+++ /dev/null
-use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter};
-use hir::def::DefKind;
-use rustc_ast as ast;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
-use rustc_hir as hir;
-use rustc_hir::def_id::{DefId, LocalDefId};
-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::ty::query::Providers;
-use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts, Subst};
-use rustc_middle::ty::trait_def::TraitSpecializationKind;
-use rustc_middle::ty::{
- self, AdtKind, DefIdTree, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeFoldable,
- TypeSuperVisitable, TypeVisitable, TypeVisitor,
-};
-use rustc_session::parse::feature_err;
-use rustc_span::symbol::{sym, Ident, Symbol};
-use rustc_span::{Span, DUMMY_SP};
-use rustc_trait_selection::autoderef::Autoderef;
-use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
-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::convert::TryInto;
-use std::iter;
-use std::ops::{ControlFlow, Deref};
-
-pub(super) struct WfCheckingCtxt<'a, 'tcx> {
- pub(super) ocx: ObligationCtxt<'a, 'tcx>,
- span: Span,
- body_id: hir::HirId,
- 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<'tcx>,
- {
- self.ocx.normalize(
- ObligationCause::new(span, self.body_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_id, ObligationCauseCode::WellFormed(loc));
- // for a type to be WF, we do not need to check if const trait predicates satisfy.
- let param_env = self.param_env.without_const();
- self.ocx.register_obligation(traits::Obligation::new(
- cause,
- param_env,
- ty::Binder::dummy(ty::PredicateKind::WellFormed(arg)).to_predicate(self.tcx()),
- ));
- }
-}
-
-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 body_id = tcx.hir().local_def_id_to_hir_id(body_def_id);
- tcx.infer_ctxt().enter(|ref infcx| {
- let ocx = ObligationCtxt::new(infcx);
-
- let assumed_wf_types = ocx.assumed_wf_types(param_env, span, body_def_id);
-
- let mut wfcx = WfCheckingCtxt { ocx, span, body_id, param_env };
-
- if !tcx.features().trivial_bounds {
- wfcx.check_false_global_bounds()
- }
- f(&mut wfcx);
- let errors = wfcx.select_all_or_error();
- if !errors.is_empty() {
- infcx.report_fulfillment_errors(&errors, None, false);
- return;
- }
-
- let implied_bounds = infcx.implied_bounds_tys(param_env, body_id, assumed_wf_types);
- let outlives_environment =
- OutlivesEnvironment::with_bounds(param_env, Some(infcx), implied_bounds);
-
- infcx.check_region_obligations_and_report_errors(body_def_id, &outlives_environment);
- })
-}
-
-fn check_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
- let node = tcx.hir().expect_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)
- }
- }
-}
-
-/// Checks that the field types (in a struct def'n) or argument types (in an enum def'n) are
-/// well-formed, meaning that they do not require any constraints not declared in the struct
-/// definition itself. For example, this definition would be illegal:
-///
-/// ```rust
-/// struct Ref<'a, T> { x: &'a T }
-/// ```
-///
-/// because the type did not declare that `T:'a`.
-///
-/// We do this check as a pre-pass before checking fn bodies because if these constraints are
-/// not included it frequently leads to confusing errors in fn bodies. So it's better to check
-/// the types first.
-#[instrument(skip(tcx), level = "debug")]
-fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
- let def_id = item.def_id;
-
- debug!(
- ?item.def_id,
- item.name = ? tcx.def_path_str(def_id.to_def_id())
- );
-
- match item.kind {
- // Right now we check that every default trait implementation
- // has an implementation of itself. Basically, a case like:
- //
- // impl Trait for T {}
- //
- // has a requirement of `T: Trait` which was required for default
- // method implementations. Although this could be improved now that
- // there's a better infrastructure in place for this, it's being left
- // for a follow-up work.
- //
- // Since there's such a requirement, we need to check *just* positive
- // implementations, otherwise things like:
- //
- // impl !Send for T {}
- //
- // won't be allowed unless there's an *explicit* implementation of `Send`
- // for `T`
- hir::ItemKind::Impl(ref impl_) => {
- let is_auto = tcx
- .impl_trait_ref(item.def_id)
- .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.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();
- }
- // We match on both `ty::ImplPolarity` and `ast::ImplPolarity` just to get the `!` span.
- match (tcx.impl_polarity(def_id), impl_.polarity) {
- (ty::ImplPolarity::Positive, _) => {
- check_impl(tcx, item, impl_.self_ty, &impl_.of_trait, impl_.constness);
- }
- (ty::ImplPolarity::Negative, ast::ImplPolarity::Negative(span)) => {
- // FIXME(#27579): what amount of WF checking do we need for neg impls?
- 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, _) => {
- // FIXME: what amount of WF checking do we need for reservation impls?
- }
- _ => unreachable!(),
- }
- }
- hir::ItemKind::Fn(ref sig, ..) => {
- check_item_fn(tcx, item.def_id, item.ident, item.span, sig.decl);
- }
- hir::ItemKind::Static(ty, ..) => {
- check_item_type(tcx, item.def_id, ty.span, false);
- }
- hir::ItemKind::Const(ty, ..) => {
- check_item_type(tcx, item.def_id, ty.span, false);
- }
- hir::ItemKind::Struct(ref struct_def, ref ast_generics) => {
- check_type_defn(tcx, item, false, |wfcx| vec![wfcx.non_enum_variant(struct_def)]);
-
- check_variances_for_type_defn(tcx, item, ast_generics);
- }
- hir::ItemKind::Union(ref struct_def, ref ast_generics) => {
- check_type_defn(tcx, item, true, |wfcx| vec![wfcx.non_enum_variant(struct_def)]);
-
- check_variances_for_type_defn(tcx, item, ast_generics);
- }
- hir::ItemKind::Enum(ref enum_def, ref ast_generics) => {
- check_type_defn(tcx, item, true, |wfcx| wfcx.enum_variants(enum_def));
-
- check_variances_for_type_defn(tcx, item, ast_generics);
- }
- hir::ItemKind::Trait(..) => {
- check_trait(tcx, item);
- }
- hir::ItemKind::TraitAlias(..) => {
- check_trait(tcx, item);
- }
- // `ForeignItem`s are handled separately.
