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Add a `ConstParamTy` trait

This commit is contained in:
Maybe Waffle 2023-02-17 13:44:35 +00:00
parent 518d348f87
commit 9a716dafbe
9 changed files with 300 additions and 122 deletions
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2
compiler/rustc_hir/src/lang_items.rs
View File

@ -293,6 +293,8 @@ language_item_table! {
PointerLike, sym::pointer_like, pointer_like, Target::Trait, GenericRequirement::Exact(0);
ConstParamTy, sym::const_param_ty, const_param_ty_trait, Target::Trait, GenericRequirement::Exact(0);
Poll, sym::Poll, poll, Target::Enum, GenericRequirement::None;
PollReady, sym::Ready, poll_ready_variant, Target::Variant, GenericRequirement::None;
PollPending, sym::Pending, poll_pending_variant, Target::Variant, GenericRequirement::None;

4
compiler/rustc_hir_analysis/messages.ftl
View File

@ -35,6 +35,10 @@ hir_analysis_field_already_declared =
hir_analysis_expected_used_symbol = expected `used`, `used(compiler)` or `used(linker)`
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
hir_analysis_ambiguous_lifetime_bound =
ambiguous lifetime bound, explicit lifetime bound required

255
compiler/rustc_hir_analysis/src/coherence/builtin.rs
View File

@ -1,9 +1,11 @@
//! Check properties that are required by built-in traits and set
//! up data structures required by type-checking/codegen.
use crate::errors::{CopyImplOnNonAdt, CopyImplOnTypeWithDtor, DropImplOnWrongItem};
use crate::errors::{
ConstParamTyImplOnNonAdt, CopyImplOnNonAdt, CopyImplOnTypeWithDtor, DropImplOnWrongItem,
};
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{struct_span_err, MultiSpan};
use rustc_errors::{struct_span_err, ErrorGuaranteed, MultiSpan};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::lang_items::LangItem;
@ -14,9 +16,11 @@ use rustc_infer::infer::{DefineOpaqueTypes, TyCtxtInferExt};
use rustc_infer::traits::Obligation;
use rustc_middle::ty::adjustment::CoerceUnsizedInfo;
use rustc_middle::ty::{self, suggest_constraining_type_params, Ty, TyCtxt, TypeVisitableExt};
use rustc_span::Span;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
use rustc_trait_selection::traits::misc::{
type_allowed_to_implement_copy, CopyImplementationError, InfringingFieldsReason,
type_allowed_to_implement_const_param_ty, type_allowed_to_implement_copy,
ConstParamTyImplementationError, CopyImplementationError, InfringingFieldsReason,
};
use rustc_trait_selection::traits::ObligationCtxt;
use rustc_trait_selection::traits::{self, ObligationCause};
@ -27,6 +31,7 @@ pub fn check_trait(tcx: TyCtxt<'_>, trait_def_id: DefId) {
Checker { tcx, trait_def_id }
.check(lang_items.drop_trait(), visit_implementation_of_drop)
.check(lang_items.copy_trait(), visit_implementation_of_copy)
.check(lang_items.const_param_ty_trait(), visit_implementation_of_const_param_ty)
.check(lang_items.coerce_unsized_trait(), visit_implementation_of_coerce_unsized)
.check(lang_items.dispatch_from_dyn_trait(), visit_implementation_of_dispatch_from_dyn);
}
@ -83,110 +88,7 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
match type_allowed_to_implement_copy(tcx, param_env, self_type, cause) {
Ok(()) => {}
Err(CopyImplementationError::InfringingFields(fields)) => {
let mut err = struct_span_err!(
tcx.sess,
span,
E0204,
"the trait `Copy` cannot be implemented for this type"
);
// We'll try to suggest constraining type parameters to fulfill the requirements of
// their `Copy` implementation.
let mut errors: BTreeMap<_, Vec<_>> = Default::default();
let mut bounds = vec![];
let mut seen_tys = FxHashSet::default();
for (field, ty, reason) in fields {
// Only report an error once per type.
if !seen_tys.insert(ty) {
continue;
}
let field_span = tcx.def_span(field.did);
err.span_label(field_span, "this field does not implement `Copy`");
match reason {
InfringingFieldsReason::Fulfill(fulfillment_errors) => {
for error in fulfillment_errors {
let error_predicate = error.obligation.predicate;
// Only note if it's not the root obligation, otherwise it's trivial and
// should be self-explanatory (i.e. a field literally doesn't implement Copy).
// FIXME: This error could be more descriptive, especially if the error_predicate
// contains a foreign type or if it's a deeply nested type...
if error_predicate != error.root_obligation.predicate {
errors
.entry((ty.to_string(), error_predicate.to_string()))
.or_default()
.push(error.obligation.cause.span);
}
if let ty::PredicateKind::Clause(ty::Clause::Trait(
ty::TraitPredicate {
trait_ref,
polarity: ty::ImplPolarity::Positive,
..
},
)) = error_predicate.kind().skip_binder()
{
let ty = trait_ref.self_ty();
if let ty::Param(_) = ty.kind() {
bounds.push((
format!("{ty}"),
trait_ref.print_only_trait_path().to_string(),
Some(trait_ref.def_id),
));
}
}
}
}
InfringingFieldsReason::Regions(region_errors) => {
for error in region_errors {
let ty = ty.to_string();
match error {
RegionResolutionError::ConcreteFailure(origin, a, b) => {
let predicate = format!("{b}: {a}");
errors
.entry((ty.clone(), predicate.clone()))
.or_default()
.push(origin.span());
if let ty::RegionKind::ReEarlyBound(ebr) = *b && ebr.has_name() {
bounds.push((b.to_string(), a.to_string(), None));
