/interpret/validity.rs @@ -574,40 +574,44 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> { let alloc_actual_mutbl = global_alloc.mutability(*self.ecx.tcx, self.ecx.typing_env); - if let GlobalAlloc::Static(did) = global_alloc { - let DefKind::Static { nested, .. } = self.ecx.tcx.def_kind(did) else { - bug!() - }; - // Special handling for pointers to statics (irrespective of their type). - assert!(!self.ecx.tcx.is_thread_local_static(did)); - assert!(self.ecx.tcx.is_static(did)); - // Mode-specific checks - match ctfe_mode { - CtfeValidationMode::Static { .. } - | CtfeValidationMode::Promoted { .. } => { - // We skip recursively checking other statics. These statics must be sound by - // themselves, and the only way to get broken statics here is by using - // unsafe code. - // The reasons we don't check other statics is twofold. For one, in all - // sound cases, the static was already validated on its own, and second, we - // trigger cycle errors if we try to compute the value of the other static - // and that static refers back to us (potentially through a promoted). - // This could miss some UB, but that's fine. - // We still walk nested allocations, as they are fundamentally part of this validation run. - // This means we will also recurse into nested statics of *other* - // statics, even though we do not recurse into other statics directly. - // That's somewhat inconsistent but harmless. - skip_recursive_check = !nested; - } - CtfeValidationMode::Const { .. } => { - // If this is mutable memory or an `extern static`, there's no point in checking it -- we'd - // just get errors trying to read the value. - if alloc_actual_mutbl.is_mut() || self.ecx.tcx.is_foreign_item(did) - { - skip_recursive_check = true; + match global_alloc { + GlobalAlloc::Static(did) => { + let DefKind::Static { nested, .. } = self.ecx.tcx.def_kind(did) else { + bug!() + }; + assert!(!self.ecx.tcx.is_thread_local_static(did)); + assert!(self.ecx.tcx.is_static(did)); + match ctfe_mode { + CtfeValidationMode::Static { .. } + | CtfeValidationMode::Promoted { .. } => { + // We skip recursively checking other statics. These statics must be sound by + // themselves, and the only way to get broken statics here is by using + // unsafe code. + // The reasons we don't check other statics is twofold. For one, in all + // sound cases, the static was already validated on its own, and second, we + // trigger cycle errors if we try to compute the value of the other static + // and that static refers back to us (potentially through a promoted). + // This could miss some UB, but that's fine. + // We still walk nested allocations, as they are fundamentally part of this validation run. + // This means we will also recurse into nested statics of *other* + // statics, even though we do not recurse into other statics directly. + // That's somewhat inconsistent but harmless. + skip_recursive_check = !nested; + } + CtfeValidationMode::Const { .. } => { + // If this is mutable memory or an `extern static`, there's no point in checking it -- we'd + // just get errors trying to read the value. + if alloc_actual_mutbl.is_mut() + || self.ecx.tcx.is_foreign_item(did) + { + skip_recursive_check = true; + } } } } + // These are controlled by rustc and not available for CTFE + GlobalAlloc::Type { .. } => skip_recursive_check = true, + _ => (), } // If this allocation has size zero, there is no actual mutability here. diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs index 10dd5ff9aa76a..50f8419200005 100644 --- a/compiler/rustc_hir/src/lang_items.rs +++ b/compiler/rustc_hir/src/lang_items.rs @@ -274,6 +274,8 @@ language_item_table! { PartialOrd, sym::partial_ord, partial_ord_trait, Target::Trait, GenericRequirement::Exact(1); CVoid, sym::c_void, c_void, Target::Enum, GenericRequirement::None; + TypeId, sym::type_id, type_id, Target::Struct, GenericRequirement::None; + // A number of panic-related lang items. The `panic` item corresponds to divide-by-zero and // various panic cases with `match`. The `panic_bounds_check` item is for indexing arrays. // diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs index cebf7d1b5324e..e3532ade32ffe 100644 --- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs +++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs @@ -93,6 +93,7 @@ fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -> hi | sym::three_way_compare | sym::discriminant_value | sym::type_id + | sym::type_id_eq | sym::select_unpredictable | sym::cold_path | sym::ptr_guaranteed_cmp @@ -220,7 +221,13 @@ pub(crate) fn check_intrinsic_type( sym::needs_drop => (1, 0, vec![], tcx.types.bool), sym::type_name => (1, 0, vec![], Ty::new_static_str(tcx)), - sym::type_id => (1, 0, vec![], tcx.types.u128), + sym::type_id => { + (1, 0, vec![], tcx.type_of(tcx.lang_items().type_id().unwrap()).instantiate_identity()) + } + sym::type_id_eq => { + let type_id = tcx.type_of(tcx.lang_items().type_id().unwrap()).instantiate_identity(); + (0, 0, vec![type_id, type_id], tcx.types.bool) + } sym::offset => (2, 0, vec![param(0), param(1)], param(0)), sym::arith_offset => ( 1, diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs index 41a166083d079..dc8985d1b962c 100644 --- a/compiler/rustc_middle/src/mir/interpret/error.rs +++ b/compiler/rustc_middle/src/mir/interpret/error.rs @@ -392,6 +392,8 @@ pub enum UndefinedBehaviorInfo<'tcx> { DerefFunctionPointer(AllocId), /// Trying to access the data behind a vtable pointer. DerefVTablePointer(AllocId), + /// Trying to access the actual type id. + DerefTypeIdPointer(AllocId), /// Using a non-boolean `u8` as bool. InvalidBool(u8), /// Using a non-character `u32` as character. diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs index ea2f84d46d7f7..cd74702b83e5f 100644 --- a/compiler/rustc_middle/src/mir/interpret/mod.rs +++ b/compiler/rustc_middle/src/mir/interpret/mod.rs @@ -103,6 +103,7 @@ enum AllocDiscriminant { Fn, VTable, Static, + Type, } pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<'tcx>>( @@ -127,6 +128,11 @@ pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<'tcx>>( ty.encode(encoder); poly_trait_ref.encode(encoder); } + GlobalAlloc::Type { ty } => { + trace!("encoding {alloc_id:?} with {ty:#?}"); + AllocDiscriminant::Type.encode(encoder); + ty.encode(encoder); + } GlobalAlloc::Static(did) => { assert!(!tcx.is_thread_local_static(did)); // References to statics doesn't need to know about their allocations, @@ -228,6 +234,12 @@ impl<'s> AllocDecodingSession<'s> { trace!("decoded vtable alloc instance: {ty:?}, {poly_trait_ref:?}"); decoder.interner().reserve_and_set_vtable_alloc(ty, poly_trait_ref, CTFE_ALLOC_SALT) } + AllocDiscriminant::Type => { + trace!("creating typeid alloc ID"); + let ty = Decodable::decode(decoder); + trace!("decoded typid: {ty:?}"); + decoder.interner().reserve_and_set_type_id_alloc(ty) + } AllocDiscriminant::Static => { trace!