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Safe Transmute: Refactor error handling and Answer type

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- Create `Answer` type that is not just a type alias of `Result`
- Remove a usage of `map_layouts` to make the code easier to read
- Don't hide errors related to Unknown Layout when computing transmutability
This commit is contained in:
Bryan Garza 2023-06-12 16:35:23 -07:00
parent 64a54df86f
commit f4cf8f65a5
9 changed files with 166 additions and 126 deletions
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8
compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
View file

@ -668,6 +668,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
scope: Ty<'tcx>, scope: Ty<'tcx>,
assume: rustc_transmute::Assume, assume: rustc_transmute::Assume,
) -> Result<Certainty, NoSolution> { ) -> Result<Certainty, NoSolution> {
use rustc_transmute::Answer;
// FIXME(transmutability): This really should be returning nested goals for `Answer::If*` // FIXME(transmutability): This really should be returning nested goals for `Answer::If*`
match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable( match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(
ObligationCause::dummy(), ObligationCause::dummy(),
@ -675,11 +676,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
scope, scope,
assume, assume,
) { ) {
Ok(None) => Ok(Certainty::Yes), Answer::Yes => Ok(Certainty::Yes),
Err(_) Answer::No(_) | Answer::If(_) => Err(NoSolution),
| Ok(Some(rustc_transmute::Condition::IfTransmutable { .. }))
| Ok(Some(rustc_transmute::Condition::IfAll(_)))
| Ok(Some(rustc_transmute::Condition::IfAny(_))) => Err(NoSolution),
} }
} }
} }

41
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View file

@ -65,6 +65,11 @@ pub struct ImplCandidate<'tcx> {
pub similarity: CandidateSimilarity, pub similarity: CandidateSimilarity,
} }
enum GetSafeTransmuteErrorAndReason {
Silent,
Error { err_msg: String, safe_transmute_explanation: String },
}
pub trait InferCtxtExt<'tcx> { pub trait InferCtxtExt<'tcx> {
/// Given some node representing a fn-like thing in the HIR map, /// Given some node representing a fn-like thing in the HIR map,
/// returns a span and `ArgKind` information that describes the /// returns a span and `ArgKind` information that describes the
@ -724,11 +729,17 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
== self.tcx.lang_items().transmute_trait() == self.tcx.lang_items().transmute_trait()
{ {
// Recompute the safe transmute reason and use that for the error reporting // Recompute the safe transmute reason and use that for the error reporting
self.get_safe_transmute_error_and_reason( match self.get_safe_transmute_error_and_reason(
obligation.clone(), obligation.clone(),
trait_ref, trait_ref,
span, span,
) ) {
GetSafeTransmuteErrorAndReason::Silent => return,
GetSafeTransmuteErrorAndReason::Error {
err_msg,
safe_transmute_explanation,
} => (err_msg, Some(safe_transmute_explanation)),
}
} else { } else {
(err_msg, None) (err_msg, None)
}; };
@ -1292,7 +1303,7 @@ trait InferCtxtPrivExt<'tcx> {
obligation: PredicateObligation<'tcx>, obligation: PredicateObligation<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>,
span: Span, span: Span,
) -> (String, Option<String>); ) -> GetSafeTransmuteErrorAndReason;
fn add_tuple_trait_message( fn add_tuple_trait_message(
&self, &self,
@ -2738,7 +2749,9 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
obligation: PredicateObligation<'tcx>, obligation: PredicateObligation<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>,
span: Span, span: Span,
) -> (String, Option<String>) { ) -> GetSafeTransmuteErrorAndReason {
use rustc_transmute::Answer;
// Erase regions because layout code doesn't particularly care about regions. // Erase regions because layout code doesn't particularly care about regions.
let trait_ref = self.tcx.erase_regions(self.tcx.erase_late_bound_regions(trait_ref)); let trait_ref = self.tcx.erase_regions(self.tcx.erase_late_bound_regions(trait_ref));
@ -2758,13 +2771,13 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
scope, scope,
assume, assume,
) { ) {
Err(reason) => { Answer::No(reason) => {
let dst = trait_ref.substs.type_at(0); let dst = trait_ref.substs.type_at(0);
let src = trait_ref.substs.type_at(1); let src = trait_ref.substs.type_at(1);
let custom_err_msg = format!( let err_msg = format!(
"`{src}` cannot be safely transmuted into `{dst}` in the defining scope of `{scope}`" "`{src}` cannot be safely transmuted into `{dst}` in the defining scope of `{scope}`"
); );
let reason_msg = match reason { let safe_transmute_explanation = match reason {
rustc_transmute::Reason::SrcIsUnspecified => { rustc_transmute::Reason::SrcIsUnspecified => {
format!("`{src}` does not have a well-specified layout") format!("`{src}` does not have a well-specified layout")
} }
@ -2794,11 +2807,21 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
rustc_transmute::Reason::DstIsMoreUnique => { rustc_transmute::Reason::DstIsMoreUnique => {
format!("`{src}` is a shared reference, but `{dst}` is a unique reference") format!("`{src}` is a shared reference, but `{dst}` is a unique reference")
} }
// Already reported by rustc
rustc_transmute::Reason::TypeError => {
return GetSafeTransmuteErrorAndReason::Silent;
}
rustc_transmute::Reason::SrcLayoutUnknown => {
format!("`{src}` has an unknown layout")
}
rustc_transmute::Reason::DstLayoutUnknown => {
format!("`{dst}` has an unknown layout")
}
}; };
(custom_err_msg, Some(reason_msg)) GetSafeTransmuteErrorAndReason::Error { err_msg, safe_transmute_explanation }
} }
// Should never get a Yes at this point! We already ran it before, and did not get a Yes. // Should never get a Yes at this point! We already ran it before, and did not get a Yes.
Ok(None) => span_bug!( Answer::Yes => span_bug!(
span, span,
"Inconsistent rustc_transmute::is_transmutable(...) result, got Yes", "Inconsistent rustc_transmute::is_transmutable(...) result, got Yes",
), ),

