| use crate::check::{Inherited, FnCtxt}; |
| use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter}; |
| |
| use crate::hir::def_id::DefId; |
| use rustc::traits::{self, ObligationCauseCode}; |
| use rustc::ty::{self, Ty, TyCtxt, GenericParamDefKind, TypeFoldable, ToPredicate}; |
| use rustc::ty::subst::{Subst, InternalSubsts}; |
| use rustc::util::nodemap::{FxHashSet, FxHashMap}; |
| use rustc::mir::interpret::ConstValue; |
| use rustc::middle::lang_items; |
| use rustc::infer::opaque_types::may_define_opaque_type; |
| |
| use syntax::ast; |
| use syntax::feature_gate::{self, GateIssue}; |
| use syntax_pos::Span; |
| use syntax::symbol::sym; |
| use errors::{DiagnosticBuilder, DiagnosticId}; |
| |
| use rustc::hir::itemlikevisit::ParItemLikeVisitor; |
| use rustc::hir; |
| |
| /// Helper type of a temporary returned by `.for_item(...)`. |
| /// This is necessary because we can't write the following bound: |
| /// |
| /// ```rust |
| /// F: for<'b, 'tcx> where 'tcx FnOnce(FnCtxt<'b, 'tcx>) |
| /// ``` |
| struct CheckWfFcxBuilder<'tcx> { |
| inherited: super::InheritedBuilder<'tcx>, |
| id: hir::HirId, |
| span: Span, |
| param_env: ty::ParamEnv<'tcx>, |
| } |
| |
| impl<'tcx> CheckWfFcxBuilder<'tcx> { |
| fn with_fcx<F>(&mut self, f: F) |
| where |
| F: for<'b> FnOnce(&FnCtxt<'b, 'tcx>, TyCtxt<'tcx>) -> Vec<Ty<'tcx>>, |
| { |
| let id = self.id; |
| let span = self.span; |
| let param_env = self.param_env; |
| self.inherited.enter(|inh| { |
| let fcx = FnCtxt::new(&inh, param_env, id); |
| if !inh.tcx.features().trivial_bounds { |
| // As predicates are cached rather than obligations, this |
| // needsto be called first so that they are checked with an |
| // empty `param_env`. |
| check_false_global_bounds(&fcx, span, id); |
| } |
| let wf_tys = f(&fcx, fcx.tcx.global_tcx()); |
| fcx.select_all_obligations_or_error(); |
| fcx.regionck_item(id, span, &wf_tys); |
| }); |
| } |
| } |
| |
| /// 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. |
| pub fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) { |
| let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| let item = tcx.hir().expect_item(hir_id); |
| |
| debug!("check_item_well_formed(it.hir_id={:?}, it.name={})", |
| item.hir_id, |
| tcx.def_path_str(def_id)); |
| |
| match item.node { |
| // 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(_, polarity, defaultness, _, ref trait_ref, ref self_ty, _) => { |
| let is_auto = tcx.impl_trait_ref(tcx.hir().local_def_id(item.hir_id)) |
| .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.def_id)); |
| if let (hir::Defaultness::Default { .. }, true) = (defaultness, is_auto) { |
| tcx.sess.span_err(item.span, "impls of auto traits cannot be default"); |
| } |
| if polarity == hir::ImplPolarity::Positive { |
| check_impl(tcx, item, self_ty, trait_ref); |
| } else { |
| // FIXME(#27579): what amount of WF checking do we need for neg impls? |
| if trait_ref.is_some() && !is_auto { |
| span_err!(tcx.sess, item.span, E0192, |
| "negative impls are only allowed for \ |
| auto traits (e.g., `Send` and `Sync`)") |
| } |
| } |
| } |
| hir::ItemKind::Fn(..) => { |
| check_item_fn(tcx, item); |
| } |
| hir::ItemKind::Static(ref ty, ..) => { |
| check_item_type(tcx, item.hir_id, ty.span, false); |
| } |
| hir::ItemKind::Const(ref ty, ..) => { |
| check_item_type(tcx, item.hir_id, ty.span, false); |
| } |
| hir::ItemKind::ForeignMod(ref module) => for it in module.items.iter() { |
| if let hir::ForeignItemKind::Static(ref ty, ..) = it.node { |
| check_item_type(tcx, it.hir_id, ty.span, true); |
| } |
| }, |
| hir::ItemKind::Struct(ref struct_def, ref ast_generics) => { |
| check_type_defn(tcx, item, false, |fcx| { |
| vec![fcx.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, |fcx| { |