("creating extern static alloc ID"); let did = >::decode(decoder); @@ -258,6 +270,9 @@ pub enum GlobalAlloc<'tcx> { Static(DefId), /// The alloc ID points to memory. Memory(ConstAllocation<'tcx>), + /// The first pointer-sized segment of a type id. On 64 bit systems, the 128 bit type id + /// is split into two segments, on 32 bit systems there are 4 segments, and so on. + Type { ty: Ty<'tcx> }, } impl<'tcx> GlobalAlloc<'tcx> { @@ -296,9 +311,10 @@ impl<'tcx> GlobalAlloc<'tcx> { pub fn address_space(&self, cx: &impl HasDataLayout) -> AddressSpace { match self { GlobalAlloc::Function { .. } => cx.data_layout().instruction_address_space, - GlobalAlloc::Static(..) | GlobalAlloc::Memory(..) | GlobalAlloc::VTable(..) => { - AddressSpace::DATA - } + GlobalAlloc::Type { .. } + | GlobalAlloc::Static(..) + | GlobalAlloc::Memory(..) + | GlobalAlloc::VTable(..) => AddressSpace::DATA, } } @@ -334,7 +350,7 @@ impl<'tcx> GlobalAlloc<'tcx> { } } GlobalAlloc::Memory(alloc) => alloc.inner().mutability, - GlobalAlloc::Function { .. } | GlobalAlloc::VTable(..) => { + GlobalAlloc::Type { .. } | GlobalAlloc::Function { .. } | GlobalAlloc::VTable(..) => { // These are immutable. Mutability::Not } @@ -380,8 +396,10 @@ impl<'tcx> GlobalAlloc<'tcx> { GlobalAlloc::Function { .. } => (Size::ZERO, Align::ONE), GlobalAlloc::VTable(..) => { // No data to be accessed here. But vtables are pointer-aligned. - return (Size::ZERO, tcx.data_layout.pointer_align.abi); + (Size::ZERO, tcx.data_layout.pointer_align.abi) } + // Fake allocation, there's nothing to access here + GlobalAlloc::Type { .. } => (Size::ZERO, Align::ONE), } } } @@ -487,6 +505,11 @@ impl<'tcx> TyCtxt<'tcx> { self.reserve_and_set_dedup(GlobalAlloc::VTable(ty, dyn_ty), salt) } + /// Generates an [AllocId] for a [core::any::TypeId]. Will get deduplicated. + pub fn reserve_and_set_type_id_alloc(self, ty: Ty<'tcx>) -> AllocId { + self.reserve_and_set_dedup(GlobalAlloc::Type { ty }, 0) + } + /// Interns the `Allocation` and return a new `AllocId`, even if there's already an identical /// `Allocation` with a different `AllocId`. /// Statics with identical content will still point to the same `Allocation`, i.e., diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs index 6b262a2750059..6bdbe711f9855 100644 --- a/compiler/rustc_middle/src/mir/pretty.rs +++ b/compiler/rustc_middle/src/mir/pretty.rs @@ -1621,6 +1621,7 @@ pub fn write_allocations<'tcx>( Some(GlobalAlloc::VTable(ty, dyn_ty)) => { write!(w, " (vtable: impl {dyn_ty} for {ty})")? } + Some(GlobalAlloc::Type { ty }) => write!(w, " (typeid for {ty})")?, Some(GlobalAlloc::Static(did)) if !tcx.is_foreign_item(did) => { write!(w, " (static: {}", tcx.def_path_str(did))?; if body.phase <= MirPhase::Runtime(RuntimePhase::PostCleanup) diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs index 1392d1d08fcb5..59644d060b1ab 100644 --- a/compiler/rustc_middle/src/ty/print/pretty.rs +++ b/compiler/rustc_middle/src/ty/print/pretty.rs @@ -1780,6 +1780,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write { } Some(GlobalAlloc::Function { .. }) => p!(""), Some(GlobalAlloc::VTable(..)) => p!(""), + Some(GlobalAlloc::Type { .. }) => p!(""), None => p!(""), } return Ok(()); diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs index 798f4da9b3bbf..2ba450d9d2d2a 100644 --- a/compiler/rustc_monomorphize/src/collector.rs +++ b/compiler/rustc_monomorphize/src/collector.rs @@ -1230,6 +1230,7 @@ fn collect_alloc<'tcx>(tcx: TyCtxt<'tcx>, alloc_id: AllocId, output: &mut MonoIt )); collect_alloc(tcx, alloc_id, output) } + GlobalAlloc::Type { .. } => {} } } diff --git a/compiler/rustc_passes/src/reachable.rs b/compiler/rustc_passes/src/reachable.rs index 7e15267a953ba..88eeebf1111d1 100644 --- a/compiler/rustc_passes/src/reachable.rs +++ b/compiler/rustc_passes/src/reachable.rs @@ -325,6 +325,7 @@ impl<'tcx> ReachableContext<'tcx> { self.visit(args); } } + GlobalAlloc::Type { ty, .. } => self.visit(ty), GlobalAlloc::Memory(alloc) => self.propagate_from_alloc(alloc), } } diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs index 85e71ed2c2550..9dd0e04e187ba 100644 --- a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs +++ b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs @@ -755,6 +755,7 @@ impl<'tcx> Stable<'tcx> for mir::interpret::GlobalAlloc<'tcx> { GlobalAlloc::Static(tables.static_def(*def)) } mir::interpret::GlobalAlloc::Memory(alloc) => GlobalAlloc::Memory(alloc.stable(tables)), + mir::interpret::GlobalAlloc::Type { .. } => todo!(), } } } diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 4b8762d0dd1c2..3dfdf118d2d19 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -2196,6 +2196,7 @@ symbols! { type_changing_struct_update, type_const, type_id, + type_id_eq, type_ir, type_ir_infer_ctxt_like, type_ir_inherent, diff --git a/library/core/Cargo.toml b/library/core/Cargo.toml index 5d65b55bcdabe..31900bcc0878c 100644 --- a/library/core/Cargo.toml +++ b/library/core/Cargo.toml @@ -23,8 +23,6 @@ optimize_for_size = [] # Make `RefCell` store additional debugging information, which is printed out when # a borrow error occurs debug_refcell = [] -# Make `TypeId` store a reference to the name of the type, so that it can print that name. -debug_typeid = [] [lints.rust.unexpected_cfgs] level = "warn" diff --git a/library/core/src/any.rs b/library/core/src/any.rs index 01dce114592a1..bc4bac77ab96f 100644 --- a/library/core/src/any.rs +++ b/library/core/src/any.rs @@ -707,19 +707,24 @@ impl dyn Any + Send + Sync { /// ``` #[derive(Clone, Copy, Eq, PartialOrd, Ord)] #[stable(feature = "rust1", since = "1.0.0")] +#[lang = "type_id"] pub struct TypeId { - // We avoid using `u128` because that imposes higher alignment requirements on many platforms. - // See issue #115620 for more information. - t: (u64, u64), - #[cfg(feature = "debug_typeid")] - name: &'static str, + pub(crate) data: [*const (); 16 / size_of::()], } +// SAFETY: the raw pointer is always an integer #[stable(feature = "rust1", since = "1.0.0")] -impl PartialEq for TypeId { +unsafe impl Send for TypeId {} +// SAFETY: the raw pointer is always an integer +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl Sync for TypeId {} + +#[stable(feature = "rust1", since = "1.0.0")] +#[rustc_const_unstable(feature = "const_type_id", issue = "77125")] +impl const PartialEq for TypeId { #[inline] fn eq(&self, other: &Self) -> bool { - self.t == other.t + crate::intrinsics::type_id_eq(*self, *other) } } @@ -742,19 +747,12 @@ impl TypeId { #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_unstable(feature = "const_type_id", issue = "77125")] pub const fn of() -> TypeId { - let t: u128 = const { intrinsics::type_id::() }; - let t1 = (t >> 64) as u64; - let t2 = t as u64; - - TypeId { - t: (t1, t2), - #[cfg(feature = "debug_typeid")] - name: type_name::(), - } + const { intrinsics::type_id::() } } fn as_u128(self) -> u128 { - u128::from(self.t.0) << 64 | u128::from(self.t.1) + // SAFETY: we know there are 16 bytes without provenance at this location + unsafe { crate::ptr::read_unaligned(&self.data as *const _ as *const u128) } } } @@ -774,22 +772,16 @@ impl hash::Hash for TypeId { // - It is correct to do so -- only hashing a subset of `self` is still // compatible with an `Eq` implementation that considers the entire // value, as ours does. - self.t.1.hash(state); + // SAFETY: we know there are 16 bytes without provenance at this location + let data = unsafe { crate::ptr::read_unaligned(&self.data as *const _ as *const u64) }; + data.hash(state); } } #[stable(feature = "rust1", since = "1.0.0")] impl fmt::Debug for TypeId { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> { - #[cfg(feature = "debug_typeid")] - { - write!(f, "TypeId({:#034x} = {})", self.as_u128(), self.name)?; - } - #[cfg(not(feature = "debug_typeid"))] - { - write!