35
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -285,28 +285,22 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
&mut self, &mut self,
obligation: &TraitObligation<'tcx>, obligation: &TraitObligation<'tcx>,
) -> Result<ImplSourceBuiltinData<PredicateObligation<'tcx>>, SelectionError<'tcx>> { ) -> Result<ImplSourceBuiltinData<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
use rustc_transmute::{Answer, Condition};
#[instrument(level = "debug", skip(tcx, obligation, predicate))] #[instrument(level = "debug", skip(tcx, obligation, predicate))]
fn flatten_answer_tree<'tcx>( fn flatten_answer_tree<'tcx>(
tcx: TyCtxt<'tcx>, tcx: TyCtxt<'tcx>,
obligation: &TraitObligation<'tcx>, obligation: &TraitObligation<'tcx>,
predicate: TraitPredicate<'tcx>, predicate: TraitPredicate<'tcx>,
answer: rustc_transmute::Condition<rustc_transmute::layout::rustc::Ref<'tcx>>, cond: Condition<rustc_transmute::layout::rustc::Ref<'tcx>>,
) -> Vec<PredicateObligation<'tcx>> { ) -> Vec<PredicateObligation<'tcx>> {
match answer { match cond {
// FIXME(bryangarza): Add separate `IfAny` case, instead of treating as `IfAll` // FIXME(bryangarza): Add separate `IfAny` case, instead of treating as `IfAll`
// Not possible until the trait solver supports disjunctions of obligations // Not possible until the trait solver supports disjunctions of obligations
rustc_transmute::Condition::IfAll(answers) Condition::IfAll(conds) | Condition::IfAny(conds) => conds
| rustc_transmute::Condition::IfAny(answers) => { .into_iter()
let mut nested = vec![]; .flat_map(|cond| flatten_answer_tree(tcx, obligation, predicate, cond))
for flattened in answers .collect(),
.into_iter() Condition::IfTransmutable { src, dst } => {
.map(|answer| flatten_answer_tree(tcx, obligation, predicate, answer))
{
nested.extend(flattened);
}
nested
}
rustc_transmute::Condition::IfTransmutable { src, dst } => {
let trait_def_id = obligation.predicate.def_id(); let trait_def_id = obligation.predicate.def_id();
let scope = predicate.trait_ref.substs.type_at(2); let scope = predicate.trait_ref.substs.type_at(2);
let assume_const = predicate.trait_ref.substs.const_at(3); let assume_const = predicate.trait_ref.substs.const_at(3);
@ -333,11 +327,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// If Dst is mutable, check bidirectionally. // If Dst is mutable, check bidirectionally.
// For example, transmuting bool -> u8 is OK as long as you can't update that u8 // 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. // to be > 1, because you could later transmute the u8 back to a bool and get UB.
let mut obligations = vec![make_obl(src.ty, dst.ty)]; match dst.mutability {
if dst.mutability == Mutability::Mut { Mutability::Not => vec![make_obl(src.ty, dst.ty)],
obligations.push(make_obl(dst.ty, src.ty)); Mutability::Mut => vec![make_obl(src.ty, dst.ty), make_obl(dst.ty, src.ty)],
} }
obligations
} }
} }
} }
@ -370,9 +363,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
); );
let fully_flattened = match maybe_transmutable { let fully_flattened = match maybe_transmutable {
Err(_) => Err(Unimplemented)?, Answer::No(_) => Err(Unimplemented)?,
Ok(Some(mt)) => flatten_answer_tree(self.tcx(), obligation, predicate, mt), Answer::If(cond) => flatten_answer_tree(self.tcx(), obligation, predicate, cond),
Ok(None) => vec![], Answer::Yes => vec![],
}; };
debug!(?fully_flattened); debug!(?fully_flattened);

