use crate::autoderef::Autoderef;
use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter};
use rustc_ast as ast;
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
use rustc_hir::lang_items::LangItem;
use rustc_hir::ItemKind;
use rustc_infer::infer::outlives::env::{OutlivesEnvironment, RegionBoundPairs};
use rustc_infer::infer::outlives::obligations::TypeOutlives;
use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
use rustc_middle::mir::ConstraintCategory;
use rustc_middle::query::Providers;
use rustc_middle::ty::trait_def::TraitSpecializationKind;
use rustc_middle::ty::{
self, AdtKind, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
TypeVisitable, TypeVisitableExt, TypeVisitor,
};
use rustc_middle::ty::{GenericArgKind, GenericArgs};
use rustc_session::parse::feature_err;
use rustc_span::symbol::{sym, Ident, Symbol};
use rustc_span::{Span, DUMMY_SP};
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
use rustc_trait_selection::traits::misc::{
type_allowed_to_implement_const_param_ty, ConstParamTyImplementationError,
};
use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
use rustc_trait_selection::traits::{
self, ObligationCause, ObligationCauseCode, ObligationCtxt, WellFormedLoc,
};
use std::cell::LazyCell;
use std::ops::{ControlFlow, Deref};
pub(super) struct WfCheckingCtxt<'a, 'tcx> {
pub(super) ocx: ObligationCtxt<'a, 'tcx>,
span: Span,
body_def_id: LocalDefId,
param_env: ty::ParamEnv<'tcx>,
}
impl<'a, 'tcx> Deref for WfCheckingCtxt<'a, 'tcx> {
type Target = ObligationCtxt<'a, 'tcx>;
fn deref(&self) -> &Self::Target {
&self.ocx
}
}
impl<'tcx> WfCheckingCtxt<'_, 'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.ocx.infcx.tcx
}
fn normalize<T>(&self, span: Span, loc: Option<WellFormedLoc>, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
self.ocx.normalize(
&ObligationCause::new(span, self.body_def_id, ObligationCauseCode::WellFormed(loc)),
self.param_env,
value,
)
}
fn register_wf_obligation(
&self,
span: Span,
loc: Option<WellFormedLoc>,
arg: ty::GenericArg<'tcx>,
) {
let cause = traits::ObligationCause::new(
span,
self.body_def_id,
ObligationCauseCode::WellFormed(loc),
);
self.ocx.register_obligation(traits::Obligation::new(
self.tcx(),
cause,
self.param_env,
ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg))),
));
}
}
pub(super) fn enter_wf_checking_ctxt<'tcx, F>(
tcx: TyCtxt<'tcx>,
span: Span,
body_def_id: LocalDefId,
f: F,
) where
F: for<'a> FnOnce(&WfCheckingCtxt<'a, 'tcx>),
{
let param_env = tcx.param_env(body_def_id);
let infcx = &tcx.infer_ctxt().build();
let ocx = ObligationCtxt::new(infcx);
let mut wfcx = WfCheckingCtxt { ocx, span, body_def_id, param_env };
if !tcx.features().trivial_bounds {
wfcx.check_false_global_bounds()
}
f(&mut wfcx);
let assumed_wf_types = match wfcx.ocx.assumed_wf_types_and_report_errors(param_env, body_def_id)
{
Ok(wf_types) => wf_types,
Err(_guar) => return,
};
let implied_bounds = infcx.implied_bounds_tys(param_env, body_def_id, assumed_wf_types);
let errors = wfcx.select_all_or_error();
if !errors.is_empty() {
infcx.err_ctxt().report_fulfillment_errors(&errors);
return;
}
let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
let _ = wfcx.ocx.resolve_regions_and_report_errors(body_def_id, &outlives_env);
}
fn check_well_formed(tcx: TyCtxt<'_>, def_id: hir::OwnerId) {
let node = tcx.hir().owner(def_id);
match node {
hir::OwnerNode::Crate(_) => {}
hir::OwnerNode::Item(item) => check_item(tcx, item),
hir::OwnerNode::TraitItem(item) => check_trait_item(tcx, item),
hir::OwnerNode::ImplItem(item) => check_impl_item(tcx, item),
hir::OwnerNode::ForeignItem(item) => check_foreign_item(tcx, item),
}
if let Some(generics) = node.generics() {
for param in generics.params {
check_param_wf(tcx, param)
}
}
}
#[instrument(skip(tcx), level = "debug")]
fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
let def_id = item.owner_id.def_id;
debug!(
?item.owner_id,
item.name = ? tcx.def_path_str(def_id)
);
match item.kind {
hir::ItemKind::Impl(impl_) => {
let is_auto = tcx
.impl_trait_ref(def_id)
.is_some_and(|trait_ref| tcx.trait_is_auto(trait_ref.skip_binder().def_id));
if let (hir::Defaultness::Default { .. }, true) = (impl_.defaultness, is_auto) {
let sp = impl_.of_trait.as_ref().map_or(item.span, |t| t.path.span);
let mut err =
tcx.sess.struct_span_err(sp, "impls of auto traits cannot be default");
err.span_labels(impl_.defaultness_span, "default because of this");
err.span_label(sp, "auto trait");
err.emit();
}
match (tcx.impl_polarity(def_id), impl_.polarity) {
(ty::ImplPolarity::Positive, _) => {
check_impl(tcx, item, impl_.self_ty, &impl_.of_trait);
}
(ty::ImplPolarity::Negative, ast::ImplPolarity::Negative(span)) => {
if let hir::Defaultness::Default { .. } = impl_.defaultness {
let mut spans = vec![span];
spans.extend(impl_.defaultness_span);
struct_span_err!(
tcx.sess,
spans,
E0750,
"negative impls cannot be default impls"
)
.emit();
}
}
(ty::ImplPolarity::Reservation, _) => {
}
_ => unreachable!(),
}
}
hir::ItemKind::Fn(ref sig, ..) => {
check_item_fn(tcx, def_id, item.ident, item.span, sig.decl);
}
hir::ItemKind::Static(ty, ..) => {
check_item_type(tcx, def_id, ty.span, UnsizedHandling::Forbid);
}
hir::ItemKind::Const(ty, ..) => {
