| // ignore-tidy-filelength FIXME(#67418) Split up this file. |
| //! Conversion from AST representation of types to the `ty.rs` representation. |
| //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an |
| //! instance of `AstConv`. |
| |
| use crate::collect::PlaceholderHirTyCollector; |
| use crate::lint; |
| use crate::middle::lang_items::SizedTraitLangItem; |
| use crate::middle::resolve_lifetime as rl; |
| use crate::namespace::Namespace; |
| use crate::require_c_abi_if_c_variadic; |
| use crate::util::common::ErrorReported; |
| use rustc::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS; |
| use rustc::session::parse::feature_err; |
| use rustc::traits; |
| use rustc::traits::astconv_object_safety_violations; |
| use rustc::traits::error_reporting::report_object_safety_error; |
| use rustc::traits::wf::object_region_bounds; |
| use rustc::ty::subst::{self, InternalSubsts, Subst, SubstsRef}; |
| use rustc::ty::{self, Const, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable}; |
| use rustc::ty::{GenericParamDef, GenericParamDefKind}; |
| use rustc_data_structures::fx::{FxHashMap, FxHashSet}; |
| use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId}; |
| use rustc_hir as hir; |
| use rustc_hir::def::{CtorOf, DefKind, Res}; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::intravisit::Visitor; |
| use rustc_hir::print; |
| use rustc_hir::{ExprKind, GenericArg, GenericArgs}; |
| use rustc_span::symbol::sym; |
| use rustc_span::{MultiSpan, Span, DUMMY_SP}; |
| use rustc_target::spec::abi; |
| use smallvec::SmallVec; |
| use syntax::ast; |
| use syntax::util::lev_distance::find_best_match_for_name; |
| |
| use std::collections::BTreeSet; |
| use std::iter; |
| use std::slice; |
| |
| use rustc::mir::interpret::LitToConstInput; |
| |
| #[derive(Debug)] |
| pub struct PathSeg(pub DefId, pub usize); |
| |
| pub trait AstConv<'tcx> { |
| fn tcx<'a>(&'a self) -> TyCtxt<'tcx>; |
| |
| fn item_def_id(&self) -> Option<DefId>; |
| |
| /// Returns predicates in scope of the form `X: Foo`, where `X` is |
| /// a type parameter `X` with the given id `def_id`. This is a |
| /// subset of the full set of predicates. |
| /// |
| /// This is used for one specific purpose: resolving "short-hand" |
| /// associated type references like `T::Item`. In principle, we |
| /// would do that by first getting the full set of predicates in |
| /// scope and then filtering down to find those that apply to `T`, |
| /// but this can lead to cycle errors. The problem is that we have |
| /// to do this resolution *in order to create the predicates in |
| /// the first place*. Hence, we have this "special pass". |
| fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx>; |
| |
| /// Returns the lifetime to use when a lifetime is omitted (and not elided). |
| fn re_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) |
| -> Option<ty::Region<'tcx>>; |
| |
| /// Returns the type to use when a type is omitted. |
| fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>; |
| |
| /// Returns `true` if `_` is allowed in type signatures in the current context. |
| fn allow_ty_infer(&self) -> bool; |
| |
| /// Returns the const to use when a const is omitted. |
| fn ct_infer( |
| &self, |
| ty: Ty<'tcx>, |
| param: Option<&ty::GenericParamDef>, |
| span: Span, |
| ) -> &'tcx Const<'tcx>; |
| |
| /// Projecting an associated type from a (potentially) |
| /// higher-ranked trait reference is more complicated, because of |
| /// the possibility of late-bound regions appearing in the |
| /// associated type binding. This is not legal in function |
| /// signatures for that reason. In a function body, we can always |
| /// handle it because we can use inference variables to remove the |
| /// late-bound regions. |
| fn projected_ty_from_poly_trait_ref( |
| &self, |
| span: Span, |
| item_def_id: DefId, |
| item_segment: &hir::PathSegment<'_>, |
| poly_trait_ref: ty::PolyTraitRef<'tcx>, |
| ) -> Ty<'tcx>; |
| |
| /// Normalize an associated type coming from the user. |
| fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>; |
| |
| /// Invoked when we encounter an error from some prior pass |
| /// (e.g., resolve) that is translated into a ty-error. This is |
| /// used to help suppress derived errors typeck might otherwise |
| /// report. |
| fn set_tainted_by_errors(&self); |
| |
| fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span); |
| } |
| |
| pub enum SizedByDefault { |
| Yes, |
| No, |
| } |
| |
| struct ConvertedBinding<'a, 'tcx> { |
| item_name: ast::Ident, |
| kind: ConvertedBindingKind<'a, 'tcx>, |
| span: Span, |
| } |
| |
| enum ConvertedBindingKind<'a, 'tcx> { |
| Equality(Ty<'tcx>), |
| Constraint(&'a [hir::GenericBound<'a>]), |
| } |
| |
| #[derive(PartialEq)] |
| enum GenericArgPosition { |
| Type, |
| Value, // e.g., functions |
| MethodCall, |
| } |
| |
| impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { |
| pub fn ast_region_to_region( |
| &self, |
| lifetime: &hir::Lifetime, |
| def: Option<&ty::GenericParamDef>, |
| ) -> ty::Region<'tcx> { |
| let tcx = self.tcx(); |
| let lifetime_name = |def_id| tcx.hir().name(tcx.hir().as_local_hir_id(def_id).unwrap()); |
| |
| let r = match tcx.named_region(lifetime.hir_id) { |
| Some(rl::Region::Static) => tcx.lifetimes.re_static, |