(f, "TypeId({:#034x})", self.as_u128())?; - } - Ok(()) + write!(f, "TypeId({:#034x})", self.as_u128()) } } diff --git a/library/core/src/intrinsics/mod.rs b/library/core/src/intrinsics/mod.rs index 4250de9fb2b33..b15456ddc99ad 100644 --- a/library/core/src/intrinsics/mod.rs +++ b/library/core/src/intrinsics/mod.rs @@ -2718,7 +2718,20 @@ pub const fn type_name() -> &'static str; #[rustc_nounwind] #[unstable(feature = "core_intrinsics", issue = "none")] #[rustc_intrinsic] -pub const fn type_id() -> u128; +pub const fn type_id() -> crate::any::TypeId; + +/// Tests (at compile-time) if two [`crate::any::TypeId`] instances identify the +/// same type. This is necessary because at const-eval time the actual discriminating +/// data is opaque and cannot be inspected directly. +/// +/// The stabilized version of this intrinsic is the [PartialEq] impl for [`core::any::TypeId`]. +#[rustc_nounwind] +#[unstable(feature = "core_intrinsics", issue = "none")] +#[rustc_intrinsic] +#[rustc_do_not_const_check] +pub const fn type_id_eq(a: crate::any::TypeId, b: crate::any::TypeId) -> bool { + a.data == b.data +} /// Lowers in MIR to `Rvalue::Aggregate` with `AggregateKind::RawPtr`. /// diff --git a/library/coretests/tests/any.rs b/library/coretests/tests/any.rs index 117ef0042380d..25002617d0bbd 100644 --- a/library/coretests/tests/any.rs +++ b/library/coretests/tests/any.rs @@ -118,14 +118,6 @@ fn any_unsized() { is_any::<[i32]>(); } -#[cfg(feature = "debug_typeid")] -#[test] -fn debug_typeid_includes_name() { - let type_id = TypeId::of::<[usize; 2]>(); - let debug_str = format!("{type_id:?}"); - assert!(debug_str.ends_with("= [usize; 2])"), "{debug_str:?} did not match"); -} - #[test] fn distinct_type_names() { // https://github.com/rust-lang/rust/issues/84666 diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml index 7c2a43ef20745..e4cb0b31c903a 100644 --- a/library/std/Cargo.toml +++ b/library/std/Cargo.toml @@ -113,8 +113,6 @@ optimize_for_size = ["core/optimize_for_size", "alloc/optimize_for_size"] # Make `RefCell` store additional debugging information, which is printed out when # a borrow error occurs debug_refcell = ["core/debug_refcell"] -# Make `TypeId` store a reference to the name of the type, so that it can print that name. -debug_typeid = ["core/debug_typeid"] # Enable std_detect default features for stdarch/crates/std_detect: diff --git a/library/sysroot/Cargo.toml b/library/sysroot/Cargo.toml index 3adc022497167..c4937c36d4c9c 100644 --- a/library/sysroot/Cargo.toml +++ b/library/sysroot/Cargo.toml @@ -22,7 +22,6 @@ compiler-builtins-no-asm = ["std/compiler-builtins-no-asm"] compiler-builtins-no-f16-f128 = ["std/compiler-builtins-no-f16-f128"] compiler-builtins-mangled-names = ["std/compiler-builtins-mangled-names"] debug_refcell = ["std/debug_refcell"] -debug_typeid = ["std/debug_typeid"] llvm-libunwind = ["std/llvm-libunwind"] system-llvm-libunwind = ["std/system-llvm-libunwind"] optimize_for_size = ["std/optimize_for_size"] diff --git a/tests/codegen/error-provide.rs b/tests/codegen/error-provide.rs index 25a66078fd4a8..b52b332b9f86f 100644 --- a/tests/codegen/error-provide.rs +++ b/tests/codegen/error-provide.rs @@ -37,8 +37,9 @@ impl std::error::Error for MyError { // and eliminate redundant ones, rather than compare one-by-one. // CHECK-NEXT: start: - // CHECK-NEXT: %[[SCRUTINEE:[^ ]+]] = load i64, ptr - // CHECK-NEXT: switch i64 %[[SCRUTINEE]], label %{{.*}} [ + // CHECK-NEXT: %[[SCRUTINEE:[^ ]+]] = load ptr, ptr + // CHECK-NEXT: %[[MAGICPTR:[^ ]+]] = ptrtoint ptr %[[SCRUTINEE]] to i64 + // CHECK-NEXT: switch i64 %[[MAGICPTR]], label %{{.*}} [ // CHECK-COUNT-3: i64 {{.*}}, label %{{.