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Auto merge of #87515 - crlf0710:trait_upcasting_part2, r=bjorn3

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Trait upcasting coercion (part2)

This is the second part of trait upcasting coercion implementation.

Currently this is blocked on #86264 .

The third part might be implemented using unsafety checking

r? `@bjorn3`
This commit is contained in:
bors 2021-08-03 16:58:56 +00:00
commit c6bc102fea
22 changed files with 1186 additions and 93 deletions
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63
compiler/rustc_codegen_cranelift/src/unsize.rs
View File

@ -25,39 +25,73 @@ pub(crate) fn unsized_info<'tcx>(
.bcx
.ins()
.iconst(fx.pointer_type, len.eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64),
(&ty::Dynamic(..), &ty::Dynamic(..)) => {
// For now, upcasts are limited to changes in marker
// traits, and hence never actually require an actual
// change to the vtable.
old_info.expect("unsized_info: missing old info for trait upcast")
(&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => {
let old_info =
old_info.expect("unsized_info: missing old info for trait upcasting coercion");
if data_a.principal_def_id() == data_b.principal_def_id() {
return old_info;
}
// trait upcasting coercion
// if both of the two `principal`s are `None`, this function would have returned early above.
// and if one of the two `principal`s is `None`, typechecking would have rejected this case.
let principal_a = data_a
.principal()
.expect("unsized_info: missing principal trait for trait upcasting coercion");
let principal_b = data_b
.principal()
.expect("unsized_info: missing principal trait for trait upcasting coercion");
let vptr_entry_idx = fx.tcx.vtable_trait_upcasting_coercion_new_vptr_slot((
principal_a.with_self_ty(fx.tcx, source),
principal_b.with_self_ty(fx.tcx, source),
));
if let Some(entry_idx) = vptr_entry_idx {
let entry_idx = u32::try_from(entry_idx).unwrap();
let entry_offset = entry_idx * fx.pointer_type.bytes();
let vptr_ptr = Pointer::new(old_info).offset_i64(fx, entry_offset.into()).load(
fx,
fx.pointer_type,
crate::vtable::vtable_memflags(),
);
vptr_ptr
} else {
old_info
}
}
(_, &ty::Dynamic(ref data, ..)) => crate::vtable::get_vtable(fx, source, data.principal()),
_ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
}
}
/// Coerce `src` to `dst_ty`. `src_ty` must be a thin pointer.
fn unsize_thin_ptr<'tcx>(
/// Coerce `src` to `dst_ty`.
fn unsize_ptr<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
src: Value,
src_layout: TyAndLayout<'tcx>,
dst_layout: TyAndLayout<'tcx>,
old_info: Option<Value>,
) -> (Value, Value) {
match (&src_layout.ty.kind(), &dst_layout.ty.kind()) {
(&ty::Ref(_, a, _), &ty::Ref(_, b, _))
| (&ty::Ref(_, a, _), &ty::RawPtr(ty::TypeAndMut { ty: b, .. }))
| (&ty::RawPtr(ty::TypeAndMut { ty: a, .. }), &ty::RawPtr(ty::TypeAndMut { ty: b, .. })) => {
assert!(!fx.layout_of(a).is_unsized());
(src, unsized_info(fx, a, b, None))
(src, unsized_info(fx, a, b, old_info))
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
let (a, b) = (src_layout.ty.boxed_ty(), dst_layout.ty.boxed_ty());
assert!(!fx.layout_of(a).is_unsized());
(src, unsized_info(fx, a, b, None))
(src, unsized_info(fx, a, b, old_info))
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
assert_eq!(def_a, def_b);
if src_layout == dst_layout {
return (src, old_info.unwrap());
}
let mut result = None;
for i in 0..src_layout.fields.count() {
let src_f = src_layout.field(fx, i);
@ -71,11 +105,11 @@ fn unsize_thin_ptr<'tcx>(
let dst_f = dst_layout.field(fx, i);
assert_ne!(src_f.ty, dst_f.ty);
assert_eq!(result, None);
result = Some(unsize_thin_ptr(fx, src, src_f, dst_f));
result = Some(unsize_ptr(fx, src, src_f, dst_f, old_info));
}
result.unwrap()
}
_ => bug!("unsize_thin_ptr: called on bad types"),
_ => bug!("unsize_ptr: called on bad types"),
}
}
@ -91,12 +125,11 @@ pub(crate) fn coerce_unsized_into<'tcx>(
let mut coerce_ptr = || {
let (base, info) =
if fx.layout_of(src.layout().ty.builtin_deref(true).unwrap().ty).is_unsized() {
// fat-ptr to fat-ptr unsize preserves the vtable
// i.e., &'a fmt::Debug+Send => &'a fmt::Debug
src.load_scalar_pair(fx)
let (old_base, old_info) = src.load_scalar_pair(fx);
unsize_ptr(fx, old_base, src.layout(), dst.layout(), Some(old_info))
} else {
let base = src.load_scalar(fx);
unsize_thin_ptr(fx, base, src.layout(), dst.layout())
unsize_ptr(fx, base, src.layout(), dst.layout(), None)
};
dst.write_cvalue(fx, CValue::by_val_pair(base, info, dst.layout()));
};

2
compiler/rustc_codegen_cranelift/src/vtable.rs
View File

@ -5,7 +5,7 @@
use crate::constant::data_id_for_alloc_id;
use crate::prelude::*;
fn vtable_memflags() -> MemFlags {
pub(crate) fn vtable_memflags() -> MemFlags {
let mut flags = MemFlags::trusted(); // A vtable access is always aligned and will never trap.
flags.set_readonly(); // A vtable is always read-only.
flags