4
compiler/rustc_transmute/src/layout/tree.rs
View file

@ -188,14 +188,14 @@ pub(crate) mod rustc {
/// The layout of the type is unspecified. /// The layout of the type is unspecified.
Unspecified, Unspecified,
/// This error will be surfaced elsewhere by rustc, so don't surface it. /// This error will be surfaced elsewhere by rustc, so don't surface it.
Unknown, UnknownLayout,
TypeError(ErrorGuaranteed), TypeError(ErrorGuaranteed),
} }
impl<'tcx> From<LayoutError<'tcx>> for Err { impl<'tcx> From<LayoutError<'tcx>> for Err {
fn from(err: LayoutError<'tcx>) -> Self { fn from(err: LayoutError<'tcx>) -> Self {
match err { match err {
LayoutError::Unknown(..) => Self::Unknown, LayoutError::Unknown(..) => Self::UnknownLayout,
err => unimplemented!("{:?}", err), err => unimplemented!("{:?}", err),
} }
} }

20
compiler/rustc_transmute/src/lib.rs
View file

@ -19,10 +19,16 @@ pub struct Assume {
pub validity: bool, pub validity: bool,
} }
/// Either we have an error, or we have an optional Condition that must hold. /// Either we have an error, transmutation is allowed, or we have an optional
pub type Answer<R> = Result<Option<Condition<R>>, Reason>; /// Condition that must hold.
#[derive(Debug, Hash, Eq, PartialEq, Clone)]
pub enum Answer<R> {
Yes,
No(Reason),
If(Condition<R>),
}
/// A condition which must hold for safe transmutation to be possible /// A condition which must hold for safe transmutation to be possible.
#[derive(Debug, Hash, Eq, PartialEq, Clone)] #[derive(Debug, Hash, Eq, PartialEq, Clone)]
pub enum Condition<R> { pub enum Condition<R> {
/// `Src` is transmutable into `Dst`, if `src` is transmutable into `dst`. /// `Src` is transmutable into `Dst`, if `src` is transmutable into `dst`.
@ -35,7 +41,7 @@ pub enum Condition<R> {
IfAny(Vec<Condition<R>>), IfAny(Vec<Condition<R>>),
} }
/// Answers: Why wasn't the source type transmutable into the destination type? /// Answers "why wasn't the source type transmutable into the destination type?"
#[derive(Debug, Hash, Eq, PartialEq, PartialOrd, Ord, Clone)] #[derive(Debug, Hash, Eq, PartialEq, PartialOrd, Ord, Clone)]
pub enum Reason { pub enum Reason {
/// The layout of the source type is unspecified. /// The layout of the source type is unspecified.
@ -52,6 +58,12 @@ pub enum Reason {
DstHasStricterAlignment { src_min_align: usize, dst_min_align: usize }, DstHasStricterAlignment { src_min_align: usize, dst_min_align: usize },
/// Can't go from shared pointer to unique pointer /// Can't go from shared pointer to unique pointer
DstIsMoreUnique, DstIsMoreUnique,
/// Encountered a type error
TypeError,
/// The layout of src is unknown
SrcLayoutUnknown,
/// The layout of dst is unknown
DstLayoutUnknown,
} }
#[cfg(feature = "rustc")] #[cfg(feature = "rustc")]