| |
| Some(rl::Region::LateBound(debruijn, id, _)) => { |
| let name = lifetime_name(id); |
| tcx.mk_region(ty::ReLateBound(debruijn, ty::BrNamed(id, name))) |
| } |
| |
| Some(rl::Region::LateBoundAnon(debruijn, index)) => { |
| tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index))) |
| } |
| |
| Some(rl::Region::EarlyBound(index, id, _)) => { |
| let name = lifetime_name(id); |
| tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion { def_id: id, index, name })) |
| } |
| |
| Some(rl::Region::Free(scope, id)) => { |
| let name = lifetime_name(id); |
| tcx.mk_region(ty::ReFree(ty::FreeRegion { |
| scope, |
| bound_region: ty::BrNamed(id, name), |
| })) |
| |
| // (*) -- not late-bound, won't change |
| } |
| |
| None => { |
| self.re_infer(def, lifetime.span).unwrap_or_else(|| { |
| // This indicates an illegal lifetime |
| // elision. `resolve_lifetime` should have |
| // reported an error in this case -- but if |
| // not, let's error out. |
| tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature"); |
| |
| // Supply some dummy value. We don't have an |
| // `re_error`, annoyingly, so use `'static`. |
| tcx.lifetimes.re_static |
| }) |
| } |
| }; |
| |
| debug!("ast_region_to_region(lifetime={:?}) yields {:?}", lifetime, r); |
| |
| r |
| } |
| |
| /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`, |
| /// returns an appropriate set of substitutions for this particular reference to `I`. |
| pub fn ast_path_substs_for_ty( |
| &self, |
| span: Span, |
| def_id: DefId, |
| item_segment: &hir::PathSegment<'_>, |
| ) -> SubstsRef<'tcx> { |
| let (substs, assoc_bindings, _) = self.create_substs_for_ast_path( |
| span, |
| def_id, |
| &[], |
| item_segment.generic_args(), |
| item_segment.infer_args, |
| None, |
| ); |
| |
| assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span)); |
| |
| substs |
| } |
| |
| /// Report error if there is an explicit type parameter when using `impl Trait`. |
| fn check_impl_trait( |
| tcx: TyCtxt<'_>, |
| seg: &hir::PathSegment<'_>, |
| generics: &ty::Generics, |
| ) -> bool { |
| let explicit = !seg.infer_args; |
| let impl_trait = generics.params.iter().any(|param| match param.kind { |
| ty::GenericParamDefKind::Type { |
| synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), |
| .. |
| } => true, |
| _ => false, |
| }); |
| |
| if explicit && impl_trait { |
| let spans = seg |
| .generic_args() |
| .args |
| .iter() |
| .filter_map(|arg| match arg { |
| GenericArg::Type(_) => Some(arg.span()), |
| _ => None, |
| }) |
| .collect::<Vec<_>>(); |
| |
| let mut err = struct_span_err! { |
| tcx.sess, |
| spans.clone(), |
| E0632, |
| "cannot provide explicit generic arguments when `impl Trait` is \ |
| used in argument position" |
| }; |
| |
| for span in spans { |
| err.span_label(span, "explicit generic argument not allowed"); |
| } |
| |
| err.emit(); |
| } |
| |
| impl_trait |
| } |
| |
| /// Checks that the correct number of generic arguments have been provided. |
| /// Used specifically for function calls. |
| pub fn check_generic_arg_count_for_call( |
| tcx: TyCtxt<'_>, |
| span: Span, |
| def: &ty::Generics, |
| seg: &hir::PathSegment<'_>, |
| is_method_call: bool, |
| ) -> bool { |
| let empty_args = hir::GenericArgs::none(); |
| let suppress_mismatch = Self::check_impl_trait(tcx, seg, &def); |
| Self::check_generic_arg_count( |
| tcx, |
| span, |
| def, |
| if let Some(ref args) = seg.args { args } else { &empty_args }, |
| if is_method_call { GenericArgPosition::MethodCall } else { GenericArgPosition::Value }, |
| def.parent.is_none() && def.has_self, // `has_self` |
| seg.infer_args || suppress_mismatch, // `infer_args` |
| ) |
| .0 |
| } |
| |
| /// Checks that the correct number of generic arguments have been provided. |
| /// This is used both for datatypes and function calls. |
| fn check_generic_arg_count( |
| tcx: TyCtxt<'_>, |
| span: Span, |
| def: &ty::Generics, |
| args: &hir::GenericArgs<'_>, |
| position: GenericArgPosition, |
| has_self: bool, |
| infer_args: bool, |
| ) -> (bool, Option<Vec<Span>>) { |
| // At this stage we are guaranteed that the generic arguments are in the correct order, e.g. |
| // that lifetimes will proceed types. So it suffices to check the number of each generic |
| // arguments in order to validate them with respect to the generic parameters. |
| let param_counts = def.own_counts(); |
| let arg_counts = args.own_counts(); |
| let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0; |
| |
| let mut defaults: ty::GenericParamCount = Default::default(); |
| for param in &def.params { |
| match param.kind { |
| GenericParamDefKind::Lifetime => {} |
| GenericParamDefKind::Type { has_default, .. } => { |
| defaults.types += has_default as usize |
| } |
| GenericParamDefKind::Const => { |
| // FIXME(const_generics:defaults) |
| } |
| }; |
| } |
| |
| if position != GenericArgPosition::Type && !args.bindings.is_empty() { |
| AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span); |
| } |
| |
| // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present. |
| let mut reported_late_bound_region_err = None; |
| if !infer_lifetimes { |
| if let Some(span_late) = def.has_late_bound_regions { |
| let msg = "cannot specify lifetime arguments explicitly \ |