}
}
RegionResolutionError::GenericBoundFailure(origin, a, b) => {
let predicate = format!("{a}: {b}");
errors
.entry((ty.clone(), predicate.clone()))
.or_default()
.push(origin.span());
if let infer::region_constraints::GenericKind::Param(_) = a {
bounds.push((a.to_string(), b.to_string(), None));
}
}
_ => continue,
}
}
}
}
}
for ((ty, error_predicate), spans) in errors {
let span: MultiSpan = spans.into();
err.span_note(
span,
&format!("the `Copy` impl for `{}` requires that `{}`", ty, error_predicate),
);
}
suggest_constraining_type_params(
tcx,
tcx.hir().get_generics(impl_did).expect("impls always have generics"),
&mut err,
bounds.iter().map(|(param, constraint, def_id)| {
(param.as_str(), constraint.as_str(), *def_id)
}),
None,
);
err.emit();
infringing_fields_error(tcx, fields, LangItem::Copy, impl_did, span);
}
Err(CopyImplementationError::NotAnAdt) => {
tcx.sess.emit_err(CopyImplOnNonAdt { span });
@ -197,6 +99,29 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
}
}
fn visit_implementation_of_const_param_ty(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
let self_type = tcx.type_of(impl_did).subst_identity();
assert!(!self_type.has_escaping_bound_vars());
let param_env = tcx.param_env(impl_did);
let span = match tcx.hir().expect_item(impl_did).expect_impl() {
hir::Impl { polarity: hir::ImplPolarity::Negative(_), .. } => return,
impl_ => impl_.self_ty.span,
};
let cause = traits::ObligationCause::misc(span, impl_did);
match type_allowed_to_implement_const_param_ty(tcx, param_env, self_type, cause) {
Ok(()) => {}
Err(ConstParamTyImplementationError::InfrigingFields(fields)) => {
infringing_fields_error(tcx, fields, LangItem::ConstParamTy, impl_did, span);
}
Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed) => {
tcx.sess.emit_err(ConstParamTyImplOnNonAdt { span });
}
}
}
fn visit_implementation_of_coerce_unsized(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
debug!("visit_implementation_of_coerce_unsized: impl_did={:?}", impl_did);
@ -593,3 +518,119 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) -> Coe
CoerceUnsizedInfo { custom_kind: kind }
}
fn infringing_fields_error(
tcx: TyCtxt<'_>,
fields: Vec<(&ty::FieldDef, Ty<'_>, InfringingFieldsReason<'_>)>,
lang_item: LangItem,
impl_did: LocalDefId,
impl_span: Span,
) -> ErrorGuaranteed {
let trait_did = tcx.require_lang_item(lang_item, Some(impl_span));
let trait_name = tcx.def_path_str(trait_did);
let mut err = struct_span_err!(
tcx.sess,
impl_span,
E0204,
"the trait `{trait_name}` cannot be implemented for this type"
);
// We'll try to suggest constraining type parameters to fulfill the requirements of
// their `Copy` implementation.
let mut errors: BTreeMap<_, Vec<_>> = Default::default();
let mut bounds = vec![];
let mut seen_tys = FxHashSet::default();
for (field, ty, reason) in fields {
// Only report an error once per type.
if !seen_tys.insert(ty) {
continue;
}
let field_span = tcx.def_span(field.did);
err.span_label(field_span, format!("this field does not implement `{trait_name}`"));
match reason {
InfringingFieldsReason::Fulfill(fulfillment_errors) => {
for error in fulfillment_errors {
let error_predicate = error.obligation.predicate;
// Only note if it's not the root obligation, otherwise it's trivial and
// should be self-explanatory (i.e. a field literally doesn't implement Copy).
// FIXME: This error could be more descriptive, especially if the error_predicate
// contains a foreign type or if it's a deeply nested type...
if error_predicate != error.root_obligation.predicate {
errors
.entry((ty.to_string(), error_predicate.to_string()))
.or_default()
.push(error.obligation.cause.span);
}
if let ty::PredicateKind::Clause(ty::Clause::Trait(ty::TraitPredicate {
trait_ref,
polarity: ty::ImplPolarity::Positive,
..
})) = error_predicate.kind().skip_binder()
{
let ty = trait_ref.self_ty();
if let ty::Param(_) = ty.kind() {
bounds.push((
format!("{ty}"),
trait_ref.print_only_trait_path().to_string(),
Some(trait_ref.def_id),
));
}
}
}
}
InfringingFieldsReason::Regions(region_errors) => {
for error in region_errors {
let ty = ty.to_string();
match error {
RegionResolutionError::ConcreteFailure(origin, a, b) => {
let predicate = format!("{b}: {a}");
errors
.entry((ty.clone(), predicate.clone()))
.or_default()
.push(origin.span());
if let ty::RegionKind::ReEarlyBound(ebr) = *b && ebr.has_name() {
bounds.push((b.to_string(), a.to_string(), None));
}
}
RegionResolutionError::GenericBoundFailure(origin, a, b) => {
let predicate = format!("{a}: {b}");
errors
.entry((ty.clone(), predicate.clone()))
.or_default()
.push(origin.span());
if let infer::region_constraints::GenericKind::Param(_) = a {
bounds.push((a.to_string(), b.to_string(), None));
}
}
_ => continue,
}
}
}
}
}
for ((ty, error_predicate), spans) in errors {
let span: MultiSpan = spans.into();
err.span_note(
span,
format!("the `{trait_name}` impl for `{ty}` requires that `{error_predicate}`"),
);
}
suggest_constraining_type_params(
tcx,
tcx.hir().get_generics(impl_did).expect("impls always have generics"),
&mut err,
bounds
.iter()
.map(|(param, constraint, def_id)| (param.as_str(), constraint.as_str(), *def_id)),
None,
);
err.emit()
}