check_item_type(tcx, def_id, ty.span, UnsizedHandling::Forbid);
}
hir::ItemKind::Struct(_, ast_generics) => {
check_type_defn(tcx, item, false);
check_variances_for_type_defn(tcx, item, ast_generics);
}
hir::ItemKind::Union(_, ast_generics) => {
check_type_defn(tcx, item, true);
check_variances_for_type_defn(tcx, item, ast_generics);
}
hir::ItemKind::Enum(_, ast_generics) => {
check_type_defn(tcx, item, true);
check_variances_for_type_defn(tcx, item, ast_generics);
}
hir::ItemKind::Trait(..) => {
check_trait(tcx, item);
}
hir::ItemKind::TraitAlias(..) => {
check_trait(tcx, item);
}
hir::ItemKind::ForeignMod { .. } => {}
hir::ItemKind::TyAlias(hir_ty, ast_generics) => {
if tcx.type_alias_is_lazy(item.owner_id) {
check_item_type(tcx, def_id, hir_ty.span, UnsizedHandling::Allow);
check_variances_for_type_defn(tcx, item, ast_generics);
}
}
_ => {}
}
}
fn check_foreign_item(tcx: TyCtxt<'_>, item: &hir::ForeignItem<'_>) {
let def_id = item.owner_id.def_id;
debug!(
?item.owner_id,
item.name = ? tcx.def_path_str(def_id)
);
match item.kind {
hir::ForeignItemKind::Fn(decl, ..) => {
check_item_fn(tcx, def_id, item.ident, item.span, decl)
}
hir::ForeignItemKind::Static(ty, ..) => {
check_item_type(tcx, def_id, ty.span, UnsizedHandling::AllowIfForeignTail)
}
hir::ForeignItemKind::Type => (),
}
}
fn check_trait_item(tcx: TyCtxt<'_>, trait_item: &hir::TraitItem<'_>) {
let def_id = trait_item.owner_id.def_id;
let (method_sig, span) = match trait_item.kind {
hir::TraitItemKind::Fn(ref sig, _) => (Some(sig), trait_item.span),
hir::TraitItemKind::Type(_bounds, Some(ty)) => (None, ty.span),
_ => (None, trait_item.span),
};
check_object_unsafe_self_trait_by_name(tcx, trait_item);
check_associated_item(tcx, def_id, span, method_sig);
if matches!(trait_item.kind, hir::TraitItemKind::Fn(..)) {
for &assoc_ty_def_id in tcx.associated_types_for_impl_traits_in_associated_fn(def_id) {
check_associated_item(
tcx,
assoc_ty_def_id.expect_local(),
tcx.def_span(assoc_ty_def_id),
None,
);
}
}
}
fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRef]) {
let mut required_bounds_by_item = FxHashMap::default();
loop {
let mut should_continue = false;
for gat_item in associated_items {
let gat_def_id = gat_item.id.owner_id;
let gat_item = tcx.associated_item(gat_def_id);
if gat_item.kind != ty::AssocKind::Type {
continue;
}
let gat_generics = tcx.generics_of(gat_def_id);
if gat_generics.params.is_empty() {
continue;
}
let mut new_required_bounds: Option<FxHashSet<ty::Clause<'_>>> = None;
for item in associated_items {
let item_def_id = item.id.owner_id;
if item_def_id == gat_def_id {
continue;
}
let param_env = tcx.param_env(item_def_id);
let item_required_bounds = match item.kind {
hir::AssocItemKind::Fn { .. } => {
let sig: ty::FnSig<'_> = tcx.liberate_late_bound_regions(
item_def_id.to_def_id(),
tcx.fn_sig(item_def_id).instantiate_identity(),
);
gather_gat_bounds(
tcx,
param_env,
item_def_id,
sig.inputs_and_output,
&sig.inputs().iter().copied().collect(),
gat_def_id.def_id,
gat_generics,
)
}
hir::AssocItemKind::Type => {
let param_env = augment_param_env(
tcx,
param_env,
required_bounds_by_item.get(&item_def_id),
);
gather_gat_bounds(
tcx,
param_env,
item_def_id,
tcx.explicit_item_bounds(item_def_id)
.instantiate_identity_iter_copied()
.collect::<Vec<_>>(),
&FxIndexSet::default(),
gat_def_id.def_id,
gat_generics,
)
}
hir::AssocItemKind::Const => None,
};
if let Some(item_required_bounds) = item_required_bounds {
if let Some(new_required_bounds) = &mut new_required_bounds {
new_required_bounds.retain(|b| item_required_bounds.contains(b));
} else {
new_required_bounds = Some(item_required_bounds);
}
}
}
if let Some(new_required_bounds) = new_required_bounds {
let required_bounds = required_bounds_by_item.entry(gat_def_id).or_default();
if new_required_bounds.into_iter().any(|p| required_bounds.insert(p)) {
should_continue = true;
}
}
}
if !should_continue {
break;
}
}
for (gat_def_id, required_bounds) in required_bounds_by_item {
let gat_item_hir = tcx.hir().expect_trait_item(gat_def_id.def_id);
debug!(?required_bounds);
let param_env = tcx.param_env(gat_def_id);
let mut unsatisfied_bounds: Vec<_> = required_bounds
.into_iter()
.filter(|clause| match clause.kind().skip_binder() {
ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => {
!region_known_to_outlive(
tcx,
gat_def_id.def_id,
param_env,
&FxIndexSet::default(),
a,
b,
)
}
ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => !ty_known_to_outlive(
tcx,
gat_def_id.def_id,
param_env,
&FxIndexSet::default(),
a,
b,
),
_ => bug!("Unexpected ClauseKind"),
})
.map(|clause| clause.to_string())
.collect();
unsatisfied_bounds.sort();
if !unsatisfied_bounds.is_empty() {
let plural = pluralize!(unsatisfied_bounds.len());
let mut err = tcx.sess.struct_span_err(
gat_item_hir.span,
format!("missing required bound{} on `{}`", plural, gat_item_hir.ident),
);
let suggestion = format!(
"{} {}",
gat_item_hir.generics.add_where_or_trailing_comma(),
unsatisfied_bounds.join(", "),
);
err.span_suggestion(
gat_item_hir.generics.tail_span_for_predicate_suggestion(),
format!("add the required where clause{plural}"),
suggestion,
Applicability::MachineApplicable,
);
let bound =
if unsatisfied_bounds.len() > 1 { "these bounds are" } else { "this bound is" };
