From 3aa14e3b2e61739e8d0ec7883f9c185821ca5da2 Mon Sep 17 00:00:00 2001
From: Jack Wrenn <jack@wrenn.fyi>
Date: Tue, 19 Mar 2024 14:49:13 +0000
Subject: [PATCH] Compute transmutability from `rustc_target::abi::Layout`
In its first step of computing transmutability, `rustc_transmutability`
constructs a byte-level representation of type layout (`Tree`). Previously, this
representation was computed for ADTs by inspecting the ADT definition and
performing our own layout computations. This process was error-prone, verbose,
and limited our ability to analyze many types (particularly default-repr types).
In this PR, we instead construct `Tree`s from `rustc_target::abi::Layout`s. This
helps ensure that layout optimizations are reflected our analyses, and increases
the kinds of types we can now analyze, including:
- default repr ADTs
- transparent unions
- `UnsafeCell`-containing types
Overall, this PR expands the expressvity of `rustc_transmutability` to be much
closer to the transmutability analysis performed by miri. Future PRs will work
to close the remaining gaps (e.g., support for `Box`, raw pointers, `NonZero*`,
coroutines, etc.).
---
.../src/traits/error_reporting/mod.rs | 2 +-
.../error_reporting/type_err_ctxt_ext.rs | 30 +-
.../src/traits/select/confirmation.rs | 42 +-
compiler/rustc_transmute/src/layout/dfa.rs | 2 +
compiler/rustc_transmute/src/layout/nfa.rs | 1 +
compiler/rustc_transmute/src/layout/tree.rs | 453 ++++++++----------
compiler/rustc_transmute/src/lib.rs | 4 +-
.../src/maybe_transmutable/mod.rs | 19 +-
.../src/maybe_transmutable/query_context.rs | 10 -
.../ui/transmutability/arrays/huge-len.stderr | 4 +-
.../should_require_well_defined_layout.stderr | 12 +-
.../enums/niche_optimization.rs | 156 ++++++
.../enums/repr/padding_differences.rs | 80 ++++
...defined_layout.rs => should_handle_all.rs} | 21 +-
.../should_require_well_defined_layout.stderr | 135 ------
.../unknown_src_field.stderr | 2 +-
tests/ui/transmutability/maybeuninit.rs | 43 ++
tests/ui/transmutability/maybeuninit.stderr | 18 +
.../transmutability/references/unsafecell.rs | 47 ++
.../references/unsafecell.stderr | 33 ++
...defined_layout.rs => should_handle_all.rs} | 29 +-
.../should_require_well_defined_layout.stderr | 267 -----------
.../transmute_infinitely_recursive_type.rs | 1 +
...transmute_infinitely_recursive_type.stderr | 19 +-
.../transmutability/transmute-padding-ice.rs | 9 +-
.../transmute-padding-ice.stderr | 22 -
tests/ui/transmutability/uninhabited.rs | 71 +++
tests/ui/transmutability/uninhabited.stderr | 86 ++++
.../unions/repr/should_handle_align.rs | 4 +-
...defined_layout.rs => should_handle_all.rs} | 24 +-
.../unions/repr/should_handle_packed.rs | 1 -
.../should_require_well_defined_layout.stderr | 47 --
32 files changed, 905 insertions(+), 789 deletions(-)
create mode 100644 tests/ui/transmutability/enums/niche_optimization.rs
create mode 100644 tests/ui/transmutability/enums/repr/padding_differences.rs
rename tests/ui/transmutability/enums/repr/{should_require_well_defined_layout.rs => should_handle_all.rs} (80%)
delete mode 100644 tests/ui/transmutability/enums/repr/should_require_well_defined_layout.stderr
create mode 100644 tests/ui/transmutability/maybeuninit.rs
create mode 100644 tests/ui/transmutability/maybeuninit.stderr
create mode 100644 tests/ui/transmutability/references/unsafecell.rs
create mode 100644 tests/ui/transmutability/references/unsafecell.stderr
rename tests/ui/transmutability/structs/repr/{should_require_well_defined_layout.rs => should_handle_all.rs} (54%)
delete mode 100644 tests/ui/transmutability/structs/repr/should_require_well_defined_layout.stderr
delete mode 100644 tests/ui/transmutability/transmute-padding-ice.stderr
create mode 100644 tests/ui/transmutability/uninhabited.rs
create mode 100644 tests/ui/transmutability/uninhabited.stderr
rename tests/ui/transmutability/unions/repr/{should_require_well_defined_layout.rs => should_handle_all.rs} (58%)
delete mode 100644 tests/ui/transmutability/unions/repr/should_require_well_defined_layout.stderr
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 0515b09ae46..cd3383dbfc2 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -40,7 +40,7 @@ pub struct ImplCandidate<'tcx> {
enum GetSafeTransmuteErrorAndReason {
Silent,
- Error { err_msg: String, safe_transmute_explanation: String },
+ Error { err_msg: String, safe_transmute_explanation: Option<String> },
}
struct UnsatisfiedConst(pub bool);
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 01f9c8bb5d1..3a989c46fc1 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -557,7 +557,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
GetSafeTransmuteErrorAndReason::Error {
err_msg,
safe_transmute_explanation,
- } => (err_msg, Some(safe_transmute_explanation)),
+ } => (err_msg, safe_transmute_explanation),
}
} else {
(err_msg, None)
@@ -3061,28 +3061,33 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
return GetSafeTransmuteErrorAndReason::Silent;
};
+ let dst = trait_ref.args.type_at(0);
+ let src = trait_ref.args.type_at(1);
+ let err_msg = format!("`{src}` cannot be safely transmuted into `{dst}`");
+
match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(
obligation.cause,
src_and_dst,
assume,
) {
Answer::No(reason) => {
- let dst = trait_ref.args.type_at(0);
- let src = trait_ref.args.type_at(1);
- let err_msg = format!("`{src}` cannot be safely transmuted into `{dst}`");
let safe_transmute_explanation = match reason {
rustc_transmute::Reason::SrcIsNotYetSupported => {
- format!("analyzing the transmutability of `{src}` is not yet supported.")
+ format!("analyzing the transmutability of `{src}` is not yet supported")
}
rustc_transmute::Reason::DstIsNotYetSupported => {
- format!("analyzing the transmutability of `{dst}` is not yet supported.")
+ format!("analyzing the transmutability of `{dst}` is not yet supported")
}
rustc_transmute::Reason::DstIsBitIncompatible => {
format!("at least one value of `{src}` isn't a bit-valid value of `{dst}`")
}
+ rustc_transmute::Reason::DstUninhabited => {
+ format!("`{dst}` is uninhabited")
+ }
+
rustc_transmute::Reason::DstMayHaveSafetyInvariants => {
format!("`{dst}` may carry safety invariants")
}
@@ -3128,14 +3133,23 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
format!("`{dst}` has an unknown layout")
}
};
- GetSafeTransmuteErrorAndReason::Error { err_msg, safe_transmute_explanation }
+ GetSafeTransmuteErrorAndReason::Error {
+ err_msg,
+ safe_transmute_explanation: Some(safe_transmute_explanation),
+ }
}
// Should never get a Yes at this point! We already ran it before, and did not get a Yes.
Answer::Yes => span_bug!(
span,
"Inconsistent rustc_transmute::is_transmutable(...) result, got Yes",
),
- other => span_bug!(span, "Unsupported rustc_transmute::Answer variant: `{other:?}`"),
+ // Reached when a different obligation (namely `Freeze`) causes the
+ // transmutability analysis to fail. In this case, silence the
+ // transmutability error message in favor of that more specific
+ // error.
+ Answer::If(_) => {
+ GetSafeTransmuteErrorAndReason::Error { err_msg, safe_transmute_explanation: None }
+ }
}
}
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 6f512a1173f..a7cfcf6b366 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -314,12 +314,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
.flat_map(|cond| flatten_answer_tree(tcx, obligation, predicate, cond))
.collect(),
Condition::IfTransmutable { src, dst } => {
- let trait_def_id = obligation.predicate.def_id();
+ let transmute_trait = obligation.predicate.def_id();
let assume_const = predicate.trait_ref.args.const_at(2);
- let make_obl = |from_ty, to_ty| {
- let trait_ref1 = ty::TraitRef::new(
+ let make_transmute_obl = |from_ty, to_ty| {
+ let trait_ref = ty::TraitRef::new(
tcx,
- trait_def_id,
+ transmute_trait,
[
ty::GenericArg::from(to_ty),
ty::GenericArg::from(from_ty),
@@ -331,17 +331,45 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation.cause.clone(),
obligation.recursion_depth + 1,
obligation.param_env,
- trait_ref1,
+ trait_ref,
)
};
+ let make_freeze_obl = |ty| {
+ let trait_ref = ty::TraitRef::new(
+ tcx,
+ tcx.lang_items().freeze_trait().unwrap(),
+ [ty::GenericArg::from(ty)],
+ );
+ Obligation::with_depth(
+ tcx,
+ obligation.cause.clone(),
+ obligation.recursion_depth + 1,
+ obligation.param_env,
+ trait_ref,
+ )
+ };
+
+ let mut obls = vec![];
+
+ // If the source is a shared reference, it must be `Freeze`;
+ // otherwise, transmuting could lead to data races.