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

@ -107,6 +107,14 @@ pub struct CopyImplOnNonAdt {
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_const_param_ty_impl_on_non_adt)]
pub struct ConstParamTyImplOnNonAdt {
#[primary_span]
#[label]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_trait_object_declared_with_no_traits, code = "E0224")]
pub struct TraitObjectDeclaredWithNoTraits {

1
compiler/rustc_span/src/symbol.rs
View File

@ -531,6 +531,7 @@ symbols! {
const_mut_refs,
const_panic,
const_panic_fmt,
const_param_ty,
const_precise_live_drops,
const_raw_ptr_deref,
const_raw_ptr_to_usize_cast,

94
compiler/rustc_trait_selection/src/traits/misc.rs
View File

@ -2,13 +2,14 @@
use crate::traits::{self, ObligationCause, ObligationCtxt};
use hir::LangItem;
use rustc_data_structures::fx::FxIndexSet;
use rustc_hir as hir;
use rustc_infer::infer::canonical::Canonical;
use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::{infer::outlives::env::OutlivesEnvironment, traits::FulfillmentError};
use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
use rustc_middle::ty::{self, AdtDef, GenericArg, List, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
use rustc_span::DUMMY_SP;
use super::outlives_bounds::InferCtxtExt;
@ -19,6 +20,11 @@ pub enum CopyImplementationError<'tcx> {
HasDestructor,
}
pub enum ConstParamTyImplementationError<'tcx> {
InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>, InfringingFieldsReason<'tcx>)>),
NotAnAdtOrBuiltinAllowed,
}
pub enum InfringingFieldsReason<'tcx> {
Fulfill(Vec<FulfillmentError<'tcx>>),
Regions(Vec<RegionResolutionError<'tcx>>),
@ -27,7 +33,10 @@ pub enum InfringingFieldsReason<'tcx> {
/// Checks that the fields of the type (an ADT) all implement copy.
///
/// If fields don't implement copy, return an error containing a list of
/// those violating fields. If it's not an ADT, returns `Err(NotAnAdt)`.
/// those violating fields.
///
/// If it's not an ADT, int ty, `bool`, float ty, `char`, raw pointer, `!`,
/// a reference or an array returns `Err(NotAnAdt)`.
pub fn type_allowed_to_implement_copy<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
@ -47,12 +56,75 @@ pub fn type_allowed_to_implement_copy<'tcx>(
| ty::Ref(_, _, hir::Mutability::Not)
| ty::Array(..) => return Ok(()),
ty::Adt(adt, substs) => (adt, substs),
&ty::Adt(adt, substs) => (adt, substs),
_ => return Err(CopyImplementationError::NotAnAdt),
};
let copy_def_id = tcx.require_lang_item(hir::LangItem::Copy, Some(parent_cause.span));
all_fields_implement_trait(
tcx,
param_env,
self_type,
adt,
substs,
parent_cause,
hir::LangItem::Copy,
)
.map_err(CopyImplementationError::InfringingFields)?;
if adt.has_dtor(tcx) {
return Err(CopyImplementationError::HasDestructor);
}
Ok(())
}
/// Checks that the fields of the type (an ADT) all implement `ConstParamTy`.
///
/// If fields don't implement `ConstParamTy`, return an error containing a list of
/// those violating fields.
///
/// If it's not an ADT, int ty, `bool` or `char`, returns `Err(NotAnAdtOrBuiltinAllowed)`.
pub fn type_allowed_to_implement_const_param_ty<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
self_type: Ty<'tcx>,
parent_cause: ObligationCause<'tcx>,
) -> Result<(), ConstParamTyImplementationError<'tcx>> {
let (adt, substs) = match self_type.kind() {
// `core` provides these impls.
ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => return Ok(()),
&ty::Adt(adt, substs) => (adt, substs),
_ => return Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed),
};
all_fields_implement_trait(
tcx,
param_env,
self_type,
adt,
substs,
parent_cause,
hir::LangItem::Copy,
)
.map_err(ConstParamTyImplementationError::InfrigingFields)?;
Ok(())
}
/// Check that all fields of a given `adt` implement `lang_item` trait.