| if late bound lifetime parameters are present"; |
| let note = "the late bound lifetime parameter is introduced here"; |
| let span = args.args[0].span(); |
| if position == GenericArgPosition::Value |
| && arg_counts.lifetimes != param_counts.lifetimes |
| { |
| let mut err = tcx.sess.struct_span_err(span, msg); |
| err.span_note(span_late, note); |
| err.emit(); |
| reported_late_bound_region_err = Some(true); |
| } else { |
| let mut multispan = MultiSpan::from_span(span); |
| multispan.push_span_label(span_late, note.to_string()); |
| tcx.lint_hir( |
| lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS, |
| args.args[0].id(), |
| multispan, |
| msg, |
| ); |
| reported_late_bound_region_err = Some(false); |
| } |
| } |
| } |
| |
| let check_kind_count = |kind, required, permitted, provided, offset| { |
| debug!( |
| "check_kind_count: kind: {} required: {} permitted: {} provided: {} offset: {}", |
| kind, required, permitted, provided, offset |
| ); |
| // We enforce the following: `required` <= `provided` <= `permitted`. |
| // For kinds without defaults (e.g.., lifetimes), `required == permitted`. |
| // For other kinds (i.e., types), `permitted` may be greater than `required`. |
| if required <= provided && provided <= permitted { |
| return (reported_late_bound_region_err.unwrap_or(false), None); |
| } |
| |
| // Unfortunately lifetime and type parameter mismatches are typically styled |
| // differently in diagnostics, which means we have a few cases to consider here. |
| let (bound, quantifier) = if required != permitted { |
| if provided < required { |
| (required, "at least ") |
| } else { |
| // provided > permitted |
| (permitted, "at most ") |
| } |
| } else { |
| (required, "") |
| }; |
| |
| let mut potential_assoc_types: Option<Vec<Span>> = None; |
| let (spans, label) = if required == permitted && provided > permitted { |
| // In the case when the user has provided too many arguments, |
| // we want to point to the unexpected arguments. |
| let spans: Vec<Span> = args.args[offset + permitted..offset + provided] |
| .iter() |
| .map(|arg| arg.span()) |
| .collect(); |
| potential_assoc_types = Some(spans.clone()); |
| (spans, format!("unexpected {} argument", kind)) |
| } else { |
| ( |
| vec![span], |
| format!( |
| "expected {}{} {} argument{}", |
| quantifier, |
| bound, |
| kind, |
| pluralize!(bound), |
| ), |
| ) |
| }; |
| |
| let mut err = tcx.sess.struct_span_err_with_code( |
| spans.clone(), |
| &format!( |
| "wrong number of {} arguments: expected {}{}, found {}", |
| kind, quantifier, bound, provided, |
| ), |
| DiagnosticId::Error("E0107".into()), |
| ); |
| for span in spans { |
| err.span_label(span, label.as_str()); |
| } |
| err.emit(); |
| |
| ( |
| provided > required, // `suppress_error` |
| potential_assoc_types, |
| ) |
| }; |
| |
| if reported_late_bound_region_err.is_none() |
| && (!infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes) |
| { |
| check_kind_count( |
| "lifetime", |
| param_counts.lifetimes, |
| param_counts.lifetimes, |
| arg_counts.lifetimes, |
| 0, |
| ); |
| } |
| // FIXME(const_generics:defaults) |
| if !infer_args || arg_counts.consts > param_counts.consts { |
| check_kind_count( |
| "const", |
| param_counts.consts, |
| param_counts.consts, |
| arg_counts.consts, |
| arg_counts.lifetimes + arg_counts.types, |
| ); |
| } |
| // Note that type errors are currently be emitted *after* const errors. |
| if !infer_args || arg_counts.types > param_counts.types - defaults.types - has_self as usize |
| { |
| check_kind_count( |
| "type", |
| param_counts.types - defaults.types - has_self as usize, |
| param_counts.types - has_self as usize, |
| arg_counts.types, |
| arg_counts.lifetimes, |
| ) |
| } else { |
| (reported_late_bound_region_err.unwrap_or(false), None) |
| } |
| } |
| |
| /// Creates the relevant generic argument substitutions |
| /// corresponding to a set of generic parameters. This is a |
| /// rather complex function. Let us try to explain the role |
| /// of each of its parameters: |
| /// |
| /// To start, we are given the `def_id` of the thing we are |
| /// creating the substitutions for, and a partial set of |
| /// substitutions `parent_substs`. In general, the substitutions |
| /// for an item begin with substitutions for all the "parents" of |
| /// that item -- e.g., for a method it might include the |
| /// parameters from the impl. |
| /// |
| /// Therefore, the method begins by walking down these parents, |
| /// starting with the outermost parent and proceed inwards until |
| /// it reaches `def_id`. For each parent `P`, it will check `parent_substs` |
| /// first to see if the parent's substitutions are listed in there. If so, |
| /// we can append those and move on. Otherwise, it invokes the |
| /// three callback functions: |
| /// |
| /// - `args_for_def_id`: given the `DefId` `P`, supplies back the |
| /// generic arguments that were given to that parent from within |
| /// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId` |
| /// might refer to the trait `Foo`, and the arguments might be |
| /// `[T]`. The boolean value indicates whether to infer values |
| /// for arguments whose values were not explicitly provided. |