107
compiler/rustc_codegen_ssa/src/base.rs
View File

@ -23,7 +23,6 @@ use rustc_middle::middle::cstore::EncodedMetadata;
use rustc_middle::middle::lang_items;
use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem};
use rustc_middle::ty::layout::{HasTyCtxt, TyAndLayout};
use rustc_middle::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
use rustc_session::cgu_reuse_tracker::CguReuse;
@ -32,6 +31,7 @@ use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_target::abi::{Align, LayoutOf, VariantIdx};
use std::convert::TryFrom;
use std::ops::{Deref, DerefMut};
use std::time::{Duration, Instant};
@ -128,55 +128,92 @@ pub fn compare_simd_types<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
///
/// The `old_info` argument is a bit odd. It is intended for use in an upcast,
/// where the new vtable for an object will be derived from the old one.
pub fn unsized_info<'tcx, Cx: CodegenMethods<'tcx>>(
cx: &Cx,
pub fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
source: Ty<'tcx>,
target: Ty<'tcx>,
old_info: Option<Cx::Value>,
) -> Cx::Value {
old_info: Option<Bx::Value>,
) -> Bx::Value {
let cx = bx.cx();
let (source, target) =
cx.tcx().struct_lockstep_tails_erasing_lifetimes(source, target, cx.param_env());
cx.tcx().struct_lockstep_tails_erasing_lifetimes(source, target, bx.param_env());
match (source.kind(), target.kind()) {
(&ty::Array(_, len), &ty::Slice(_)) => {
cx.const_usize(len.eval_usize(cx.tcx(), ty::ParamEnv::reveal_all()))
}
(&ty::Dynamic(..), &ty::Dynamic(..)) => {
// For now, upcasts are limited to changes in marker
// traits, and hence never actually require an actual
// change to the vtable.
old_info.expect("unsized_info: missing old info for trait upcast")
(&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => {
let old_info =
old_info.expect("unsized_info: missing old info for trait upcasting coercion");
if data_a.principal_def_id() == data_b.principal_def_id() {
return old_info;
}
// trait upcasting coercion
// if both of the two `principal`s are `None`, this function would have returned early above.
// and if one of the two `principal`s is `None`, typechecking would have rejected this case.
let principal_a = data_a
.principal()
.expect("unsized_info: missing principal trait for trait upcasting coercion");
let principal_b = data_b
.principal()
.expect("unsized_info: missing principal trait for trait upcasting coercion");
let vptr_entry_idx = cx.tcx().vtable_trait_upcasting_coercion_new_vptr_slot((
principal_a.with_self_ty(cx.tcx(), source),
principal_b.with_self_ty(cx.tcx(), source),
));
if let Some(entry_idx) = vptr_entry_idx {
let ptr_ty = cx.type_i8p();
let ptr_align = cx.tcx().data_layout.pointer_align.abi;
let llvtable = bx.pointercast(old_info, bx.type_ptr_to(ptr_ty));
let gep =
bx.inbounds_gep(llvtable, &[bx.const_usize(u64::try_from(entry_idx).unwrap())]);
let new_vptr = bx.load(ptr_ty, gep, ptr_align);
bx.nonnull_metadata(new_vptr);
// Vtable loads are invariant.
bx.set_invariant_load(new_vptr);
new_vptr
} else {
old_info
}
}
(_, &ty::Dynamic(ref data, ..)) => {
let vtable_ptr = cx.layout_of(cx.tcx().mk_mut_ptr(target)).field(cx, FAT_PTR_EXTRA);
cx.const_ptrcast(
meth::get_vtable(cx, source, data.principal()),
cx.backend_type(vtable_ptr),
)
let vtable_ptr_ty = cx.scalar_pair_element_backend_type(
cx.layout_of(cx.tcx().mk_mut_ptr(target)),
1,
true,
);
cx.const_ptrcast(meth::get_vtable(cx, source, data.principal()), vtable_ptr_ty)
}
_ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
}
}
/// Coerces `src` to `dst_ty`. `src_ty` must be a thin pointer.
pub fn unsize_thin_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
/// Coerces `src` to `dst_ty`. `src_ty` must be a pointer.
pub fn unsize_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
src: Bx::Value,
src_ty: Ty<'tcx>,
dst_ty: Ty<'tcx>,
old_info: Option<Bx::Value>,
) -> (Bx::Value, Bx::Value) {
debug!("unsize_thin_ptr: {:?} => {:?}", src_ty, dst_ty);
debug!("unsize_ptr: {:?} => {:?}", src_ty, dst_ty);
match (src_ty.kind(), dst_ty.kind()) {
(&ty::Ref(_, a, _), &ty::Ref(_, b, _) | &ty::RawPtr(ty::TypeAndMut { ty: b, .. }))
| (&ty::RawPtr(ty::TypeAndMut { ty: a, .. }), &ty::RawPtr(ty::TypeAndMut { ty: b, .. })) => {
assert!(bx.cx().type_is_sized(a));
assert_eq!(bx.cx().type_is_sized(a), old_info.is_none());
let ptr_ty = bx.cx().type_ptr_to(bx.cx().backend_type(bx.cx().layout_of(b)));
(bx.pointercast(src, ptr_ty), unsized_info(bx.cx(), a, b, None))
(bx.pointercast(src, ptr_ty), unsized_info(bx, a, b, old_info))
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
assert_eq!(def_a, def_b);
let src_layout = bx.cx().layout_of(src_ty);
let dst_layout = bx.cx().layout_of(dst_ty);
if src_ty == dst_ty {
return (src, old_info.unwrap());
}
let mut result = None;
for i in 0..src_layout.fields.count() {
let src_f = src_layout.field(bx.cx(), i);
@ -190,18 +227,15 @@ pub fn unsize_thin_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
let dst_f = dst_layout.field(bx.cx(), i);
assert_ne!(src_f.ty, dst_f.ty);
assert_eq!(result, None);
result = Some(unsize_thin_ptr(bx, src, src_f.ty, dst_f.ty));
result = Some(unsize_ptr(bx, src, src_f.ty, dst_f.ty, old_info));
}
let (lldata, llextra) = result.unwrap();
let lldata_ty = bx.cx().scalar_pair_element_backend_type(dst_layout, 0, true);
let llextra_ty = bx.cx().scalar_pair_element_backend_type(dst_layout, 1, true);
// HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
// FIXME(eddyb) move these out of this `match` arm, so they're always
// applied, uniformly, no matter the source/destination types.
(
bx.bitcast(lldata, bx.cx().scalar_pair_element_backend_type(dst_layout, 0, true)),
bx.bitcast(llextra, bx.cx().scalar_pair_element_backend_type(dst_layout, 1, true)),
)
(bx.bitcast(lldata, lldata_ty), bx.bitcast(llextra, llextra_ty))
}
_ => bug!("unsize_thin_ptr: called on bad types"),
_ => bug!("unsize_ptr: called on bad types"),
}
}
@ -217,17 +251,8 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
match (src_ty.kind(), dst_ty.kind()) {
(&ty::Ref(..), &ty::Ref(..) | &ty::RawPtr(..)) | (&ty::RawPtr(..), &ty::RawPtr(..)) => {
let (base, info) = match bx.load_operand(src).val {
OperandValue::Pair(base, info) => {
// fat-ptr to fat-ptr unsize preserves the vtable
// i.e., &'a fmt::Debug+Send => &'a fmt::Debug
// So we need to pointercast the base to ensure
// the types match up.
// FIXME(eddyb) use `scalar_pair_element_backend_type` here,
// like `unsize_thin_ptr` does.
let thin_ptr = dst.layout.field(bx.cx(), FAT_PTR_ADDR);
(bx.pointercast(base, bx.cx().backend_type(thin_ptr)), info)
}
OperandValue::Immediate(base) => unsize_thin_ptr(bx, base, src_ty, dst_ty),
OperandValue::Pair(base, info) => unsize_ptr(bx, base, src_ty, dst_ty, Some(info)),
OperandValue::Immediate(base) => unsize_ptr(bx, base, src_ty, dst_ty, None),
OperandValue::Ref(..) => bug!(),
};
OperandValue::Pair(base, info).store(bx, dst);