+ if src.mutability == Mutability::Not {
+ obls.extend([make_freeze_obl(src.ty), make_freeze_obl(dst.ty)])
+ }
+
// If Dst is mutable, check bidirectionally.
// For example, transmuting bool -> u8 is OK as long as you can't update that u8
// to be > 1, because you could later transmute the u8 back to a bool and get UB.
match dst.mutability {
- Mutability::Not => vec![make_obl(src.ty, dst.ty)],
- Mutability::Mut => vec![make_obl(src.ty, dst.ty), make_obl(dst.ty, src.ty)],
+ Mutability::Not => obls.push(make_transmute_obl(src.ty, dst.ty)),
+ Mutability::Mut => obls.extend([
+ make_transmute_obl(src.ty, dst.ty),
+ make_transmute_obl(dst.ty, src.ty),
+ ]),
}
+
+ obls
}
}
}
diff --git a/compiler/rustc_transmute/src/layout/dfa.rs b/compiler/rustc_transmute/src/layout/dfa.rs
index b8922696e30..77d5a48f158 100644
--- a/compiler/rustc_transmute/src/layout/dfa.rs
+++ b/compiler/rustc_transmute/src/layout/dfa.rs
@@ -35,6 +35,7 @@ impl<R> Transitions<R>
where
R: Ref,
{
+ #[allow(dead_code)]
fn insert(&mut self, transition: Transition<R>, state: State) {
match transition {
Transition::Byte(b) => {
@@ -82,6 +83,7 @@ impl<R> Dfa<R>
where
R: Ref,
{
+ #[allow(dead_code)]
pub(crate) fn unit() -> Self {
let transitions: Map<State, Transitions<R>> = Map::default();
let start = State::new();
diff --git a/compiler/rustc_transmute/src/layout/nfa.rs b/compiler/rustc_transmute/src/layout/nfa.rs
index 78fcceb5f2c..3c5963202c6 100644
--- a/compiler/rustc_transmute/src/layout/nfa.rs
+++ b/compiler/rustc_transmute/src/layout/nfa.rs
@@ -160,6 +160,7 @@ where
Self { transitions, start, accepting }
}
+ #[allow(dead_code)]
pub(crate) fn edges_from(&self, start: State) -> Option<&Map<Transition<R>, Set<State>>> {
self.transitions.get(&start)
}
diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs
index f6bc224c7e7..12c984f1603 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -173,16 +173,20 @@ pub(crate) mod rustc {
use super::Tree;
use crate::layout::rustc::{Def, Ref};
+ use rustc_middle::ty::layout::HasTyCtxt;
+ use rustc_middle::ty::layout::LayoutCx;
use rustc_middle::ty::layout::LayoutError;
+ use rustc_middle::ty::layout::LayoutOf;
use rustc_middle::ty::AdtDef;
- use rustc_middle::ty::GenericArgsRef;
- use rustc_middle::ty::ParamEnv;
+ use rustc_middle::ty::AdtKind;
+ use rustc_middle::ty::List;
use rustc_middle::ty::ScalarInt;
- use rustc_middle::ty::VariantDef;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
use rustc_span::ErrorGuaranteed;
- use rustc_target::abi::Align;
- use std::alloc;
+ use rustc_target::abi::FieldsShape;
+ use rustc_target::abi::Size;
+ use rustc_target::abi::TyAndLayout;
+ use rustc_target::abi::Variants;
#[derive(Debug, Copy, Clone)]
pub(crate) enum Err {
@@ -206,176 +210,64 @@ pub(crate) mod rustc {
}
}
- trait LayoutExt {
- fn clamp_align(&self, min_align: Align, max_align: Align) -> Self;
- }
-
- impl LayoutExt for alloc::Layout {
- fn clamp_align(&self, min_align: Align, max_align: Align) -> Self {
- let min_align = min_align.bytes().try_into().unwrap();
- let max_align = max_align.bytes().try_into().unwrap();
- Self::from_size_align(self.size(), self.align().clamp(min_align, max_align)).unwrap()
- }
- }
-
- struct LayoutSummary {
- total_align: Align,
- total_size: usize,
- discriminant_size: usize,
- discriminant_align: Align,
- }
-
- impl LayoutSummary {
- 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};
-
- let param_env = ParamEnv::reveal_all();
- let param_env_and_type = ParamEnvAnd { param_env, value: ty };
- let TyAndLayout { layout, .. } = ctx.layout_of(param_env_and_type)?;
-
- let total_size: usize = layout.size().bytes_usize();
- let total_align: Align = layout.align().abi;
- let discriminant_align: Align;
- let discriminant_size: usize;
-
- if let Variants::Multiple { tag, .. } = layout.variants() {
- discriminant_align = tag.align(&ctx).abi;
- discriminant_size = tag.size(&ctx).bytes_usize();
- } else {
- discriminant_align = Align::ONE;
- discriminant_size = 0;
- };
-
- Ok(Self { total_align, total_size, discriminant_align, discriminant_size })
- }
-
- fn into(&self) -> alloc::Layout {
- alloc::Layout::from_size_align(
- self.total_size,
- self.total_align.bytes().try_into().unwrap(),
- )
- .unwrap()
- }
- }
-
impl<'tcx> Tree<Def<'tcx>, Ref<'tcx>> {
- pub fn from_ty(ty: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Result<Self, Err> {
- use rustc_middle::ty::FloatTy::*;
- use rustc_middle::ty::IntTy::*;
- use rustc_middle::ty::UintTy::*;
+ pub fn from_ty(
+ ty_and_layout: TyAndLayout<'tcx, Ty<'tcx>>,
+ cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+ ) -> Result<Self, Err> {
use rustc_target::abi::HasDataLayout;
- if let Err(e) = ty.error_reported() {
+ if let Err(e) = ty_and_layout.ty.error_reported() {
return Err(Err::TypeError(e));
}
- let target = tcx.data_layout();
+ let target = cx.tcx.data_layout();
+ let pointer_size = target.pointer_size;
- match ty.kind() {
+ match ty_and_layout.ty.kind() {
ty::Bool => Ok(Self::bool()),
- ty::Int(I8) | ty::Uint(U8) => Ok(Self::u8()),
- ty::Int(I16) | ty::Uint(U16) => Ok(Self::number(2)),
- ty::Int(I32) | ty::Uint(U32) | ty::Float(F32) => Ok(Self::number(4)),
- ty::Int(I64) | ty::Uint(U64) | ty::Float(F64) => Ok(Self::number(8)),
- ty::Int(I128) | ty::Uint(U128) => Ok(Self::number(16)),
- ty::Int(Isize) | ty::Uint(Usize) => {
- Ok(Self::number(target.pointer_size.bytes_usize()))
+ ty::Float(nty) => {
+ let width = nty.bit_width() / 8;
+ Ok(Self::number(width as _))
}
- ty::Tuple(members) => {
- if members.len() == 0 {
- Ok(Tree::unit())
- } else {
- Err(Err::NotYetSupported)
- }
+ ty::Int(nty) => {
+ let width = nty.normalize(pointer_size.bits() as _).bit_width().unwrap() / 8;
+ Ok(Self::number(width as _))
}
- ty::Array(ty, len) => {
- let len = len
- .try_eval_target_usize(tcx, ParamEnv::reveal_all())
- .ok_or(Err::NotYetSupported)?;
- let elt = Tree::from_ty(*ty, tcx)?;
+ ty::Uint(nty) => {
+ let width = nty.normalize(pointer_size.bits() as _).bit_width().unwrap() / 8;
+ Ok(Self::number(width as _))
+ }
+
+ ty::Tuple(members) => Self::from_tuple(ty_and_layout, members, cx),
+
+ ty::Array(inner_ty, len) => {
+ let FieldsShape::Array { stride, count } = &ty_and_layout.fields else {
+ return Err(Err::NotYetSupported);
+ };
+ let inner_ty_and_layout = cx.layout_of(*inner_ty)?;
+ assert_eq!(*stride, inner_ty_and_layout.size);
+ let elt = Tree::from_ty(inner_ty_and_layout, cx)?;
Ok(std::iter::repeat(elt)
- .take(len as usize)
+ .take(*count as usize)
.fold(Tree::unit(), |tree, elt| tree.then(elt)))
}
- ty::Adt(adt_def, args_ref) => {
- use rustc_middle::ty::AdtKind;
-
- // If the layout is ill-specified, halt.
- if !(adt_def.repr().c() || adt_def.repr().int.is_some()) {
- return Err(Err::NotYetSupported);
+ ty::Adt(adt_def, _args_ref) if !ty_and_layout.ty.is_box() => {
+ match adt_def.adt_kind() {
+ AdtKind::Struct => Self::from_struct(ty_and_layout, *adt_def, cx),
+ AdtKind::Enum => Self::from_enum(ty_and_layout, *adt_def, cx),
+ AdtKind::Union => Self::from_union(ty_and_layout, *adt_def, cx),
}
-
- // Compute a summary of the type's layout.