- hir::ItemKind::ForeignMod { .. } => {}
- _ => {}
- }
-}
-
-fn check_foreign_item(tcx: TyCtxt<'_>, item: &hir::ForeignItem<'_>) {
- let def_id = item.def_id;
-
- debug!(
- ?item.def_id,
- item.name = ? tcx.def_path_str(def_id.to_def_id())
- );
-
- match item.kind {
- hir::ForeignItemKind::Fn(decl, ..) => {
- check_item_fn(tcx, item.def_id, item.ident, item.span, decl)
- }
- hir::ForeignItemKind::Static(ty, ..) => check_item_type(tcx, item.def_id, ty.span, true),
- hir::ForeignItemKind::Type => (),
- }
-}
-
-fn check_trait_item(tcx: TyCtxt<'_>, trait_item: &hir::TraitItem<'_>) {
- let def_id = trait_item.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, trait_item.def_id, span, method_sig);
-
- let encl_trait_def_id = tcx.local_parent(def_id);
- let encl_trait = tcx.hir().expect_item(encl_trait_def_id);
- let encl_trait_def_id = encl_trait.def_id.to_def_id();
- let fn_lang_item_name = if Some(encl_trait_def_id) == tcx.lang_items().fn_trait() {
- Some("fn")
- } else if Some(encl_trait_def_id) == tcx.lang_items().fn_mut_trait() {
- Some("fn_mut")
- } else {
- None
- };
-
- if let (Some(fn_lang_item_name), "call") =
- (fn_lang_item_name, trait_item.ident.name.to_ident_string().as_str())
- {
- // We are looking at the `call` function of the `fn` or `fn_mut` lang item.
- // Do some rudimentary sanity checking to avoid an ICE later (issue #83471).
- if let Some(hir::FnSig { decl, span, .. }) = method_sig {
- if let [self_ty, _] = decl.inputs {
- if !matches!(self_ty.kind, hir::TyKind::Rptr(_, _)) {
- tcx.sess
- .struct_span_err(
- self_ty.span,
- &format!(
- "first argument of `call` in `{fn_lang_item_name}` lang item must be a reference",
- ),
- )
- .emit();
- }
- } else {
- tcx.sess
- .struct_span_err(
- *span,
- &format!(
- "`call` function in `{fn_lang_item_name}` lang item takes exactly two arguments",
- ),
- )
- .emit();
- }
- } else {
- tcx.sess
- .struct_span_err(
- trait_item.span,
- &format!(
- "`call` trait item in `{fn_lang_item_name}` lang item must be a function",
- ),
- )
- .emit();
- }
- }
-}
-
-/// Require that the user writes where clauses on GATs for the implicit
-/// outlives bounds involving trait parameters in trait functions and
-/// lifetimes passed as GAT substs. See `self-outlives-lint` test.
-///
-/// We use the following trait as an example throughout this function:
-/// ```rust,ignore (this code fails due to this lint)
-/// trait IntoIter {
-/// type Iter<'a>: Iterator<Item = Self::Item<'a>>;
-/// type Item<'a>;
-/// fn into_iter<'a>(&'a self) -> Self::Iter<'a>;
-/// }
-/// ```
-fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRef]) {
- // Associates every GAT's def_id to a list of possibly missing bounds detected by this lint.
- let mut required_bounds_by_item = FxHashMap::default();
-
- // Loop over all GATs together, because if this lint suggests adding a where-clause bound
- // to one GAT, it might then require us to an additional bound on another GAT.
- // In our `IntoIter` example, we discover a missing `Self: 'a` bound on `Iter<'a>`, which
- // then in a second loop adds a `Self: 'a` bound to `Item` due to the relationship between
- // those GATs.
- loop {
- let mut should_continue = false;
- for gat_item in associated_items {
- let gat_def_id = gat_item.id.def_id;
- let gat_item = tcx.associated_item(gat_def_id);
- // If this item is not an assoc ty, or has no substs, then it's not a GAT
- if gat_item.kind != ty::AssocKind::Type {
- continue;
- }
- let gat_generics = tcx.generics_of(gat_def_id);
- // FIXME(jackh726): we can also warn in the more general case
- if gat_generics.params.is_empty() {
- continue;
- }
-
- // Gather the bounds with which all other items inside of this trait constrain the GAT.
- // This is calculated by taking the intersection of the bounds that each item
- // constrains the GAT with individually.
- let mut new_required_bounds: Option<FxHashSet<ty::Predicate<'_>>> = None;
- for item in associated_items {
- let item_def_id = item.id.def_id;
- // Skip our own GAT, since it does not constrain itself at all.
- if item_def_id == gat_def_id {
- continue;
- }
-
- let item_hir_id = item.id.hir_id();
- let param_env = tcx.param_env(item_def_id);
-
- let item_required_bounds = match item.kind {
- // In our example, this corresponds to `into_iter` method
- hir::AssocItemKind::Fn { .. } => {
- // For methods, we check the function signature's return type for any GATs
- // to constrain. In the `into_iter` case, we see that the return type
- // `Self::Iter<'a>` is a GAT we want to gather any potential missing bounds from.
- let sig: ty::FnSig<'_> = tcx.liberate_late_bound_regions(
- item_def_id.to_def_id(),
- tcx.fn_sig(item_def_id),
- );
- gather_gat_bounds(
- tcx,
- param_env,
- item_hir_id,
- sig.inputs_and_output,
- // We also assume that all of the function signature's parameter types
- // are well formed.
- &sig.inputs().iter().copied().collect(),
- gat_def_id,
- gat_generics,
- )
- }
- // In our example, this corresponds to the `Iter` and `Item` associated types
- hir::AssocItemKind::Type => {
- // If our associated item is a GAT with missing bounds, add them to
- // the param-env here. This allows this GAT to propagate missing bounds
- // to other GATs.
- let param_env = augment_param_env(
- tcx,
- param_env,
- required_bounds_by_item.get(&item_def_id),
- );
- gather_gat_bounds(
- tcx,
- param_env,
- item_hir_id,
- tcx.explicit_item_bounds(item_def_id)
- .iter()
- .copied()
- .collect::<Vec<_>>(),
- &FxHashSet::default(),
- gat_def_id,
- gat_generics,
- )
- }
- hir::AssocItemKind::Const => None,
- };
-
- if let Some(item_required_bounds) = item_required_bounds {
- // Take the intersection of the required bounds for this GAT, and
- // the item_required_bounds which are the ones implied by just
- // this item alone.