| /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`, |
| /// instantiate a `GenericArg`. |
| /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then |
| /// creates a suitable inference variable. |
| pub fn create_substs_for_generic_args<'b>( |
| tcx: TyCtxt<'tcx>, |
| def_id: DefId, |
| parent_substs: &[subst::GenericArg<'tcx>], |
| has_self: bool, |
| self_ty: Option<Ty<'tcx>>, |
| args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs<'b>>, bool), |
| provided_kind: impl Fn(&GenericParamDef, &GenericArg<'_>) -> subst::GenericArg<'tcx>, |
| mut inferred_kind: impl FnMut( |
| Option<&[subst::GenericArg<'tcx>]>, |
| &GenericParamDef, |
| bool, |
| ) -> subst::GenericArg<'tcx>, |
| ) -> SubstsRef<'tcx> { |
| // Collect the segments of the path; we need to substitute arguments |
| // for parameters throughout the entire path (wherever there are |
| // generic parameters). |
| let mut parent_defs = tcx.generics_of(def_id); |
| let count = parent_defs.count(); |
| let mut stack = vec![(def_id, parent_defs)]; |
| while let Some(def_id) = parent_defs.parent { |
| parent_defs = tcx.generics_of(def_id); |
| stack.push((def_id, parent_defs)); |
| } |
| |
| // We manually build up the substitution, rather than using convenience |
| // methods in `subst.rs`, so that we can iterate over the arguments and |
| // parameters in lock-step linearly, instead of trying to match each pair. |
| let mut substs: SmallVec<[subst::GenericArg<'tcx>; 8]> = SmallVec::with_capacity(count); |
| |
| // Iterate over each segment of the path. |
| while let Some((def_id, defs)) = stack.pop() { |
| let mut params = defs.params.iter().peekable(); |
| |
| // If we have already computed substitutions for parents, we can use those directly. |
| while let Some(¶m) = params.peek() { |
| if let Some(&kind) = parent_substs.get(param.index as usize) { |
| substs.push(kind); |
| params.next(); |
| } else { |
| break; |
| } |
| } |
| |
| // `Self` is handled first, unless it's been handled in `parent_substs`. |
| if has_self { |
| if let Some(¶m) = params.peek() { |
| if param.index == 0 { |
| if let GenericParamDefKind::Type { .. } = param.kind { |
| substs.push( |
| self_ty |
| .map(|ty| ty.into()) |
| .unwrap_or_else(|| inferred_kind(None, param, true)), |
| ); |
| params.next(); |
| } |
| } |
| } |
| } |
| |
| // Check whether this segment takes generic arguments and the user has provided any. |
| let (generic_args, infer_args) = args_for_def_id(def_id); |
| |
| let mut args = |
| generic_args.iter().flat_map(|generic_args| generic_args.args.iter()).peekable(); |
| |
| loop { |
| // We're going to iterate through the generic arguments that the user |
| // provided, matching them with the generic parameters we expect. |
| // Mismatches can occur as a result of elided lifetimes, or for malformed |
| // input. We try to handle both sensibly. |
| match (args.peek(), params.peek()) { |
| (Some(&arg), Some(¶m)) => { |
| match (arg, ¶m.kind) { |
| (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime) |
| | (GenericArg::Type(_), GenericParamDefKind::Type { .. }) |
| | (GenericArg::Const(_), GenericParamDefKind::Const) => { |
| substs.push(provided_kind(param, arg)); |
| args.next(); |
| params.next(); |
| } |
| (GenericArg::Type(_), GenericParamDefKind::Lifetime) |
| | (GenericArg::Const(_), GenericParamDefKind::Lifetime) => { |
| // We expected a lifetime argument, but got a type or const |
| // argument. That means we're inferring the lifetimes. |
| substs.push(inferred_kind(None, param, infer_args)); |
| params.next(); |
| } |
| (_, _) => { |
| // We expected one kind of parameter, but the user provided |
| // another. This is an error, but we need to handle it |
| // gracefully so we can report sensible errors. |
| // In this case, we're simply going to infer this argument. |
| args.next(); |
| } |
| } |
| } |
| (Some(_), None) => { |
| // We should never be able to reach this point with well-formed input. |
| // Getting to this point means the user supplied more arguments than |
| // there are parameters. |
| args.next(); |
| } |
| (None, Some(¶m)) => { |
| // If there are fewer arguments than parameters, it means |
| // we're inferring the remaining arguments. |
| substs.push(inferred_kind(Some(&substs), param, infer_args)); |
| args.next(); |
| params.next(); |
| } |
| (None, None) => break, |
| } |
| } |
| } |
| |
| tcx.intern_substs(&substs) |
| } |
| |
| /// Given the type/lifetime/const arguments provided to some path (along with |
| /// an implicit `Self`, if this is a trait reference), returns the complete |
| /// set of substitutions. This may involve applying defaulted type parameters. |
| /// Also returns back constriants on associated types. |
| /// |
| /// Example: |
| /// |
| /// ``` |
| /// T: std::ops::Index<usize, Output = u32> |
| /// ^1 ^^^^^^^^^^^^^^2 ^^^^3 ^^^^^^^^^^^4 |
| /// ``` |
| /// |
| /// 1. The `self_ty` here would refer to the type `T`. |
| /// 2. The path in question is the path to the trait `std::ops::Index`, |
| /// which will have been resolved to a `def_id` |
| /// 3. The `generic_args` contains info on the `<...>` contents. The `usize` type |
| /// parameters are returned in the `SubstsRef`, the associated type bindings like |
| /// `Output = u32` are returned in the `Vec<ConvertedBinding...>` result. |