- let layout_summary = LayoutSummary::from_ty(ty, tcx)?;
-
- // The layout begins with this adt's visibility.
- let vis = Self::def(Def::Adt(*adt_def));
-
- // And is followed the layout(s) of its variants
- Ok(vis.then(match adt_def.adt_kind() {
- AdtKind::Struct => Self::from_repr_c_variant(
- ty,
- *adt_def,
- args_ref,
- &layout_summary,
- None,
- adt_def.non_enum_variant(),
- tcx,
- )?,
- AdtKind::Enum => {
- trace!(?adt_def, "treeifying enum");
- let mut tree = Tree::uninhabited();
-
- for (idx, variant) in adt_def.variants().iter_enumerated() {
- let tag = tcx.tag_for_variant((ty, idx));
- tree = tree.or(Self::from_repr_c_variant(
- ty,
- *adt_def,
- args_ref,
- &layout_summary,
- tag,
- variant,
- tcx,
- )?);
- }
-
- tree
- }
- AdtKind::Union => {
- // is the layout well-defined?
- if !adt_def.repr().c() {
- return Err(Err::NotYetSupported);
- }
-
- let ty_layout = layout_of(tcx, ty)?;
-
- let mut tree = Tree::uninhabited();
-
- for field in adt_def.all_fields() {
- let variant_ty = field.ty(tcx, args_ref);
- let variant_layout = layout_of(tcx, variant_ty)?;
- let padding_needed = ty_layout.size() - variant_layout.size();
- let variant = Self::def(Def::Field(field))
- .then(Self::from_ty(variant_ty, tcx)?)
- .then(Self::padding(padding_needed));
-
- tree = tree.or(variant);
- }
-
- tree
- }
- }))
}
ty::Ref(lifetime, ty, mutability) => {
- let layout = layout_of(tcx, *ty)?;
- let align = layout.align();
- let size = layout.size();
+ let ty_and_layout = cx.layout_of(*ty)?;
+ let align = ty_and_layout.align.abi.bytes() as usize;
+ let size = ty_and_layout.size.bytes_usize();
Ok(Tree::Ref(Ref {
lifetime: *lifetime,
ty: *ty,
@@ -389,80 +281,143 @@ pub(crate) mod rustc {
}
}
- fn from_repr_c_variant(
- ty: Ty<'tcx>,
- adt_def: AdtDef<'tcx>,
- args_ref: GenericArgsRef<'tcx>,
- layout_summary: &LayoutSummary,
- tag: Option<ScalarInt>,
- variant_def: &'tcx VariantDef,
- tcx: TyCtxt<'tcx>,
+ /// Constructs a `Tree` from a tuple.
+ fn from_tuple(
+ ty_and_layout: TyAndLayout<'tcx, Ty<'tcx>>,
+ members: &'tcx List<Ty<'tcx>>,
+ cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
) -> Result<Self, Err> {
- let mut tree = Tree::unit();
-
- let repr = adt_def.repr();
- let min_align = repr.align.unwrap_or(Align::ONE);
- let max_align = repr.pack.unwrap_or(Align::MAX);
-
- let variant_span = trace_span!(
- "treeifying variant",
- min_align = ?min_align,
- max_align = ?max_align,
- )
- .entered();
-
- let mut variant_layout = alloc::Layout::from_size_align(
- 0,
- layout_summary.total_align.bytes().try_into().unwrap(),
- )
- .unwrap();
-
- // The layout of the variant is prefixed by the tag, if any.
- if let Some(tag) = tag {
- let tag_layout =
- alloc::Layout::from_size_align(tag.size().bytes_usize(), 1).unwrap();
- tree = tree.then(Self::from_tag(tag, tcx));
- variant_layout = variant_layout.extend(tag_layout).unwrap().0;
- }
-
- // Next come fields.
- let fields_span = trace_span!("treeifying fields").entered();
- for field_def in variant_def.fields.iter() {
- let field_ty = field_def.ty(tcx, args_ref);
- let _span = trace_span!("treeifying field", field = ?field_ty).entered();
-
- // begin with the field's visibility
- tree = tree.then(Self::def(Def::Field(field_def)));
-
- // compute the field's layout characteristics
- let field_layout = layout_of(tcx, field_ty)?.clamp_align(min_align, max_align);
-
- // next comes the field's padding
- let padding_needed = variant_layout.padding_needed_for(field_layout.align());
- if padding_needed > 0 {
- tree = tree.then(Self::padding(padding_needed));
+ match &ty_and_layout.fields {
+ FieldsShape::Primitive => {
+ assert_eq!(members.len(), 1);
+ let inner_ty = members[0];
+ let inner_ty_and_layout = cx.layout_of(inner_ty)?;
+ assert_eq!(ty_and_layout.layout, inner_ty_and_layout.layout);
+ Self::from_ty(inner_ty_and_layout, cx)
}
-
- // finally, the field's layout
- tree = tree.then(Self::from_ty(field_ty, tcx)?);
-
- // extend the variant layout with the field layout
- variant_layout = variant_layout.extend(field_layout).unwrap().0;
+ FieldsShape::Arbitrary { offsets, .. } => {
+ assert_eq!(offsets.len(), members.len());
+ Self::from_variant(Def::Primitive, None, ty_and_layout, ty_and_layout.size, cx)
+ }
+ FieldsShape::Array { .. } | FieldsShape::Union(_) => Err(Err::NotYetSupported),
}
- drop(fields_span);
-
- // finally: padding
- let padding_span = trace_span!("adding trailing padding").entered();
- if layout_summary.total_size > variant_layout.size() {
- let padding_needed = layout_summary.total_size - variant_layout.size();
- tree = tree.then(Self::padding(padding_needed));
- };
- drop(padding_span);
- drop(variant_span);
- Ok(tree)
}
- pub fn from_tag(tag: ScalarInt, tcx: TyCtxt<'tcx>) -> Self {
+ /// Constructs a `Tree` from a struct.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `def` is not a struct definition.
+ fn from_struct(
+ ty_and_layout: TyAndLayout<'tcx, Ty<'tcx>>,
+ def: AdtDef<'tcx>,
+ cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+ ) -> Result<Self, Err> {
+ assert!(def.is_struct());
+ let def = Def::Adt(def);
+ Self::from_variant(def, None, ty_and_layout, ty_and_layout.size, cx)
+ }
+
+ /// Constructs a `Tree` from an enum.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `def` is not an enum definition.
+ fn from_enum(
+ ty_and_layout: TyAndLayout<'tcx, Ty<'tcx>>,
+ def: AdtDef<'tcx>,
+ cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+ ) -> Result<Self, Err> {
+ assert!(def.is_enum());
+ let layout = ty_and_layout.layout;
+
+ if let Variants::Multiple { tag_field, .. } = layout.variants() {
+ // For enums (but not coroutines), the tag field is
+ // currently always the first field of the layout.
+ assert_eq!(*tag_field, 0);
+ }
+
+ let variants = def.discriminants(cx.tcx()).try_fold(
+ Self::uninhabited(),
+ |variants, (idx, ref discriminant)| {
+ let tag = cx.tcx.tag_for_variant((ty_and_layout.ty, idx));
+ let variant_def = Def::Variant(def.variant(idx));
+ let variant_ty_and_layout = ty_and_layout.for_variant(&cx, idx);
+ let variant = Self::from_variant(
+ variant_def,
+ tag,
+ variant_ty_and_layout,
+ layout.size,
+ cx,
+ )?;
+ Result::<Self, Err>::Ok(variants.or(variant))
+ },
+ )?;
+
+ return Ok(Self::def(Def::Adt(def)).then(variants));
+ }
+
+ /// Constructs a `Tree` from a 'variant-like' layout.
+ ///
+ /// A 'variant-like' layout includes those of structs and, of course,
+ /// enum variants. Pragmatically speaking, this method supports anything
+ /// with `FieldsShape::Arbitrary`.
+ ///
+ /// Note: This routine assumes that the optional `tag` is the first
+ /// field, and enum callers should check that `tag_field` is, in fact,
+ /// `0`.
+ fn from_variant(
+ def: Def<'tcx>,
+ tag: Option<ScalarInt>,
+ ty_and_layout: TyAndLayout<'tcx, Ty<'tcx>>,
+ total_size: Size,
+ cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+ ) -> Result<Self, Err> {
+ // This constructor does not support non-`FieldsShape::Arbitrary`
+ // layouts.
+ let FieldsShape::Arbitrary { offsets, memory_index } = ty_and_layout.layout.fields()
+ else {
+ return Err(Err::NotYetSupported);
+ };
+
+ // When this function is invoked with enum variants,
+ // `ty_and_layout.size` does not encompass the entire size of the
+ // enum. We rely on `total_size` for this.
+ assert!(ty_and_layout.size <= total_size);
+
+ let mut size = Size::ZERO;
+ let mut struct_tree = Self::def(def);
+
+ // If a `tag` is provided, place it at the start of the layout.
+ if let Some(tag) = tag {
+ size += tag.size();
+ struct_tree = struct_tree.then(Self::from_tag(tag, cx.tcx));
+ }
+
+ // Append the fields, in memory order, to the layout.