- // This is why we use an Option<_>, since we need to distinguish
- // the empty set of bounds from the _uninitialized_ set of 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)) {
- // Iterate until our required_bounds no longer change
- // Since they changed here, we should continue the loop
- should_continue = true;
- }
- }
- }
- // We know that this loop will eventually halt, since we only set `should_continue` if the
- // `required_bounds` for this item grows. Since we are not creating any new region or type
- // variables, the set of all region and type bounds that we could ever insert are limited
- // by the number of unique types and regions we observe in a given item.
- 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);
- debug!(?required_bounds);
- let param_env = tcx.param_env(gat_def_id);
- let gat_hir = gat_item_hir.hir_id();
-
- let mut unsatisfied_bounds: Vec<_> = required_bounds
- .into_iter()
- .filter(|clause| match clause.kind().skip_binder() {
- ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => {
- !region_known_to_outlive(tcx, gat_hir, param_env, &FxHashSet::default(), a, b)
- }
- ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
- !ty_known_to_outlive(tcx, gat_hir, param_env, &FxHashSet::default(), a, b)
- }
- _ => bug!("Unexpected PredicateKind"),
- })
- .map(|clause| clause.to_string())
- .collect();
-
- // We sort so that order is predictable
- 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!(
- "{} currently required to ensure that impls have maximum flexibility",
- bound
- ));
- err.note(
- "we are soliciting feedback, see issue #87479 \
- <https://github.com/rust-lang/rust/issues/87479> \
- for more information",
- );
-
- err.emit();
- }
- }
-}
-
-/// Add a new set of predicates to the caller_bounds of an existing param_env.
-fn augment_param_env<'tcx>(
- tcx: TyCtxt<'tcx>,
- param_env: ty::ParamEnv<'tcx>,
- new_predicates: Option<&FxHashSet<ty::Predicate<'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_predicates(param_env.caller_bounds().iter().chain(new_predicates.iter().cloned()));
- // FIXME(compiler-errors): Perhaps there is a case where we need to normalize this
- // i.e. traits::normalize_param_env_or_error
- ty::ParamEnv::new(bounds, param_env.reveal(), param_env.constness())
-}
-
-/// We use the following trait as an example throughout this function.
-/// Specifically, let's assume that `to_check` here is the return type
-/// of `into_iter`, and the GAT we are checking this for is `Iter`.
-/// ```rust,ignore (this code fails due to this lint)
-/// trait IntoIter {
-/// type Iter<'a>: Iterator<Item = Self::Item<'a>>;
-/// type Item<'a>;
-/// fn into_iter<'a>(&'a self) -> Self::Iter<'a>;
-/// }
-/// ```
-fn gather_gat_bounds<'tcx, T: TypeFoldable<'tcx>>(
- tcx: TyCtxt<'tcx>,
- param_env: ty::ParamEnv<'tcx>,
- item_hir: hir::HirId,
- to_check: T,
- wf_tys: &FxHashSet<Ty<'tcx>>,
- gat_def_id: LocalDefId,
- gat_generics: &'tcx ty::Generics,
-) -> Option<FxHashSet<ty::Predicate<'tcx>>> {
- // The bounds we that we would require from `to_check`
- let mut bounds = FxHashSet::default();
-
- let (regions, types) = GATSubstCollector::visit(gat_def_id.to_def_id(), to_check);
-
- // If both regions and types are empty, then this GAT isn't in the
- // set of types we are checking, and we shouldn't try to do clause analysis
- // (particularly, doing so would end up with an empty set of clauses,
- // since the current method would require none, and we take the
- // intersection of requirements of all methods)
- if types.is_empty() && regions.is_empty() {
- return None;
- }
-
- for (region_a, region_a_idx) in ®ions {
- // Ignore `'static` lifetimes for the purpose of this lint: it's
- // because we know it outlives everything and so doesn't give meaningful
- // clues
- if let ty::ReStatic = **region_a {
- continue;
- }
- // For each region argument (e.g., `'a` in our example), check for a
- // relationship to the type arguments (e.g., `Self`). If there is an
- // outlives relationship (`Self: 'a`), then we want to ensure that is
- // reflected in a where clause on the GAT itself.
- for (ty, ty_idx) in &types {
- // In our example, requires that `Self: 'a`
- if ty_known_to_outlive(tcx, item_hir, param_env, &wf_tys, *ty, *region_a) {
- debug!(?ty_idx, ?region_a_idx);
- debug!("required clause: {ty} must outlive {region_a}");
- // Translate into the generic parameters of the GAT. In
- // our example, the type was `Self`, which will also be
- // `Self` in the GAT.
- let ty_param = gat_generics.param_at(*ty_idx, tcx);
- let ty_param = tcx
- .mk_ty(ty::Param(ty::ParamTy { index: ty_param.index, name: ty_param.name }));
- // Same for the region. In our example, 'a corresponds
- // to the 'me parameter.
- let region_param = gat_generics.param_at(*region_a_idx, tcx);
- let region_param =
- tcx.mk_region(ty::RegionKind::ReEarlyBound(ty::EarlyBoundRegion {
- def_id: region_param.def_id,
- index: region_param.index,
- name: region_param.name,
- }));
- // The predicate we expect to see. (In our example,
- // `Self: 'me`.)
- let clause =
- ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty_param, region_param));
- let clause = tcx.mk_predicate(ty::Binder::dummy(clause));
- bounds.insert(clause);
- }
- }
-
- // For each region argument (e.g., `'a` in our example), also check for a
- // relationship to the other region arguments. If there is an outlives
- // relationship, then we want to ensure that is reflected in the where clause
- // on the GAT itself.
- for (region_b, region_b_idx) in ®ions {
- // Again, skip `'static` because it outlives everything. Also, we trivially
- // know that a region outlives itself.
- if ty::ReStatic == **region_b || region_a == region_b {
- continue;
- }
- if region_known_to_outlive(tcx, item_hir, param_env, &wf_tys, *region_a, *region_b) {
- debug!(?region_a_idx, ?region_b_idx);
- debug!("required clause: {region_a} must outlive {region_b}");
- // Translate into the generic parameters of the GAT.