| vec![fcx.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, |fcx| { |
| fcx.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); |
| } |
| _ => {} |
| } |
| } |
| |
| pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: DefId) { |
| let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| let trait_item = tcx.hir().expect_trait_item(hir_id); |
| |
| let method_sig = match trait_item.node { |
| hir::TraitItemKind::Method(ref sig, _) => Some(sig), |
| _ => None |
| }; |
| check_associated_item(tcx, trait_item.hir_id, trait_item.span, method_sig); |
| } |
| |
| pub fn check_impl_item(tcx: TyCtxt<'_>, def_id: DefId) { |
| let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| let impl_item = tcx.hir().expect_impl_item(hir_id); |
| |
| let method_sig = match impl_item.node { |
| hir::ImplItemKind::Method(ref sig, _) => Some(sig), |
| _ => None |
| }; |
| check_associated_item(tcx, impl_item.hir_id, impl_item.span, method_sig); |
| } |
| |
| fn check_associated_item( |
| tcx: TyCtxt<'_>, |
| item_id: hir::HirId, |
| span: Span, |
| sig_if_method: Option<&hir::MethodSig>, |
| ) { |
| debug!("check_associated_item: {:?}", item_id); |
| |
| let code = ObligationCauseCode::MiscObligation; |
| for_id(tcx, item_id, span).with_fcx(|fcx, tcx| { |
| let item = fcx.tcx.associated_item(fcx.tcx.hir().local_def_id(item_id)); |
| |
| let (mut implied_bounds, self_ty) = match item.container { |
| ty::TraitContainer(_) => (vec![], fcx.tcx.mk_self_type()), |
| ty::ImplContainer(def_id) => (fcx.impl_implied_bounds(def_id, span), |
| fcx.tcx.type_of(def_id)) |
| }; |
| |
| match item.kind { |
| ty::AssocKind::Const => { |
| let ty = fcx.tcx.type_of(item.def_id); |
| let ty = fcx.normalize_associated_types_in(span, &ty); |
| fcx.register_wf_obligation(ty, span, code.clone()); |
| } |
| ty::AssocKind::Method => { |
| let sig = fcx.tcx.fn_sig(item.def_id); |
| let sig = fcx.normalize_associated_types_in(span, &sig); |
| check_fn_or_method(tcx, fcx, span, sig, |
| item.def_id, &mut implied_bounds); |
| let sig_if_method = sig_if_method.expect("bad signature for method"); |
| check_method_receiver(fcx, sig_if_method, &item, self_ty); |
| } |
| ty::AssocKind::Type => { |
| if item.defaultness.has_value() { |
| let ty = fcx.tcx.type_of(item.def_id); |
| let ty = fcx.normalize_associated_types_in(span, &ty); |
| fcx.register_wf_obligation(ty, span, code.clone()); |
| } |
| } |
| ty::AssocKind::OpaqueTy => { |
| // Do nothing: opaque types check themselves. |
| } |
| } |
| |
| implied_bounds |
| }) |
| } |
| |
| fn for_item<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item) -> CheckWfFcxBuilder<'tcx> { |
| for_id(tcx, item.hir_id, item.span) |
| } |
| |
| fn for_id(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) -> CheckWfFcxBuilder<'_> { |
| let def_id = tcx.hir().local_def_id(id); |
| CheckWfFcxBuilder { |
| inherited: Inherited::build(tcx, def_id), |
| id, |
| span, |
| param_env: tcx.param_env(def_id), |
| } |
| } |
| |
| /// 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, |
| all_sized: bool, |
| mut lookup_fields: F, |
| ) where |
| F: for<'fcx> FnMut(&FnCtxt<'fcx, 'tcx>) -> Vec<AdtVariant<'tcx>>, |
| { |
| for_item(tcx, item).with_fcx(|fcx, fcx_tcx| { |
| let variants = lookup_fields(fcx); |
| let def_id = fcx.tcx.hir().local_def_id(item.hir_id); |
| let packed = fcx.tcx.adt_def(def_id).repr.packed(); |
| |
| for variant in &variants { |
| // 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 = fcx.tcx.erase_regions(&ty); |
| if ty.has_local_value() { |
| fcx_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(fcx_tcx, fcx_tcx.param_env(def_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[..variant.fields.len() - unsized_len] |
| .iter() |
| .enumerate() |
| { |