+ let inverse_memory_index = memory_index.invert_bijective_mapping();
+ for (memory_idx, field_idx) in inverse_memory_index.iter_enumerated() {
+ // Add interfield padding.
+ let padding_needed = offsets[*field_idx] - size;
+ let padding = Self::padding(padding_needed.bytes_usize());
+
+ let field_ty_and_layout = ty_and_layout.field(&cx, field_idx.as_usize());
+ let field_tree = Self::from_ty(field_ty_and_layout, cx)?;
+
+ struct_tree = struct_tree.then(padding).then(field_tree);
+
+ size += padding_needed + field_ty_and_layout.size;
+ }
+
+ // Add trailing padding.
+ let padding_needed = total_size - size;
+ let trailing_padding = Self::padding(padding_needed.bytes_usize());
+
+ Ok(struct_tree.then(trailing_padding))
+ }
+
+ /// Constructs a `Tree` representing the value of a enum tag.
+ fn from_tag(tag: ScalarInt, tcx: TyCtxt<'tcx>) -> Self {
use rustc_target::abi::Endian;
let size = tag.size();
let bits = tag.to_bits(size).unwrap();
@@ -479,24 +434,42 @@ pub(crate) mod rustc {
};
Self::Seq(bytes.iter().map(|&b| Self::from_bits(b)).collect())
}
- }
- fn layout_of<'tcx>(
- ctx: TyCtxt<'tcx>,
- ty: Ty<'tcx>,
- ) -> Result<alloc::Layout, &'tcx LayoutError<'tcx>> {
- use rustc_middle::ty::ParamEnvAnd;
- use rustc_target::abi::TyAndLayout;
+ /// Constructs a `Tree` from a union.
+ ///
+ /// # Panics
+ ///
+ /// Panics if `def` is not a union definition.
+ fn from_union(
+ ty_and_layout: TyAndLayout<'tcx, Ty<'tcx>>,
+ def: AdtDef<'tcx>,
+ cx: LayoutCx<'tcx, TyCtxt<'tcx>>,
+ ) -> Result<Self, Err> {
+ assert!(def.is_union());
- let param_env = ParamEnv::reveal_all();
- let param_env_and_type = ParamEnvAnd { param_env, value: ty };
- let TyAndLayout { layout, .. } = ctx.layout_of(param_env_and_type)?;
- let layout = alloc::Layout::from_size_align(
- layout.size().bytes_usize(),
- layout.align().abi.bytes().try_into().unwrap(),
- )
- .unwrap();
- trace!(?ty, ?layout, "computed layout for type");
- Ok(layout)
+ let union_layout = ty_and_layout.layout;
+
+ // This constructor does not support non-`FieldsShape::Union`
+ // layouts. Fields of this shape are all placed at offset 0.
+ let FieldsShape::Union(fields) = union_layout.fields() else {
+ return Err(Err::NotYetSupported);
+ };
+
+ let fields = &def.non_enum_variant().fields;
+ let fields = fields.iter_enumerated().try_fold(
+ Self::uninhabited(),
+ |fields, (idx, ref field_def)| {
+ let field_def = Def::Field(field_def);
+ let field_ty_and_layout = ty_and_layout.field(&cx, idx.as_usize());
+ let field = Self::from_ty(field_ty_and_layout, cx)?;
+ let trailing_padding_needed = union_layout.size - field_ty_and_layout.size;
+ let trailing_padding = Self::padding(trailing_padding_needed.bytes_usize());
+ let field_and_padding = field.then(trailing_padding);
+ Result::<Self, Err>::Ok(fields.or(field_and_padding))
+ },
+ )?;
+
+ Ok(Self::def(Def::Adt(def)).then(fields))
+ }
}
}
diff --git a/compiler/rustc_transmute/src/lib.rs b/compiler/rustc_transmute/src/lib.rs
index b6f937ebe47..12312271646 100644
--- a/compiler/rustc_transmute/src/lib.rs
+++ b/compiler/rustc_transmute/src/lib.rs
@@ -1,6 +1,6 @@
#![feature(alloc_layout_extra)]
#![feature(never_type)]
-#![allow(dead_code, unused_variables)]
+#![allow(unused_variables)]
#[macro_use]
extern crate tracing;
@@ -49,6 +49,8 @@ pub enum Reason<T> {
DstIsNotYetSupported,
/// The layout of the destination type is bit-incompatible with the source type.
DstIsBitIncompatible,
+ /// The destination type is uninhabited.
+ DstUninhabited,
/// The destination type may carry safety invariants.
DstMayHaveSafetyInvariants,
/// `Dst` is larger than `Src`, and the excess bytes were not exclusively uninitialized.
diff --git a/compiler/rustc_transmute/src/maybe_transmutable/mod.rs b/compiler/rustc_transmute/src/maybe_transmutable/mod.rs
index 16d15580a05..2789fe8f6b1 100644
--- a/compiler/rustc_transmute/src/maybe_transmutable/mod.rs
+++ b/compiler/rustc_transmute/src/maybe_transmutable/mod.rs
@@ -33,6 +33,9 @@ mod rustc {
use super::*;
use crate::layout::tree::rustc::Err;
+ use rustc_middle::ty::layout::LayoutCx;
+ use rustc_middle::ty::layout::LayoutOf;
+ use rustc_middle::ty::ParamEnv;
use rustc_middle::ty::Ty;
use rustc_middle::ty::TyCtxt;
@@ -43,12 +46,20 @@ mod rustc {
pub fn answer(self) -> Answer<<TyCtxt<'tcx> as QueryContext>::Ref> {
let Self { src, dst, assume, context } = self;
+ let layout_cx = LayoutCx { tcx: context, param_env: ParamEnv::reveal_all() };
+ let layout_of = |ty| {
+ layout_cx
+ .layout_of(ty)
+ .map_err(|_| Err::NotYetSupported)
+ .and_then(|tl| Tree::from_ty(tl, layout_cx))
+ };
+
// Convert `src` and `dst` from their rustc representations, to `Tree`-based
// representations. If these conversions fail, conclude that the transmutation is
// unacceptable; the layouts of both the source and destination types must be
// well-defined.
- let src = Tree::from_ty(src, context);
- let dst = Tree::from_ty(dst, context);
+ let src = layout_of(src);
+ let dst = layout_of(dst);
match (src, dst) {
(Err(Err::TypeError(_)), _) | (_, Err(Err::TypeError(_))) => {
@@ -86,6 +97,10 @@ where
// references.
let src = src.prune(&|def| false);
+ if src.is_inhabited() && !dst.is_inhabited() {
+ return Answer::No(Reason::DstUninhabited);
+ }
+
trace!(?src, "pruned src");
// Remove all `Def` nodes from `dst`, additionally...
diff --git a/compiler/rustc_transmute/src/maybe_transmutable/query_context.rs b/compiler/rustc_transmute/src/maybe_transmutable/query_context.rs
index 54ed03d44e6..1ccb6f36c8e 100644
--- a/compiler/rustc_transmute/src/maybe_transmutable/query_context.rs
+++ b/compiler/rustc_transmute/src/maybe_transmutable/query_context.rs
@@ -5,8 +5,6 @@ pub(crate) trait QueryContext {
type Def: layout::Def;
type Ref: layout::Ref;
type Scope: Copy;
-
- fn min_align(&self, reference: Self::Ref) -> usize;
}
#[cfg(test)]
@@ -31,10 +29,6 @@ pub(crate) mod test {
type Def = Def;
type Ref = !;
type Scope = ();
-
- fn min_align(&self, reference: !) -> usize {
- unimplemented!()
- }
}
}
@@ -48,9 +42,5 @@ mod rustc {
type Ref = layout::rustc::Ref<'tcx>;
type Scope = Ty<'tcx>;
-
- fn min_align(&self, reference: Self::Ref) -> usize {
- unimplemented!()
- }
}
}
diff --git a/tests/ui/transmutability/arrays/huge-len.stderr b/tests/ui/transmutability/arrays/huge-len.stderr
index 37160c5c959..3fc652f47c1 100644
--- a/tests/ui/transmutability/arrays/huge-len.stderr
+++ b/tests/ui/transmutability/arrays/huge-len.stderr
@@ -2,7 +2,7 @@ error[E0277]: `()` cannot be safely transmuted into `ExplicitlyPadded`
--> $DIR/huge-len.rs:21:41
|
LL | assert::is_maybe_transmutable::<(), ExplicitlyPadded>();
- | ^^^^^^^^^^^^^^^^ values of the type `ExplicitlyPadded` are too big for the current architecture
+ | ^^^^^^^^^^^^^^^^ analyzing the transmutability of `ExplicitlyPadded` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/huge-len.rs:8:14
@@ -17,7 +17,7 @@ error[E0277]: `ExplicitlyPadded` cannot be safely transmuted into `()`
--> $DIR/huge-len.rs:24:55
|
LL | assert::is_maybe_transmutable::<ExplicitlyPadded, ()>();
- | ^^ values of the type `ExplicitlyPadded` are too big for the current architecture
+ | ^^ analyzing the transmutability of `ExplicitlyPadded` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/huge-len.rs:8:14
diff --git a/tests/ui/transmutability/arrays/should_require_well_defined_layout.stderr b/tests/ui/transmutability/arrays/should_require_well_defined_layout.stderr
index e486928a445..b4cd70142c4 100644
--- a/tests/ui/transmutability/arrays/should_require_well_defined_layout.stderr
+++ b/tests/ui/transmutability/arrays/should_require_well_defined_layout.stderr
@@ -2,7 +2,7 @@ error[E0277]: `[String; 0]` cannot be safely transmuted into `()`
--> $DIR/should_require_well_defined_layout.rs:25:52
|
LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `[String; 0]` is not yet supported.