- let region_a_param = gat_generics.param_at(*region_a_idx, tcx);
- let region_a_param =
- tcx.mk_region(ty::RegionKind::ReEarlyBound(ty::EarlyBoundRegion {
- def_id: region_a_param.def_id,
- index: region_a_param.index,
- name: region_a_param.name,
- }));
- // Same for the region.
- let region_b_param = gat_generics.param_at(*region_b_idx, tcx);
- let region_b_param =
- tcx.mk_region(ty::RegionKind::ReEarlyBound(ty::EarlyBoundRegion {
- def_id: region_b_param.def_id,
- index: region_b_param.index,
- name: region_b_param.name,
- }));
- // The predicate we expect to see.
- let clause = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(
- region_a_param,
- region_b_param,
- ));
- let clause = tcx.mk_predicate(ty::Binder::dummy(clause));
- bounds.insert(clause);
- }
- }
- }
-
- Some(bounds)
-}
-
-/// Given a known `param_env` and a set of well formed types, can we prove that
-/// `ty` outlives `region`.
-fn ty_known_to_outlive<'tcx>(
- tcx: TyCtxt<'tcx>,
- id: hir::HirId,
- param_env: ty::ParamEnv<'tcx>,
- wf_tys: &FxHashSet<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);
- })
-}
-
-/// Given a known `param_env` and a set of well formed types, can we prove that
-/// `region_a` outlives `region_b`
-fn region_known_to_outlive<'tcx>(
- tcx: TyCtxt<'tcx>,
- id: hir::HirId,
- param_env: ty::ParamEnv<'tcx>,
- wf_tys: &FxHashSet<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);
- // `region_a: region_b` -> `region_b <= region_a`
- infcx.push_sub_region_constraint(
- origin,
- region_b,
- region_a,
- ConstraintCategory::BoringNoLocation,
- );
- })
-}
-
-/// Given a known `param_env` and a set of well formed types, set up an
-/// `InferCtxt`, call the passed function (to e.g. set up region constraints
-/// to be tested), then resolve region and return errors
-fn resolve_regions_with_wf_tys<'tcx>(
- tcx: TyCtxt<'tcx>,
- id: hir::HirId,
- param_env: ty::ParamEnv<'tcx>,
- wf_tys: &FxHashSet<Ty<'tcx>>,
- add_constraints: impl for<'a> FnOnce(&'a InferCtxt<'a, 'tcx>, &'a RegionBoundPairs<'tcx>),
-) -> bool {
- // Unfortunately, we have to use a new `InferCtxt` each call, because
- // region constraints get added and solved there and we need to test each
- // call individually.
- tcx.infer_ctxt().enter(|infcx| {
- let outlives_environment = OutlivesEnvironment::with_bounds(
- param_env,
- Some(&infcx),
- 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");
-
- // If we were able to prove that the type outlives the region without
- // an error, it must be because of the implied or explicit bounds...
- errors.is_empty()
- })
-}
-
-/// TypeVisitor that looks for uses of GATs like
-/// `<P0 as Trait<P1..Pn>>::GAT<Pn..Pm>` and adds the arguments `P0..Pm` into
-/// the two vectors, `regions` and `types` (depending on their kind). For each
-/// parameter `Pi` also track the index `i`.
-struct GATSubstCollector<'tcx> {
- gat: DefId,
- // Which region appears and which parameter index its substituted for
- regions: FxHashSet<(ty::Region<'tcx>, usize)>,
- // Which params appears and which parameter index its substituted for
- types: FxHashSet<(Ty<'tcx>, usize)>,
-}
-
-impl<'tcx> GATSubstCollector<'tcx> {
- fn visit<T: TypeFoldable<'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<'tcx> for GATSubstCollector<'tcx> {
- type BreakTy = !;
-
- fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
- match t.kind() {
- ty::Projection(p) if p.item_def_id == self.gat => {
- for (idx, subst) in p.substs.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,
- }
-}
-
-/// Detect when an object unsafe trait is referring to itself in one of its associated items.
-/// When this is done, suggest using `Self` instead.
-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())) {
- hir::Node::Item(item) => match item.kind {
- hir::ItemKind::Trait(..) => (item.ident, item.def_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, 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, ty) {
- trait_should_be_self.push(ty.span);
- }
- }
- match sig.decl.output {
- hir::FnRetTy::Return(ty) if could_be_self(trait_def_id, ty) => {
- trait_should_be_self.push(ty.span);
- }
- _ => {}
- }
- }
- _ => {}
- }
- if !trait_should_be_self.is_empty() {
- if tcx.object_safety_violations(trait_def_id).is_empty() {
- 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 def_id = impl_item.def_id;
-
- let (method_sig, span) = match impl_item.kind {
- hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span),
- // Constrain binding and overflow error spans to `<Ty>` in `type foo = <Ty>`.
- hir::ImplItemKind::TyAlias(ty) if ty.span != DUMMY_SP => (None, ty.span),
- _ => (None, impl_item.span),
- };
-
- check_associated_item(tcx, def_id, span, method_sig);
-}
-
-fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
- match param.kind {
- // We currently only check wf of const params here.
- hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. } => (),
-
- // Const parameters are well formed if their type is structural match.
- hir::GenericParamKind::Const { ty: hir_ty, default: _ } => {
- let ty = tcx.type_of(tcx.hir().local_def_id(param.hir_id));
-
- if tcx.features().adt_const_params {
- if let Some(non_structural_match_ty) =
- traits::search_for_adt_const_param_violation(param.span, tcx, ty)
- {
- // We use the same error code in both branches, because this is really the same
- // issue: we just special-case the message for type parameters to make it
- // clearer.
- match non_structural_match_ty.kind() {
- ty::Param(_) => {
- // Const parameters may not have type parameters as their types,
- // because we cannot be sure that the type parameter derives `PartialEq`
- // and `Eq` (just implementing them is not enough for `structural_match`).