27
compiler/rustc_codegen_ssa/src/mir/rvalue.rs
View File

@ -220,34 +220,23 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
mir::CastKind::Pointer(PointerCast::Unsize) => {
assert!(bx.cx().is_backend_scalar_pair(cast));
match operand.val {
let (lldata, llextra) = match operand.val {
OperandValue::Pair(lldata, llextra) => {
// unsize from a fat pointer -- this is a
// "trait-object-to-supertrait" coercion, for
// example, `&'a fmt::Debug + Send => &'a fmt::Debug`.
// HACK(eddyb) have to bitcast pointers
// until LLVM removes pointee types.
let lldata = bx.pointercast(
lldata,
bx.cx().scalar_pair_element_backend_type(cast, 0, true),
);
OperandValue::Pair(lldata, llextra)
// "trait-object-to-supertrait" coercion.
(lldata, Some(llextra))
}
OperandValue::Immediate(lldata) => {
// "standard" unsize
let (lldata, llextra) = base::unsize_thin_ptr(
&mut bx,
lldata,
operand.layout.ty,
cast.ty,
);
OperandValue::Pair(lldata, llextra)
(lldata, None)
}
OperandValue::Ref(..) => {
bug!("by-ref operand {:?} in `codegen_rvalue_operand`", operand);
}
}
};
let (lldata, llextra) =
base::unsize_ptr(&mut bx, lldata, operand.layout.ty, cast.ty, llextra);
OperandValue::Pair(lldata, llextra)
}
mir::CastKind::Pointer(PointerCast::MutToConstPointer)
| mir::CastKind::Misc

5
compiler/rustc_middle/src/query/mod.rs
View File

@ -977,6 +977,11 @@ rustc_queries! {
desc { |tcx| "finding all vtable entries for trait {}", tcx.def_path_str(key.def_id()) }
}
query vtable_trait_upcasting_coercion_new_vptr_slot(key: (ty::PolyTraitRef<'tcx>, ty::PolyTraitRef<'tcx>)) -> Option<usize> {
desc { |tcx| "finding the slot within vtable for trait {} vtable ptr during trait upcasting coercion from {} vtable",
tcx.def_path_str(key.1.def_id()), tcx.def_path_str(key.0.def_id()) }
}
query codegen_fulfill_obligation(
key: (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>)
) -> Result<ImplSource<'tcx, ()>, ErrorReported> {

32
compiler/rustc_mir/src/interpret/cast.rs
View File

@ -269,12 +269,34 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Immediate::new_slice(ptr, length.eval_usize(*self.tcx, self.param_env), self);
self.write_immediate(val, dest)
}
(&ty::Dynamic(..), &ty::Dynamic(..)) => {
// For now, upcasts are limited to changes in marker
// traits, and hence never actually require an actual
// change to the vtable.
(&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => {
let val = self.read_immediate(src)?;
self.write_immediate(*val, dest)
if data_a.principal_def_id() == data_b.principal_def_id() {
return self.write_immediate(*val, dest);
}
// trait upcasting coercion
let principal_a = data_a.principal().expect(
"unsize_into_ptr: missing principal trait for trait upcasting coercion",
);
let principal_b = data_b.principal().expect(
"unsize_into_ptr: missing principal trait for trait upcasting coercion",
);
let vptr_entry_idx = self.tcx.vtable_trait_upcasting_coercion_new_vptr_slot((
principal_a.with_self_ty(*self.tcx, src_pointee_ty),
principal_b.with_self_ty(*self.tcx, src_pointee_ty),
));
if let Some(entry_idx) = vptr_entry_idx {
let entry_idx = u64::try_from(entry_idx).unwrap();
let (old_data, old_vptr) = val.to_scalar_pair()?;
let old_vptr = self.scalar_to_ptr(old_vptr);
let new_vptr = self
.read_new_vtable_after_trait_upcasting_from_vtable(old_vptr, entry_idx)?;
self.write_immediate(Immediate::new_dyn_trait(old_data, new_vptr, self), dest)
} else {
self.write_immediate(*val, dest)
}
}
(_, &ty::Dynamic(ref data, _)) => {
// Initial cast from sized to dyn trait