| let last = idx == variant.fields.len() - 1; |
| fcx.register_bound( |
| field.ty, |
| fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem), |
| traits::ObligationCause::new( |
| field.span, |
| fcx.body_id, |
| traits::FieldSized { |
| adt_kind: match item.node.adt_kind() { |
| Some(i) => i, |
| None => bug!(), |
| }, |
| last |
| } |
| ) |
| ); |
| } |
| |
| // All field types must be well-formed. |
| for field in &variant.fields { |
| fcx.register_wf_obligation(field.ty, field.span, |
| ObligationCauseCode::MiscObligation) |
| } |
| } |
| |
| check_where_clauses(tcx, fcx, item.span, def_id, None); |
| |
| // No implied bounds in a struct definition. |
| vec![] |
| }); |
| } |
| |
| fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item) { |
| debug!("check_trait: {:?}", item.hir_id); |
| |
| let trait_def_id = tcx.hir().local_def_id(item.hir_id); |
| |
| let trait_def = tcx.trait_def(trait_def_id); |
| if trait_def.is_marker { |
| for associated_def_id in &*tcx.associated_item_def_ids(trait_def_id) { |
| struct_span_err!( |
| tcx.sess, |
| tcx.def_span(*associated_def_id), |
| E0714, |
| "marker traits cannot have associated items", |
| ).emit(); |
| } |
| } |
| |
| for_item(tcx, item).with_fcx(|fcx, _| { |
| check_where_clauses(tcx, fcx, item.span, trait_def_id, None); |
| vec![] |
| }); |
| } |
| |
| fn check_item_fn(tcx: TyCtxt<'_>, item: &hir::Item) { |
| for_item(tcx, item).with_fcx(|fcx, tcx| { |
| let def_id = fcx.tcx.hir().local_def_id(item.hir_id); |
| let sig = fcx.tcx.fn_sig(def_id); |
| let sig = fcx.normalize_associated_types_in(item.span, &sig); |
| let mut implied_bounds = vec![]; |
| check_fn_or_method(tcx, fcx, item.span, sig, |
| def_id, &mut implied_bounds); |
| implied_bounds |
| }) |
| } |
| |
| fn check_item_type( |
| tcx: TyCtxt<'_>, |
| item_id: hir::HirId, |
| ty_span: Span, |
| allow_foreign_ty: bool, |
| ) { |
| debug!("check_item_type: {:?}", item_id); |
| |
| for_id(tcx, item_id, ty_span).with_fcx(|fcx, gcx| { |
| let ty = gcx.type_of(gcx.hir().local_def_id(item_id)); |
| let item_ty = fcx.normalize_associated_types_in(ty_span, &ty); |
| |
| let mut forbid_unsized = true; |
| if allow_foreign_ty { |
| let tail = fcx.tcx.struct_tail_erasing_lifetimes(item_ty, fcx.param_env); |
| if let ty::Foreign(_) = tail.sty { |
| forbid_unsized = false; |
| } |
| } |
| |
| fcx.register_wf_obligation(item_ty, ty_span, ObligationCauseCode::MiscObligation); |
| if forbid_unsized { |
| fcx.register_bound( |
| item_ty, |
| fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem), |
| traits::ObligationCause::new(ty_span, fcx.body_id, traits::MiscObligation), |
| ); |
| } |
| |
| // No implied bounds in a const, etc. |
| vec![] |
| }); |
| } |
| |
| fn check_impl<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| item: &hir::Item, |
| ast_self_ty: &hir::Ty, |
| ast_trait_ref: &Option<hir::TraitRef>, |
| ) { |
| debug!("check_impl: {:?}", item); |
| |
| for_item(tcx, item).with_fcx(|fcx, tcx| { |
| let item_def_id = fcx.tcx.hir().local_def_id(item.hir_id); |
| |
| match *ast_trait_ref { |
| Some(ref ast_trait_ref) => { |
| let trait_ref = fcx.tcx.impl_trait_ref(item_def_id).unwrap(); |
| let trait_ref = |
| fcx.normalize_associated_types_in( |
| ast_trait_ref.path.span, &trait_ref); |
| let obligations = |
| ty::wf::trait_obligations(fcx, |
| fcx.param_env, |
| fcx.body_id, |
| &trait_ref, |
| ast_trait_ref.path.span); |
| for obligation in obligations { |
| fcx.register_predicate(obligation); |
| } |
| } |
| None => { |
| let self_ty = fcx.tcx.type_of(item_def_id); |
| let self_ty = fcx.normalize_associated_types_in(item.span, &self_ty); |
| fcx.register_wf_obligation(self_ty, ast_self_ty.span, |
| ObligationCauseCode::MiscObligation); |
| } |
| } |
| |