| /// |
| /// Note that the type listing given here is *exactly* what the user provided. |
| /// |
| /// For (generic) associated types |
| /// |
| /// ``` |
| /// <Vec<u8> as Iterable<u8>>::Iter::<'a> |
| /// ``` |
| /// |
| /// We have the parent substs are the substs for the parent trait: |
| /// `[Vec<u8>, u8]` and `generic_args` are the arguments for the associated |
| /// type itself: `['a]`. The returned `SubstsRef` concatenates these two |
| /// lists: `[Vec<u8>, u8, 'a]`. |
| fn create_substs_for_ast_path<'a>( |
| &self, |
| span: Span, |
| def_id: DefId, |
| parent_substs: &[subst::GenericArg<'tcx>], |
| generic_args: &'a hir::GenericArgs<'_>, |
| infer_args: bool, |
| self_ty: Option<Ty<'tcx>>, |
| ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'a, 'tcx>>, Option<Vec<Span>>) { |
| // If the type is parameterized by this region, then replace this |
| // region with the current anon region binding (in other words, |
| // whatever & would get replaced with). |
| debug!( |
| "create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \ |
| generic_args={:?})", |
| def_id, self_ty, generic_args |
| ); |
| |
| let tcx = self.tcx(); |
| let generic_params = tcx.generics_of(def_id); |
| |
| if generic_params.has_self { |
| if generic_params.parent.is_some() { |
| // The parent is a trait so it should have at least one subst |
| // for the `Self` type. |
| assert!(!parent_substs.is_empty()) |
| } else { |
| // This item (presumably a trait) needs a self-type. |
| assert!(self_ty.is_some()); |
| } |
| } else { |
| assert!(self_ty.is_none() && parent_substs.is_empty()); |
| } |
| |
| let (_, potential_assoc_types) = Self::check_generic_arg_count( |
| tcx, |
| span, |
| &generic_params, |
| &generic_args, |
| GenericArgPosition::Type, |
| self_ty.is_some(), |
| infer_args, |
| ); |
| |
| let is_object = self_ty.map_or(false, |ty| ty == self.tcx().types.trait_object_dummy_self); |
| let default_needs_object_self = |param: &ty::GenericParamDef| { |
| if let GenericParamDefKind::Type { has_default, .. } = param.kind { |
| if is_object && has_default { |
| let self_param = tcx.types.self_param; |
| if tcx.at(span).type_of(param.def_id).walk().any(|ty| ty == self_param) { |
| // There is no suitable inference default for a type parameter |
| // that references self, in an object type. |
| return true; |
| } |
| } |
| } |
| |
| false |
| }; |
| |
| let mut missing_type_params = vec![]; |
| let substs = Self::create_substs_for_generic_args( |
| tcx, |
| def_id, |
| parent_substs, |
| self_ty.is_some(), |
| self_ty, |
| // Provide the generic args, and whether types should be inferred. |
| |_| (Some(generic_args), infer_args), |
| // Provide substitutions for parameters for which (valid) arguments have been provided. |
| |param, arg| match (¶m.kind, arg) { |
| (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => { |
| self.ast_region_to_region(<, Some(param)).into() |
| } |
| (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => { |
| self.ast_ty_to_ty(&ty).into() |
| } |
| (GenericParamDefKind::Const, GenericArg::Const(ct)) => { |
| self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into() |
| } |
| _ => unreachable!(), |
| }, |
| // Provide substitutions for parameters for which arguments are inferred. |
| |substs, param, infer_args| { |
| match param.kind { |
| GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(), |
| GenericParamDefKind::Type { has_default, .. } => { |
| if !infer_args && has_default { |
| // No type parameter provided, but a default exists. |
| |
| // If we are converting an object type, then the |
| // `Self` parameter is unknown. However, some of the |
| // other type parameters may reference `Self` in their |
| // defaults. This will lead to an ICE if we are not |
| // careful! |
| if default_needs_object_self(param) { |
| missing_type_params.push(param.name.to_string()); |
| tcx.types.err.into() |
| } else { |
| // This is a default type parameter. |
| self.normalize_ty( |
| span, |
| tcx.at(span).type_of(param.def_id).subst_spanned( |
| tcx, |
| substs.unwrap(), |
| Some(span), |
| ), |
| ) |
| .into() |
| } |
| } else if infer_args { |
| // No type parameters were provided, we can infer all. |
| let param = |
| if !default_needs_object_self(param) { Some(param) } else { None }; |
| self.ty_infer(param, span).into() |
| } else { |
| // We've already errored above about the mismatch. |
| tcx.types.err.into() |
| } |
| } |
| GenericParamDefKind::Const => { |
| // FIXME(const_generics:defaults) |
| if infer_args { |
| // No const parameters were provided, we can infer all. |
| let ty = tcx.at(span).type_of(param.def_id); |
| self.ct_infer(ty, Some(param), span).into() |
| } else { |
| // We've already errored above about the mismatch. |
| tcx.consts.err.into() |
| } |
| } |
| } |
| }, |
| ); |
| |
| self.complain_about_missing_type_params( |
| missing_type_params, |
| def_id, |
| span, |
| generic_args.args.is_empty(), |
| ); |
| |
| // Convert associated-type bindings or constraints into a separate vector. |
| // Example: Given this: |
| // |
| // T: Iterator<Item = u32> |
| // |
| // The `T` is passed in as a self-type; the `Item = u32` is |
| // not a "type parameter" of the `Iterator` trait, but rather |