20
compiler/rustc_mir/src/interpret/operand.rs
View File

@ -63,15 +63,19 @@ impl<'tcx, Tag: Provenance> Immediate<Tag> {
Immediate::ScalarPair(val.into(), Scalar::from_machine_usize(len, cx).into())
}
pub fn new_dyn_trait(val: Scalar<Tag>, vtable: Pointer<Tag>, cx: &impl HasDataLayout) -> Self {
Immediate::ScalarPair(val.into(), ScalarMaybeUninit::from_pointer(vtable, cx))
pub fn new_dyn_trait(
val: Scalar<Tag>,
vtable: Pointer<Option<Tag>>,
cx: &impl HasDataLayout,
) -> Self {
Immediate::ScalarPair(val.into(), ScalarMaybeUninit::from_maybe_pointer(vtable, cx))
}
#[inline]
pub fn to_scalar_or_uninit(self) -> ScalarMaybeUninit<Tag> {
match self {
Immediate::Scalar(val) => val,
Immediate::ScalarPair(..) => bug!("Got a wide pointer where a scalar was expected"),
Immediate::ScalarPair(..) => bug!("Got a scalar pair where a scalar was expected"),
}
}
@ -79,6 +83,16 @@ impl<'tcx, Tag: Provenance> Immediate<Tag> {
pub fn to_scalar(self) -> InterpResult<'tcx, Scalar<Tag>> {
self.to_scalar_or_uninit().check_init()
}
#[inline]
pub fn to_scalar_pair(self) -> InterpResult<'tcx, (Scalar<Tag>, Scalar<Tag>)> {
match self {
Immediate::ScalarPair(val1, val2) => Ok((val1.check_init()?, val2.check_init()?)),
Immediate::Scalar(..) => {
bug!("Got a scalar where a scalar pair was expected")
}
}
}
}
// ScalarPair needs a type to interpret, so we often have an immediate and a type together

22
compiler/rustc_mir/src/interpret/traits.rs
View File

@ -21,7 +21,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
&mut self,
ty: Ty<'tcx>,
poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
) -> InterpResult<'tcx, Pointer<M::PointerTag>> {
) -> InterpResult<'tcx, Pointer<Option<M::PointerTag>>> {
trace!("get_vtable(trait_ref={:?})", poly_trait_ref);
let (ty, poly_trait_ref) = self.tcx.erase_regions((ty, poly_trait_ref));
@ -34,7 +34,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let vtable_ptr = self.memory.global_base_pointer(Pointer::from(vtable_allocation))?;
Ok(vtable_ptr)
Ok(vtable_ptr.into())
}
/// Resolves the function at the specified slot in the provided
@ -121,4 +121,22 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
Ok((Size::from_bytes(size), align))
}
pub fn read_new_vtable_after_trait_upcasting_from_vtable(
&self,
vtable: Pointer<Option<M::PointerTag>>,
idx: u64,
) -> InterpResult<'tcx, Pointer<Option<M::PointerTag>>> {
let pointer_size = self.pointer_size();
let vtable_slot = vtable.offset(pointer_size * idx, self)?;
let new_vtable = self
.memory
.get(vtable_slot, pointer_size, self.tcx.data_layout.pointer_align.abi)?
.expect("cannot be a ZST");
let new_vtable = self.scalar_to_ptr(new_vtable.read_ptr_sized(Size::ZERO)?.check_init()?);
Ok(new_vtable)
}
}

10
compiler/rustc_query_impl/src/keys.rs
View File

@ -282,6 +282,16 @@ impl<'tcx> Key for ty::PolyTraitRef<'tcx> {
}
}
impl<'tcx> Key for (ty::PolyTraitRef<'tcx>, ty::PolyTraitRef<'tcx>) {
#[inline(always)]
fn query_crate_is_local(&self) -> bool {
self.0.def_id().krate == LOCAL_CRATE
}
fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
tcx.def_span(self.0.def_id())
}
}
impl<'tcx> Key for GenericArg<'tcx> {
#[inline(always)]
fn query_crate_is_local(&self) -> bool {

16
compiler/rustc_trait_selection/src/traits/mod.rs
View File

@ -756,16 +756,17 @@ fn vtable_trait_first_method_offset<'tcx>(
}
/// Find slot offset for trait vptr within vtable entries of another trait
/// FIXME: This function is not yet used. Remove `#[allow(dead_code)]` when it's used in upcoming pr.
#[allow(dead_code)]
fn vtable_trait_vptr_slot_offset<'tcx>(
pub fn vtable_trait_upcasting_coercion_new_vptr_slot(
tcx: TyCtxt<'tcx>,
key: (
ty::PolyTraitRef<'tcx>, // trait_to_be_found
ty::PolyTraitRef<'tcx>, // trait_owning_vtable
ty::PolyTraitRef<'tcx>, // trait owning vtable
ty::PolyTraitRef<'tcx>, // super trait ref
),
) -> Option<usize> {
let (trait_to_be_found, trait_owning_vtable) = key;
let (trait_owning_vtable, super_trait_ref) = key;
let super_trait_did = super_trait_ref.def_id();
// FIXME: take substsref part into account here after upcasting coercion allows the same def_id occur
// multiple times.
let vtable_segment_callback = {
let mut vptr_offset = 0;
@ -776,7 +777,7 @@ fn vtable_trait_vptr_slot_offset<'tcx>(
}
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
vptr_offset += util::count_own_vtable_entries(tcx, trait_ref);
if trait_ref == trait_to_be_found {
if trait_ref.def_id() == super_trait_did {
if emit_vptr {
return ControlFlow::Break(Some(vptr_offset));
} else {
@ -810,6 +811,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
specializes: specialize::specializes,
codegen_fulfill_obligation: codegen::codegen_fulfill_obligation,
vtable_entries,
vtable_trait_upcasting_coercion_new_vptr_slot,
subst_and_check_impossible_predicates,
mir_abstract_const: |tcx, def_id| {
let def_id = def_id.expect_local();