150
compiler/rustc_transmute/src/maybe_transmutable/mod.rs
View file

@ -33,6 +33,7 @@ where
Self { src, dst, scope, assume, context } Self { src, dst, scope, assume, context }
} }
// FIXME(bryangarza): Delete this when all usages are removed
pub(crate) fn map_layouts<F, M>( pub(crate) fn map_layouts<F, M>(
self, self,
f: F, f: F,
@ -67,30 +68,26 @@ mod rustc {
/// then computes an answer using those trees. /// then computes an answer using those trees.
#[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))] #[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))]
pub fn answer(self) -> Answer<<TyCtxt<'tcx> as QueryContext>::Ref> { pub fn answer(self) -> Answer<<TyCtxt<'tcx> as QueryContext>::Ref> {
let query_or_answer = self.map_layouts(|src, dst, scope, &context| { let Self { src, dst, scope, assume, context } = self;
// 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);
match (src, dst) { // Convert `src` and `dst` from their rustc representations, to `Tree`-based
// Answer `Ok(None)` here, because 'unknown layout' and type errors will already // representations. If these conversions fail, conclude that the transmutation is
// be reported by rustc. No need to spam the user with more errors. // unacceptable; the layouts of both the source and destination types must be
(Err(Err::TypeError(_)), _) // well-defined.
| (_, Err(Err::TypeError(_))) let src = Tree::from_ty(src, context);
| (Err(Err::Unknown), _) let dst = Tree::from_ty(dst, context);
| (_, Err(Err::Unknown)) => Err(Ok(None)),
(Err(Err::Unspecified), _) => Err(Err(Reason::SrcIsUnspecified)), match (src, dst) {
(_, Err(Err::Unspecified)) => Err(Err(Reason::DstIsUnspecified)), (Err(Err::TypeError(_)), _) | (_, Err(Err::TypeError(_))) => {
(Ok(src), Ok(dst)) => Ok((src, dst)), Answer::No(Reason::TypeError)
}
(Err(Err::UnknownLayout), _) => Answer::No(Reason::SrcLayoutUnknown),
(_, Err(Err::UnknownLayout)) => Answer::No(Reason::DstLayoutUnknown),
(Err(Err::Unspecified), _) => Answer::No(Reason::SrcIsUnspecified),
(_, Err(Err::Unspecified)) => Answer::No(Reason::DstIsUnspecified),
(Ok(src), Ok(dst)) => {
MaybeTransmutableQuery { src, dst, scope, assume, context }.answer()
} }
});
match query_or_answer {
Ok(query) => query.answer(),
Err(answer) => answer,
} }
} }
} }
@ -108,6 +105,7 @@ where
#[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))] #[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))]
pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> { pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> {
let assume_visibility = self.assume.safety; let assume_visibility = self.assume.safety;
// FIXME(bryangarza): Refactor this code to get rid of `map_layouts`
let query_or_answer = self.map_layouts(|src, dst, scope, context| { let query_or_answer = self.map_layouts(|src, dst, scope, context| {
// Remove all `Def` nodes from `src`, without checking their visibility. // Remove all `Def` nodes from `src`, without checking their visibility.
let src = src.prune(&|def| true); let src = src.prune(&|def| true);
@ -128,12 +126,13 @@ where
// Convert `src` from a tree-based representation to an NFA-based representation. // Convert `src` from a tree-based representation to an NFA-based representation.
// If the conversion fails because `src` is uninhabited, conclude that the transmutation // If the conversion fails because `src` is uninhabited, conclude that the transmutation