| // a restriction on `<T as Iterator>::Item`, so it is passed |
| // back separately. |
| let assoc_bindings = generic_args |
| .bindings |
| .iter() |
| .map(|binding| { |
| let kind = match binding.kind { |
| hir::TypeBindingKind::Equality { ref ty } => { |
| ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty)) |
| } |
| hir::TypeBindingKind::Constraint { ref bounds } => { |
| ConvertedBindingKind::Constraint(bounds) |
| } |
| }; |
| ConvertedBinding { item_name: binding.ident, kind, span: binding.span } |
| }) |
| .collect(); |
| |
| debug!( |
| "create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}", |
| generic_params, self_ty, substs |
| ); |
| |
| (substs, assoc_bindings, potential_assoc_types) |
| } |
| |
| crate fn create_substs_for_associated_item( |
| &self, |
| tcx: TyCtxt<'tcx>, |
| span: Span, |
| item_def_id: DefId, |
| item_segment: &hir::PathSegment<'_>, |
| parent_substs: SubstsRef<'tcx>, |
| ) -> SubstsRef<'tcx> { |
| if tcx.generics_of(item_def_id).params.is_empty() { |
| self.prohibit_generics(slice::from_ref(item_segment)); |
| |
| parent_substs |
| } else { |
| self.create_substs_for_ast_path( |
| span, |
| item_def_id, |
| parent_substs, |
| item_segment.generic_args(), |
| item_segment.infer_args, |
| None, |
| ) |
| .0 |
| } |
| } |
| |
| /// On missing type parameters, emit an E0393 error and provide a structured suggestion using |
| /// the type parameter's name as a placeholder. |
| fn complain_about_missing_type_params( |
| &self, |
| missing_type_params: Vec<String>, |
| def_id: DefId, |
| span: Span, |
| empty_generic_args: bool, |
| ) { |
| if missing_type_params.is_empty() { |
| return; |
| } |
| let display = |
| missing_type_params.iter().map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", "); |
| let mut err = struct_span_err!( |
| self.tcx().sess, |
| span, |
| E0393, |
| "the type parameter{} {} must be explicitly specified", |
| pluralize!(missing_type_params.len()), |
| display, |
| ); |
| err.span_label( |
| self.tcx().def_span(def_id), |
| &format!( |
| "type parameter{} {} must be specified for this", |
| pluralize!(missing_type_params.len()), |
| display, |
| ), |
| ); |
| let mut suggested = false; |
| if let (Ok(snippet), true) = ( |
| self.tcx().sess.source_map().span_to_snippet(span), |
| // Don't suggest setting the type params if there are some already: the order is |
| // tricky to get right and the user will already know what the syntax is. |
| empty_generic_args, |
| ) { |
| if snippet.ends_with('>') { |
| // The user wrote `Trait<'a, T>` or similar. To provide an accurate suggestion |
| // we would have to preserve the right order. For now, as clearly the user is |
| // aware of the syntax, we do nothing. |
| } else { |
| // The user wrote `Iterator`, so we don't have a type we can suggest, but at |
| // least we can clue them to the correct syntax `Iterator<Type>`. |
| err.span_suggestion( |
| span, |
| &format!( |
| "set the type parameter{plural} to the desired type{plural}", |
| plural = pluralize!(missing_type_params.len()), |
| ), |
| format!("{}<{}>", snippet, missing_type_params.join(", ")), |
| Applicability::HasPlaceholders, |
| ); |
| suggested = true; |
| } |
| } |
| if !suggested { |
| err.span_label( |
| span, |
| format!( |
| "missing reference{} to {}", |
| pluralize!(missing_type_params.len()), |
| display, |
| ), |
| ); |
| } |
| err.note(&format!( |
| "because of the default `Self` reference, type parameters must be \ |
| specified on object types" |
| )); |
| err.emit(); |
| } |
| |
| /// Instantiates the path for the given trait reference, assuming that it's |
| /// bound to a valid trait type. Returns the `DefId` of the defining trait. |
| /// The type _cannot_ be a type other than a trait type. |
| /// |
| /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>` |
| /// are disallowed. Otherwise, they are pushed onto the vector given. |
| pub fn instantiate_mono_trait_ref( |
| &self, |
| trait_ref: &hir::TraitRef<'_>, |
| self_ty: Ty<'tcx>, |
| ) -> ty::TraitRef<'tcx> { |
| self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1); |
| |
| self.ast_path_to_mono_trait_ref( |
| trait_ref.path.span, |
| trait_ref.trait_def_id(), |
| self_ty, |
| trait_ref.path.segments.last().unwrap(), |
| ) |
| } |
| |
| /// The given trait-ref must actually be a trait. |
| pub(super) fn instantiate_poly_trait_ref_inner( |
| &self, |
| trait_ref: &hir::TraitRef<'_>, |
| span: Span, |
| self_ty: Ty<'tcx>, |
| bounds: &mut Bounds<'tcx>, |
| speculative: bool, |
| ) -> Option<Vec<Span>> { |
| let trait_def_id = trait_ref.trait_def_id(); |
| |
| debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id); |
| |
| self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1); |
| |
| let path_span = if let [segment] = &trait_ref.path.segments[..] { |
| // FIXME: `trait_ref.path.span` can point to a full path with multiple |
| // segments, even though `trait_ref.path.segments` is of length `1`. Work |
| // around that bug here, even though it should be fixed elsewhere. |
| // This would otherwise cause an invalid suggestion. For an example, look at |
| // `src/test/ui/issues/issue-28344.rs`. |
| segment.ident.span |
| } else { |
| trait_ref.path.span |
| }; |