27
src/doc/unstable-book/src/language-features/trait-upcasting.md Normal file
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@ -0,0 +1,27 @@
# `trait_upcasting`
The tracking issue for this feature is: [#65991]
[#65991]: https://github.com/rust-lang/rust/issues/65991
------------------------
The `trait_upcasting` feature adds support for trait upcasting coercion. This allows a
trait object of type `dyn Bar` to be cast to a trait object of type `dyn Foo`
so long as `Bar: Foo`.
```rust,edition2018
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait Foo {}
trait Bar: Foo {}
impl Foo for i32 {}
impl<T: Foo + ?Sized> Bar for T {}
let bar: &dyn Bar = &123;
let foo: &dyn Foo = bar;
```

87
src/test/ui/traits/trait-upcasting/basic.rs Normal file
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@ -0,0 +1,87 @@
// run-pass
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
fn a(&self) -> i32 {
10
}
fn z(&self) -> i32 {
11
}
fn y(&self) -> i32 {
12
}
}
trait Bar: Foo {
fn b(&self) -> i32 {
20
}
fn w(&self) -> i32 {
21
}
}
trait Baz: Bar {
fn c(&self) -> i32 {
30
}
}
impl Foo for i32 {
fn a(&self) -> i32 {
100
}
}
impl Bar for i32 {
fn b(&self) -> i32 {
200
}
}
impl Baz for i32 {
fn c(&self) -> i32 {
300
}
}
fn main() {
let baz: &dyn Baz = &1;
let _: &dyn std::fmt::Debug = baz;
assert_eq!(*baz, 1);
assert_eq!(baz.a(), 100);
assert_eq!(baz.b(), 200);
assert_eq!(baz.c(), 300);
assert_eq!(baz.z(), 11);
assert_eq!(baz.y(), 12);
assert_eq!(baz.w(), 21);
let bar: &dyn Bar = baz;
let _: &dyn std::fmt::Debug = bar;
assert_eq!(*bar, 1);
assert_eq!(bar.a(), 100);
assert_eq!(bar.b(), 200);
assert_eq!(bar.z(), 11);
assert_eq!(bar.y(), 12);
assert_eq!(bar.w(), 21);
let foo: &dyn Foo = baz;
let _: &dyn std::fmt::Debug = foo;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
let foo: &dyn Foo = bar;
let _: &dyn std::fmt::Debug = foo;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
}

13
src/test/ui/traits/trait-upcasting/cyclic-trait-resolution.rs Normal file
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@ -0,0 +1,13 @@
trait A: B + A {}
//~^ ERROR cycle detected when computing the super predicates of `A` [E0391]
trait B {}
impl A for () {}
impl B for () {}
fn main() {
let a: Box<dyn A> = Box::new(());
let _b: Box<dyn B> = a;
}

21
src/test/ui/traits/trait-upcasting/cyclic-trait-resolution.stderr Normal file
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@ -0,0 +1,21 @@
error[E0391]: cycle detected when computing the super predicates of `A`
--> $DIR/cyclic-trait-resolution.rs:1:1
|
LL | trait A: B + A {}
| ^^^^^^^^^^^^^^
|
note: ...which requires computing the super traits of `A`...
--> $DIR/cyclic-trait-resolution.rs:1:14
|
LL | trait A: B + A {}
| ^
= note: ...which again requires computing the super predicates of `A`, completing the cycle
note: cycle used when collecting item types in top-level module
--> $DIR/cyclic-trait-resolution.rs:1:1
|
LL | trait A: B + A {}
| ^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0391`.

115
src/test/ui/traits/trait-upcasting/diamond.rs Normal file
View File

@ -0,0 +1,115 @@
// run-pass
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
fn a(&self) -> i32 {
10
}
fn z(&self) -> i32 {
11
}
fn y(&self) -> i32 {
12
}
}
trait Bar1: Foo {
fn b(&self) -> i32 {
20
}
fn w(&self) -> i32 {
21
}
}
trait Bar2: Foo {
fn c(&self) -> i32 {
30
}
fn v(&self) -> i32 {
31
}
}
trait Baz: Bar1 + Bar2 {
fn d(&self) -> i32 {
40
}
}
impl Foo for i32 {
fn a(&self) -> i32 {
100
}
}
impl Bar1 for i32 {
fn b(&self) -> i32 {
200
}
}
impl Bar2 for i32 {
fn c(&self) -> i32 {
300
}
}
impl Baz for i32 {
fn d(&self) -> i32 {
400
}
}
fn main() {
let baz: &dyn Baz = &1;
let _: &dyn std::fmt::Debug = baz;
assert_eq!(*baz, 1);
assert_eq!(baz.a(), 100);
assert_eq!(baz.b(), 200);
assert_eq!(baz.c(), 300);
assert_eq!(baz.d(), 400);
assert_eq!(baz.z(), 11);
assert_eq!(baz.y(), 12);
assert_eq!(baz.w(), 21);
assert_eq!(baz.v(), 31);
let bar1: &dyn Bar1 = baz;
let _: &dyn std::fmt::Debug = bar1;
assert_eq!(*bar1, 1);
assert_eq!(bar1.a(), 100);
assert_eq!(bar1.b(), 200);
assert_eq!(bar1.z(), 11);
assert_eq!(bar1.y(), 12);
assert_eq!(bar1.w(), 21);
let bar2: &dyn Bar2 = baz;
let _: &dyn std::fmt::Debug = bar2;
assert_eq!(*bar2, 1);
assert_eq!(bar2.a(), 100);
assert_eq!(bar2.c(), 300);
assert_eq!(bar2.z(), 11);
assert_eq!(bar2.y(), 12);
assert_eq!(bar2.v(), 31);
let foo: &dyn Foo = baz;
let _: &dyn std::fmt::Debug = foo;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
let foo: &dyn Foo = bar1;
let _: &dyn std::fmt::Debug = foo;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
let foo: &dyn Foo = bar2;
let _: &dyn std::fmt::Debug = foo;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
}