+ | ^^ analyzing the transmutability of `[String; 0]` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/should_require_well_defined_layout.rs:12:14
@@ -23,7 +23,7 @@ error[E0277]: `u128` cannot be safely transmuted into `[String; 0]`
--> $DIR/should_require_well_defined_layout.rs:26:47
|
LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `[String; 0]` is not yet supported.
+ | ^^^^^^^^^ analyzing the transmutability of `[String; 0]` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/should_require_well_defined_layout.rs:12:14
@@ -44,7 +44,7 @@ error[E0277]: `[String; 1]` cannot be safely transmuted into `()`
--> $DIR/should_require_well_defined_layout.rs:31:52
|
LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `[String; 1]` is not yet supported.
+ | ^^ analyzing the transmutability of `[String; 1]` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/should_require_well_defined_layout.rs:12:14
@@ -65,7 +65,7 @@ error[E0277]: `u128` cannot be safely transmuted into `[String; 1]`
--> $DIR/should_require_well_defined_layout.rs:32:47
|
LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `[String; 1]` is not yet supported.
+ | ^^^^^^^^^ analyzing the transmutability of `[String; 1]` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/should_require_well_defined_layout.rs:12:14
@@ -86,7 +86,7 @@ error[E0277]: `[String; 2]` cannot be safely transmuted into `()`
--> $DIR/should_require_well_defined_layout.rs:37:52
|
LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `[String; 2]` is not yet supported.
+ | ^^ analyzing the transmutability of `[String; 2]` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/should_require_well_defined_layout.rs:12:14
@@ -107,7 +107,7 @@ error[E0277]: `u128` cannot be safely transmuted into `[String; 2]`
--> $DIR/should_require_well_defined_layout.rs:38:47
|
LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `[String; 2]` is not yet supported.
+ | ^^^^^^^^^ analyzing the transmutability of `[String; 2]` is not yet supported
|
note: required by a bound in `is_maybe_transmutable`
--> $DIR/should_require_well_defined_layout.rs:12:14
diff --git a/tests/ui/transmutability/enums/niche_optimization.rs b/tests/ui/transmutability/enums/niche_optimization.rs
new file mode 100644
index 00000000000..23f57ecad75
--- /dev/null
+++ b/tests/ui/transmutability/enums/niche_optimization.rs
@@ -0,0 +1,156 @@
+//@ check-pass
+//! Checks that niche optimizations are encoded correctly.
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code, incomplete_features, non_camel_case_types)]
+
+mod assert {
+ use std::mem::{Assume, BikeshedIntrinsicFrom};
+
+ pub fn is_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, {
+ Assume {
+ alignment: false,
+ lifetimes: false,
+ safety: true,
+ validity: false,
+ }
+ }>
+ {}
+
+ pub fn is_maybe_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, {
+ Assume {
+ alignment: false,
+ lifetimes: false,
+ safety: true,
+ validity: true,
+ }
+ }>
+ {}
+}
+
+#[repr(u8)] enum V0 { V = 0 }
+#[repr(u8)] enum V1 { V = 1 }
+#[repr(u8)] enum V2 { V = 2 }
+#[repr(u8)] enum V253 { V = 253 }
+#[repr(u8)] enum V254 { V = 254 }
+#[repr(u8)] enum V255 { V = 255 }
+
+fn bool() {
+ enum OptionLike {
+ A(bool),
+ B,
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<OptionLike>() == 1);
+ };
+
+ assert::is_transmutable::<OptionLike, u8>();
+
+ assert::is_transmutable::<bool, OptionLike>();
+ assert::is_transmutable::<V0, OptionLike>();
+ assert::is_transmutable::<V1, OptionLike>();
+ assert::is_transmutable::<V2, OptionLike>();
+}
+
+fn one_niche() {
+ #[repr(u8)]
+ enum N1 {
+ S = 0,
+ E = 255 - 1,
+ }
+
+ enum OptionLike {
+ A(N1),
+ B,
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<OptionLike>() == 1);
+ };
+
+ assert::is_transmutable::<OptionLike, u8>();
+ assert::is_transmutable::<V0, OptionLike>();
+ assert::is_transmutable::<V254, OptionLike>();
+ assert::is_transmutable::<V255, OptionLike>();
+}
+
+fn one_niche_alt() {
+ #[repr(u8)]
+ enum N1 {
+ S = 1,
+ E = 255 - 1,
+ }
+
+ enum OptionLike {
+ A(N1),
+ B,
+ C,
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<OptionLike>() == 1);
+ };
+
+ assert::is_transmutable::<OptionLike, u8>();
+ assert::is_transmutable::<V0, OptionLike>();
+ assert::is_transmutable::<V254, OptionLike>();
+ assert::is_transmutable::<V255, OptionLike>();
+}
+
+fn two_niche() {
+ #[repr(u8)]
+ enum Niche {
+ S = 0,
+ E = 255 - 2,
+ }
+
+ enum OptionLike {
+ A(Niche),
+ B,
+ C,
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<OptionLike>() == 1);
+ };
+
+ assert::is_transmutable::<OptionLike, u8>();
+ assert::is_transmutable::<V0, OptionLike>();
+ assert::is_transmutable::<V253, OptionLike>();
+ assert::is_transmutable::<V254, OptionLike>();
+ assert::is_transmutable::<V255, OptionLike>();
+}
+
+fn no_niche() {
+ use std::mem::MaybeUninit;
+
+ #[repr(u8)]
+ enum Niche {
+ S = 0,
+ E = 255 - 1,
+ }
+
+ enum OptionLike {
+ A(Niche),
+ B,
+ C,
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<OptionLike>() == 2);
+ };
+
+ #[repr(C)]
+ struct Pair<T, U>(T, U);
+
+ assert::is_transmutable::<V0, Niche>();
+ assert::is_transmutable::<V254, Niche>();
+ assert::is_transmutable::<Pair<V0, Niche>, OptionLike>();
+ assert::is_transmutable::<Pair<V1, MaybeUninit<u8>>, OptionLike>();
+ assert::is_transmutable::<Pair<V2, MaybeUninit<u8>>, OptionLike>();
+}
diff --git a/tests/ui/transmutability/enums/repr/padding_differences.rs b/tests/ui/transmutability/enums/repr/padding_differences.rs
new file mode 100644
index 00000000000..d0e1502b5e2
--- /dev/null
+++ b/tests/ui/transmutability/enums/repr/padding_differences.rs
@@ -0,0 +1,80 @@
+//@ check-pass
+//! Adapted from https://rust-lang.github.io/unsafe-code-guidelines/layout/enums.html#explicit-repr-annotation-without-c-compatibility
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code, incomplete_features, non_camel_case_types)]
+
+use std::mem::MaybeUninit;
+
+mod assert {
+ use std::mem::{Assume, BikeshedIntrinsicFrom};
+
+ pub fn is_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, {
+ Assume {
+ alignment: false,
+ lifetimes: false,
+ safety: true,
+ validity: false,
+ }
+ }>
+ {}
+
+ pub fn is_maybe_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, {
+ Assume {
+ alignment: false,
+ lifetimes: false,
+ safety: true,
+ validity: true,
+ }
+ }>
+ {}
+}
+
+#[repr(u8)] enum V0 { V = 0 }
+#[repr(u8)] enum V1 { V = 1 }
+
+fn repr_u8() {
+ #[repr(u8)]
+ enum TwoCases {
+ A(u8, u16), // 0x00 INIT INIT INIT
+ B(u16), // 0x01 PADD INIT INIT
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<TwoCases>() == 4);
+ };
+
+ #[repr(C)] struct TwoCasesA(V0, u8, u8, u8);
+ #[repr(C)] struct TwoCasesB(V1, MaybeUninit<u8>, u8, u8);
+
+ assert::is_transmutable::<TwoCasesA, TwoCases>();
+ assert::is_transmutable::<TwoCasesB, TwoCases>();
+
+ assert::is_maybe_transmutable::<TwoCases, TwoCasesA>();
+ assert::is_maybe_transmutable::<TwoCases, TwoCasesB>();
+}
+
+fn repr_c_u8() {
+ #[repr(C, u8)]
+ enum TwoCases {
+ A(u8, u16), // 0x00 PADD INIT PADD INIT INIT
+ B(u16), // 0x01 PADD INIT INIT PADD PADD
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<TwoCases>() == 6);
+ };
+
+ #[repr(C)] struct TwoCasesA(V0, MaybeUninit<u8>, u8, MaybeUninit<u8>, u8, u8);
+ #[repr(C)] struct TwoCasesB(V1, MaybeUninit<u8>, u8, u8, MaybeUninit<u8>, MaybeUninit<u8>);
+
+ assert::is_transmutable::<TwoCasesA, TwoCases>();
+ assert::is_transmutable::<TwoCasesB, TwoCases>();
+
+ assert::is_maybe_transmutable::<TwoCases, TwoCasesA>();
+ assert::is_maybe_transmutable::<TwoCases, TwoCasesB>();
+}
diff --git a/tests/ui/transmutability/enums/repr/should_require_well_defined_layout.rs b/tests/ui/transmutability/enums/repr/should_handle_all.rs
similarity index 80%
rename from tests/ui/transmutability/enums/repr/should_require_well_defined_layout.rs
rename to tests/ui/transmutability/enums/repr/should_handle_all.rs
index 630e662b926..a8ec86fa40d 100644
--- a/tests/ui/transmutability/enums/repr/should_require_well_defined_layout.rs
+++ b/tests/ui/transmutability/enums/repr/should_handle_all.rs
@@ -1,5 +1,4 @@
-//! An enum must have a well-defined layout to participate in a transmutation.