- struct_span_err!(
- tcx.sess,
- hir_ty.span,
- E0741,
- "`{ty}` is not guaranteed to `#[derive(PartialEq, Eq)]`, so may not be \
- used as the type of a const parameter",
- )
- .span_label(
- hir_ty.span,
- format!("`{ty}` may not derive both `PartialEq` and `Eq`"),
- )
- .note(
- "it is not currently possible to use a type parameter as the type of a \
- const parameter",
- )
- .emit();
- }
- ty::Float(_) => {
- struct_span_err!(
- tcx.sess,
- hir_ty.span,
- E0741,
- "`{ty}` is forbidden as the type of a const generic parameter",
- )
- .note("floats do not derive `Eq` or `Ord`, which are required for const parameters")
- .emit();
- }
- ty::FnPtr(_) => {
- struct_span_err!(
- tcx.sess,
- hir_ty.span,
- E0741,
- "using function pointers as const generic parameters is forbidden",
- )
- .emit();
- }
- ty::RawPtr(_) => {
- struct_span_err!(
- tcx.sess,
- hir_ty.span,
- E0741,
- "using raw pointers as const generic parameters is forbidden",
- )
- .emit();
- }
- _ => {
- let mut diag = struct_span_err!(
- tcx.sess,
- hir_ty.span,
- E0741,
- "`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \
- the type of a const parameter",
- non_structural_match_ty,
- );
-
- if ty == non_structural_match_ty {
- diag.span_label(
- hir_ty.span,
- format!("`{ty}` doesn't derive both `PartialEq` and `Eq`"),
- );
- }
-
- diag.emit();
- }
- }
- }
- } else {
- let err_ty_str;
- let mut is_ptr = true;
-
- let err = match ty.kind() {
- ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Error(_) => None,
- ty::FnPtr(_) => Some("function pointers"),
- ty::RawPtr(_) => Some("raw pointers"),
- _ => {
- is_ptr = false;
- err_ty_str = format!("`{ty}`");
- Some(err_ty_str.as_str())
- }
- };
-
- if let Some(unsupported_type) = err {
- if is_ptr {
- tcx.sess.span_err(
- hir_ty.span,
- &format!(
- "using {unsupported_type} as const generic parameters is forbidden",
- ),
- );
- } else {
- let mut err = tcx.sess.struct_span_err(
- hir_ty.span,
- &format!(
- "{unsupported_type} is forbidden as the type of a const generic parameter",
- ),
- );
- err.note("the only supported types are integers, `bool` and `char`");
- if tcx.sess.is_nightly_build() {
- err.help(
- "more complex types are supported with `#![feature(adt_const_params)]`",
- );
- }
- err.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)),
- };
-
- match item.kind {
- ty::AssocKind::Const => {
- let ty = tcx.type_of(item.def_id);
- 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);
- 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);
- 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,
- }
-}
-
-/// In a type definition, we check that to ensure that the types of the fields are well-formed.
-fn check_type_defn<'tcx, F>(
- tcx: TyCtxt<'tcx>,
- item: &hir::Item<'tcx>,
- all_sized: bool,
- mut lookup_fields: F,
-) where
- F: FnMut(&WfCheckingCtxt<'_, 'tcx>) -> Vec<AdtVariant<'tcx>>,
-{
- enter_wf_checking_ctxt(tcx, item.span, item.def_id, |wfcx| {
- let variants = lookup_fields(wfcx);
- let packed = tcx.adt_def(item.def_id).repr().packed();
-
- for variant in &variants {
- // All field types must be well-formed.
- for field in &variant.fields {
- wfcx.register_wf_obligation(
- field.span,
- Some(WellFormedLoc::Ty(field.def_id)),
- field.ty.into(),
- )
- }
-
- // For DST, or when drop needs to copy things around, all
- // intermediate types must be sized.
- let needs_drop_copy = || {
- packed && {
- let ty = variant.fields.last().unwrap().ty;
- let ty = tcx.erase_regions(ty);
- if ty.needs_infer() {
- tcx.sess
- .delay_span_bug(item.span, &format!("inference variables in {:?}", ty));
- // Just treat unresolved type expression as if it needs drop.
- true
- } else {
- ty.needs_drop(tcx, tcx.param_env(item.def_id))
- }
- }
- };
- // All fields (except for possibly the last) should be sized.
- 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[..variant.fields.len() - unsized_len].iter().enumerate()
- {
- let last = idx == variant.fields.len() - 1;
- wfcx.register_bound(
- traits::ObligationCause::new(
- field.span,
- wfcx.body_id,
- traits::FieldSized {
- adt_kind: match item_adt_kind(&item.kind) {
- Some(i) => i,
- None => bug!(),
- },
- span: field.span,
- last,
- },
- ),
- wfcx.param_env,
- field.ty,
- tcx.require_lang_item(LangItem::Sized, None),
- );
- }
-
- // Explicit `enum` discriminant values must const-evaluate successfully.
- if let Some(discr_def_id) = variant.explicit_discr {
- let discr_substs = InternalSubsts::identity_for_item(tcx, discr_def_id.to_def_id());
-
- let cause = traits::ObligationCause::new(
- tcx.def_span(discr_def_id),
- wfcx.body_id,
- traits::MiscObligation,
- );
- wfcx.register_obligation(traits::Obligation::new(
- cause,
- wfcx.param_env,
- ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ty::Unevaluated::new(
- ty::WithOptConstParam::unknown(discr_def_id.to_def_id()),
- discr_substs,
- )))
- .to_predicate(tcx),
- ));
- }
- }
-
- check_where_clauses(wfcx, item.span, item.def_id);
- });
-}
-
-#[instrument(skip(tcx, item))]
-fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) {
- debug!(?item.def_id);
-
- let trait_def = tcx.trait_def(item.def_id);
- if trait_def.is_marker
- || matches!(trait_def.specialization_kind, TraitSpecializationKind::Marker)
- {
- for associated_def_id in &*tcx.associated_item_def_ids(item.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, item.def_id, |wfcx| {
- check_where_clauses(wfcx, item.span, item.def_id)
- });
-
- // Only check traits, don't check trait aliases
- if let hir::ItemKind::Trait(_, _, _, _, items) = item.kind {
- check_gat_where_clauses(tcx, items);
- }
-}
-
-/// Checks all associated type defaults of trait `trait_def_id`.
-///
-/// Assuming the defaults are used, check that all predicates (bounds on the
-/// assoc type and where clauses on the trait) hold.