*}} // CHECK-NEXT: ] request diff --git a/tests/mir-opt/gvn_type_id_polymorphic.rs b/tests/mir-opt/gvn_type_id_polymorphic.rs index 39bc5c24ecc68..6285dca9d95ea 100644 --- a/tests/mir-opt/gvn_type_id_polymorphic.rs +++ b/tests/mir-opt/gvn_type_id_polymorphic.rs @@ -6,7 +6,20 @@ fn generic() {} const fn type_id_of_val(_: &T) -> u128 { - std::intrinsics::type_id::() + let name = std::intrinsics::type_name::(); + let len = name.len() as u64; + let len = u64::to_be_bytes(len); + let mut ret = [0; 16]; + let mut i = 0; + while i < 8 { + ret[i] = len[i]; + i += 1; + } + while i < 16 { + ret[i] = name.as_bytes()[i - 8]; + i += 1; + } + u128::from_be_bytes(ret) } // EMIT_MIR gvn_type_id_polymorphic.cursed_is_i32.GVN.diff diff --git a/tests/ui/const-generics/issues/issue-90318.rs b/tests/ui/const-generics/issues/issue-90318.rs index 317ddad49cd4e..dfba90a557512 100644 --- a/tests/ui/const-generics/issues/issue-90318.rs +++ b/tests/ui/const-generics/issues/issue-90318.rs @@ -1,5 +1,6 @@ #![feature(const_type_id)] #![feature(generic_const_exprs)] +#![feature(const_trait_impl)] #![feature(core_intrinsics)] #![allow(incomplete_features)] @@ -13,7 +14,6 @@ fn consume(_val: T) where If<{ TypeId::of::() != TypeId::of::<()>() }>: True, //~^ ERROR overly complex generic constant - //~| ERROR: cannot call { } @@ -21,7 +21,6 @@ fn test() where If<{ TypeId::of::() != TypeId::of::<()>() }>: True, //~^ ERROR overly complex generic constant - //~| ERROR: cannot call { } diff --git a/tests/ui/const-generics/issues/issue-90318.stderr b/tests/ui/const-generics/issues/issue-90318.stderr index 9c7cb5ceb58c0..7031230db91c3 100644 --- a/tests/ui/const-generics/issues/issue-90318.stderr +++ b/tests/ui/const-generics/issues/issue-90318.stderr @@ -1,5 +1,5 @@ error: overly complex generic constant - --> $DIR/issue-90318.rs:14:8 + --> $DIR/issue-90318.rs:15:8 | LL | If<{ TypeId::of::() != TypeId::of::<()>() }>: True, | ^^-----------------^^^^^^^^^^^^^^^^^^^^^^^^ @@ -20,26 +20,5 @@ LL | If<{ TypeId::of::() != TypeId::of::<()>() }>: True, = help: consider moving this anonymous constant into a `const` function = note: this operation may be supported in the future -error[E0015]: cannot call non-const operator in constants - --> $DIR/issue-90318.rs:14:10 - | -LL | If<{ TypeId::of::() != TypeId::of::<()>() }>: True, - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - | -note: impl defined here, but it is not `const` - --> $SRC_DIR/core/src/any.rs:LL:COL - = note: calls in constants are limited to constant functions, tuple structs and tuple variants - -error[E0015]: cannot call non-const operator in constants - --> $DIR/issue-90318.rs:22:10 - | -LL | If<{ TypeId::of::() != TypeId::of::<()>() }>: True, - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - | -note: impl defined here, but it is not `const` - --> $SRC_DIR/core/src/any.rs:LL:COL - = note: calls in constants are limited to constant functions, tuple structs and tuple variants - -error: aborting due to 4 previous errors +error: aborting due to 2 previous errors -For more information about this error, try `rustc --explain E0015`. diff --git a/tests/ui/consts/const_cmp_type_id.rs b/tests/ui/consts/const_cmp_type_id.rs index dca0615083a78..def615bd92bb5 100644 --- a/tests/ui/consts/const_cmp_type_id.rs +++ b/tests/ui/consts/const_cmp_type_id.rs @@ -6,10 +6,9 @@ use std::any::TypeId; fn main() { const { assert!(TypeId::of::() == TypeId::of::()); - //~^ ERROR the trait bound `TypeId: const PartialEq` is not satisfied assert!