// is acceptable, because instances of the `src` type do not exist. // is acceptable, because instances of the `src` type do not exist.
let src = Nfa::from_tree(src).map_err(|Uninhabited| Ok(None))?; let src = Nfa::from_tree(src).map_err(|Uninhabited| Answer::Yes)?;
// Convert `dst` from a tree-based representation to an NFA-based representation. // Convert `dst` from a tree-based representation to an NFA-based representation.
// If the conversion fails because `src` is uninhabited, conclude that the transmutation // If the conversion fails because `src` is uninhabited, conclude that the transmutation
// is unacceptable, because instances of the `dst` type do not exist. // is unacceptable, because instances of the `dst` type do not exist.
let dst = Nfa::from_tree(dst).map_err(|Uninhabited| Err(Reason::DstIsPrivate))?; let dst =
Nfa::from_tree(dst).map_err(|Uninhabited| Answer::No(Reason::DstIsPrivate))?;
Ok((src, dst)) Ok((src, dst))
}); });
@ -155,6 +154,7 @@ where
#[inline(always)] #[inline(always)]
#[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))] #[instrument(level = "debug", skip(self), fields(src = ?self.src, dst = ?self.dst))]
pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> { pub(crate) fn answer(self) -> Answer<<C as QueryContext>::Ref> {
// FIXME(bryangarza): Refactor this code to get rid of `map_layouts`
let query_or_answer = self let query_or_answer = self
.map_layouts(|src, dst, scope, context| Ok((Dfa::from_nfa(src), Dfa::from_nfa(dst)))); .map_layouts(|src, dst, scope, context| Ok((Dfa::from_nfa(src), Dfa::from_nfa(dst))));
@ -226,13 +226,13 @@ where
// So, if it's possible to transmute to a smaller Dst by truncating, and we can guarantee // So, if it's possible to transmute to a smaller Dst by truncating, and we can guarantee
// that none of the actually-used data can introduce an invalid state for Dst's type, we // that none of the actually-used data can introduce an invalid state for Dst's type, we
// are able to safely transmute, even with truncation. // are able to safely transmute, even with truncation.
Ok(None) Answer::Yes
} else if src_state == self.src.accepting { } else if src_state == self.src.accepting {
// extension: `size_of(Src) >= size_of(Dst)` // extension: `size_of(Src) >= size_of(Dst)`
if let Some(dst_state_prime) = self.dst.byte_from(dst_state, Byte::Uninit) { if let Some(dst_state_prime) = self.dst.byte_from(dst_state, Byte::Uninit) {
self.answer_memo(cache, src_state, dst_state_prime) self.answer_memo(cache, src_state, dst_state_prime)
} else { } else {
Err(Reason::DstIsTooBig) Answer::No(Reason::DstIsTooBig)
} }
} else { } else {
let src_quantifier = if self.assume.validity { let src_quantifier = if self.assume.validity {
@ -265,7 +265,7 @@ where
} else { } else {
// otherwise, we've exhausted our options. // otherwise, we've exhausted our options.
// the DFAs, from this point onwards, are bit-incompatible. // the DFAs, from this point onwards, are bit-incompatible.
Err(Reason::DstIsBitIncompatible) Answer::No(Reason::DstIsBitIncompatible)
} }
}, },
), ),
@ -282,8 +282,8 @@ where
// the algoritm; only its performance. // the algoritm; only its performance.
debug!(?bytes_answer); debug!(?bytes_answer);
match bytes_answer { match bytes_answer {