-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.iter().flat_map(|&(bound, bound_span)| {
- let normalized_bound = wfcx.normalize(span, None, bound);
- traits::wf::predicate_obligations(
- wfcx.infcx,
- wfcx.param_env,
- wfcx.body_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);
- check_fn_or_method(wfcx, ident.span, sig, decl, def_id);
- })
-}
-
-fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_foreign_ty: bool) {
- debug!("check_item_type: {:?}", item_id);
-
- enter_wf_checking_ctxt(tcx, ty_span, item_id, |wfcx| {
- let ty = tcx.type_of(item_id);
- let item_ty = wfcx.normalize(ty_span, Some(WellFormedLoc::Ty(item_id)), ty);
-
- let mut forbid_unsized = true;
- if allow_foreign_ty {
- let tail = tcx.struct_tail_erasing_lifetimes(item_ty, wfcx.param_env);
- if let ty::Foreign(_) = tail.kind() {
- forbid_unsized = false;
- }
- }
-
- 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_id, traits::WellFormed(None)),
- wfcx.param_env,
- item_ty,
- tcx.require_lang_item(LangItem::Sized, None),
- );
- }
-
- // Ensure that the end result is `Sync` in a non-thread local `static`.
- 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_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<'_>>,
- constness: hir::Constness,
-) {
- enter_wf_checking_ctxt(tcx, item.span, item.def_id, |wfcx| {
- match *ast_trait_ref {
- Some(ref ast_trait_ref) => {
- // `#[rustc_reservation_impl]` impls are not real impls and
- // therefore don't need to be WF (the trait's `Self: Trait` predicate
- // won't hold).
- let trait_ref = tcx.impl_trait_ref(item.def_id).unwrap();
- let trait_ref = wfcx.normalize(ast_trait_ref.path.span, None, trait_ref);
- let trait_pred = ty::TraitPredicate {
- trait_ref,
- constness: match constness {
- hir::Constness::Const => ty::BoundConstness::ConstIfConst,
- hir::Constness::NotConst => ty::BoundConstness::NotConst,
- },
- polarity: ty::ImplPolarity::Positive,
- };
- let obligations = traits::wf::trait_obligations(
- wfcx.infcx,
- wfcx.param_env,
- wfcx.body_id,
- &trait_pred,
- ast_trait_ref.path.span,
- item,
- );
- debug!(?obligations);
- wfcx.register_obligations(obligations);
- }
- None => {
- let self_ty = tcx.type_of(item.def_id);
- let self_ty = wfcx.normalize(
- item.span,
- Some(WellFormedLoc::Ty(item.hir_id().expect_owner())),
- self_ty,
- );
- wfcx.register_wf_obligation(
- ast_self_ty.span,
- Some(WellFormedLoc::Ty(item.hir_id().expect_owner())),
- self_ty.into(),
- );
- }
- }
-
- check_where_clauses(wfcx, item.span, item.def_id);
- });
-}
-
-/// Checks where-clauses and inline bounds that are declared on `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.bound_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!(),
- };
-
- // Check that concrete defaults are well-formed. See test `type-check-defaults.rs`.
- // For example, this forbids the declaration:
- //
- // struct Foo<T = Vec<[u32]>> { .. }
- //
- // Here, the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold.
- for param in &generics.params {
- match param.kind {
- GenericParamDefKind::Type { .. } => {
- if is_our_default(param) {
- let ty = tcx.type_of(param.def_id);
- // Ignore dependent defaults -- that is, where the default of one type
- // parameter includes another (e.g., `<T, U = T>`). In those cases, we can't
- // be sure if it will error or not as user might always specify the other.
- if !ty.needs_subst() {
- 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) {
- // FIXME(const_generics_defaults): This
- // is incorrect when dealing with unused substs, for example
- // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>`
- // we should eagerly error.
- let default_ct = tcx.const_param_default(param.def_id);
- if !default_ct.needs_subst() {
- wfcx.register_wf_obligation(
- tcx.def_span(param.def_id),
- None,
- default_ct.into(),
- );
- }
- }
- }
- // Doesn't have defaults.
- GenericParamDefKind::Lifetime => {}
- }
- }
-
- // Check that trait predicates are WF when params are substituted by their defaults.
- // We don't want to overly constrain the predicates that may be written but we want to
- // catch cases where a default my never be applied such as `struct Foo<T: Copy = String>`.
- // Therefore we check if a predicate which contains a single type param
- // with a concrete default is WF with that default substituted.
- // For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`.
- //
- // First we build the defaulted substitution.
- let substs = InternalSubsts::for_item(tcx, def_id.to_def_id(), |param, _| {
- match param.kind {
- GenericParamDefKind::Lifetime => {
- // All regions are identity.
- tcx.mk_param_from_def(param)
- }
-
- GenericParamDefKind::Type { .. } => {
- // If the param has a default, ...
- if is_our_default(param) {
- let default_ty = tcx.type_of(param.def_id);
- // ... and it's not a dependent default, ...
- if !default_ty.needs_subst() {
- // ... then substitute it with the default.
- return default_ty.into();
- }
- }
-
- tcx.mk_param_from_def(param)
- }
- GenericParamDefKind::Const { .. } => {
- // If the param has a default, ...
- if is_our_default(param) {
- let default_ct = tcx.const_param_default(param.def_id);
- // ... and it's not a dependent default, ...
- if !default_ct.needs_subst() {
- // ... then substitute it with the default.
- return default_ct.into();
- }
- }
-
- tcx.mk_param_from_def(param)
- }
- }
- });
-
- // Now we build the substituted predicates.
- let default_obligations = predicates
- .0
- .predicates
- .iter()
- .flat_map(|&(pred, sp)| {
- #[derive(Default)]
- struct CountParams {
- params: FxHashSet<u32>,
- }
- impl<'tcx> ty::visit::TypeVisitor<'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 = predicates.rebind(pred).subst(tcx, substs);
- // Don't check non-defaulted params, dependent defaults (including lifetimes)
- // or preds with multiple params.
- if substituted_pred.has_param_types_or_consts()
- || param_count.params.len() > 1
- || has_region
- {
- None
- } else if predicates.0.predicates.iter().any(|&(p, _)| p == substituted_pred) {
- // Avoid duplication of predicates that contain no parameters, for example.
- None
- } else {
- Some((substituted_pred, sp))
- }
- })
- .map(|(pred, sp)| {
- // Convert each of those into an obligation. So if you have
- // something like `struct Foo<T: Copy = String>`, we would
- // take that predicate `T: Copy`, substitute to `String: Copy`
- // (actually that happens in the previous `flat_map` call),
- // and then try to prove it (in this case, we'll fail).