-
+//@ check-pass
#![crate_type = "lib"]
#![feature(repr128)]
#![feature(transmutability)]
@@ -21,23 +20,17 @@ mod assert {
{}
}
-fn should_reject_repr_rust() {
- fn void() {
- enum repr_rust {}
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
- }
-
+fn should_accept_repr_rust() {
fn singleton() {
enum repr_rust { V }
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
fn duplex() {
enum repr_rust { A, B }
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
}
@@ -116,7 +109,7 @@ fn should_accept_primitive_reprs()
}
}
-fn should_accept_repr_C() {
+fn should_accept_repr_c() {
#[repr(C)] enum repr_c { V }
assert::is_maybe_transmutable::<repr_c, ()>();
assert::is_maybe_transmutable::<i128, repr_c>();
diff --git a/tests/ui/transmutability/enums/repr/should_require_well_defined_layout.stderr b/tests/ui/transmutability/enums/repr/should_require_well_defined_layout.stderr
deleted file mode 100644
index 2a683de6a65..00000000000
--- a/tests/ui/transmutability/enums/repr/should_require_well_defined_layout.stderr
+++ /dev/null
@@ -1,135 +0,0 @@
-error[E0277]: `void::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:27:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `void::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:13:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `void::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:28:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `void::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:13:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `singleton::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:33:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `singleton::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:13:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `singleton::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:34:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `singleton::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:13:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `duplex::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:39:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `duplex::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:13:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `duplex::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:40:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `duplex::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:13:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error: aborting due to 6 previous errors
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/transmutability/malformed-program-gracefulness/unknown_src_field.stderr b/tests/ui/transmutability/malformed-program-gracefulness/unknown_src_field.stderr
index eeed8a62a2a..cabc7bcfef7 100644
--- a/tests/ui/transmutability/malformed-program-gracefulness/unknown_src_field.stderr
+++ b/tests/ui/transmutability/malformed-program-gracefulness/unknown_src_field.stderr
@@ -8,7 +8,7 @@ error[E0277]: `Src` cannot be safely transmuted into `Dst`
--> $DIR/unknown_src_field.rs:19:36
|
LL | assert::is_transmutable::<Src, Dst>();
- | ^^^ `Dst` has an unknown layout
+ | ^^^ analyzing the transmutability of `Dst` is not yet supported
|
note: required by a bound in `is_transmutable`
--> $DIR/unknown_src_field.rs:12:14
diff --git a/tests/ui/transmutability/maybeuninit.rs b/tests/ui/transmutability/maybeuninit.rs
new file mode 100644
index 00000000000..77c3381c774
--- /dev/null
+++ b/tests/ui/transmutability/maybeuninit.rs
@@ -0,0 +1,43 @@
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code, incomplete_features, non_camel_case_types)]
+
+use std::mem::MaybeUninit;
+
+mod assert {
+ use std::mem::{Assume, BikeshedIntrinsicFrom};
+
+ pub fn is_maybe_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, { Assume::SAFETY }>
+ {}
+}
+
+fn validity() {
+ // An initialized byte is a valid uninitialized byte.
+ assert::is_maybe_transmutable::<u8, MaybeUninit<u8>>();
+
+ // An uninitialized byte is never a valid initialized byte.
+ assert::is_maybe_transmutable::<MaybeUninit<u8>, u8>(); //~ ERROR: cannot be safely transmuted
+}
+
+fn padding() {
+ #[repr(align(8))]
+ struct Align8;
+
+ #[repr(u8)]
+ enum ImplicitlyPadded {
+ A(Align8),
+ }
+
+ #[repr(u8)]
+ enum V0 {
+ V0 = 0,
+ }
+
+ #[repr(C)]
+ struct ExplicitlyPadded(V0, MaybeUninit<[u8; 7]>);
+
+ assert::is_maybe_transmutable::<ExplicitlyPadded, ImplicitlyPadded>();
+ assert::is_maybe_transmutable::<ImplicitlyPadded, ExplicitlyPadded>();
+}
diff --git a/tests/ui/transmutability/maybeuninit.stderr b/tests/ui/transmutability/maybeuninit.stderr
new file mode 100644
index 00000000000..be7dcaf35ea
--- /dev/null
+++ b/tests/ui/transmutability/maybeuninit.stderr
@@ -0,0 +1,18 @@
+error[E0277]: `MaybeUninit<u8>` cannot be safely transmuted into `u8`
+ --> $DIR/maybeuninit.rs:21:54
+ |
+LL | assert::is_maybe_transmutable::<MaybeUninit<u8>, u8>();
+ | ^^ at least one value of `MaybeUninit<u8>` isn't a bit-valid value of `u8`
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/maybeuninit.rs:12:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, { Assume::SAFETY }>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_maybe_transmutable`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/transmutability/references/unsafecell.rs b/tests/ui/transmutability/references/unsafecell.rs
new file mode 100644
index 00000000000..a8a1f969fb4
--- /dev/null
+++ b/tests/ui/transmutability/references/unsafecell.rs
@@ -0,0 +1,47 @@
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code, incomplete_features, non_camel_case_types)]
+
+use std::cell::UnsafeCell;
+
+mod assert {
+ use std::mem::{Assume, BikeshedIntrinsicFrom};
+
+ pub fn is_maybe_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, { Assume::SAFETY }>
+ {}
+}
+
+fn value_to_value() {
+ // We accept value-to-value transmutations of `UnsafeCell`-containing types,
+ // because owning a value implies exclusive access.
+ assert::is_maybe_transmutable::<UnsafeCell<u8>, u8>();
+ assert::is_maybe_transmutable::<u8, UnsafeCell<u8>>();
+ assert::is_maybe_transmutable::<UnsafeCell<u8>, UnsafeCell<u8>>();
+}
+
+fn ref_to_ref() {
+ // We forbid `UnsafeCell`-containing ref-to-ref transmutations, because the
+ // two types may use different, incompatible synchronization strategies.
+ assert::is_maybe_transmutable::<&'static u8, &'static UnsafeCell<u8>>(); //~ ERROR: cannot be safely transmuted
+
+ assert::is_maybe_transmutable::<&'static UnsafeCell<u8>, &'static UnsafeCell<u8>>(); //~ ERROR: cannot be safely transmuted
+}
+
+fn mut_to_mut() {
+ // `UnsafeCell` does't matter for `&mut T` to `&mut U`, since exclusive
+ // borrows can't be used for shared access.
+ assert::is_maybe_transmutable::<&'static mut u8, &'static mut UnsafeCell<u8>>();
+ assert::is_maybe_transmutable::<&'static mut UnsafeCell<u8>, &'static mut u8>();
+ assert::is_maybe_transmutable::<&'static mut UnsafeCell<u8>, &'static mut UnsafeCell<u8>>();
+}
+
+fn mut_to_ref() {
+ // We don't care about `UnsafeCell` for transmutations in the form `&mut T
+ // -> &U`, because downgrading a `&mut T` to a `&U` deactivates `&mut T` for
+ // the lifetime of `&U`.
