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improve compile errors for invalid ptr-to-ptr casts with trait objects #130234

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merged 7 commits into from
Sep 25, 2024
Merged

improve compile errors for invalid ptr-to-ptr casts with trait objects #130234

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46ecb23
unify dyn* coercions with other pointer coercions
Sep 15, 2024
b52dea8
add another test
Sep 10, 2024
d1e82d4
use more accurate spans for user type ascriptions
Sep 10, 2024
5e60d1f
replace "cast" with "coercion" where applicable
Sep 10, 2024
bd31e3e
be even more precise about "cast" vs "coercion"
Sep 15, 2024
39f66ba
improve errors for invalid pointer casts
Sep 10, 2024
b62e72c
update doc comment
Sep 15, 2024
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8 changes: 6 additions & 2 deletions compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -333,7 +333,11 @@ impl<'tcx> BorrowExplanation<'tcx> {
}
}

if let ConstraintCategory::Cast { unsize_to: Some(unsize_ty) } = category {
if let ConstraintCategory::Cast {
is_implicit_coercion: true,
unsize_to: Some(unsize_ty),
} = category
{
self.add_object_lifetime_default_note(tcx, err, unsize_ty);
}
self.add_lifetime_bound_suggestion_to_diagnostic(err, &category, span, region_name);
Expand Down Expand Up @@ -740,7 +744,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
// If we see an unsized cast, then if it is our data we should check
// whether it is being cast to a trait object.
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::Unsize),
CastKind::PointerCoercion(PointerCoercion::Unsize, _),
operand,
ty,
) => {
Expand Down
3 changes: 2 additions & 1 deletion compiler/rustc_borrowck/src/diagnostics/region_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,8 @@ impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> {
ConstraintCategory::Yield => "yielding this value ",
ConstraintCategory::UseAsConst => "using this value as a constant ",
ConstraintCategory::UseAsStatic => "using this value as a static ",
ConstraintCategory::Cast { .. } => "cast ",
ConstraintCategory::Cast { is_implicit_coercion: false, .. } => "cast ",
ConstraintCategory::Cast { is_implicit_coercion: true, .. } => "coercion ",
ConstraintCategory::CallArgument(_) => "argument ",
ConstraintCategory::TypeAnnotation => "type annotation ",
ConstraintCategory::ClosureBounds => "closure body ",
Expand Down
71 changes: 44 additions & 27 deletions compiler/rustc_borrowck/src/type_check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1975,8 +1975,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
Rvalue::Cast(cast_kind, op, ty) => {
self.check_operand(op, location);

match cast_kind {
CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
match *cast_kind {
CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, coercion_source) => {
let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
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nitpick: Maybe just have a CoercionSource field in ConstraintCategory::Cast too, instead of a bool and this conversion?

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I considered this, but decided against it, because the Ord of ConstraintCategory is relevant for the diagnostic output and I didn't want this property to spread all over the compiler.

let src_sig = op.ty(body, tcx).fn_sig(tcx);

// HACK: This shouldn't be necessary... We can remove this when we actually
Expand Down Expand Up @@ -2007,15 +2008,15 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
self.prove_predicate(
ty::ClauseKind::WellFormed(src_ty.into()),
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
);

let src_ty = self.normalize(src_ty, location);
if let Err(terr) = self.sub_types(
src_ty,
*ty,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
) {
span_mirbug!(
self,
Expand All @@ -2036,7 +2037,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
self.prove_predicate(
ty::ClauseKind::WellFormed(src_ty.into()),
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
);

// The type that we see in the fcx is like
Expand All @@ -2049,7 +2050,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
src_ty,
*ty,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
) {
span_mirbug!(
self,
Expand All @@ -2062,19 +2063,23 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
}
}

CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(safety)) => {
CastKind::PointerCoercion(
PointerCoercion::ClosureFnPointer(safety),
coercion_source,
) => {
let sig = match op.ty(body, tcx).kind() {
ty::Closure(_, args) => args.as_closure().sig(),
_ => bug!(),
};
let ty_fn_ptr_from =
Ty::new_fn_ptr(tcx, tcx.signature_unclosure(sig, *safety));
Ty::new_fn_ptr(tcx, tcx.signature_unclosure(sig, safety));

let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
if let Err(terr) = self.sub_types(
ty_fn_ptr_from,
*ty,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
) {
span_mirbug!(
self,
Expand All @@ -2087,7 +2092,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
}
}

CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
CastKind::PointerCoercion(
PointerCoercion::UnsafeFnPointer,
coercion_source,
) => {
let fn_sig = op.ty(body, tcx).fn_sig(tcx);

// The type that we see in the fcx is like
Expand All @@ -2099,11 +2107,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {

let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);

let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
if let Err(terr) = self.sub_types(
ty_fn_ptr_from,
*ty,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
) {
span_mirbug!(
self,
Expand All @@ -2116,30 +2125,29 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
}
}

CastKind::PointerCoercion(PointerCoercion::Unsize) => {
CastKind::PointerCoercion(PointerCoercion::Unsize, coercion_source) => {
let &ty = ty;
let trait_ref = ty::TraitRef::new(
tcx,
tcx.require_lang_item(LangItem::CoerceUnsized, Some(span)),
[op.ty(body, tcx), ty],
);

let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
let unsize_to = tcx.fold_regions(ty, |r, _| {
if let ty::ReVar(_) = r.kind() { tcx.lifetimes.re_erased } else { r }
});
self.prove_trait_ref(
trait_ref,
location.to_locations(),
ConstraintCategory::Cast {
unsize_to: Some(tcx.fold_regions(ty, |r, _| {
if let ty::ReVar(_) = r.kind() {
tcx.lifetimes.re_erased
} else {
r
}
})),
is_implicit_coercion,
unsize_to: Some(unsize_to),
},
);
}