Err(_) if !self.assume.validity => return bytes_answer, Answer::No(_) if !self.assume.validity => return bytes_answer,
Ok(None) if self.assume.validity => return bytes_answer, Answer::Yes if self.assume.validity => return bytes_answer,
_ => {} _ => {}
}; };
@ -299,11 +299,11 @@ where
.into_iter() .into_iter()
.map(|(&dst_ref, &dst_state_prime)| { .map(|(&dst_ref, &dst_state_prime)| {
if !src_ref.is_mutable() && dst_ref.is_mutable() { if !src_ref.is_mutable() && dst_ref.is_mutable() {
Err(Reason::DstIsMoreUnique) Answer::No(Reason::DstIsMoreUnique)
} else if !self.assume.alignment } else if !self.assume.alignment
&& src_ref.min_align() < dst_ref.min_align() && src_ref.min_align() < dst_ref.min_align()
{ {
Err(Reason::DstHasStricterAlignment { Answer::No(Reason::DstHasStricterAlignment {
src_min_align: src_ref.min_align(), src_min_align: src_ref.min_align(),
dst_min_align: dst_ref.min_align(), dst_min_align: dst_ref.min_align(),
}) })
@ -311,10 +311,10 @@ where
// ...such that `src` is transmutable into `dst`, if // ...such that `src` is transmutable into `dst`, if
// `src_ref` is transmutability into `dst_ref`. // `src_ref` is transmutability into `dst_ref`.
and( and(
Ok(Some(Condition::IfTransmutable { Answer::If(Condition::IfTransmutable {
src: src_ref, src: src_ref,
dst: dst_ref, dst: dst_ref,
})), }),
self.answer_memo( self.answer_memo(
cache, cache,
src_state_prime, src_state_prime,
@ -346,65 +346,56 @@ fn and<R>(lhs: Answer<R>, rhs: Answer<R>) -> Answer<R>
where where
R: PartialEq, R: PartialEq,
{ {
// If both are errors, then we should return the more specific one match (lhs, rhs) {
if lhs.is_err() && rhs.is_err() { // If both are errors, then we should return the more specific one
if lhs == Err(Reason::DstIsBitIncompatible) { (Answer::No(Reason::DstIsBitIncompatible), Answer::No(reason))
return rhs; | (Answer::No(reason), Answer::No(_))
} else { // If either is an error, return it
return lhs; | (Answer::No(reason), _) | (_, Answer::No(reason)) => Answer::No(reason),
}
}
Ok(match (lhs?, rhs?) {
// If only one side has a condition, pass it along // If only one side has a condition, pass it along
(None, other) | (other, None) => other, | (Answer::Yes, other) | (other, Answer::Yes) => other,
// If both sides have IfAll conditions, merge them // If both sides have IfAll conditions, merge them
(Some(Condition::IfAll(mut lhs)), Some(Condition::IfAll(ref mut rhs))) => { (Answer::If(Condition::IfAll(mut lhs)), Answer::If(Condition::IfAll(ref mut rhs))) => {
lhs.append(rhs); lhs.append(rhs);
Some(Condition::IfAll(lhs)) Answer::If(Condition::IfAll(lhs))
} }
// If only one side is an IfAll, add the other Condition to it // If only one side is an IfAll, add the other Condition to it
(Some(cond), Some(Condition::IfAll(mut conds))) (Answer::If(cond), Answer::If(Condition::IfAll(mut conds)))
| (Some(Condition::IfAll(mut conds)), Some(cond)) => { | (Answer::If(Condition::IfAll(mut conds)), Answer::If(cond)) => {
conds.push(cond); conds.push(cond);
Some(Condition::IfAll(conds)) Answer::If(Condition::IfAll(conds))
} }
// Otherwise, both lhs and rhs conditions can be combined in a parent IfAll // Otherwise, both lhs and rhs conditions can be combined in a parent IfAll
(Some(lhs), Some(rhs)) => Some(Condition::IfAll(vec![lhs, rhs])), (Answer::If(lhs), Answer::If(rhs)) => Answer::If(Condition::IfAll(vec![lhs, rhs])),