| check_where_clauses(tcx, fcx, item.span, item_def_id, None); |
| |
| fcx.impl_implied_bounds(item_def_id, item.span) |
| }); |
| } |
| |
| /// Checks where-clauses and inline bounds that are declared on `def_id`. |
| fn check_where_clauses<'tcx, 'fcx>( |
| tcx: TyCtxt<'tcx>, |
| fcx: &FnCtxt<'fcx, 'tcx>, |
| span: Span, |
| def_id: DefId, |
| return_ty: Option<Ty<'tcx>>, |
| ) { |
| debug!("check_where_clauses(def_id={:?}, return_ty={:?})", def_id, return_ty); |
| |
| let predicates = fcx.tcx.predicates_of(def_id); |
| let generics = tcx.generics_of(def_id); |
| |
| let is_our_default = |def: &ty::GenericParamDef| { |
| match def.kind { |
| GenericParamDefKind::Type { has_default, .. } => { |
| has_default && def.index >= generics.parent_count as u32 |
| } |
| _ => 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 { |
| if let GenericParamDefKind::Type { .. } = param.kind { |
| if is_our_default(¶m) { |
| let ty = fcx.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() { |
| fcx.register_wf_obligation(ty, fcx.tcx.def_span(param.def_id), |
| ObligationCauseCode::MiscObligation); |
| } |
| } |
| } |
| } |
| |
| // 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(fcx.tcx, def_id, |param, _| { |
| match param.kind { |
| GenericParamDefKind::Lifetime => { |
| // All regions are identity. |
| fcx.tcx.mk_param_from_def(param) |
| } |
| |
| GenericParamDefKind::Type { .. } => { |
| // If the param has a default, ... |
| if is_our_default(param) { |
| let default_ty = fcx.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(); |
| } |
| } |
| // Mark unwanted params as error. |
| fcx.tcx.types.err.into() |
| } |
| |
| GenericParamDefKind::Const => { |
| // FIXME(const_generics:defaults) |
| fcx.tcx.consts.err.into() |
| } |
| } |
| }); |
| |
| // Now we build the substituted predicates. |
| let default_obligations = predicates.predicates.iter().flat_map(|&(pred, _)| { |
| #[derive(Default)] |
| struct CountParams { params: FxHashSet<u32> } |
| impl<'tcx> ty::fold::TypeVisitor<'tcx> for CountParams { |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> bool { |
| if let ty::Param(param) = t.sty { |
| self.params.insert(param.index); |
| } |
| t.super_visit_with(self) |
| } |
| |
| fn visit_region(&mut self, _: ty::Region<'tcx>) -> bool { |
| true |
| } |
| |
| fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> bool { |
| if let ConstValue::Param(param) = c.val { |
| 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); |
| let substituted_pred = pred.subst(fcx.tcx, substs); |
| // Don't check non-defaulted params, dependent defaults (including lifetimes) |
| // or preds with multiple params. |
| if substituted_pred.references_error() || param_count.params.len() > 1 || has_region { |
| None |
| } else if predicates.predicates.iter().any(|&(p, _)| p == substituted_pred) { |
| // Avoid duplication of predicates that contain no parameters, for example. |
| None |
| } else { |
| Some(substituted_pred) |
| } |
| }).map(|pred| { |
| // 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 = fcx.normalize_associated_types_in(span, &pred); |
| let cause = traits::ObligationCause::new(span, fcx.body_id, traits::ItemObligation(def_id)); |
| traits::Obligation::new(cause, fcx.param_env, pred) |
| }); |
| |
| let mut predicates = predicates.instantiate_identity(fcx.tcx); |
| |
| if let Some(return_ty) = return_ty { |
| predicates.predicates.extend(check_opaque_types(tcx, fcx, def_id, span, return_ty)); |
| } |
| |
| let predicates = fcx.normalize_associated_types_in(span, &predicates); |
| |
| debug!("check_where_clauses: predicates={:?}", predicates.predicates); |
| let wf_obligations = |
| predicates.predicates |
| .iter() |
| .flat_map(|p| ty::wf::predicate_obligations(fcx, |
| fcx.param_env, |
| fcx.body_id, |