CastKind::DynStar => {
CastKind::PointerCoercion(PointerCoercion::DynStar, coercion_source) => {
// get the constraints from the target type (`dyn* Clone`)
//
// apply them to prove that the source type `Foo` implements `Clone` etc
Expand All @@ -2150,12 +2158,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {

let self_ty = op.ty(body, tcx);

let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
self.prove_predicates(
existential_predicates
.iter()
.map(|predicate| predicate.with_self_ty(tcx, self_ty)),
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
);

let outlives_predicate = tcx.mk_predicate(Binder::dummy(
Expand All @@ -2166,11 +2175,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
self.prove_predicate(
outlives_predicate,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
);
}

CastKind::PointerCoercion(PointerCoercion::MutToConstPointer) => {
CastKind::PointerCoercion(
PointerCoercion::MutToConstPointer,
coercion_source,
) => {
let ty::RawPtr(ty_from, hir::Mutability::Mut) = op.ty(body, tcx).kind()
else {
span_mirbug!(self, rvalue, "unexpected base type for cast {:?}", ty,);
Expand All @@ -2180,11 +2192,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
span_mirbug!(self, rvalue, "unexpected target type for cast {:?}", ty,);
return;
};
let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
if let Err(terr) = self.sub_types(
*ty_from,
*ty_to,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
) {
span_mirbug!(
self,
Expand All @@ -2197,7 +2210,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
}
}

CastKind::PointerCoercion(PointerCoercion::ArrayToPointer) => {
CastKind::PointerCoercion(PointerCoercion::ArrayToPointer, coercion_source) => {
let ty_from = op.ty(body, tcx);

let opt_ty_elem_mut = match ty_from.kind() {
Expand Down Expand Up @@ -2242,11 +2255,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
return;
}

let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
if let Err(terr) = self.sub_types(
*ty_elem,
*ty_to,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
) {
span_mirbug!(
self,
Expand Down Expand Up @@ -2427,7 +2441,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
src_obj,
dst_obj,
location.to_locations(),
ConstraintCategory::Cast { unsize_to: None },
ConstraintCategory::Cast {
is_implicit_coercion: false,
unsize_to: None,
},
)
.unwrap();
}
Expand Down
15 changes: 10 additions & 5 deletions compiler/rustc_codegen_cranelift/src/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -652,7 +652,7 @@ fn codegen_stmt<'tcx>(
lval.write_cvalue(fx, res);
}
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer),
CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _),
ref operand,
to_ty,
) => {
Expand All @@ -677,7 +677,7 @@ fn codegen_stmt<'tcx>(
}
}
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer),
CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer, _),
ref operand,
to_ty,
) => {
Expand All @@ -688,6 +688,7 @@ fn codegen_stmt<'tcx>(
Rvalue::Cast(
CastKind::PointerCoercion(
PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
_,
),
..,
) => {
Expand Down Expand Up @@ -741,7 +742,7 @@ fn codegen_stmt<'tcx>(
}
}
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)),
CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _),
ref operand,
_to_ty,
) => {
Expand All @@ -763,14 +764,18 @@ fn codegen_stmt<'tcx>(
}
}
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::Unsize),
CastKind::PointerCoercion(PointerCoercion::Unsize, _),
ref operand,
_to_ty,
) => {
let operand = codegen_operand(fx, operand);
crate::unsize::coerce_unsized_into(fx, operand, lval);
}
Rvalue::Cast(CastKind::DynStar, ref operand, _) => {
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::DynStar, _),
ref operand,
_,
) => {
let operand = codegen_operand(fx, operand);
crate::unsize::coerce_dyn_star(fx, operand, lval);
}
Expand Down
14 changes: 7 additions & 7 deletions compiler/rustc_codegen_ssa/src/mir/rvalue.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}

mir::Rvalue::Cast(
mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
mir::CastKind::PointerCoercion(PointerCoercion::Unsize, _),
ref source,
_,
) => {
Expand Down Expand Up @@ -465,7 +465,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let lladdr = bx.ptrtoint(llptr, llcast_ty);
OperandValue::Immediate(lladdr)
}
mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _) => {
match *operand.layout.ty.kind() {
ty::FnDef(def_id, args) => {
let instance = ty::Instance::resolve_for_fn_ptr(
Expand All @@ -481,7 +481,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
_ => bug!("{} cannot be reified to a fn ptr", operand.layout.ty),
}
}
mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)) => {
mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _) => {
match *operand.layout.ty.kind() {
ty::Closure(def_id, args) => {
let instance = Instance::resolve_closure(
Expand All @@ -496,19 +496,19 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
_ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),
}
}
mir::CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
mir::CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer, _) => {
// This is a no-op at the LLVM level.
operand.val
}
mir::CastKind::PointerCoercion(PointerCoercion::Unsize) => {
mir::CastKind::PointerCoercion(PointerCoercion::Unsize, _) => {
assert!(bx.cx().is_backend_scalar_pair(cast));
let (lldata, llextra) = operand.val.pointer_parts();
let (lldata, llextra) =
base::unsize_ptr(bx, lldata, operand.layout.ty, cast.ty, llextra);
OperandValue::Pair(lldata, llextra)
}
mir::CastKind::PointerCoercion(
PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer, _
) => {
bug!("{kind:?} is for borrowck, and should never appear in codegen");
}
Expand All @@ -526,7 +526,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
bug!("unexpected non-pair operand");
}
}
mir::CastKind::DynStar => {
mir::CastKind::PointerCoercion(PointerCoercion::DynStar, _) => {
let (lldata, llextra) = operand.val.pointer_parts();
let (lldata, llextra) =
base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
Expand Down
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