err.note(format!(
"{bound} currently required to ensure that impls have maximum flexibility"
));
err.note(
"we are soliciting feedback, see issue #87479 \
<https://github.com/rust-lang/rust/issues/87479> \
for more information",
);
err.emit();
}
}
}
fn augment_param_env<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
new_predicates: Option<&FxHashSet<ty::Clause<'tcx>>>,
) -> ty::ParamEnv<'tcx> {
let Some(new_predicates) = new_predicates else {
return param_env;
};
if new_predicates.is_empty() {
return param_env;
}
let bounds = tcx.mk_clauses_from_iter(
param_env.caller_bounds().iter().chain(new_predicates.iter().cloned()),
);
ty::ParamEnv::new(bounds, param_env.reveal())
}
fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
item_def_id: hir::OwnerId,
to_check: T,
wf_tys: &FxIndexSet<Ty<'tcx>>,
gat_def_id: LocalDefId,
gat_generics: &'tcx ty::Generics,
) -> Option<FxHashSet<ty::Clause<'tcx>>> {
let mut bounds = FxHashSet::default();
let (regions, types) = GATSubstCollector::visit(gat_def_id.to_def_id(), to_check);
if types.is_empty() && regions.is_empty() {
return None;
}
for (region_a, region_a_idx) in ®ions {
if let ty::ReStatic | ty::ReError(_) = **region_a {
continue;
}
for (ty, ty_idx) in &types {
if ty_known_to_outlive(tcx, item_def_id.def_id, param_env, &wf_tys, *ty, *region_a) {
debug!(?ty_idx, ?region_a_idx);
debug!("required clause: {ty} must outlive {region_a}");
let ty_param = gat_generics.param_at(*ty_idx, tcx);
let ty_param = Ty::new_param(tcx, ty_param.index, ty_param.name);
let region_param = gat_generics.param_at(*region_a_idx, tcx);
let region_param = ty::Region::new_early_bound(
tcx,
ty::EarlyBoundRegion {
def_id: region_param.def_id,
index: region_param.index,
name: region_param.name,
},
);
bounds.insert(
ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty_param, region_param))
.to_predicate(tcx),
);
}
}
for (region_b, region_b_idx) in ®ions {
if matches!(**region_b, ty::ReStatic | ty::ReError(_)) || region_a == region_b {
continue;
}
if region_known_to_outlive(
tcx,
item_def_id.def_id,
param_env,
&wf_tys,
*region_a,
*region_b,
) {
debug!(?region_a_idx, ?region_b_idx);
debug!("required clause: {region_a} must outlive {region_b}");
let region_a_param = gat_generics.param_at(*region_a_idx, tcx);
let region_a_param = ty::Region::new_early_bound(
tcx,
ty::EarlyBoundRegion {
def_id: region_a_param.def_id,
index: region_a_param.index,
name: region_a_param.name,
},
);
let region_b_param = gat_generics.param_at(*region_b_idx, tcx);
let region_b_param = ty::Region::new_early_bound(
tcx,
ty::EarlyBoundRegion {
def_id: region_b_param.def_id,
index: region_b_param.index,
name: region_b_param.name,
},
);
bounds.insert(
ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(
region_a_param,
region_b_param,
))
.to_predicate(tcx),
);
}
}
}
Some(bounds)
}
fn ty_known_to_outlive<'tcx>(
tcx: TyCtxt<'tcx>,
id: LocalDefId,
param_env: ty::ParamEnv<'tcx>,
wf_tys: &FxIndexSet<Ty<'tcx>>,
ty: Ty<'tcx>,
region: ty::Region<'tcx>,
) -> bool {
resolve_regions_with_wf_tys(tcx, id, param_env, &wf_tys, |infcx, region_bound_pairs| {
let origin = infer::RelateParamBound(DUMMY_SP, ty, None);
let outlives = &mut TypeOutlives::new(infcx, tcx, region_bound_pairs, None, param_env);
outlives.type_must_outlive(origin, ty, region, ConstraintCategory::BoringNoLocation);
})
}
fn region_known_to_outlive<'tcx>(
tcx: TyCtxt<'tcx>,
id: LocalDefId,
param_env: ty::ParamEnv<'tcx>,
wf_tys: &FxIndexSet<Ty<'tcx>>,
region_a: ty::Region<'tcx>,
region_b: ty::Region<'tcx>,
) -> bool {
resolve_regions_with_wf_tys(tcx, id, param_env, &wf_tys, |mut infcx, _| {
use rustc_infer::infer::outlives::obligations::TypeOutlivesDelegate;
let origin = infer::RelateRegionParamBound(DUMMY_SP);
infcx.push_sub_region_constraint(
origin,
region_b,
region_a,
ConstraintCategory::BoringNoLocation,
);
})
}
fn resolve_regions_with_wf_tys<'tcx>(
tcx: TyCtxt<'tcx>,
id: LocalDefId,
param_env: ty::ParamEnv<'tcx>,
wf_tys: &FxIndexSet<Ty<'tcx>>,
add_constraints: impl for<'a> FnOnce(&'a InferCtxt<'tcx>, &'a RegionBoundPairs<'tcx>),
) -> bool {
let infcx = tcx.infer_ctxt().build();
let outlives_environment = OutlivesEnvironment::with_bounds(
param_env,
infcx.implied_bounds_tys(param_env, id, wf_tys.clone()),
);
let region_bound_pairs = outlives_environment.region_bound_pairs();
add_constraints(&infcx, region_bound_pairs);
let errors = infcx.resolve_regions(&outlives_environment);
debug!(?errors, "errors");
errors.is_empty()
}
struct GATSubstCollector<'tcx> {
gat: DefId,
regions: FxHashSet<(ty::Region<'tcx>, usize)>,
types: FxHashSet<(Ty<'tcx>, usize)>,
}
impl<'tcx> GATSubstCollector<'tcx> {
fn visit<T: TypeFoldable<TyCtxt<'tcx>>>(
gat: DefId,
t: T,
) -> (FxHashSet<(ty::Region<'tcx>, usize)>, FxHashSet<(Ty<'tcx>, usize)>) {
let mut visitor =
GATSubstCollector { gat, regions: FxHashSet::default(), types: FxHashSet::default() };
t.visit_with(&mut visitor);
(visitor.regions, visitor.types)
}
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for GATSubstCollector<'tcx> {
type BreakTy = !;
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
match t.kind() {
ty::Alias(ty::Projection, p) if p.def_id == self.gat => {
for (idx, subst) in p.args.iter().enumerate() {
match subst.unpack() {