}) }
} }
fn or<R>(lhs: Answer<R>, rhs: Answer<R>) -> Answer<R> fn or<R>(lhs: Answer<R>, rhs: Answer<R>) -> Answer<R>
where where
R: PartialEq, R: PartialEq,
{ {
// If both are errors, then we should return the more specific one match (lhs, rhs) {
if lhs.is_err() && rhs.is_err() { // If both are errors, then we should return the more specific one
if lhs == Err(Reason::DstIsBitIncompatible) { (Answer::No(Reason::DstIsBitIncompatible), Answer::No(reason))
return rhs; | (Answer::No(reason), Answer::No(_)) => Answer::No(reason),
} else { // Otherwise, errors can be ignored for the rest of the pattern matching
return lhs; (Answer::No(_), other) | (other, Answer::No(_)) => or(other, Answer::Yes),
}
}
// Otherwise, errors can be ignored for the rest of the pattern matching
let lhs = lhs.unwrap_or(None);
let rhs = rhs.unwrap_or(None);
Ok(match (lhs, rhs) {
// If only one side has a condition, pass it along // If only one side has a condition, pass it along
(None, other) | (other, None) => other, (Answer::Yes, other) | (other, Answer::Yes) => other,
// If both sides have IfAny conditions, merge them // If both sides have IfAny conditions, merge them
(Some(Condition::IfAny(mut lhs)), Some(Condition::IfAny(ref mut rhs))) => { (Answer::If(Condition::IfAny(mut lhs)), Answer::If(Condition::IfAny(ref mut rhs))) => {
lhs.append(rhs); lhs.append(rhs);
Some(Condition::IfAny(lhs)) Answer::If(Condition::IfAny(lhs))
} }
// If only one side is an IfAny, add the other Condition to it // If only one side is an IfAny, add the other Condition to it
(Some(cond), Some(Condition::IfAny(mut conds))) (Answer::If(cond), Answer::If(Condition::IfAny(mut conds)))
| (Some(Condition::IfAny(mut conds)), Some(cond)) => { | (Answer::If(Condition::IfAny(mut conds)), Answer::If(cond)) => {
conds.push(cond); conds.push(cond);
Some(Condition::IfAny(conds)) Answer::If(Condition::IfAny(conds))
} }
// Otherwise, both lhs and rhs conditions can be combined in a parent IfAny // Otherwise, both lhs and rhs conditions can be combined in a parent IfAny
(Some(lhs), Some(rhs)) => Some(Condition::IfAny(vec![lhs, rhs])), (Answer::If(lhs), Answer::If(rhs)) => Answer::If(Condition::IfAny(vec![lhs, rhs])),
}) }
} }
pub enum Quantifier { pub enum Quantifier {
@ -421,16 +412,21 @@ impl Quantifier {
use std::ops::ControlFlow::{Break, Continue}; use std::ops::ControlFlow::{Break, Continue};
let (init, try_fold_f): (_, fn(_, _) -> _) = match self { let (init, try_fold_f): (_, fn(_, _) -> _) = match self {
Self::ThereExists => (Err(Reason::DstIsBitIncompatible), |accum: Answer<R>, next| { Self::ThereExists => {
match or(accum, next) { (Answer::No(Reason::DstIsBitIncompatible), |accum: Answer<R>, next| {
Ok(None) => Break(Ok(None)), match or(accum, next) {
Answer::Yes => Break(Answer::Yes),
maybe => Continue(maybe),
}
})
}
Self::ForAll => (Answer::Yes, |accum: Answer<R>, next| {
let answer = and(accum, next);
match answer {
Answer::No(_) => Break(answer),
maybe => Continue(maybe), maybe => Continue(maybe),
} }
}), }),
Self::ForAll => (Ok(None), |accum: Answer<R>, next| match and(accum, next) {
Err(reason) => Break(Err(reason)),
maybe => Continue(maybe),
}),
}; };
let (Continue(result) | Break(result)) = iter.into_iter().try_fold(init, try_fold_f); let (Continue(result) | Break(result)) = iter.into_iter().try_fold(init, try_fold_f);