87
src/test/ui/traits/trait-upcasting/invalid-upcast.rs Normal file
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@ -0,0 +1,87 @@
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait Foo {
fn a(&self) -> i32 {
10
}
fn z(&self) -> i32 {
11
}
fn y(&self) -> i32 {
12
}
}
trait Bar {
fn b(&self) -> i32 {
20
}
fn w(&self) -> i32 {
21
}
}
trait Baz {
fn c(&self) -> i32 {
30
}
}
impl Foo for i32 {
fn a(&self) -> i32 {
100
}
}
impl Bar for i32 {
fn b(&self) -> i32 {
200
}
}
impl Baz for i32 {
fn c(&self) -> i32 {
300
}
}
fn main() {
let baz: &dyn Baz = &1;
let _: &dyn std::fmt::Debug = baz;
//~^ ERROR mismatched types [E0308]
let _: &dyn Send = baz;
//~^ ERROR mismatched types [E0308]
let _: &dyn Sync = baz;
//~^ ERROR mismatched types [E0308]
let bar: &dyn Bar = baz;
//~^ ERROR mismatched types [E0308]
let _: &dyn std::fmt::Debug = bar;
//~^ ERROR mismatched types [E0308]
let _: &dyn Send = bar;
//~^ ERROR mismatched types [E0308]
let _: &dyn Sync = bar;
//~^ ERROR mismatched types [E0308]
let foo: &dyn Foo = baz;
//~^ ERROR mismatched types [E0308]
let _: &dyn std::fmt::Debug = foo;
//~^ ERROR mismatched types [E0308]
let _: &dyn Send = foo;
//~^ ERROR mismatched types [E0308]
let _: &dyn Sync = foo;
//~^ ERROR mismatched types [E0308]
let foo: &dyn Foo = bar;
//~^ ERROR mismatched types [E0308]
let _: &dyn std::fmt::Debug = foo;
//~^ ERROR mismatched types [E0308]
let _: &dyn Send = foo;
//~^ ERROR mismatched types [E0308]
let _: &dyn Sync = foo;
//~^ ERROR mismatched types [E0308]
}

168
src/test/ui/traits/trait-upcasting/invalid-upcast.stderr Normal file
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@ -0,0 +1,168 @@
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:54:35
|
LL | let _: &dyn std::fmt::Debug = baz;
| -------------------- ^^^ expected trait `Debug`, found trait `Baz`
| |
| expected due to this
|
= note: expected reference `&dyn Debug`
found reference `&dyn Baz`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:56:24
|
LL | let _: &dyn Send = baz;
| --------- ^^^ expected trait `Send`, found trait `Baz`
| |
| expected due to this
|
= note: expected reference `&dyn Send`
found reference `&dyn Baz`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:58:24
|
LL | let _: &dyn Sync = baz;
| --------- ^^^ expected trait `Sync`, found trait `Baz`
| |
| expected due to this
|
= note: expected reference `&dyn Sync`
found reference `&dyn Baz`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:61:25
|
LL | let bar: &dyn Bar = baz;
| -------- ^^^ expected trait `Bar`, found trait `Baz`
| |
| expected due to this
|
= note: expected reference `&dyn Bar`
found reference `&dyn Baz`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:63:35
|
LL | let _: &dyn std::fmt::Debug = bar;
| -------------------- ^^^ expected trait `Debug`, found trait `Bar`
| |
| expected due to this
|
= note: expected reference `&dyn Debug`
found reference `&dyn Bar`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:65:24
|
LL | let _: &dyn Send = bar;
| --------- ^^^ expected trait `Send`, found trait `Bar`
| |
| expected due to this
|
= note: expected reference `&dyn Send`
found reference `&dyn Bar`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:67:24
|
LL | let _: &dyn Sync = bar;
| --------- ^^^ expected trait `Sync`, found trait `Bar`
| |
| expected due to this
|
= note: expected reference `&dyn Sync`
found reference `&dyn Bar`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:70:25
|
LL | let foo: &dyn Foo = baz;
| -------- ^^^ expected trait `Foo`, found trait `Baz`
| |
| expected due to this
|
= note: expected reference `&dyn Foo`
found reference `&dyn Baz`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:72:35
|
LL | let _: &dyn std::fmt::Debug = foo;
| -------------------- ^^^ expected trait `Debug`, found trait `Foo`
| |
| expected due to this
|
= note: expected reference `&dyn Debug`
found reference `&dyn Foo`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:74:24
|
LL | let _: &dyn Send = foo;
| --------- ^^^ expected trait `Send`, found trait `Foo`
| |
| expected due to this
|
= note: expected reference `&dyn Send`
found reference `&dyn Foo`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:76:24
|
LL | let _: &dyn Sync = foo;
| --------- ^^^ expected trait `Sync`, found trait `Foo`
| |
| expected due to this
|
= note: expected reference `&dyn Sync`
found reference `&dyn Foo`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:79:25
|
LL | let foo: &dyn Foo = bar;
| -------- ^^^ expected trait `Foo`, found trait `Bar`
| |
| expected due to this
|
= note: expected reference `&dyn Foo`
found reference `&dyn Bar`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:81:35
|
LL | let _: &dyn std::fmt::Debug = foo;
| -------------------- ^^^ expected trait `Debug`, found trait `Foo`
| |
| expected due to this
|
= note: expected reference `&dyn Debug`
found reference `&dyn Foo`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:83:24
|
LL | let _: &dyn Send = foo;
| --------- ^^^ expected trait `Send`, found trait `Foo`
| |
| expected due to this
|
= note: expected reference `&dyn Send`
found reference `&dyn Foo`
error[E0308]: mismatched types
--> $DIR/invalid-upcast.rs:85:24
|
LL | let _: &dyn Sync = foo;
| --------- ^^^ expected trait `Sync`, found trait `Foo`
| |
| expected due to this
|
= note: expected reference `&dyn Sync`
found reference `&dyn Foo`
error: aborting due to 15 previous errors
For more information about this error, try `rustc --explain E0308`.