GenericArgKind::Lifetime(lt) if !lt.is_late_bound() => {
self.regions.insert((lt, idx));
}
GenericArgKind::Type(t) => {
self.types.insert((t, idx));
}
_ => {}
}
}
}
_ => {}
}
t.super_visit_with(self)
}
}
fn could_be_self(trait_def_id: LocalDefId, ty: &hir::Ty<'_>) -> bool {
match ty.kind {
hir::TyKind::TraitObject([trait_ref], ..) => match trait_ref.trait_ref.path.segments {
[s] => s.res.opt_def_id() == Some(trait_def_id.to_def_id()),
_ => false,
},
_ => false,
}
}
fn check_object_unsafe_self_trait_by_name(tcx: TyCtxt<'_>, item: &hir::TraitItem<'_>) {
let (trait_name, trait_def_id) =
match tcx.hir().get_by_def_id(tcx.hir().get_parent_item(item.hir_id()).def_id) {
hir::Node::Item(item) => match item.kind {
hir::ItemKind::Trait(..) => (item.ident, item.owner_id),
_ => return,
},
_ => return,
};
let mut trait_should_be_self = vec![];
match &item.kind {
hir::TraitItemKind::Const(ty, _) | hir::TraitItemKind::Type(_, Some(ty))
if could_be_self(trait_def_id.def_id, ty) =>
{
trait_should_be_self.push(ty.span)
}
hir::TraitItemKind::Fn(sig, _) => {
for ty in sig.decl.inputs {
if could_be_self(trait_def_id.def_id, ty) {
trait_should_be_self.push(ty.span);
}
}
match sig.decl.output {
hir::FnRetTy::Return(ty) if could_be_self(trait_def_id.def_id, ty) => {
trait_should_be_self.push(ty.span);
}
_ => {}
}
}
_ => {}
}
if !trait_should_be_self.is_empty() {
if tcx.check_is_object_safe(trait_def_id) {
return;
}
let sugg = trait_should_be_self.iter().map(|span| (*span, "Self".to_string())).collect();
tcx.sess
.struct_span_err(
trait_should_be_self,
"associated item referring to unboxed trait object for its own trait",
)
.span_label(trait_name.span, "in this trait")
.multipart_suggestion(
"you might have meant to use `Self` to refer to the implementing type",
sugg,
Applicability::MachineApplicable,
)
.emit();
}
}
fn check_impl_item(tcx: TyCtxt<'_>, impl_item: &hir::ImplItem<'_>) {
let (method_sig, span) = match impl_item.kind {
hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span),
hir::ImplItemKind::Type(ty) if ty.span != DUMMY_SP => (None, ty.span),
_ => (None, impl_item.span),
};
check_associated_item(tcx, impl_item.owner_id.def_id, span, method_sig);
}
fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
match param.kind {
hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. } => (),
hir::GenericParamKind::Const { ty: hir_ty, default: _ } => {
let ty = tcx.type_of(param.def_id).instantiate_identity();
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,
param.def_id,
ObligationCauseCode::ConstParam(ty),
),
wfcx.param_env,
ty,
trait_def_id,
);
});
} else {
let diag = match ty.kind() {
ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Error(_) => None,
ty::FnPtr(_) => Some(tcx.sess.struct_span_err(
hir_ty.span,
"using function pointers as const generic parameters is forbidden",
)),
ty::RawPtr(_) => Some(tcx.sess.struct_span_err(
hir_ty.span,
"using raw pointers as const generic parameters is forbidden",
)),
_ => Some(tcx.sess.struct_span_err(
hir_ty.span,
format!("`{}` is forbidden as the type of a const generic parameter", ty),
)),
};
if let Some(mut diag) = diag {
diag.note("the only supported types are integers, `bool` and `char`");
let cause = ObligationCause::misc(hir_ty.span, param.def_id);
let may_suggest_feature = match type_allowed_to_implement_const_param_ty(
tcx,
tcx.param_env(param.def_id),
ty,
cause,
) {
Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed) => false,
Err(ConstParamTyImplementationError::InfrigingFields(..)) => {
fn ty_is_local(ty: Ty<'_>) -> bool {
match ty.kind() {
ty::Adt(adt_def, ..) => adt_def.did().is_local(),
ty::Array(ty, ..) => ty_is_local(*ty),
ty::Slice(ty) => ty_is_local(*ty),
ty::Ref(_, ty, ast::Mutability::Not) => ty_is_local(*ty),
ty::Tuple(tys) => tys.iter().any(|ty| ty_is_local(ty)),
_ => false,
}
}
ty_is_local(ty)
}
Ok(..) => true,
};
if may_suggest_feature && tcx.sess.is_nightly_build() {
diag.help(
"add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types",
);
}
diag.emit();
}
}
}
}
}
#[instrument(level = "debug", skip(tcx, span, sig_if_method))]
fn check_associated_item(
tcx: TyCtxt<'_>,
item_id: LocalDefId,
span: Span,
sig_if_method: Option<&hir::FnSig<'_>>,
) {
let loc = Some(WellFormedLoc::Ty(item_id));
enter_wf_checking_ctxt(tcx, span, item_id, |wfcx| {
let item = tcx.associated_item(item_id);
let self_ty = match item.container {
ty::TraitContainer => tcx.types.self_param,
ty::ImplContainer => tcx.type_of(item.container_id(tcx)).instantiate_identity(),
};
match item.kind {
ty::AssocKind::Const => {
let ty = tcx.type_of(item.def_id).instantiate_identity();
let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
wfcx.register_wf_obligation(span, loc, ty.into());
}
ty::AssocKind::Fn => {
let sig = tcx.fn_sig(item.def_id).instantiate_identity();
let hir_sig = sig_if_method.expect("bad signature for method");
check_fn_or_method(
wfcx,
item.ident(tcx).span,
sig,
hir_sig.decl,
item.def_id.expect_local(),
);
check_method_receiver(wfcx, hir_sig, item, self_ty);
}
ty::AssocKind::Type => {
if let ty::AssocItemContainer::TraitContainer = item.container {
check_associated_type_bounds(wfcx, item, span)
}
if item.defaultness(tcx).has_value() {
let ty = tcx.type_of(item.def_id).instantiate_identity();