(TypeId::of::<()>() != TypeId::of::()); - //~^ ERROR the trait bound `TypeId: const PartialEq` is not satisfied let _a = TypeId::of::() < TypeId::of::(); + //~^ ERROR: cannot call non-const operator in constants // can't assert `_a` because it is not deterministic // FIXME(const_trait_impl) make it pass } diff --git a/tests/ui/consts/const_cmp_type_id.stderr b/tests/ui/consts/const_cmp_type_id.stderr index a8242a200eff1..540eec5098b40 100644 --- a/tests/ui/consts/const_cmp_type_id.stderr +++ b/tests/ui/consts/const_cmp_type_id.stderr @@ -1,15 +1,13 @@ -error[E0277]: the trait bound `TypeId: const PartialEq` is not satisfied - --> $DIR/const_cmp_type_id.rs:8:17 +error[E0015]: cannot call non-const operator in constants + --> $DIR/const_cmp_type_id.rs:10:18 | -LL | assert!(TypeId::of::() == TypeId::of::()); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -error[E0277]: the trait bound `TypeId: const PartialEq` is not satisfied - --> $DIR/const_cmp_type_id.rs:10:17 +LL | let _a = TypeId::of::() < TypeId::of::(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -LL | assert!(TypeId::of::<()>() != TypeId::of::()); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +note: impl defined here, but it is not `const` + --> $SRC_DIR/core/src/any.rs:LL:COL + = note: calls in constants are limited to constant functions, tuple structs and tuple variants -error: aborting due to 2 previous errors +error: aborting due to 1 previous error -For more information about this error, try `rustc --explain E0277`. +For more information about this error, try `rustc --explain E0015`. diff --git a/tests/ui/consts/const_transmute_type_id.rs b/tests/ui/consts/const_transmute_type_id.rs new file mode 100644 index 0000000000000..52cc2853ab821 --- /dev/null +++ b/tests/ui/consts/const_transmute_type_id.rs @@ -0,0 +1,11 @@ +#![feature(const_type_id, const_trait_impl)] + +use std::any::TypeId; + +const _: () = { + let id = TypeId::of::(); + let id: u8 = unsafe { (&id as *const TypeId).cast::().read() }; + //~^ ERROR: unable to turn pointer into integer +}; + +fn main() {} diff --git a/tests/ui/consts/const_transmute_type_id.stderr b/tests/ui/consts/const_transmute_type_id.stderr new file mode 100644 index 0000000000000..fafced4d48b97 --- /dev/null +++ b/tests/ui/consts/const_transmute_type_id.stderr @@ -0,0 +1,12 @@ +error[E0080]: unable to turn pointer into integer + --> $DIR/const_transmute_type_id.rs:7:27 + | +LL | let id: u8 = unsafe { (&id as *const TypeId).cast::().read() }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of `_` failed here + | + = help: this code performed an operation that depends on the underlying bytes representing a pointer + = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported + +error: aborting due to 1 previous error + +For more information about this error, try `rustc --explain E0080`. diff --git a/tests/ui/consts/issue-73976-monomorphic.rs b/tests/ui/consts/issue-73976-monomorphic.rs index 561c197605117..3bfdb397afb23 100644 --- a/tests/ui/consts/issue-73976-monomorphic.rs +++ b/tests/ui/consts/issue-73976-monomorphic.rs @@ -1,4 +1,4 @@ -//@ known-bug: #110395 +//@ check-pass // // This test is complement to the test in issue-73976-polymorphic.rs. // In that test we ensure that polymorphic use of type_id and type_name in patterns diff --git a/tests/ui/consts/issue-73976-monomorphic.stderr b/tests/ui/consts/issue-73976-monomorphic.stderr deleted file mode 100644 index 367d5be09da4e..0000000000000 --- a/tests/ui/consts/issue-73976-monomorphic.stderr +++ /dev/null @@ -1,9 +0,0 @@ -error[E0277]: the trait bound `TypeId: [const] PartialEq` is not satisfied - --> $DIR/issue-73976-monomorphic.rs:21:5 - | -LL | GetTypeId::::VALUE == GetTypeId::::VALUE - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -error: aborting due to 1 previous error - -For more information about this error, try `rustc --explain E0277`.