- //
- // Note the subtle difference from how we handle `predicates`
- // below: there, we are not trying to prove those predicates
- // to be *true* but merely *well-formed*.
- let pred = wfcx.normalize(sp, None, pred);
- let cause = traits::ObligationCause::new(
- sp,
- wfcx.body_id,
- traits::ItemObligation(def_id.to_def_id()),
- );
- traits::Obligation::new(cause, wfcx.param_env, pred)
- });
-
- let predicates = predicates.0.instantiate_identity(tcx);
-
- let predicates = wfcx.normalize(span, None, predicates);
-
- debug!(?predicates.predicates);
- assert_eq!(predicates.predicates.len(), predicates.spans.len());
- let wf_obligations =
- iter::zip(&predicates.predicates, &predicates.spans).flat_map(|(&p, &sp)| {
- traits::wf::predicate_obligations(
- infcx,
- wfcx.param_env.without_const(),
- wfcx.body_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 sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
-
- // Normalize the input and output types one at a time, using a different
- // `WellFormedLoc` for each. We cannot call `normalize_associated_types`
- // on the entire `FnSig`, since this would use the same `WellFormedLoc`
- // for each type, preventing the HIR wf check from generating
- // a nice error message.
- let ty::FnSig { mut inputs_and_output, c_variadic, unsafety, abi } = sig;
- inputs_and_output = tcx.mk_type_list(inputs_and_output.iter().enumerate().map(|(i, ty)| {
- wfcx.normalize(
- span,
- Some(WellFormedLoc::Param {
- function: def_id,
- // Note that the `param_idx` of the output type is
- // one greater than the index of the last input type.
- param_idx: i.try_into().unwrap(),
- }),
- ty,
- )
- }));
- // Manually call `normalize_associated_types_in` on the other types
- // in `FnSig`. This ensures that if the types of these fields
- // ever change to include projections, we will start normalizing
- // them automatically.
- let sig = ty::FnSig {
- inputs_and_output,
- c_variadic: wfcx.normalize(span, None, c_variadic),
- unsafety: wfcx.normalize(span, None, unsafety),
- abi: wfcx.normalize(span, None, abi),
- };
-
- for (i, (&input_ty, ty)) in iter::zip(sig.inputs(), hir_decl.inputs).enumerate() {
- wfcx.register_wf_obligation(
- ty.span,
- Some(WellFormedLoc::Param { function: def_id, param_idx: i.try_into().unwrap() }),
- input_ty.into(),
- );
- }
-
- wfcx.register_wf_obligation(
- hir_decl.output.span(),
- Some(WellFormedLoc::Param {
- function: def_id,
- param_idx: sig.inputs().len().try_into().unwrap(),
- }),
- sig.output().into(),
- );
-
- check_where_clauses(wfcx, span, def_id);
-
- check_return_position_impl_trait_in_trait_bounds(
- tcx,
- wfcx,
- def_id,
- sig.output(),
- hir_decl.output.span(),
- );
-}
-
-/// Basically `check_associated_type_bounds`, but separated for now and should be
-/// deduplicated when RPITITs get lowered into real associated items.
-fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
- tcx: TyCtxt<'tcx>,
- wfcx: &WfCheckingCtxt<'_, 'tcx>,
- fn_def_id: LocalDefId,
- fn_output: Ty<'tcx>,
- span: Span,
-) {
- if let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id())
- && assoc_item.container == ty::AssocItemContainer::TraitContainer
- {
- for arg in fn_output.walk() {
- if let ty::GenericArgKind::Type(ty) = arg.unpack()
- && let ty::Projection(proj) = ty.kind()
- && tcx.def_kind(proj.item_def_id) == DefKind::ImplTraitPlaceholder
- && tcx.impl_trait_in_trait_parent(proj.item_def_id) == fn_def_id.to_def_id()
- {
- let bounds = wfcx.tcx().explicit_item_bounds(proj.item_def_id);
- let wf_obligations = bounds.iter().flat_map(|&(bound, bound_span)| {
- let normalized_bound = wfcx.normalize(span, None, bound);
- traits::wf::predicate_obligations(
- wfcx.infcx,
- wfcx.param_env,
- wfcx.body_id,
- normalized_bound,
- bound_span,
- )
- });
- wfcx.register_obligations(wf_obligations);
- }
- }
- }
-}
-
-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);
- 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) {
- // Report error; `arbitrary_self_types` was enabled.
- 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) {
- // Report error; would have worked with `arbitrary_self_types`.
- 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 {
- // Report error; would not have worked with `arbitrary_self_types`.
- e0307(tcx, span, receiver_ty);
- }
- }
- }
-}
-
-fn e0307<'tcx>(tcx: TyCtxt<'tcx>, 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();
-}
-
-/// Returns whether `receiver_ty` would be considered a valid receiver type for `self_ty`. If
-/// `arbitrary_self_types` is enabled, `receiver_ty` must transitively deref to `self_ty`, possibly
-/// through a `*const/mut T` raw pointer. If the feature is not enabled, the requirements are more
-/// strict: `receiver_ty` must implement `Receiver` and directly implement
-/// `Deref<Target = self_ty>`.
-///
-/// N.B., there are cases this function returns `true` but causes an error to be emitted,
-/// particularly when `receiver_ty` derefs to a type that is the same as `self_ty` but has the
-/// wrong lifetime. Be careful of this if you are calling this function speculatively.
-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_id, traits::ObligationCauseCode::MethodReceiver);
-
- let can_eq_self = |ty| infcx.can_eq(wfcx.param_env, self_ty, ty).is_ok();
-
- // `self: Self` is always valid.
- if can_eq_self(receiver_ty) {
- if let Err(err) = wfcx.equate_types(&cause, wfcx.param_env, self_ty, receiver_ty) {
- infcx.report_mismatched_types(&cause, self_ty, receiver_ty, err).emit();
- }
- return true;
- }
-
- let mut autoderef =
- Autoderef::new(infcx, wfcx.param_env, wfcx.body_id, span, receiver_ty, span);
-
- // The `arbitrary_self_types` feature allows raw pointer receivers like `self: *const Self`.
- if arbitrary_self_types_enabled {
- autoderef = autoderef.include_raw_pointers();
- }
-
- // The first type is `receiver_ty`, which we know its not equal to `self_ty`; skip it.