96
src/test/ui/traits/trait-upcasting/lifetime.rs Normal file
View File

@ -0,0 +1,96 @@
// run-pass
// ignore-compare-mode-nll
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
fn a(&self) -> i32 {
10
}
fn z(&self) -> i32 {
11
}
fn y(&self) -> i32 {
12
}
}
trait Bar: Foo {
fn b(&self) -> i32 {
20
}
fn w(&self) -> i32 {
21
}
}
trait Baz: Bar {
fn c(&self) -> i32 {
30
}
}
impl Foo for i32 {
fn a(&self) -> i32 {
100
}
}
impl Bar for i32 {
fn b(&self) -> i32 {
200
}
}
impl Baz for i32 {
fn c(&self) -> i32 {
300
}
}
// Note: upcast lifetime means a shorter lifetime.
fn upcast_baz<'a: 'b, 'b, T>(v: Box<dyn Baz + 'a>, _l: &'b T) -> Box<dyn Baz + 'b> {
v
}
fn upcast_bar<'a: 'b, 'b, T>(v: Box<dyn Bar + 'a>, _l: &'b T) -> Box<dyn Bar + 'b> {
v
}
fn upcast_foo<'a: 'b, 'b, T>(v: Box<dyn Foo + 'a>, _l: &'b T) -> Box<dyn Foo + 'b> {
v
}
fn main() {
let v = Box::new(1);
let l = &(); // dummy lifetime (shorter than `baz`)
let baz: Box<dyn Baz> = v.clone();
let u = upcast_baz(baz, &l);
assert_eq!(*u, 1);
assert_eq!(u.a(), 100);
assert_eq!(u.b(), 200);
assert_eq!(u.c(), 300);
let baz: Box<dyn Baz> = v.clone();
let bar: Box<dyn Bar> = baz;
let u = upcast_bar(bar, &l);
assert_eq!(*u, 1);
assert_eq!(u.a(), 100);
assert_eq!(u.b(), 200);
let baz: Box<dyn Baz> = v.clone();
let foo: Box<dyn Foo> = baz;
let u = upcast_foo(foo, &l);
assert_eq!(*u, 1);
assert_eq!(u.a(), 100);
let baz: Box<dyn Baz> = v.clone();
let bar: Box<dyn Bar> = baz;
let foo: Box<dyn Foo> = bar;
let u = upcast_foo(foo, &l);
assert_eq!(*u, 1);
assert_eq!(u.a(), 100);
}

49
src/test/ui/traits/trait-upcasting/replace-vptr.rs Normal file
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@ -0,0 +1,49 @@
// run-pass
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait A {
fn foo_a(&self);
}
trait B {
fn foo_b(&self);
}
trait C: A + B {
fn foo_c(&self);
}
struct S(i32);
impl A for S {
fn foo_a(&self) {
unreachable!();
}
}
impl B for S {
fn foo_b(&self) {
assert_eq!(42, self.0);
}
}
impl C for S {
fn foo_c(&self) {
unreachable!();
}
}
fn invoke_inner(b: &dyn B) {
b.foo_b();
}
fn invoke_outer(c: &dyn C) {
invoke_inner(c);
}
fn main() {
let s = S(42);
invoke_outer(&s);
}

174
src/test/ui/traits/trait-upcasting/struct.rs Normal file
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@ -0,0 +1,174 @@
// run-pass
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
use std::rc::Rc;
use std::sync::Arc;
trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
fn a(&self) -> i32 {
10
}
fn z(&self) -> i32 {
11
}
fn y(&self) -> i32 {
12
}
}
trait Bar: Foo {
fn b(&self) -> i32 {
20
}
fn w(&self) -> i32 {
21
}
}
trait Baz: Bar {
fn c(&self) -> i32 {
30
}
}
impl Foo for i32 {
fn a(&self) -> i32 {
100
}
}
impl Bar for i32 {
fn b(&self) -> i32 {
200
}
}
impl Baz for i32 {
fn c(&self) -> i32 {
300
}
}
fn test_box() {
let v = Box::new(1);
let baz: Box<dyn Baz> = v.clone();
assert_eq!(*baz, 1);
assert_eq!(baz.a(), 100);
assert_eq!(baz.b(), 200);
assert_eq!(baz.c(), 300);
assert_eq!(baz.z(), 11);
assert_eq!(baz.y(), 12);
assert_eq!(baz.w(), 21);
let baz: Box<dyn Baz> = v.clone();
let bar: Box<dyn Bar> = baz;
assert_eq!(*bar, 1);
assert_eq!(bar.a(), 100);
assert_eq!(bar.b(), 200);
assert_eq!(bar.z(), 11);
assert_eq!(bar.y(), 12);
assert_eq!(bar.w(), 21);
let baz: Box<dyn Baz> = v.clone();
let foo: Box<dyn Foo> = baz;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
let baz: Box<dyn Baz> = v.clone();
let bar: Box<dyn Bar> = baz;
let foo: Box<dyn Foo> = bar;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
}
fn test_rc() {
let v = Rc::new(1);
let baz: Rc<dyn Baz> = v.clone();
assert_eq!(*baz, 1);
assert_eq!(baz.a(), 100);
assert_eq!(baz.b(), 200);
assert_eq!(baz.c(), 300);
assert_eq!(baz.z(), 11);
assert_eq!(baz.y(), 12);
assert_eq!(baz.w(), 21);
let baz: Rc<dyn Baz> = v.clone();
let bar: Rc<dyn Bar> = baz;
assert_eq!(*bar, 1);
assert_eq!(bar.a(), 100);
assert_eq!(bar.b(), 200);
assert_eq!(bar.z(), 11);
assert_eq!(bar.y(), 12);
assert_eq!(bar.w(), 21);
let baz: Rc<dyn Baz> = v.clone();
let foo: Rc<dyn Foo> = baz;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
let baz: Rc<dyn Baz> = v.clone();
let bar: Rc<dyn Bar> = baz;
let foo: Rc<dyn Foo> = bar;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
}
fn test_arc() {
let v = Arc::new(1);
let baz: Arc<dyn Baz> = v.clone();
assert_eq!(*baz, 1);
assert_eq!(baz.a(), 100);
assert_eq!(baz.b(), 200);
assert_eq!(baz.c(), 300);
assert_eq!(baz.z(), 11);
assert_eq!(baz.y(), 12);
assert_eq!(baz.w(), 21);
let baz: Arc<dyn Baz> = v.clone();
let bar: Arc<dyn Bar> = baz;
assert_eq!(*bar, 1);
assert_eq!(bar.a(), 100);
assert_eq!(bar.b(), 200);
assert_eq!(bar.z(), 11);
assert_eq!(bar.y(), 12);
assert_eq!(bar.w(), 21);
let baz: Arc<dyn Baz> = v.clone();
let foo: Arc<dyn Foo> = baz;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
let baz: Arc<dyn Baz> = v.clone();
let bar: Arc<dyn Bar> = baz;
let foo: Arc<dyn Foo> = bar;
assert_eq!(*foo, 1);
assert_eq!(foo.a(), 100);
assert_eq!(foo.z(), 11);
assert_eq!(foo.y(), 12);
}
fn main() {
test_box();
test_rc();
test_arc();
}