| p, |
| span)); |
| |
| for obligation in wf_obligations.chain(default_obligations) { |
| debug!("next obligation cause: {:?}", obligation.cause); |
| fcx.register_predicate(obligation); |
| } |
| } |
| |
| fn check_fn_or_method<'fcx, 'tcx>( |
| tcx: TyCtxt<'tcx>, |
| fcx: &FnCtxt<'fcx, 'tcx>, |
| span: Span, |
| sig: ty::PolyFnSig<'tcx>, |
| def_id: DefId, |
| implied_bounds: &mut Vec<Ty<'tcx>>, |
| ) { |
| let sig = fcx.normalize_associated_types_in(span, &sig); |
| let sig = fcx.tcx.liberate_late_bound_regions(def_id, &sig); |
| |
| for input_ty in sig.inputs() { |
| fcx.register_wf_obligation(&input_ty, span, ObligationCauseCode::MiscObligation); |
| } |
| implied_bounds.extend(sig.inputs()); |
| |
| fcx.register_wf_obligation(sig.output(), span, ObligationCauseCode::MiscObligation); |
| |
| // FIXME(#25759) return types should not be implied bounds |
| implied_bounds.push(sig.output()); |
| |
| check_where_clauses(tcx, fcx, span, def_id, Some(sig.output())); |
| } |
| |
| /// Checks "defining uses" of opaque `impl Trait` types to ensure that they meet the restrictions |
| /// laid for "higher-order pattern unification". |
| /// This ensures that inference is tractable. |
| /// In particular, definitions of opaque types can only use other generics as arguments, |
| /// and they cannot repeat an argument. Example: |
| /// |
| /// ```rust |
| /// type Foo<A, B> = impl Bar<A, B>; |
| /// |
| /// // Okay -- `Foo` is applied to two distinct, generic types. |
| /// fn a<T, U>() -> Foo<T, U> { .. } |
| /// |
| /// // Not okay -- `Foo` is applied to `T` twice. |
| /// fn b<T>() -> Foo<T, T> { .. } |
| /// |
| /// // Not okay -- `Foo` is applied to a non-generic type. |
| /// fn b<T>() -> Foo<T, u32> { .. } |
| /// ``` |
| /// |
| fn check_opaque_types<'fcx, 'tcx>( |
| tcx: TyCtxt<'tcx>, |
| fcx: &FnCtxt<'fcx, 'tcx>, |
| fn_def_id: DefId, |
| span: Span, |
| ty: Ty<'tcx>, |
| ) -> Vec<ty::Predicate<'tcx>> { |
| trace!("check_opaque_types(ty={:?})", ty); |
| let mut substituted_predicates = Vec::new(); |
| ty.fold_with(&mut ty::fold::BottomUpFolder { |
| tcx: fcx.tcx, |
| ty_op: |ty| { |
| if let ty::Opaque(def_id, substs) = ty.sty { |
| trace!("check_opaque_types: opaque_ty, {:?}, {:?}", def_id, substs); |
| let generics = tcx.generics_of(def_id); |
| // Only check named `impl Trait` types defined in this crate. |
| if generics.parent.is_none() && def_id.is_local() { |
| let opaque_hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| if may_define_opaque_type(tcx, fn_def_id, opaque_hir_id) { |
| trace!("check_opaque_types: may define, generics={:#?}", generics); |
| let mut seen: FxHashMap<_, Vec<_>> = FxHashMap::default(); |
| for (subst, param) in substs.iter().zip(&generics.params) { |
| match subst.unpack() { |
| ty::subst::UnpackedKind::Type(ty) => match ty.sty { |
| ty::Param(..) => {} |
| // Prevent `fn foo() -> Foo<u32>` from being defining. |
| _ => { |
| tcx.sess |
| .struct_span_err( |
| span, |
| "non-defining opaque type use \ |
| in defining scope", |
| ) |
| .span_note( |
| tcx.def_span(param.def_id), |
| &format!( |
| "used non-generic type {} for \ |
| generic parameter", |
| ty, |
| ), |
| ) |
| .emit(); |
| } |
| } |
| |
| ty::subst::UnpackedKind::Lifetime(region) => { |
| let param_span = tcx.def_span(param.def_id); |
| if let ty::ReStatic = region { |
| tcx |
| .sess |
| .struct_span_err( |
| span, |
| "non-defining opaque type use \ |
| in defining scope", |
| ) |
| .span_label( |
| param_span, |
| "cannot use static lifetime; use a bound lifetime \ |
| instead or remove the lifetime parameter from the \ |
| opaque type", |
| ) |
| .emit(); |
| } else { |
| seen.entry(region).or_default().push(param_span); |
| } |
| } |
| |
| ty::subst::UnpackedKind::Const(ct) => match ct.val { |