12
compiler/rustc_transmute/src/maybe_transmutable/tests.rs
View file

@ -4,6 +4,8 @@ use crate::{layout, Reason};
use itertools::Itertools; use itertools::Itertools;
mod bool { mod bool {
use crate::Answer;
use super::*; use super::*;
#[test] #[test]
@ -17,7 +19,7 @@ mod bool {
UltraMinimal, UltraMinimal,
) )
.answer(); .answer();
assert_eq!(answer, Ok(None)); assert_eq!(answer, Answer::Yes);
} }
#[test] #[test]
@ -30,7 +32,7 @@ mod bool {
UltraMinimal, UltraMinimal,
) )
.answer(); .answer();
assert_eq!(answer, Ok(None)); assert_eq!(answer, Answer::Yes);
} }
#[test] #[test]
@ -65,7 +67,7 @@ mod bool {
if src_set.is_subset(&dst_set) { if src_set.is_subset(&dst_set) {
assert_eq!( assert_eq!(
Ok(None), Answer::Yes,
MaybeTransmutableQuery::new( MaybeTransmutableQuery::new(
src_layout.clone(), src_layout.clone(),
dst_layout.clone(), dst_layout.clone(),
@ -80,7 +82,7 @@ mod bool {
); );
} else if !src_set.is_disjoint(&dst_set) { } else if !src_set.is_disjoint(&dst_set) {
assert_eq!( assert_eq!(
Ok(None), Answer::Yes,
MaybeTransmutableQuery::new( MaybeTransmutableQuery::new(
src_layout.clone(), src_layout.clone(),
dst_layout.clone(), dst_layout.clone(),
@ -95,7 +97,7 @@ mod bool {
); );
} else { } else {
assert_eq!( assert_eq!(
Err(Reason::DstIsBitIncompatible), Answer::No(Reason::DstIsBitIncompatible),
MaybeTransmutableQuery::new( MaybeTransmutableQuery::new(
src_layout.clone(), src_layout.clone(),
dst_layout.clone(), dst_layout.clone(),

2
tests/ui/transmutability/malformed-program-gracefulness/unknown_src_field.rs
View file

@ -18,5 +18,5 @@ fn should_gracefully_handle_unknown_dst_field() {
struct Context; struct Context;
#[repr(C)] struct Src; #[repr(C)] struct Src;
#[repr(C)] struct Dst(Missing); //~ cannot find type #[repr(C)] struct Dst(Missing); //~ cannot find type
assert::is_transmutable::<Src, Dst, Context>(); assert::is_transmutable::<Src, Dst, Context>(); //~ ERROR cannot be safely transmuted
} }

20
tests/ui/transmutability/malformed-program-gracefulness/unknown_src_field.stderr
View file

@ -4,6 +4,22 @@ error[E0412]: cannot find type `Missing` in this scope
LL | #[repr(C)] struct Dst(Missing); LL | #[repr(C)] struct Dst(Missing);
| ^^^^^^^ not found in this scope | ^^^^^^^ not found in this scope
error: aborting due to previous error error[E0277]: `Src` cannot be safely transmuted into `Dst` in the defining scope of `should_gracefully_handle_unknown_dst_field::Context`
--> $DIR/unknown_src_field.rs:21:36
|
LL | assert::is_transmutable::<Src, Dst, Context>();
| ^^^ `Dst` has an unknown layout
|
note: required by a bound in `is_transmutable`
--> $DIR/unknown_src_field.rs:13:14
|
LL | pub fn is_transmutable<Src, Dst, Context>()
| --------------- required by a bound in this function
LL | where
LL | Dst: BikeshedIntrinsicFrom<Src, Context>
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_transmutable`
For more information about this error, try `rustc --explain E0412`. error: aborting due to 2 previous errors
Some errors have detailed explanations: E0277, E0412.
For more information about an error, try `rustc --explain E0277`.