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Forbid !Sized types and references

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This commit is contained in:
Boxy 2024-07-14 12:50:41 +01:00 committed by Boxy
parent cb12b52f16
commit 42cc42b942
7 changed files with 167 additions and 39 deletions
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4
compiler/rustc_feature/src/unstable.rs
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@ -339,8 +339,8 @@ pub fn internal(&self, feature: Symbol) -> bool {
(unstable, abi_riscv_interrupt, "1.73.0", Some(111889)),
/// Allows `extern "x86-interrupt" fn()`.
(unstable, abi_x86_interrupt, "1.17.0", Some(40180)),
/// Allows additional const parameter types, such as `&'static str` or user defined types
(incomplete, adt_const_params, "1.56.0", Some(95174)),
/// Allows additional const parameter types, such as `[u8; 10]` or user defined types
(unstable, adt_const_params, "1.56.0", Some(95174)),
/// Allows defining an `#[alloc_error_handler]`.
(unstable, alloc_error_handler, "1.29.0", Some(51540)),
/// Allows trait methods with arbitrary self types.

4
compiler/rustc_hir_analysis/messages.ftl
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@ -78,6 +78,10 @@ hir_analysis_const_impl_for_non_const_trait =
.note = marking a trait with `#[const_trait]` ensures all default method bodies are `const`
.adding = adding a non-const method body in the future would be a breaking change
hir_analysis_const_param_ty_impl_on_unsized =
the trait `ConstParamTy` may not be implemented for this type
.label = type is not `Sized`
hir_analysis_const_param_ty_impl_on_non_adt =
the trait `ConstParamTy` may not be implemented for this type
.label = type is not a structure or enumeration

16
compiler/rustc_hir_analysis/src/check/wfcheck.rs
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@ -924,8 +924,6 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) -> Result<(),
if tcx.features().adt_const_params {
enter_wf_checking_ctxt(tcx, hir_ty.span, param.def_id, |wfcx| {
let trait_def_id =
tcx.require_lang_item(LangItem::ConstParamTy, Some(hir_ty.span));
wfcx.register_bound(
ObligationCause::new(
hir_ty.span,
@ -934,7 +932,13 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) -> Result<(),
),
wfcx.param_env,
ty,
trait_def_id,
tcx.require_lang_item(LangItem::ConstParamTy, Some(hir_ty.span)),
);
wfcx.register_bound(
ObligationCause::new(hir_ty.span, param.def_id, ObligationCauseCode::Misc),
wfcx.param_env,
ty,
tcx.require_lang_item(LangItem::Sized, Some(hir_ty.span)),
);
Ok(())
})
@ -965,7 +969,11 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) -> Result<(),
cause,
) {
// Can never implement `ConstParamTy`, don't suggest anything.
Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed) => false,
Err(
ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed
| ConstParamTyImplementationError::InvalidInnerTyOfBuiltinTy(..)
| ConstParamTyImplementationError::TypeNotSized,
) => false,
// May be able to implement `ConstParamTy`. Only emit the feature help
// if the type is local, since the user may be able to fix the local type.
Err(ConstParamTyImplementationError::InfrigingFields(..)) => {