| ConstValue::Param(_) => {} |
| _ => { |
| tcx.sess |
| .struct_span_err( |
| span, |
| "non-defining opaque type use \ |
| in defining scope", |
| ) |
| .span_note( |
| tcx.def_span(param.def_id), |
| &format!( |
| "used non-generic const {} for \ |
| generic parameter", |
| ty, |
| ), |
| ) |
| .emit(); |
| } |
| } |
| } // match subst |
| } // for (subst, param) |
| for (_, spans) in seen { |
| if spans.len() > 1 { |
| tcx |
| .sess |
| .struct_span_err( |
| span, |
| "non-defining opaque type use \ |
| in defining scope", |
| ). |
| span_note( |
| spans, |
| "lifetime used multiple times", |
| ) |
| .emit(); |
| } |
| } |
| } // if may_define_opaque_type |
| |
| // Now register the bounds on the parameters of the opaque type |
| // so the parameters given by the function need to fulfill them. |
| // |
| // type Foo<T: Bar> = impl Baz + 'static; |
| // fn foo<U>() -> Foo<U> { .. *} |
| // |
| // becomes |
| // |
| // type Foo<T: Bar> = impl Baz + 'static; |
| // fn foo<U: Bar>() -> Foo<U> { .. *} |
| let predicates = tcx.predicates_of(def_id); |
| trace!( |
| "check_opaque_types: may define, predicates={:#?}", |
| predicates, |
| ); |
| for &(pred, _) in predicates.predicates.iter() { |
| let substituted_pred = pred.subst(fcx.tcx, substs); |
| // Avoid duplication of predicates that contain no parameters, for example. |
| if !predicates.predicates.iter().any(|&(p, _)| p == substituted_pred) { |
| substituted_predicates.push(substituted_pred); |
| } |
| } |
| } // if is_named_opaque_type |
| } // if let Opaque |
| ty |
| }, |
| lt_op: |lt| lt, |
| ct_op: |ct| ct, |
| }); |
| substituted_predicates |
| } |
| |
| fn check_method_receiver<'fcx, 'tcx>( |
| fcx: &FnCtxt<'fcx, 'tcx>, |
| method_sig: &hir::MethodSig, |
| method: &ty::AssocItem, |
| self_ty: Ty<'tcx>, |
| ) { |
| 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`)"; |
| // Check that the method has a valid receiver type, given the type `Self`. |
| debug!("check_method_receiver({:?}, self_ty={:?})", |
| method, self_ty); |
| |
| if !method.method_has_self_argument { |
| return; |
| } |
| |
| let span = method_sig.decl.inputs[0].span; |
| |
| let sig = fcx.tcx.fn_sig(method.def_id); |
| let sig = fcx.normalize_associated_types_in(span, &sig); |
| let sig = fcx.tcx.liberate_late_bound_regions(method.def_id, &sig); |
| |
| debug!("check_method_receiver: sig={:?}", sig); |
| |
| let self_ty = fcx.normalize_associated_types_in(span, &self_ty); |
| let self_ty = fcx.tcx.liberate_late_bound_regions( |
| method.def_id, |
| &ty::Binder::bind(self_ty) |
| ); |
| |
| let receiver_ty = sig.inputs()[0]; |
| |
| let receiver_ty = fcx.normalize_associated_types_in(span, &receiver_ty); |
| let receiver_ty = fcx.tcx.liberate_late_bound_regions( |
| method.def_id, |
| &ty::Binder::bind(receiver_ty) |
| ); |
| |
| if fcx.tcx.features().arbitrary_self_types { |
| if !receiver_is_valid(fcx, span, receiver_ty, self_ty, true) { |
| // Report error; `arbitrary_self_types` was enabled. |
| fcx.tcx.sess.diagnostic().mut_span_err( |
| span, &format!("invalid method receiver type: {:?}", receiver_ty) |
| ).note("type of `self` must be `Self` or a type that dereferences to it") |
| .help(HELP_FOR_SELF_TYPE) |
| .code(DiagnosticId::Error("E0307".into())) |
| .emit(); |
| } |
| } else { |
| if !receiver_is_valid(fcx, span, receiver_ty, self_ty, false) { |
| if receiver_is_valid(fcx, span, receiver_ty, self_ty, true) { |
| // Report error; would have worked with `arbitrary_self_types`. |
| feature_gate::feature_err( |
| &fcx.tcx.sess.parse_sess, |
| sym::arbitrary_self_types, |
| span, |
| GateIssue::Language, |
| &format!( |
| "`{}` cannot be used as the type of `self` without \ |
| the `arbitrary_self_types` feature", |
| receiver_ty, |
| ), |
| ).help(HELP_FOR_SELF_TYPE) |