+ assert::is_maybe_transmutable::<&'static mut u8, &'static UnsafeCell<u8>>();
+ assert::is_maybe_transmutable::<&'static mut UnsafeCell<u8>, &'static u8>();
+ assert::is_maybe_transmutable::<&'static mut UnsafeCell<u8>, &'static UnsafeCell<u8>>();
+}
diff --git a/tests/ui/transmutability/references/unsafecell.stderr b/tests/ui/transmutability/references/unsafecell.stderr
new file mode 100644
index 00000000000..651eb8ceb26
--- /dev/null
+++ b/tests/ui/transmutability/references/unsafecell.stderr
@@ -0,0 +1,33 @@
+error[E0277]: `&u8` cannot be safely transmuted into `&UnsafeCell<u8>`
+ --> $DIR/unsafecell.rs:27:50
+ |
+LL | assert::is_maybe_transmutable::<&'static u8, &'static UnsafeCell<u8>>();
+ | ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Freeze` is not implemented for `&'static UnsafeCell<u8>`
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/unsafecell.rs:12:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, { Assume::SAFETY }>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_maybe_transmutable`
+
+error[E0277]: `&UnsafeCell<u8>` cannot be safely transmuted into `&UnsafeCell<u8>`
+ --> $DIR/unsafecell.rs:29:62
+ |
+LL | assert::is_maybe_transmutable::<&'static UnsafeCell<u8>, &'static UnsafeCell<u8>>();
+ | ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Freeze` is not implemented for `&'static UnsafeCell<u8>`
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/unsafecell.rs:12:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, { Assume::SAFETY }>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_maybe_transmutable`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/transmutability/structs/repr/should_require_well_defined_layout.rs b/tests/ui/transmutability/structs/repr/should_handle_all.rs
similarity index 54%
rename from tests/ui/transmutability/structs/repr/should_require_well_defined_layout.rs
rename to tests/ui/transmutability/structs/repr/should_handle_all.rs
index 2e673601baf..52c24eecf12 100644
--- a/tests/ui/transmutability/structs/repr/should_require_well_defined_layout.rs
+++ b/tests/ui/transmutability/structs/repr/should_handle_all.rs
@@ -1,3 +1,4 @@
+//@ check-pass
//! A struct must have a well-defined layout to participate in a transmutation.
#![crate_type = "lib"]
@@ -20,47 +21,47 @@ mod assert {
{}
}
-fn should_reject_repr_rust()
+fn should_accept_repr_rust()
{
fn unit() {
struct repr_rust;
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
fn tuple() {
struct repr_rust();
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
fn braces() {
struct repr_rust{}
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
fn aligned() {
#[repr(align(1))] struct repr_rust{}
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
fn packed() {
#[repr(packed)] struct repr_rust{}
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
fn nested() {
struct repr_rust;
#[repr(C)] struct repr_c(repr_rust);
- assert::is_maybe_transmutable::<repr_c, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_c>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_c, ()>();
+ assert::is_maybe_transmutable::<u128, repr_c>();
}
}
-fn should_accept_repr_C()
+fn should_accept_repr_c()
{
fn unit() {
#[repr(C)] struct repr_c;
diff --git a/tests/ui/transmutability/structs/repr/should_require_well_defined_layout.stderr b/tests/ui/transmutability/structs/repr/should_require_well_defined_layout.stderr
deleted file mode 100644
index 77788f72c21..00000000000
--- a/tests/ui/transmutability/structs/repr/should_require_well_defined_layout.stderr
+++ /dev/null
@@ -1,267 +0,0 @@
-error[E0277]: `should_reject_repr_rust::unit::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:27:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `should_reject_repr_rust::unit::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `should_reject_repr_rust::unit::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:28:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `should_reject_repr_rust::unit::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `should_reject_repr_rust::tuple::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:33:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `should_reject_repr_rust::tuple::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `should_reject_repr_rust::tuple::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:34:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `should_reject_repr_rust::tuple::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `should_reject_repr_rust::braces::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:39:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `should_reject_repr_rust::braces::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `should_reject_repr_rust::braces::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:40:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `should_reject_repr_rust::braces::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `aligned::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:45:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `aligned::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `aligned::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:46:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `aligned::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `packed::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:51:52
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `packed::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `packed::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:52:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `packed::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `nested::repr_c` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:58:49
- |
-LL | assert::is_maybe_transmutable::<repr_c, ()>();
- | ^^ analyzing the transmutability of `nested::repr_c` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `nested::repr_c`
- --> $DIR/should_require_well_defined_layout.rs:59:47
- |
-LL | assert::is_maybe_transmutable::<u128, repr_c>();
- | ^^^^^^ analyzing the transmutability of `nested::repr_c` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error: aborting due to 12 previous errors
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.rs b/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.rs
index 4c285a616b3..64110753832 100644
--- a/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.rs
+++ b/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.rs
@@ -22,4 +22,5 @@ fn should_pad_explicitly_packed_field() {
//~^ ERROR: recursive type
assert::is_maybe_transmutable::<ExplicitlyPadded, ()>();
+ //~^ ERROR: cannot be safely transmuted
}
diff --git a/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.stderr b/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.stderr
index 7fb051f6625..ebfb5361143 100644
--- a/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.stderr
+++ b/tests/ui/transmutability/structs/repr/transmute_infinitely_recursive_type.stderr
@@ -15,7 +15,22 @@ error[E0391]: cycle detected when computing layout of `should_pad_explicitly_pac
= note: cycle used when evaluating trait selection obligation `(): core::mem::transmutability::BikeshedIntrinsicFrom<should_pad_explicitly_packed_field::ExplicitlyPadded, core::mem::transmutability::Assume { alignment: false, lifetimes: false, safety: false, validity: false }>`
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
-error: aborting due to 2 previous errors
+error[E0277]: `ExplicitlyPadded` cannot be safely transmuted into `()`
+ --> $DIR/transmute_infinitely_recursive_type.rs:24:55
+ |
+LL | assert::is_maybe_transmutable::<ExplicitlyPadded, ()>();
+ | ^^ analyzing the transmutability of `ExplicitlyPadded` is not yet supported
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/transmute_infinitely_recursive_type.rs:14:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src>,
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_maybe_transmutable`
-Some errors have detailed explanations: E0072, E0391.
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0072, E0277, E0391.
For more information about an error, try `rustc --explain E0072`.
diff --git a/tests/ui/transmutability/transmute-padding-ice.rs b/tests/ui/transmutability/transmute-padding-ice.rs
index 3f3f75bc086..f5935a0009e 100644
--- a/tests/ui/transmutability/transmute-padding-ice.rs
+++ b/tests/ui/transmutability/transmute-padding-ice.rs
@@ -1,7 +1,13 @@
+//@ check-pass
+//! This UI test was introduced as check-fail by a buggy bug-fix for an ICE. In
+//! fact, this transmutation should be valid.
+
#![crate_type = "lib"]
#![feature(transmutability)]
#![allow(dead_code)]
+use std::mem::size_of;
+
mod assert {
use std::mem::{Assume, BikeshedIntrinsicFrom};
@@ -22,6 +28,7 @@ fn test() {
#[repr(C)]
struct B(u8, u8);
+ assert_eq!(size_of::<A>(), size_of::<B>());
+
assert::is_maybe_transmutable::<B, A>();
- //~^ ERROR cannot be safely transmuted
}
diff --git a/tests/ui/transmutability/transmute-padding-ice.stderr b/tests/ui/transmutability/transmute-padding-ice.stderr
deleted file mode 100644
index 4c121d463c6..00000000000
--- a/tests/ui/transmutability/transmute-padding-ice.stderr
+++ /dev/null
@@ -1,22 +0,0 @@
-error[E0277]: `B` cannot be safely transmuted into `A`
- --> $DIR/transmute-padding-ice.rs:25:40
- |
-LL | assert::is_maybe_transmutable::<B, A>();
- | ^ the size of `B` is smaller than the size of `A`
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/transmute-padding-ice.rs:10:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<
- | ______________^
-LL | | Src,
-LL | | { Assume { alignment: true, lifetimes: true, safety: true, validity: true } },
-LL | | >,
- | |_________^ required by this bound in `is_maybe_transmutable`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/transmutability/uninhabited.rs b/tests/ui/transmutability/uninhabited.rs
new file mode 100644
index 00000000000..b61b110f6a1
--- /dev/null
+++ b/tests/ui/transmutability/uninhabited.rs
@@ -0,0 +1,71 @@
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code, incomplete_features, non_camel_case_types)]
+
+mod assert {
+ use std::mem::{Assume, BikeshedIntrinsicFrom};
+
+ pub fn is_maybe_transmutable<Src, Dst>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, {
+ Assume {
+ alignment: true,
+ lifetimes: true,
+ safety: true,
+ validity: true,
+ }
+ }>
+ {}
+}
+
+fn void() {
+ enum Void {}
+
+ // This transmutation is vacuously acceptable; since one cannot construct a
+ // `Void`, unsoundness cannot directly arise from transmuting a void into
+ // anything else.
+ assert::is_maybe_transmutable::<Void, u128>();
+
+ assert::is_maybe_transmutable::<(), Void>(); //~ ERROR: cannot be safely transmuted
+}
+
+// Non-ZST uninhabited types are, nonetheless, uninhabited.
+fn yawning_void() {
+ enum Void {}
+
+ struct YawningVoid(Void, u128);
+
+ const _: () = {
+ assert!(std::mem::size_of::<YawningVoid>() == std::mem::size_of::<u128>());
+ // Just to be sure the above constant actually evaluated:
+ assert!(false); //~ ERROR: evaluation of constant value failed
+ };
+
+ // This transmutation is vacuously acceptable; since one cannot construct a
+ // `Void`, unsoundness cannot directly arise from transmuting a void into
+ // anything else.