42
compiler/rustc_hir_analysis/src/coherence/builtin.rs
View File

@ -103,7 +103,13 @@ fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaran
Ok(()) => Ok(()),
Err(CopyImplementationError::InfringingFields(fields)) => {
let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
Err(infringing_fields_error(tcx, fields, LangItem::Copy, impl_did, span))
Err(infringing_fields_error(
tcx,
fields.into_iter().map(|(field, ty, reason)| (tcx.def_span(field.did), ty, reason)),
LangItem::Copy,
impl_did,
span,
))
}
Err(CopyImplementationError::NotAnAdt) => {
let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
@ -125,7 +131,7 @@ fn visit_implementation_of_const_param_ty(checker: &Checker<'_>) -> Result<(), E
let param_env = tcx.param_env(impl_did);
if let ty::ImplPolarity::Negative = header.polarity {
if let ty::ImplPolarity::Negative | ty::ImplPolarity::Reservation = header.polarity {
return Ok(());
}
@ -134,12 +140,32 @@ fn visit_implementation_of_const_param_ty(checker: &Checker<'_>) -> Result<(), E
Ok(()) => Ok(()),
Err(ConstParamTyImplementationError::InfrigingFields(fields)) => {
let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
Err(infringing_fields_error(tcx, fields, LangItem::ConstParamTy, impl_did, span))
Err(infringing_fields_error(
tcx,
fields.into_iter().map(|(field, ty, reason)| (tcx.def_span(field.did), ty, reason)),
LangItem::ConstParamTy,
impl_did,
span,
))
}
Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed) => {
let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
Err(tcx.dcx().emit_err(errors::ConstParamTyImplOnNonAdt { span }))
}
Err(ConstParamTyImplementationError::InvalidInnerTyOfBuiltinTy(infringing_tys)) => {
let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
Err(infringing_fields_error(
tcx,
infringing_tys.into_iter().map(|(ty, reason)| (span, ty, reason)),
LangItem::ConstParamTy,
impl_did,
span,
))
}
Err(ConstParamTyImplementationError::TypeNotSized) => {
let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span;
Err(tcx.dcx().emit_err(errors::ConstParamTyImplOnUnsized { span }))
}
}
}
@ -501,9 +527,9 @@ pub fn coerce_unsized_info<'tcx>(
Ok(CoerceUnsizedInfo { custom_kind: kind })
}
fn infringing_fields_error(
tcx: TyCtxt<'_>,
fields: Vec<(&ty::FieldDef, Ty<'_>, InfringingFieldsReason<'_>)>,
fn infringing_fields_error<'tcx>(
tcx: TyCtxt<'tcx>,
infringing_tys: impl Iterator<Item = (Span, Ty<'tcx>, InfringingFieldsReason<'tcx>)>,
lang_item: LangItem,
impl_did: LocalDefId,
impl_span: Span,
@ -521,13 +547,13 @@ fn infringing_fields_error(
let mut label_spans = Vec::new();
for (field, ty, reason) in fields {
for (span, ty, reason) in infringing_tys {
// Only report an error once per type.
if !seen_tys.insert(ty) {
continue;
}
label_spans.push(tcx.def_span(field.did));
label_spans.push(span);
match reason {
InfringingFieldsReason::Fulfill(fulfillment_errors) => {

8
compiler/rustc_hir_analysis/src/errors.rs
View File

@ -278,6 +278,14 @@ pub struct CopyImplOnNonAdt {
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_const_param_ty_impl_on_unsized)]
pub struct ConstParamTyImplOnUnsized {
#[primary_span]
#[label]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_const_param_ty_impl_on_non_adt)]
pub struct ConstParamTyImplOnNonAdt {