- autoderef.next();
-
- let receiver_trait_def_id = tcx.require_lang_item(LangItem::Receiver, None);
-
- // Keep dereferencing `receiver_ty` until we get to `self_ty`.
- 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.equate_types(&cause, wfcx.param_env, self_ty, potential_self_ty)
- {
- infcx.report_mismatched_types(&cause, self_ty, potential_self_ty, err).emit();
- }
-
- break;
- } else {
- // Without `feature(arbitrary_self_types)`, we require that each step in the
- // deref chain implement `receiver`
- 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);
- // If the receiver already has errors reported due to it, consider it valid to avoid
- // unnecessary errors (#58712).
- return receiver_ty.references_error();
- }
- }
-
- // Without `feature(arbitrary_self_types)`, we require that `receiver_ty` implements `Receiver`.
- 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::Binder::dummy(ty::TraitRef {
- def_id: receiver_trait_def_id,
- substs: tcx.mk_substs_trait(receiver_ty, &[]),
- });
-
- let obligation =
- traits::Obligation::new(cause, wfcx.param_env, trait_ref.without_const().to_predicate(tcx));
-
- 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 ty = tcx.type_of(item.def_id);
- if tcx.has_error_field(ty) {
- return;
- }
-
- let ty_predicates = tcx.predicates_of(item.def_id);
- assert_eq!(ty_predicates.parent, None);
- let variances = tcx.variances_of(item.def_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);
-
- // Lazily calculated because it is only needed in case of an error.
- let explicitly_bounded_params = LazyCell::new(|| {
- let icx = crate::collect::ItemCtxt::new(tcx, item.def_id.to_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<_>>()
- });
-
- for (index, _) in variances.iter().enumerate() {
- let parameter = Parameter(index as u32);
-
- if constrained_parameters.contains(¶meter) {
- continue;
- }
-
- let param = &hir_generics.params[index];
-
- match param.name {
- hir::ParamName::Error => {}
- _ => {
- let has_explicit_bounds = explicitly_bounded_params.contains(¶meter);
- report_bivariance(tcx, 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();
- // Help is available only in presence of lang items.
- 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 `{0}` to be a const parameter, use `const {0}: usize` instead",
- param_name
- ));
- }
- err.emit()
-}
-
-impl<'tcx> WfCheckingCtxt<'_, 'tcx> {
- /// Feature gates RFC 2056 -- trivial bounds, checking for global bounds that
- /// aren't true.
- #[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 def_id = tcx.hir().local_def_id(self.body_id);
- let predicates_with_span = tcx.predicates_of(def_id).predicates.iter().copied();
- // Check elaborated bounds.
- let implied_obligations = traits::elaborate_predicates_with_span(tcx, predicates_with_span);
-
- for obligation in implied_obligations {
- // We lower empty bounds like `Vec<dyn Copy>:` as
- // `WellFormed(Vec<dyn Copy>)`, which will later get checked by
- // regular WF checking
- if let ty::PredicateKind::WellFormed(..) = obligation.predicate.kind().skip_binder() {
- continue;
- }
- let pred = obligation.predicate;
- // Match the existing behavior.
- if pred.is_global() && !pred.has_late_bound_regions() {
- let pred = self.normalize(span, None, pred);
- let hir_node = tcx.hir().find(self.body_id);
-
- // only use the span of the predicate clause (#90869)
-
- if let Some(hir::Generics { predicates, .. }) =
- hir_node.and_then(|node| node.generics())
- {
- let obligation_span = obligation.cause.span();
-
- span = predicates
- .iter()
- // There seems to be no better way to find out which predicate we are in
- .find(|pred| pred.span().contains(obligation_span))
- .map(|pred| pred.span())
- .unwrap_or(obligation_span);
- }
-
- let obligation = traits::Obligation::new(
- traits::ObligationCause::new(span, self.body_id, traits::TrivialBound),
- empty_env,
- pred,
- );
- self.ocx.register_obligation(obligation);
- }
- }
- }
-}
-
-fn check_mod_type_wf(tcx: TyCtxt<'_>, module: LocalDefId) {
- let items = tcx.hir_module_items(module);
- items.par_items(|item| tcx.ensure().check_well_formed(item.def_id));
- items.par_impl_items(|item| tcx.ensure().check_well_formed(item.def_id));
- items.par_trait_items(|item| tcx.ensure().check_well_formed(item.def_id));
- items.par_foreign_items(|item| tcx.ensure().check_well_formed(item.def_id));
-}
-
-///////////////////////////////////////////////////////////////////////////
-// ADT
-
-// FIXME(eddyb) replace this with getting fields/discriminants through `ty::AdtDef`.
-struct AdtVariant<'tcx> {
- /// Types of fields in the variant, that must be well-formed.
- fields: Vec<AdtField<'tcx>>,
-
- /// Explicit discriminant of this variant (e.g. `A = 123`),
- /// that must evaluate to a constant value.
- explicit_discr: Option<LocalDefId>,
-}
-
-struct AdtField<'tcx> {
- ty: Ty<'tcx>,
- def_id: LocalDefId,
- span: Span,
-}
-
-impl<'a, 'tcx> WfCheckingCtxt<'a, 'tcx> {
- // FIXME(eddyb) replace this with getting fields through `ty::AdtDef`.
- fn non_enum_variant(&self, struct_def: &hir::VariantData<'_>) -> AdtVariant<'tcx> {
- let fields = struct_def
- .fields()
- .iter()
- .map(|field| {
- let def_id = self.tcx().hir().local_def_id(field.hir_id);
- let field_ty = self.tcx().type_of(def_id);
- let field_ty = self.normalize(field.ty.span, None, field_ty);
- debug!("non_enum_variant: type of field {:?} is {:?}", field, field_ty);
- AdtField { ty: field_ty, span: field.ty.span, def_id }
- })
- .collect();
- AdtVariant { fields, explicit_discr: None }
- }
-
- fn enum_variants(&self, enum_def: &hir::EnumDef<'_>) -> Vec<AdtVariant<'tcx>> {
- enum_def
- .variants
- .iter()
- .map(|variant| AdtVariant {
- fields: self.non_enum_variant(&variant.data).fields,
- explicit_discr: variant
- .disr_expr
- .map(|explicit_discr| self.tcx().hir().local_def_id(explicit_discr.hir_id)),
- })
- .collect()
- }
-}
-
-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 };
-}
projects / rustc.git / blobdiff