let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
wfcx.register_wf_obligation(span, loc, ty.into());
}
}
}
})
}
fn item_adt_kind(kind: &ItemKind<'_>) -> Option<AdtKind> {
match kind {
ItemKind::Struct(..) => Some(AdtKind::Struct),
ItemKind::Union(..) => Some(AdtKind::Union),
ItemKind::Enum(..) => Some(AdtKind::Enum),
_ => None,
}
}
fn check_type_defn<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, all_sized: bool) {
let _ = tcx.representability(item.owner_id.def_id);
let adt_def = tcx.adt_def(item.owner_id);
enter_wf_checking_ctxt(tcx, item.span, item.owner_id.def_id, |wfcx| {
let variants = adt_def.variants();
let packed = adt_def.repr().packed();
for variant in variants.iter() {
for field in &variant.fields {
let field_id = field.did.expect_local();
let hir::FieldDef { ty: hir_ty, .. } =
tcx.hir().get_by_def_id(field_id).expect_field();
let ty = wfcx.normalize(
hir_ty.span,
None,
tcx.type_of(field.did).instantiate_identity(),
);
wfcx.register_wf_obligation(
hir_ty.span,
Some(WellFormedLoc::Ty(field_id)),
ty.into(),
)
}
let needs_drop_copy = || {
packed && {
let ty = tcx.type_of(variant.tail().did).instantiate_identity();
let ty = tcx.erase_regions(ty);
if ty.has_infer() {
tcx.sess
.delay_span_bug(item.span, format!("inference variables in {ty:?}"));
true
} else {
ty.needs_drop(tcx, tcx.param_env(item.owner_id))
}
}
};
let all_sized = all_sized || variant.fields.is_empty() || needs_drop_copy();
let unsized_len = if all_sized { 0 } else { 1 };
for (idx, field) in
variant.fields.raw[..variant.fields.len() - unsized_len].iter().enumerate()
{
let last = idx == variant.fields.len() - 1;
let field_id = field.did.expect_local();
let hir::FieldDef { ty: hir_ty, .. } =
tcx.hir().get_by_def_id(field_id).expect_field();
let ty = wfcx.normalize(
hir_ty.span,
None,
tcx.type_of(field.did).instantiate_identity(),
);
wfcx.register_bound(
traits::ObligationCause::new(
hir_ty.span,
wfcx.body_def_id,
traits::FieldSized {
adt_kind: match item_adt_kind(&item.kind) {
Some(i) => i,
None => bug!(),
},
span: hir_ty.span,
last,
},
),
wfcx.param_env,
ty,
tcx.require_lang_item(LangItem::Sized, None),
);
}
if let ty::VariantDiscr::Explicit(discr_def_id) = variant.discr {
let cause = traits::ObligationCause::new(
tcx.def_span(discr_def_id),
wfcx.body_def_id,
traits::MiscObligation,
);
wfcx.register_obligation(traits::Obligation::new(
tcx,
cause,
wfcx.param_env,
ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(
ty::Const::from_anon_const(tcx, discr_def_id.expect_local()),
))),
));
}
}
check_where_clauses(wfcx, item.span, item.owner_id.def_id);
});
}
#[instrument(skip(tcx, item))]
fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) {
debug!(?item.owner_id);
let def_id = item.owner_id.def_id;
let trait_def = tcx.trait_def(def_id);
if trait_def.is_marker
|| matches!(trait_def.specialization_kind, TraitSpecializationKind::Marker)
{
for associated_def_id in &*tcx.associated_item_def_ids(def_id) {
struct_span_err!(
tcx.sess,
tcx.def_span(*associated_def_id),
E0714,
"marker traits cannot have associated items",
)
.emit();
}
}
enter_wf_checking_ctxt(tcx, item.span, def_id, |wfcx| {
check_where_clauses(wfcx, item.span, def_id)
});
if let hir::ItemKind::Trait(_, _, _, _, items) = item.kind {
check_gat_where_clauses(tcx, items);
}
}
fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocItem, span: Span) {
let bounds = wfcx.tcx().explicit_item_bounds(item.def_id);
debug!("check_associated_type_bounds: bounds={:?}", bounds);
let wf_obligations =
bounds.instantiate_identity_iter_copied().flat_map(|(bound, bound_span)| {
let normalized_bound = wfcx.normalize(span, None, bound);
traits::wf::clause_obligations(
wfcx.infcx,
wfcx.param_env,
wfcx.body_def_id,
normalized_bound,
bound_span,
)
});
wfcx.register_obligations(wf_obligations);
}
fn check_item_fn(
tcx: TyCtxt<'_>,
def_id: LocalDefId,
ident: Ident,
span: Span,
decl: &hir::FnDecl<'_>,
) {
enter_wf_checking_ctxt(tcx, span, def_id, |wfcx| {
let sig = tcx.fn_sig(def_id).instantiate_identity();
check_fn_or_method(wfcx, ident.span, sig, decl, def_id);
})
}
enum UnsizedHandling {
Forbid,
Allow,
AllowIfForeignTail,
}
fn check_item_type(
tcx: TyCtxt<'_>,
item_id: LocalDefId,
ty_span: Span,
unsized_handling: UnsizedHandling,
) {
debug!("check_item_type: {:?}", item_id);
enter_wf_checking_ctxt(tcx, ty_span, item_id, |wfcx| {
let ty = tcx.type_of(item_id).instantiate_identity();
let item_ty = wfcx.normalize(ty_span, Some(WellFormedLoc::Ty(item_id)), ty);
let forbid_unsized = match unsized_handling {
UnsizedHandling::Forbid => true,
UnsizedHandling::Allow => false,
UnsizedHandling::AllowIfForeignTail => {
let tail = tcx.struct_tail_erasing_lifetimes(item_ty, wfcx.param_env);
!matches!(tail.kind(), ty::Foreign(_))
}
};
wfcx.register_wf_obligation(ty_span, Some(WellFormedLoc::Ty(item_id)), item_ty.into());
if forbid_unsized {
wfcx.register_bound(
traits::ObligationCause::new(ty_span, wfcx.body_def_id, traits::WellFormed(None)),
wfcx.param_env,
item_ty,
tcx.require_lang_item(LangItem::Sized, None),
);
}
let should_check_for_sync = tcx.static_mutability(item_id.to_def_id())
== Some(hir::Mutability::Not)
&& !tcx.is_foreign_item(item_id.to_def_id())
&& !tcx.is_thread_local_static(item_id.to_def_id());