pub fn all_fields_implement_trait<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
self_type: Ty<'tcx>,
adt: AdtDef<'tcx>,
substs: &'tcx List<GenericArg<'tcx>>,
parent_cause: ObligationCause<'tcx>,
lang_item: LangItem,
) -> Result<(), Vec<(&'tcx ty::FieldDef, Ty<'tcx>, InfringingFieldsReason<'tcx>)>> {
let trait_def_id = tcx.require_lang_item(lang_item, Some(parent_cause.span));
let mut infringing = Vec::new();
for variant in adt.variants() {
@ -93,7 +165,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
// between expected and found const-generic types. Don't report an
// additional copy error here, since it's not typically useful.
if !normalization_errors.is_empty() || ty.references_error() {
tcx.sess.delay_span_bug(field_span, format!("couldn't normalize struct field `{unnormalized_ty}` when checking Copy implementation"));
tcx.sess.delay_span_bug(field_span, format!("couldn't normalize struct field `{unnormalized_ty}` when checking {tr} implementation", tr = tcx.def_path_str(trait_def_id)));
continue;
}
@ -101,7 +173,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
ObligationCause::dummy_with_span(field_ty_span),
param_env,
ty,
copy_def_id,
trait_def_id,
);
let errors = ocx.select_all_or_error();
if !errors.is_empty() {
@ -124,15 +196,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
}
}
if !infringing.is_empty() {
return Err(CopyImplementationError::InfringingFields(infringing));
}
if adt.has_dtor(tcx) {
return Err(CopyImplementationError::HasDestructor);
}
Ok(())
if infringing.is_empty() { Ok(()) } else { Err(infringing) }
}
pub fn check_tys_might_be_eq<'tcx>(

34
library/core/src/marker.rs
View File

@ -912,6 +912,40 @@ pub trait Tuple {}
)]
pub trait PointerLike {}
/// A marker for types which can be used as types of `const` generic parameters.
#[cfg_attr(not(bootstrap), lang = "const_param_ty")]
#[unstable(feature = "const_param_ty_trait", issue = "none")]
#[rustc_on_unimplemented(message = "`{Self}` can't be used as a const parameter type")]
pub trait ConstParamTy: StructuralEq {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for usize {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for u8 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for u16 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for u32 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for u64 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for u128 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for isize {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for i8 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for i16 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for i32 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for i64 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for i128 {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for bool {}
#[unstable(feature = "const_param_ty_trait", issue = "none")]
impl ConstParamTy for char {}
/// Implementations of `Copy` for primitive types.
///
/// Implementations that cannot be described in Rust

12
tests/ui/const-generics/const_patam_ty_impl_bad_field.rs Normal file
View File

@ -0,0 +1,12 @@
#![feature(const_param_ty_trait)]
#[derive(PartialEq)]
struct NotParam;
#[derive(PartialEq)]
struct CantParam(NotParam);
impl std::marker::ConstParamTy for CantParam {}
//~^ error: the trait `ConstParamTy` may not be implemented for this type
fn main() {}

12
tests/ui/const-generics/const_patam_ty_impl_bad_field.stderr Normal file
View File

@ -0,0 +1,12 @@
error[E0204]: the trait `ConstParamTy` may not be implemented for this type
--> $DIR/const_patam_ty_impl_bad_field.rs:9:36
|
LL | struct CantParam(NotParam);
| -------- this field does not implement `ConstParamTy`
LL |
LL | impl std::marker::ConstParamTy for CantParam {}
| ^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0204`.