| let (substs, assoc_bindings, potential_assoc_types) = self.create_substs_for_ast_trait_ref( |
| path_span, |
| trait_def_id, |
| self_ty, |
| trait_ref.path.segments.last().unwrap(), |
| ); |
| let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs)); |
| |
| bounds.trait_bounds.push((poly_trait_ref, span)); |
| |
| let mut dup_bindings = FxHashMap::default(); |
| for binding in &assoc_bindings { |
| // Specify type to assert that error was already reported in `Err` case. |
| let _: Result<_, ErrorReported> = self.add_predicates_for_ast_type_binding( |
| trait_ref.hir_ref_id, |
| poly_trait_ref, |
| binding, |
| bounds, |
| speculative, |
| &mut dup_bindings, |
| span, |
| ); |
| // Okay to ignore `Err` because of `ErrorReported` (see above). |
| } |
| |
| debug!( |
| "instantiate_poly_trait_ref({:?}, bounds={:?}) -> {:?}", |
| trait_ref, bounds, poly_trait_ref |
| ); |
| potential_assoc_types |
| } |
| |
| /// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct |
| /// a full trait reference. The resulting trait reference is returned. This may also generate |
| /// auxiliary bounds, which are added to `bounds`. |
| /// |
| /// Example: |
| /// |
| /// ``` |
| /// poly_trait_ref = Iterator<Item = u32> |
| /// self_ty = Foo |
| /// ``` |
| /// |
| /// this would return `Foo: Iterator` and add `<Foo as Iterator>::Item = u32` into `bounds`. |
| /// |
| /// **A note on binders:** against our usual convention, there is an implied bounder around |
| /// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions. |
| /// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>` |
| /// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be |
| /// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly, |
| /// however. |
| pub fn instantiate_poly_trait_ref( |
| &self, |
| poly_trait_ref: &hir::PolyTraitRef<'_>, |
| self_ty: Ty<'tcx>, |
| bounds: &mut Bounds<'tcx>, |
| ) -> Option<Vec<Span>> { |
| self.instantiate_poly_trait_ref_inner( |
| &poly_trait_ref.trait_ref, |
| poly_trait_ref.span, |
| self_ty, |
| bounds, |
| false, |
| ) |
| } |
| |
| fn ast_path_to_mono_trait_ref( |
| &self, |
| span: Span, |
| trait_def_id: DefId, |
| self_ty: Ty<'tcx>, |
| trait_segment: &hir::PathSegment<'_>, |
| ) -> ty::TraitRef<'tcx> { |
| let (substs, assoc_bindings, _) = |
| self.create_substs_for_ast_trait_ref(span, trait_def_id, self_ty, trait_segment); |
| assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span)); |
| ty::TraitRef::new(trait_def_id, substs) |
| } |
| |
| /// When the code is using the `Fn` traits directly, instead of the `Fn(A) -> B` syntax, emit |
| /// an error and attempt to build a reasonable structured suggestion. |
| fn complain_about_internal_fn_trait( |
| &self, |
| span: Span, |
| trait_def_id: DefId, |
| trait_segment: &'a hir::PathSegment<'a>, |
| ) { |
| let trait_def = self.tcx().trait_def(trait_def_id); |
| |
| if !self.tcx().features().unboxed_closures |
| && trait_segment.generic_args().parenthesized != trait_def.paren_sugar |
| { |
| // For now, require that parenthetical notation be used only with `Fn()` etc. |
| let (msg, sugg) = if trait_def.paren_sugar { |
| ( |
| "the precise format of `Fn`-family traits' type parameters is subject to \ |
| change", |
| Some(format!( |
| "{}{} -> {}", |
| trait_segment.ident, |
| trait_segment |
| .args |
| .as_ref() |
| .and_then(|args| args.args.get(0)) |
| .and_then(|arg| match arg { |
| hir::GenericArg::Type(ty) => { |
| Some(print::to_string(print::NO_ANN, |s| s.print_type(ty))) |
| } |
| _ => None, |
| }) |
| .unwrap_or_else(|| "()".to_string()), |
| trait_segment |
| .generic_args() |
| .bindings |
| .iter() |
| .filter_map(|b| match (b.ident.as_str() == "Output", &b.kind) { |
| (true, hir::TypeBindingKind::Equality { ty }) => { |
| Some(print::to_string(print::NO_ANN, |s| s.print_type(ty))) |
| } |
| _ => None, |
| }) |
| .next() |
| .unwrap_or_else(|| "()".to_string()), |
| )), |
| ) |
| } else { |
| ("parenthetical notation is only stable when used with `Fn`-family traits", None) |
| }; |
| let sess = &self.tcx().sess.parse_sess; |
| let mut err = feature_err(sess, sym::unboxed_closures, span, msg); |
| if let Some(sugg) = sugg { |
| let msg = "use parenthetical notation instead"; |
| err.span_suggestion(span, msg, sugg, Applicability::MaybeIncorrect); |
| } |
| err.emit(); |
| } |
| } |
| |
| fn create_substs_for_ast_trait_ref<'a>( |
| &self, |
| span: Span, |
| trait_def_id: DefId, |
| self_ty: Ty<'tcx>, |
| trait_segment: &'a hir::PathSegment<'a>, |
| ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'a, 'tcx>>, Option<Vec<Span>>) { |
| debug!("create_substs_for_ast_trait_ref(trait_segment={:?})", trait_segment); |
| |
| self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment); |
| |
| self.create_substs_for_ast_path( |
| span, |
| trait_def_id, |
| &[], |
| trait_segment.generic_args(), |
| trait_segment.infer_args, |
| Some(self_ty), |
| ) |
| } |
| |
| fn trait_defines_associated_type_named( |
| &self, |
| trait_def_id: DefId, |
| assoc_name: ast::Ident, |
| ) -> bool { |
| self.tcx().associated_items(trait_def_id).any(|item| { |
| item.kind == ty::AssocKind::Type |
| && self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id) |
| }) |
| } |
| |
| // Returns `true` if a bounds list includes `?Sized`. |