if should_check_for_sync {
wfcx.register_bound(
traits::ObligationCause::new(ty_span, wfcx.body_def_id, traits::SharedStatic),
wfcx.param_env,
item_ty,
tcx.require_lang_item(LangItem::Sync, Some(ty_span)),
);
}
});
}
#[instrument(level = "debug", skip(tcx, ast_self_ty, ast_trait_ref))]
fn check_impl<'tcx>(
tcx: TyCtxt<'tcx>,
item: &'tcx hir::Item<'tcx>,
ast_self_ty: &hir::Ty<'_>,
ast_trait_ref: &Option<hir::TraitRef<'_>>,
) {
enter_wf_checking_ctxt(tcx, item.span, item.owner_id.def_id, |wfcx| {
match ast_trait_ref {
Some(ast_trait_ref) => {
let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().instantiate_identity();
let trait_ref = wfcx.normalize(
ast_trait_ref.path.span,
Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
trait_ref,
);
let trait_pred =
ty::TraitPredicate { trait_ref, polarity: ty::ImplPolarity::Positive };
let mut obligations = traits::wf::trait_obligations(
wfcx.infcx,
wfcx.param_env,
wfcx.body_def_id,
trait_pred,
ast_trait_ref.path.span,
item,
);
for obligation in &mut obligations {
if let Some(pred) = obligation.predicate.to_opt_poly_trait_pred()
&& pred.self_ty().skip_binder() == trait_ref.self_ty()
{
obligation.cause.span = ast_self_ty.span;
}
}
debug!(?obligations);
wfcx.register_obligations(obligations);
}
None => {
let self_ty = tcx.type_of(item.owner_id).instantiate_identity();
let self_ty = wfcx.normalize(
item.span,
Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
self_ty,
);
wfcx.register_wf_obligation(
ast_self_ty.span,
Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
self_ty.into(),
);
}
}
check_where_clauses(wfcx, item.span, item.owner_id.def_id);
});
}
#[instrument(level = "debug", skip(wfcx))]
fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id: LocalDefId) {
let infcx = wfcx.infcx;
let tcx = wfcx.tcx();
let predicates = tcx.predicates_of(def_id.to_def_id());
let generics = tcx.generics_of(def_id);
let is_our_default = |def: &ty::GenericParamDef| match def.kind {
GenericParamDefKind::Type { has_default, .. }
| GenericParamDefKind::Const { has_default, .. } => {
has_default && def.index >= generics.parent_count as u32
}
GenericParamDefKind::Lifetime => unreachable!(),
};
for param in &generics.params {
match param.kind {
GenericParamDefKind::Type { .. } => {
if is_our_default(param) {
let ty = tcx.type_of(param.def_id).instantiate_identity();
if !ty.has_param() {
wfcx.register_wf_obligation(
tcx.def_span(param.def_id),
Some(WellFormedLoc::Ty(param.def_id.expect_local())),
ty.into(),
);
}
}
}
GenericParamDefKind::Const { .. } => {
if is_our_default(param) {
let default_ct = tcx.const_param_default(param.def_id).instantiate_identity();
if !default_ct.has_param() {
wfcx.register_wf_obligation(
tcx.def_span(param.def_id),
None,
default_ct.into(),
);
}
}
}
GenericParamDefKind::Lifetime => {}
}
}
let args = GenericArgs::for_item(tcx, def_id.to_def_id(), |param, _| {
match param.kind {
GenericParamDefKind::Lifetime => {
tcx.mk_param_from_def(param)
}
GenericParamDefKind::Type { .. } => {
if is_our_default(param) {
let default_ty = tcx.type_of(param.def_id).instantiate_identity();
if !default_ty.has_param() {
return default_ty.into();
}
}
tcx.mk_param_from_def(param)
}
GenericParamDefKind::Const { .. } => {
if is_our_default(param) {
let default_ct = tcx.const_param_default(param.def_id).instantiate_identity();
if !default_ct.has_param() {
return default_ct.into();
}
}
tcx.mk_param_from_def(param)
}
}
});
let default_obligations = predicates
.predicates
.iter()
.flat_map(|&(pred, sp)| {
#[derive(Default)]
struct CountParams {
params: FxHashSet<u32>,
}
impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for CountParams {
type BreakTy = ();
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if let ty::Param(param) = t.kind() {
self.params.insert(param.index);
}
t.super_visit_with(self)
}
fn visit_region(&mut self, _: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}
fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
if let ty::ConstKind::Param(param) = c.kind() {
self.params.insert(param.index);
}
c.super_visit_with(self)
}
}
let mut param_count = CountParams::default();
let has_region = pred.visit_with(&mut param_count).is_break();
let substituted_pred = ty::EarlyBinder::bind(pred).instantiate(tcx, args);
if substituted_pred.has_non_region_param() || param_count.params.len() > 1 || has_region
{
None
} else if predicates.predicates.iter().any(|&(p, _)| p == substituted_pred) {
None
} else {
Some((substituted_pred, sp))
}
})
.map(|(pred, sp)| {
let pred = wfcx.normalize(sp, None, pred);
let cause = traits::ObligationCause::new(
sp,
wfcx.body_def_id,
traits::ItemObligation(def_id.to_def_id()),
);
traits::Obligation::new(tcx, cause, wfcx.param_env, pred)
});
let predicates = predicates.instantiate_identity(tcx);
let predicates = wfcx.normalize(span, None, predicates);
debug!(?predicates.predicates);
assert_eq!(predicates.predicates.len(), predicates.spans.len());
let wf_obligations = predicates.into_iter().flat_map(|(p, sp)| {
traits::wf::clause_obligations(infcx, wfcx.param_env, wfcx.body_def_id, p, sp)
});
let obligations: Vec<_> = wf_obligations.chain(default_obligations).collect();
wfcx.register_obligations(obligations);
}
#[instrument(level = "debug", skip(wfcx, span, hir_decl))]