70
src/test/ui/traits/trait-upcasting/subtrait-method.rs Normal file
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@ -0,0 +1,70 @@
#![feature(trait_upcasting)]
#![allow(incomplete_features)]
trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
fn a(&self) -> i32 {
10
}
fn z(&self) -> i32 {
11
}
fn y(&self) -> i32 {
12
}
}
trait Bar: Foo {
fn b(&self) -> i32 {
20
}
fn w(&self) -> i32 {
21
}
}
trait Baz: Bar {
fn c(&self) -> i32 {
30
}
}
impl Foo for i32 {
fn a(&self) -> i32 {
100
}
}
impl Bar for i32 {
fn b(&self) -> i32 {
200
}
}
impl Baz for i32 {
fn c(&self) -> i32 {
300
}
}
fn main() {
let baz: &dyn Baz = &1;
let bar: &dyn Bar = baz;
bar.c();
//~^ ERROR no method named `c` found for reference `&dyn Bar` in the current scope [E0599]
let foo: &dyn Foo = baz;
foo.b();
//~^ ERROR no method named `b` found for reference `&dyn Foo` in the current scope [E0599]
foo.c();
//~^ ERROR no method named `c` found for reference `&dyn Foo` in the current scope [E0599]
let foo: &dyn Foo = bar;
foo.b();
//~^ ERROR no method named `b` found for reference `&dyn Foo` in the current scope [E0599]
foo.c();
//~^ ERROR no method named `c` found for reference `&dyn Foo` in the current scope [E0599]
}

68
src/test/ui/traits/trait-upcasting/subtrait-method.stderr Normal file
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error[E0599]: no method named `c` found for reference `&dyn Bar` in the current scope
--> $DIR/subtrait-method.rs:56:9
|
LL | bar.c();
| ^ help: there is an associated function with a similar name: `a`
|
= help: items from traits can only be used if the trait is implemented and in scope
note: `Baz` defines an item `c`, perhaps you need to implement it
--> $DIR/subtrait-method.rs:28:1
|
LL | trait Baz: Bar {
| ^^^^^^^^^^^^^^
error[E0599]: no method named `b` found for reference `&dyn Foo` in the current scope
--> $DIR/subtrait-method.rs:60:9
|
LL | foo.b();
| ^ help: there is an associated function with a similar name: `a`
|
= help: items from traits can only be used if the trait is implemented and in scope
note: `Bar` defines an item `b`, perhaps you need to implement it
--> $DIR/subtrait-method.rs:18:1
|
LL | trait Bar: Foo {
| ^^^^^^^^^^^^^^
error[E0599]: no method named `c` found for reference `&dyn Foo` in the current scope
--> $DIR/subtrait-method.rs:62:9
|
LL | foo.c();
| ^ help: there is an associated function with a similar name: `a`
|
= help: items from traits can only be used if the trait is implemented and in scope
note: `Baz` defines an item `c`, perhaps you need to implement it
--> $DIR/subtrait-method.rs:28:1
|
LL | trait Baz: Bar {
| ^^^^^^^^^^^^^^
error[E0599]: no method named `b` found for reference `&dyn Foo` in the current scope
--> $DIR/subtrait-method.rs:66:9
|
LL | foo.b();
| ^ help: there is an associated function with a similar name: `a`
|
= help: items from traits can only be used if the trait is implemented and in scope
note: `Bar` defines an item `b`, perhaps you need to implement it
--> $DIR/subtrait-method.rs:18:1
|
LL | trait Bar: Foo {
| ^^^^^^^^^^^^^^
error[E0599]: no method named `c` found for reference `&dyn Foo` in the current scope
--> $DIR/subtrait-method.rs:68:9
|
LL | foo.c();
| ^ help: there is an associated function with a similar name: `a`
|
= help: items from traits can only be used if the trait is implemented and in scope
note: `Baz` defines an item `c`, perhaps you need to implement it
--> $DIR/subtrait-method.rs:28:1
|
LL | trait Baz: Bar {
| ^^^^^^^^^^^^^^
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0599`.