| .emit(); |
| } else { |
| // Report error; would not have worked with `arbitrary_self_types`. |
| fcx.tcx.sess.diagnostic().mut_span_err( |
| span, &format!("invalid method receiver type: {:?}", receiver_ty) |
| ).note("type must be `Self` or a type that dereferences to it") |
| .help(HELP_FOR_SELF_TYPE) |
| .code(DiagnosticId::Error("E0307".into())) |
| .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<'fcx, 'tcx>( |
| fcx: &FnCtxt<'fcx, 'tcx>, |
| span: Span, |
| receiver_ty: Ty<'tcx>, |
| self_ty: Ty<'tcx>, |
| arbitrary_self_types_enabled: bool, |
| ) -> bool { |
| let cause = fcx.cause(span, traits::ObligationCauseCode::MethodReceiver); |
| |
| let can_eq_self = |ty| fcx.infcx.can_eq(fcx.param_env, self_ty, ty).is_ok(); |
| |
| // `self: Self` is always valid. |
| if can_eq_self(receiver_ty) { |
| if let Some(mut err) = fcx.demand_eqtype_with_origin(&cause, self_ty, receiver_ty) { |
| err.emit(); |
| } |
| return true |
| } |
| |
| let mut autoderef = fcx.autoderef(span, receiver_ty); |
| |
| // 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(); |
| |
| // 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) { |
| autoderef.finalize(fcx); |
| |
| if let Some(mut err) = fcx.demand_eqtype_with_origin( |
| &cause, self_ty, potential_self_ty |
| ) { |
| err.emit(); |
| } |
| |
| break |
| } |
| } else { |
| debug!("receiver_is_valid: type `{:?}` does not deref to `{:?}`", |
| receiver_ty, self_ty); |
| // If he receiver already has errors reported due to it, consider it valid to avoid |
| // unecessary errors (#58712). |
| return receiver_ty.references_error(); |
| } |
| |
| // Without the `arbitrary_self_types` feature, `receiver_ty` must directly deref to |
| // `self_ty`. Enforce this by only doing one iteration of the loop. |
| if !arbitrary_self_types_enabled { |
| return false |
| } |
| } |
| |
| // Without `feature(arbitrary_self_types)`, we require that `receiver_ty` implements `Receiver`. |
| if !arbitrary_self_types_enabled { |
| let trait_def_id = match fcx.tcx.lang_items().receiver_trait() { |
| Some(did) => did, |
| None => { |
| debug!("receiver_is_valid: missing Receiver trait"); |
| return false |
| } |
| }; |
| |
| let trait_ref = ty::TraitRef{ |
| def_id: trait_def_id, |
| substs: fcx.tcx.mk_substs_trait(receiver_ty, &[]), |
| }; |
| |
| let obligation = traits::Obligation::new( |
| cause, |
| fcx.param_env, |
| trait_ref.to_predicate() |
| ); |
| |
| if !fcx.predicate_must_hold_modulo_regions(&obligation) { |
| debug!("receiver_is_valid: type `{:?}` does not implement `Receiver` trait", |
| receiver_ty); |
| return false |
| } |
| } |
| |
| true |
| } |
| |
| fn check_variances_for_type_defn<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| item: &hir::Item, |
| hir_generics: &hir::Generics, |
| ) { |
| let item_def_id = tcx.hir().local_def_id(item.hir_id); |
| 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, |
| ); |
| |
| for (index, _) in variances.iter().enumerate() { |
| if constrained_parameters.contains(&Parameter(index as u32)) { |
| continue; |
| } |
| |
| let param = &hir_generics.params[index]; |
| |
| match param.name { |
| hir::ParamName::Error => { } |
| _ => report_bivariance(tcx, param.span, param.name.ident().name), |
| } |
| } |
| } |
| |
| fn report_bivariance(tcx: TyCtxt<'_>, span: Span, param_name: ast::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. |
| if let Some(def_id) = suggested_marker_id { |
| err.help(&format!("consider removing `{}` or using a marker such as `{}`", |
| param_name, |
| tcx.def_path_str(def_id))); |
| } |
| err.emit(); |
| } |
| |
| /// Feature gates RFC 2056 -- trivial bounds, checking for global bounds that |
| /// aren't true. |
| fn check_false_global_bounds(fcx: &FnCtxt<'_, '_>, span: Span, id: hir::HirId) { |