fn check_fn_or_method<'tcx>(
wfcx: &WfCheckingCtxt<'_, 'tcx>,
span: Span,
sig: ty::PolyFnSig<'tcx>,
hir_decl: &hir::FnDecl<'_>,
def_id: LocalDefId,
) {
let tcx = wfcx.tcx();
let mut sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
let arg_span =
|idx| hir_decl.inputs.get(idx).map_or(hir_decl.output.span(), |arg: &hir::Ty<'_>| arg.span);
sig.inputs_and_output =
tcx.mk_type_list_from_iter(sig.inputs_and_output.iter().enumerate().map(|(idx, ty)| {
wfcx.normalize(
arg_span(idx),
Some(WellFormedLoc::Param {
function: def_id,
param_idx: idx.try_into().unwrap(),
}),
ty,
)
}));
for (idx, ty) in sig.inputs_and_output.iter().enumerate() {
wfcx.register_wf_obligation(
arg_span(idx),
Some(WellFormedLoc::Param { function: def_id, param_idx: idx.try_into().unwrap() }),
ty.into(),
);
}
check_where_clauses(wfcx, span, def_id);
if sig.abi == Abi::RustCall {
let span = tcx.def_span(def_id);
let has_implicit_self = hir_decl.implicit_self != hir::ImplicitSelfKind::None;
let mut inputs = sig.inputs().iter().skip(if has_implicit_self { 1 } else { 0 });
if let Some(ty) = inputs.next() {
wfcx.register_bound(
ObligationCause::new(span, wfcx.body_def_id, ObligationCauseCode::RustCall),
wfcx.param_env,
*ty,
tcx.require_lang_item(hir::LangItem::Tuple, Some(span)),
);
wfcx.register_bound(
ObligationCause::new(span, wfcx.body_def_id, ObligationCauseCode::RustCall),
wfcx.param_env,
*ty,
tcx.require_lang_item(hir::LangItem::Sized, Some(span)),
);
} else {
tcx.sess.span_err(
hir_decl.inputs.last().map_or(span, |input| input.span),
"functions with the \"rust-call\" ABI must take a single non-self tuple argument",
);
}
if inputs.next().is_some() {
tcx.sess.span_err(
hir_decl.inputs.last().map_or(span, |input| input.span),
"functions with the \"rust-call\" ABI must take a single non-self tuple argument",
);
}
}
}
const HELP_FOR_SELF_TYPE: &str = "consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, \
`self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one \
of the previous types except `Self`)";
#[instrument(level = "debug", skip(wfcx))]
fn check_method_receiver<'tcx>(
wfcx: &WfCheckingCtxt<'_, 'tcx>,
fn_sig: &hir::FnSig<'_>,
method: ty::AssocItem,
self_ty: Ty<'tcx>,
) {
let tcx = wfcx.tcx();
if !method.fn_has_self_parameter {
return;
}
let span = fn_sig.decl.inputs[0].span;
let sig = tcx.fn_sig(method.def_id).instantiate_identity();
let sig = tcx.liberate_late_bound_regions(method.def_id, sig);
let sig = wfcx.normalize(span, None, sig);
debug!("check_method_receiver: sig={:?}", sig);
let self_ty = wfcx.normalize(span, None, self_ty);
let receiver_ty = sig.inputs()[0];
let receiver_ty = wfcx.normalize(span, None, receiver_ty);
if tcx.features().arbitrary_self_types {
if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
e0307(tcx, span, receiver_ty);
}
} else {
if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, false) {
if receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
feature_err(
&tcx.sess.parse_sess,
sym::arbitrary_self_types,
span,
format!(
"`{receiver_ty}` cannot be used as the type of `self` without \
the `arbitrary_self_types` feature",
),
)
.help(HELP_FOR_SELF_TYPE)
.emit();
} else {
e0307(tcx, span, receiver_ty);
}
}
}
}
fn e0307(tcx: TyCtxt<'_>, span: Span, receiver_ty: Ty<'_>) {
struct_span_err!(
tcx.sess.diagnostic(),
span,
E0307,
"invalid `self` parameter type: {receiver_ty}"
)
.note("type of `self` must be `Self` or a type that dereferences to it")
.help(HELP_FOR_SELF_TYPE)
.emit();
}
fn receiver_is_valid<'tcx>(
wfcx: &WfCheckingCtxt<'_, 'tcx>,
span: Span,
receiver_ty: Ty<'tcx>,
self_ty: Ty<'tcx>,
arbitrary_self_types_enabled: bool,
) -> bool {
let infcx = wfcx.infcx;
let tcx = wfcx.tcx();
let cause =
ObligationCause::new(span, wfcx.body_def_id, traits::ObligationCauseCode::MethodReceiver);
let can_eq_self = |ty| infcx.can_eq(wfcx.param_env, self_ty, ty);
if can_eq_self(receiver_ty) {
if let Err(err) = wfcx.eq(&cause, wfcx.param_env, self_ty, receiver_ty) {
infcx.err_ctxt().report_mismatched_types(&cause, self_ty, receiver_ty, err).emit();
}
return true;
}
let mut autoderef = Autoderef::new(infcx, wfcx.param_env, wfcx.body_def_id, span, receiver_ty);
if arbitrary_self_types_enabled {
autoderef = autoderef.include_raw_pointers();
}
autoderef.next();
let receiver_trait_def_id = tcx.require_lang_item(LangItem::Receiver, Some(span));
loop {
if let Some((potential_self_ty, _)) = autoderef.next() {
debug!(
"receiver_is_valid: potential self type `{:?}` to match `{:?}`",
potential_self_ty, self_ty
);
if can_eq_self(potential_self_ty) {
wfcx.register_obligations(autoderef.into_obligations());
if let Err(err) = wfcx.eq(&cause, wfcx.param_env, self_ty, potential_self_ty) {
infcx
.err_ctxt()
.report_mismatched_types(&cause, self_ty, potential_self_ty, err)
.emit();
}
break;
} else {
if !arbitrary_self_types_enabled
&& !receiver_is_implemented(
wfcx,
receiver_trait_def_id,
cause.clone(),
potential_self_ty,
)
{
return false;
}
}
} else {
debug!("receiver_is_valid: type `{:?}` does not deref to `{:?}`", receiver_ty, self_ty);
return receiver_ty.references_error();
}
}
if !arbitrary_self_types_enabled
&& !receiver_is_implemented(wfcx, receiver_trait_def_id, cause.clone(), receiver_ty)
{
return false;
}
true
}
fn receiver_is_implemented<'tcx>(