117
compiler/rustc_trait_selection/src/traits/misc.rs
View File

@ -19,6 +19,8 @@ pub enum CopyImplementationError<'tcx> {
}
pub enum ConstParamTyImplementationError<'tcx> {
TypeNotSized,
InvalidInnerTyOfBuiltinTy(Vec<(Ty<'tcx>, InfringingFieldsReason<'tcx>)>),
InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>, InfringingFieldsReason<'tcx>)>),
NotAnAdtOrBuiltinAllowed,
}
@ -89,33 +91,104 @@ pub fn type_allowed_to_implement_const_param_ty<'tcx>(
self_type: Ty<'tcx>,
parent_cause: ObligationCause<'tcx>,
) -> Result<(), ConstParamTyImplementationError<'tcx>> {
let (adt, args) = match self_type.kind() {
// `core` provides these impls.
ty::Uint(_)
| ty::Int(_)
| ty::Bool
| ty::Char
| ty::Str
| ty::Array(..)
| ty::Slice(_)
| ty::Ref(.., hir::Mutability::Not)
| ty::Tuple(_) => return Ok(()),
{
// Check for sizedness before recursing into ADT fields so that if someone tries to write:
// ```rust
// #[derive(ConstParamTy)]
// struct Foo([u8])
// ```
// They are told that const parameter types must be sized, instead of it saying that
// the trait implementation `[u8]: ConstParamTy` is not satisfied.
let infcx = tcx.infer_ctxt().build();
let ocx = traits::ObligationCtxt::new_with_diagnostics(&infcx);
&ty::Adt(adt, args) => (adt, args),
ocx.register_bound(
parent_cause.clone(),
param_env,
self_type,
tcx.require_lang_item(LangItem::Sized, Some(parent_cause.span)),
);
if !ocx.select_all_or_error().is_empty() {
return Err(ConstParamTyImplementationError::TypeNotSized);
}
};
let inner_tys: Vec<_> = match *self_type.kind() {
// Trivially okay as these types are all:
// - Sized
// - Contain no nested types
// - Have structural equality
ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => return Ok(()),
ty::Ref(..) => return Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed),
// Even if we currently require const params to be `Sized` we may aswell handle them correctly
// here anyway.
ty::Slice(inner_ty) | ty::Array(inner_ty, _) => vec![inner_ty],
// `str` morally acts like a newtype around `[u8]`
ty::Str => vec![Ty::new_slice(tcx, tcx.types.u8)],
ty::Tuple(inner_tys) => inner_tys.into_iter().collect(),
ty::Adt(adt, args) if adt.is_enum() || adt.is_struct() => {
all_fields_implement_trait(
tcx,
param_env,
self_type,
adt,
args,
parent_cause.clone(),
hir::LangItem::ConstParamTy,
)
.map_err(ConstParamTyImplementationError::InfrigingFields)?;
vec![]
}
_ => return Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed),
};
all_fields_implement_trait(
tcx,
param_env,
self_type,
adt,
args,
parent_cause,
hir::LangItem::ConstParamTy,
)
.map_err(ConstParamTyImplementationError::InfrigingFields)?;
let mut infringing_inner_tys = vec![];
for inner_ty in inner_tys {
// We use an ocx per inner ty for better diagnostics
let infcx = tcx.infer_ctxt().build();
let ocx = traits::ObligationCtxt::new_with_diagnostics(&infcx);
ocx.register_bound(
parent_cause.clone(),
param_env,
inner_ty,
tcx.require_lang_item(LangItem::ConstParamTy, Some(parent_cause.span)),
);
let errors = ocx.select_all_or_error();
if !errors.is_empty() {
infringing_inner_tys.push((inner_ty, InfringingFieldsReason::Fulfill(errors)));
continue;
}
// Check regions assuming the self type of the impl is WF
let outlives_env = OutlivesEnvironment::with_bounds(
param_env,
infcx.implied_bounds_tys(
param_env,
parent_cause.body_id,
&FxIndexSet::from_iter([self_type]),
),
);
let errors = infcx.resolve_regions(&outlives_env);
if !errors.is_empty() {
infringing_inner_tys.push((inner_ty, InfringingFieldsReason::Regions(errors)));
continue;
}
}
if !infringing_inner_tys.is_empty() {
return Err(ConstParamTyImplementationError::InvalidInnerTyOfBuiltinTy(
infringing_inner_tys,
));
}
Ok(())
}

15
library/core/src/marker.rs
View File

@ -995,13 +995,22 @@ pub trait ConstParamTy: StructuralPartialEq + Eq {}
isize, i8, i16, i32, i64, i128,
bool,
char,
str /* Technically requires `[u8]: ConstParamTy` */,
(),
{T: ConstParamTy, const N: usize} [T; N],
{T: ConstParamTy} [T],
{T: ?Sized + ConstParamTy} &T,
}
#[unstable(feature = "adt_const_params", issue = "95174")]
#[rustc_reservation_impl = "types that are not `Sized` are not supported as the type of a const generic parameter"]
impl<T> ConstParamTy for [T] {}
#[unstable(feature = "adt_const_params", issue = "95174")]
#[rustc_reservation_impl = "types that are not `Sized` are not supported as the type of a const generic parameter"]
impl ConstParamTy for str {}
#[unstable(feature = "adt_const_params", issue = "95174")]
#[rustc_reservation_impl = "references are not supported as the type of a const generic parameter"]
impl<T: ?Sized> ConstParamTy for &T {}
/// A common trait implemented by all function pointers.
#[unstable(
feature = "fn_ptr_trait",