+ assert::is_maybe_transmutable::<YawningVoid, u128>();
+
+ assert::is_maybe_transmutable::<(), Void>(); //~ ERROR: cannot be safely transmuted
+}
+
+// References to uninhabited types are, logically, uninhabited, but for layout
+// purposes are not ZSTs, and aren't treated as uninhabited when they appear in
+// enum variants.
+fn distant_void() {
+ enum Void {}
+
+ enum DistantVoid {
+ A(&'static Void)
+ }
+
+ const _: () = {
+ assert!(std::mem::size_of::<DistantVoid>() == std::mem::size_of::<usize>());
+ // Just to be sure the above constant actually evaluated:
+ assert!(false); //~ ERROR: evaluation of constant value failed
+ };
+
+ assert::is_maybe_transmutable::<DistantVoid, ()>();
+ assert::is_maybe_transmutable::<DistantVoid, &'static Void>();
+ assert::is_maybe_transmutable::<u128, DistantVoid>(); //~ ERROR: cannot be safely transmuted
+}
diff --git a/tests/ui/transmutability/uninhabited.stderr b/tests/ui/transmutability/uninhabited.stderr
new file mode 100644
index 00000000000..60219b0f263
--- /dev/null
+++ b/tests/ui/transmutability/uninhabited.stderr
@@ -0,0 +1,86 @@
+error[E0080]: evaluation of constant value failed
+ --> $DIR/uninhabited.rs:41:9
+ |
+LL | assert!(false);
+ | ^^^^^^^^^^^^^^ the evaluated program panicked at 'assertion failed: false', $DIR/uninhabited.rs:41:9
+ |
+ = note: this error originates in the macro `assert` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0080]: evaluation of constant value failed
+ --> $DIR/uninhabited.rs:65:9
+ |
+LL | assert!(false);
+ | ^^^^^^^^^^^^^^ the evaluated program panicked at 'assertion failed: false', $DIR/uninhabited.rs:65:9
+ |
+ = note: this error originates in the macro `assert` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: `()` cannot be safely transmuted into `void::Void`
+ --> $DIR/uninhabited.rs:29:41
+ |
+LL | assert::is_maybe_transmutable::<(), Void>();
+ | ^^^^ `void::Void` is uninhabited
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/uninhabited.rs:10:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, {
+ | ______________^
+LL | | Assume {
+LL | | alignment: true,
+LL | | lifetimes: true,
+... |
+LL | | }
+LL | | }>
+ | |__________^ required by this bound in `is_maybe_transmutable`
+
+error[E0277]: `()` cannot be safely transmuted into `yawning_void::Void`
+ --> $DIR/uninhabited.rs:49:41
+ |
+LL | assert::is_maybe_transmutable::<(), Void>();
+ | ^^^^ `yawning_void::Void` is uninhabited
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/uninhabited.rs:10:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, {
+ | ______________^
+LL | | Assume {
+LL | | alignment: true,
+LL | | lifetimes: true,
+... |
+LL | | }
+LL | | }>
+ | |__________^ required by this bound in `is_maybe_transmutable`
+
+error[E0277]: `u128` cannot be safely transmuted into `DistantVoid`
+ --> $DIR/uninhabited.rs:70:43
+ |
+LL | assert::is_maybe_transmutable::<u128, DistantVoid>();
+ | ^^^^^^^^^^^ at least one value of `u128` isn't a bit-valid value of `DistantVoid`
+ |
+note: required by a bound in `is_maybe_transmutable`
+ --> $DIR/uninhabited.rs:10:14
+ |
+LL | pub fn is_maybe_transmutable<Src, Dst>()
+ | --------------------- required by a bound in this function
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, {
+ | ______________^
+LL | | Assume {
+LL | | alignment: true,
+LL | | lifetimes: true,
+... |
+LL | | }
+LL | | }>
+ | |__________^ required by this bound in `is_maybe_transmutable`
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0080, E0277.
+For more information about an error, try `rustc --explain E0080`.
diff --git a/tests/ui/transmutability/unions/repr/should_handle_align.rs b/tests/ui/transmutability/unions/repr/should_handle_align.rs
index 8668cca3cb5..ba4e904e161 100644
--- a/tests/ui/transmutability/unions/repr/should_handle_align.rs
+++ b/tests/ui/transmutability/unions/repr/should_handle_align.rs
@@ -25,13 +25,13 @@ fn should_pad_explicitly_aligned_field() {
#[derive(Clone, Copy)] #[repr(u8)] enum V0u8 { V = 0 }
#[derive(Clone, Copy)] #[repr(u8)] enum V1u8 { V = 1 }
- #[repr(C)]
+ #[repr(align(1))]
pub union Uninit {
a: (),
b: V1u8,
}
- #[repr(C, align(2))]
+ #[repr(align(2))]
pub union align_2 {
a: V0u8,
}
diff --git a/tests/ui/transmutability/unions/repr/should_require_well_defined_layout.rs b/tests/ui/transmutability/unions/repr/should_handle_all.rs
similarity index 58%
rename from tests/ui/transmutability/unions/repr/should_require_well_defined_layout.rs
rename to tests/ui/transmutability/unions/repr/should_handle_all.rs
index 8495b0ea88f..85d48dd9b7f 100644
--- a/tests/ui/transmutability/unions/repr/should_require_well_defined_layout.rs
+++ b/tests/ui/transmutability/unions/repr/should_handle_all.rs
@@ -1,7 +1,7 @@
-//! A struct must have a well-defined layout to participate in a transmutation.
+//@ check-pass
#![crate_type = "lib"]
-#![feature(transmutability)]
+#![feature(transmutability, transparent_unions)]
#![allow(dead_code, incomplete_features, non_camel_case_types)]
mod assert {
@@ -20,17 +20,17 @@ mod assert {
{}
}
-fn should_reject_repr_rust()
+fn should_accept_repr_rust()
{
union repr_rust {
a: u8
}
- assert::is_maybe_transmutable::<repr_rust, ()>(); //~ ERROR cannot be safely transmuted
- assert::is_maybe_transmutable::<u128, repr_rust>(); //~ ERROR cannot be safely transmuted
+ assert::is_maybe_transmutable::<repr_rust, ()>();
+ assert::is_maybe_transmutable::<u128, repr_rust>();
}
-fn should_accept_repr_C()
+fn should_accept_repr_c()
{
#[repr(C)]
union repr_c {
@@ -41,3 +41,15 @@ fn should_accept_repr_C()
assert::is_maybe_transmutable::<repr_c, ()>();
assert::is_maybe_transmutable::<u128, repr_c>();
}
+
+
+fn should_accept_transparent()
+{
+ #[repr(transparent)]
+ union repr_transparent {
+ a: u8
+ }
+
+ assert::is_maybe_transmutable::<repr_transparent, ()>();
+ assert::is_maybe_transmutable::<u128, repr_transparent>();
+}
diff --git a/tests/ui/transmutability/unions/repr/should_handle_packed.rs b/tests/ui/transmutability/unions/repr/should_handle_packed.rs
index 4af6c1d3a61..fc06eba4353 100644
--- a/tests/ui/transmutability/unions/repr/should_handle_packed.rs
+++ b/tests/ui/transmutability/unions/repr/should_handle_packed.rs
@@ -27,7 +27,6 @@ fn should_pad_explicitly_packed_field() {
#[derive(Clone, Copy)] #[repr(u8)] enum V2u8 { V = 2 }
#[derive(Clone, Copy)] #[repr(u32)] enum V3u32 { V = 3 }
- #[repr(C)]
pub union Uninit {
a: (),
b: V1u8,
diff --git a/tests/ui/transmutability/unions/repr/should_require_well_defined_layout.stderr b/tests/ui/transmutability/unions/repr/should_require_well_defined_layout.stderr
deleted file mode 100644
index bec07f13103..00000000000
--- a/tests/ui/transmutability/unions/repr/should_require_well_defined_layout.stderr
+++ /dev/null
@@ -1,47 +0,0 @@
-error[E0277]: `should_reject_repr_rust::repr_rust` cannot be safely transmuted into `()`
- --> $DIR/should_require_well_defined_layout.rs:29:48
- |
-LL | assert::is_maybe_transmutable::<repr_rust, ()>();
- | ^^ analyzing the transmutability of `should_reject_repr_rust::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error[E0277]: `u128` cannot be safely transmuted into `should_reject_repr_rust::repr_rust`
- --> $DIR/should_require_well_defined_layout.rs:30:43
- |
-LL | assert::is_maybe_transmutable::<u128, repr_rust>();
- | ^^^^^^^^^ analyzing the transmutability of `should_reject_repr_rust::repr_rust` is not yet supported.
- |
-note: required by a bound in `is_maybe_transmutable`
- --> $DIR/should_require_well_defined_layout.rs:12:14
- |
-LL | pub fn is_maybe_transmutable<Src, Dst>()
- | --------------------- required by a bound in this function
-LL | where
-LL | Dst: BikeshedIntrinsicFrom<Src, {
- | ______________^
-LL | | Assume {
-LL | | alignment: true,
-LL | | lifetimes: true,
-... |
-LL | | }
-LL | | }>
- | |__________^ required by this bound in `is_maybe_transmutable`
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0277`.