wfcx: &WfCheckingCtxt<'_, 'tcx>,
receiver_trait_def_id: DefId,
cause: ObligationCause<'tcx>,
receiver_ty: Ty<'tcx>,
) -> bool {
let tcx = wfcx.tcx();
let trait_ref = ty::TraitRef::new(tcx, receiver_trait_def_id, [receiver_ty]);
let obligation = traits::Obligation::new(tcx, cause, wfcx.param_env, trait_ref);
if wfcx.infcx.predicate_must_hold_modulo_regions(&obligation) {
true
} else {
debug!(
"receiver_is_implemented: type `{:?}` does not implement `Receiver` trait",
receiver_ty
);
false
}
}
fn check_variances_for_type_defn<'tcx>(
tcx: TyCtxt<'tcx>,
item: &hir::Item<'tcx>,
hir_generics: &hir::Generics<'_>,
) {
let identity_args = ty::GenericArgs::identity_for_item(tcx, item.owner_id);
match item.kind {
ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
for field in tcx.adt_def(item.owner_id).all_fields() {
if field.ty(tcx, identity_args).references_error() {
return;
}
}
}
ItemKind::TyAlias(..) => {
if tcx.type_alias_is_lazy(item.owner_id) {
if tcx.type_of(item.owner_id).skip_binder().references_error() {
return;
}
} else {
bug!();
}
}
_ => bug!(),
}
let ty_predicates = tcx.predicates_of(item.owner_id);
assert_eq!(ty_predicates.parent, None);
let variances = tcx.variances_of(item.owner_id);
let mut constrained_parameters: FxHashSet<_> = variances
.iter()
.enumerate()
.filter(|&(_, &variance)| variance != ty::Bivariant)
.map(|(index, _)| Parameter(index as u32))
.collect();
identify_constrained_generic_params(tcx, ty_predicates, None, &mut constrained_parameters);
let explicitly_bounded_params = LazyCell::new(|| {
let icx = crate::collect::ItemCtxt::new(tcx, item.owner_id.def_id);
hir_generics
.predicates
.iter()
.filter_map(|predicate| match predicate {
hir::WherePredicate::BoundPredicate(predicate) => {
match icx.to_ty(predicate.bounded_ty).kind() {
ty::Param(data) => Some(Parameter(data.index)),
_ => None,
}
}
_ => None,
})
.collect::<FxHashSet<_>>()
});
let ty_generics = tcx.generics_of(item.owner_id);
for (index, _) in variances.iter().enumerate() {
let parameter = Parameter(index as u32);
if constrained_parameters.contains(¶meter) {
continue;
}
let ty_param = &ty_generics.params[index];
let hir_param = &hir_generics.params[index];
if ty_param.def_id != hir_param.def_id.into() {
tcx.sess
.delay_span_bug(hir_param.span, "hir generics and ty generics in different order");
continue;
}
match hir_param.name {
hir::ParamName::Error => {}
_ => {
let has_explicit_bounds = explicitly_bounded_params.contains(¶meter);
report_bivariance(tcx, hir_param, has_explicit_bounds);
}
}
}
}
fn report_bivariance(
tcx: TyCtxt<'_>,
param: &rustc_hir::GenericParam<'_>,
has_explicit_bounds: bool,
) -> ErrorGuaranteed {
let span = param.span;
let param_name = param.name.ident().name;
let mut err = error_392(tcx, span, param_name);
let suggested_marker_id = tcx.lang_items().phantom_data();
let msg = if let Some(def_id) = suggested_marker_id {
format!(
"consider removing `{}`, referring to it in a field, or using a marker such as `{}`",
param_name,
tcx.def_path_str(def_id),
)
} else {
format!("consider removing `{param_name}` or referring to it in a field")
};
err.help(msg);
if matches!(param.kind, hir::GenericParamKind::Type { .. }) && !has_explicit_bounds {
err.help(format!(
"if you intended `{param_name}` to be a const parameter, use `const {param_name}: usize` instead"
));
}
err.emit()
}
impl<'tcx> WfCheckingCtxt<'_, 'tcx> {
#[instrument(level = "debug", skip(self))]
fn check_false_global_bounds(&mut self) {
let tcx = self.ocx.infcx.tcx;
let mut span = self.span;
let empty_env = ty::ParamEnv::empty();
let predicates_with_span = tcx.predicates_of(self.body_def_id).predicates.iter().copied();
let implied_obligations = traits::elaborate(tcx, predicates_with_span);
for (pred, obligation_span) in implied_obligations {
if let ty::ClauseKind::WellFormed(..) = pred.kind().skip_binder() {
continue;
}
if pred.is_global() && !pred.has_late_bound_vars() {
let pred = self.normalize(span, None, pred);
let hir_node = tcx.hir().find_by_def_id(self.body_def_id);
if let Some(hir::Generics { predicates, .. }) =
hir_node.and_then(|node| node.generics())
{
span = predicates
.iter()
.find(|pred| pred.span().contains(obligation_span))
.map(|pred| pred.span())
.unwrap_or(obligation_span);
}
let obligation = traits::Obligation::new(
tcx,
traits::ObligationCause::new(span, self.body_def_id, traits::TrivialBound),
empty_env,
pred,
);
self.ocx.register_obligation(obligation);
}
}
}
}
fn check_mod_type_wf(tcx: TyCtxt<'_>, module: LocalModDefId) {
let items = tcx.hir_module_items(module);
items.par_items(|item| tcx.ensure().check_well_formed(item.owner_id));
items.par_impl_items(|item| tcx.ensure().check_well_formed(item.owner_id));
items.par_trait_items(|item| tcx.ensure().check_well_formed(item.owner_id));
items.par_foreign_items(|item| tcx.ensure().check_well_formed(item.owner_id));
}
fn error_392(
tcx: TyCtxt<'_>,
span: Span,
param_name: Symbol,
) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
let mut err = struct_span_err!(tcx.sess, span, E0392, "parameter `{param_name}` is never used");
err.span_label(span, "unused parameter");
err
}
pub fn provide(providers: &mut Providers) {
*providers = Providers { check_mod_type_wf, check_well_formed, ..*providers };
}