| let empty_env = ty::ParamEnv::empty(); |
| |
| let def_id = fcx.tcx.hir().local_def_id(id); |
| let predicates = fcx.tcx.predicates_of(def_id).predicates |
| .iter() |
| .map(|(p, _)| *p) |
| .collect(); |
| // Check elaborated bounds. |
| let implied_obligations = traits::elaborate_predicates(fcx.tcx, predicates); |
| |
| for pred in implied_obligations { |
| // Match the existing behavior. |
| if pred.is_global() && !pred.has_late_bound_regions() { |
| let pred = fcx.normalize_associated_types_in(span, &pred); |
| let obligation = traits::Obligation::new( |
| traits::ObligationCause::new( |
| span, |
| id, |
| traits::TrivialBound, |
| ), |
| empty_env, |
| pred, |
| ); |
| fcx.register_predicate(obligation); |
| } |
| } |
| |
| fcx.select_all_obligations_or_error(); |
| } |
| |
| pub struct CheckTypeWellFormedVisitor<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| } |
| |
| impl CheckTypeWellFormedVisitor<'tcx> { |
| pub fn new(tcx: TyCtxt<'tcx>) -> CheckTypeWellFormedVisitor<'tcx> { |
| CheckTypeWellFormedVisitor { |
| tcx, |
| } |
| } |
| } |
| |
| impl ParItemLikeVisitor<'tcx> for CheckTypeWellFormedVisitor<'tcx> { |
| fn visit_item(&self, i: &'tcx hir::Item) { |
| debug!("visit_item: {:?}", i); |
| let def_id = self.tcx.hir().local_def_id(i.hir_id); |
| self.tcx.ensure().check_item_well_formed(def_id); |
| } |
| |
| fn visit_trait_item(&self, trait_item: &'tcx hir::TraitItem) { |
| debug!("visit_trait_item: {:?}", trait_item); |
| let def_id = self.tcx.hir().local_def_id(trait_item.hir_id); |
| self.tcx.ensure().check_trait_item_well_formed(def_id); |
| } |
| |
| fn visit_impl_item(&self, impl_item: &'tcx hir::ImplItem) { |
| debug!("visit_impl_item: {:?}", impl_item); |
| let def_id = self.tcx.hir().local_def_id(impl_item.hir_id); |
| self.tcx.ensure().check_impl_item_well_formed(def_id); |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // ADT |
| |
| struct AdtVariant<'tcx> { |
| fields: Vec<AdtField<'tcx>>, |
| } |
| |
| struct AdtField<'tcx> { |
| ty: Ty<'tcx>, |
| span: Span, |
| } |
| |
| impl<'a, 'tcx> FnCtxt<'a, 'tcx> { |
| fn non_enum_variant(&self, struct_def: &hir::VariantData) -> AdtVariant<'tcx> { |
| let fields = struct_def.fields().iter().map(|field| { |
| let field_ty = self.tcx.type_of(self.tcx.hir().local_def_id(field.hir_id)); |
| let field_ty = self.normalize_associated_types_in(field.span, |
| &field_ty); |
| let field_ty = self.resolve_vars_if_possible(&field_ty); |
| debug!("non_enum_variant: type of field {:?} is {:?}", field, field_ty); |
| AdtField { ty: field_ty, span: field.span } |
| }) |
| .collect(); |
| AdtVariant { fields } |
| } |
| |
| fn enum_variants(&self, enum_def: &hir::EnumDef) -> Vec<AdtVariant<'tcx>> { |
| enum_def.variants.iter() |
| .map(|variant| self.non_enum_variant(&variant.data)) |
| .collect() |
| } |
| |
| fn impl_implied_bounds(&self, impl_def_id: DefId, span: Span) -> Vec<Ty<'tcx>> { |
| match self.tcx.impl_trait_ref(impl_def_id) { |
| Some(ref trait_ref) => { |
| // Trait impl: take implied bounds from all types that |
| // appear in the trait reference. |
| let trait_ref = self.normalize_associated_types_in(span, trait_ref); |
| trait_ref.substs.types().collect() |
| } |
| |
| None => { |
| // Inherent impl: take implied bounds from the `self` type. |
| let self_ty = self.tcx.type_of(impl_def_id); |
| let self_ty = self.normalize_associated_types_in(span, &self_ty); |
| vec![self_ty] |
| } |
| } |
| } |
| } |
| |
| fn error_392( |
| tcx: TyCtxt<'_>, |
| span: Span, |
| param_name: ast::Name, |
| ) -> DiagnosticBuilder<'_> { |
| let mut err = struct_span_err!(tcx.sess, span, E0392, |
| "parameter `{}` is never used", param_name); |
| err.span_label(span, "unused parameter"); |
| err |
| } |