| pub fn is_unsized(&self, ast_bounds: &[hir::GenericBound<'_>], span: Span) -> bool { |
| let tcx = self.tcx(); |
| |
| // Try to find an unbound in bounds. |
| let mut unbound = None; |
| for ab in ast_bounds { |
| if let &hir::GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = ab { |
| if unbound.is_none() { |
| unbound = Some(&ptr.trait_ref); |
| } else { |
| struct_span_err!( |
| tcx.sess, |
| span, |
| E0203, |
| "type parameter has more than one relaxed default \ |
| bound, only one is supported" |
| ) |
| .emit(); |
| } |
| } |
| } |
| |
| let kind_id = tcx.lang_items().require(SizedTraitLangItem); |
| match unbound { |
| Some(tpb) => { |
| // FIXME(#8559) currently requires the unbound to be built-in. |
| if let Ok(kind_id) = kind_id { |
| if tpb.path.res != Res::Def(DefKind::Trait, kind_id) { |
| tcx.sess.span_warn( |
| span, |
| "default bound relaxed for a type parameter, but \ |
| this does nothing because the given bound is not \ |
| a default; only `?Sized` is supported", |
| ); |
| } |
| } |
| } |
| _ if kind_id.is_ok() => { |
| return false; |
| } |
| // No lang item for `Sized`, so we can't add it as a bound. |
| None => {} |
| } |
| |
| true |
| } |
| |
| /// This helper takes a *converted* parameter type (`param_ty`) |
| /// and an *unconverted* list of bounds: |
| /// |
| /// ``` |
| /// fn foo<T: Debug> |
| /// ^ ^^^^^ `ast_bounds` parameter, in HIR form |
| /// | |
| /// `param_ty`, in ty form |
| /// ``` |
| /// |
| /// It adds these `ast_bounds` into the `bounds` structure. |
| /// |
| /// **A note on binders:** there is an implied binder around |
| /// `param_ty` and `ast_bounds`. See `instantiate_poly_trait_ref` |
| /// for more details. |
| fn add_bounds( |
| &self, |
| param_ty: Ty<'tcx>, |
| ast_bounds: &[hir::GenericBound<'_>], |
| bounds: &mut Bounds<'tcx>, |
| ) { |
| let mut trait_bounds = Vec::new(); |
| let mut region_bounds = Vec::new(); |
| |
| for ast_bound in ast_bounds { |
| match *ast_bound { |
| hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) => { |
| trait_bounds.push(b) |
| } |
| hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {} |
| hir::GenericBound::Outlives(ref l) => region_bounds.push(l), |
| } |
| } |
| |
| for bound in trait_bounds { |
| let _ = self.instantiate_poly_trait_ref(bound, param_ty, bounds); |
| } |
| |
| bounds.region_bounds.extend( |
| region_bounds.into_iter().map(|r| (self.ast_region_to_region(r, None), r.span)), |
| ); |
| } |
| |
| /// Translates a list of bounds from the HIR into the `Bounds` data structure. |
| /// The self-type for the bounds is given by `param_ty`. |
| /// |
| /// Example: |
| /// |
| /// ``` |
| /// fn foo<T: Bar + Baz>() { } |
| /// ^ ^^^^^^^^^ ast_bounds |
| /// param_ty |
| /// ``` |
| /// |
| /// The `sized_by_default` parameter indicates if, in this context, the `param_ty` should be |
| /// considered `Sized` unless there is an explicit `?Sized` bound. This would be true in the |
| /// example above, but is not true in supertrait listings like `trait Foo: Bar + Baz`. |
| /// |
| /// `span` should be the declaration size of the parameter. |
| pub fn compute_bounds( |
| &self, |
| param_ty: Ty<'tcx>, |
| ast_bounds: &[hir::GenericBound<'_>], |
| sized_by_default: SizedByDefault, |
| span: Span, |
| ) -> Bounds<'tcx> { |
| let mut bounds = Bounds::default(); |
| |
| self.add_bounds(param_ty, ast_bounds, &mut bounds); |
| bounds.trait_bounds.sort_by_key(|(t, _)| t.def_id()); |
| |
| bounds.implicitly_sized = if let SizedByDefault::Yes = sized_by_default { |
| if !self.is_unsized(ast_bounds, span) { Some(span) } else { None } |
| } else { |
| None |
| }; |
| |
| bounds |
| } |
| |
| /// Given an HIR binding like `Item = Foo` or `Item: Foo`, pushes the corresponding predicates |
| /// onto `bounds`. |
| /// |
| /// **A note on binders:** given something like `T: for<'a> Iterator<Item = &'a u32>`, the |
| /// `trait_ref` here will be `for<'a> T: Iterator`. The `binding` data however is from *inside* |
| /// the binder (e.g., `&'a u32`) and hence may reference bound regions. |
| fn add_predicates_for_ast_type_binding( |
| &self, |
| hir_ref_id: hir::HirId, |
| trait_ref: ty::PolyTraitRef<'tcx>, |
| binding: &ConvertedBinding<'_, 'tcx>, |
| bounds: &mut Bounds<'tcx>, |
| speculative: bool, |
| dup_bindings: &mut FxHashMap<DefId, Span>, |
| path_span: Span, |
| ) -> Result<(), ErrorReported> { |
| let tcx = self.tcx(); |
| |
| if !speculative { |
| // Given something like `U: SomeTrait<T = X>`, we want to produce a |
| // predicate like `<U as SomeTrait>::T = X`. This is somewhat |
| // subtle in the event that `T` is defined in a supertrait of |
| // `SomeTrait`, because in that case we need to upcast. |
| // |
| // That is, consider this case: |
| // |
| // ``` |
| // trait SubTrait: SuperTrait<int> { } |
| // trait SuperTrait<A> { type T; } |
| // |
| // ... B: SubTrait<T = foo> ... |
| // ``` |
| // |
| // We want to produce `<B as SuperTrait<int>>::T == foo`. |
| |
| // Find any late-bound regions declared in `ty` that are not |
| // declared in the trait-ref. These are not well-formed. |
| // |
| // Example: |
| // |
| // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad |
| // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok |
| if let ConvertedBindingKind::Equality(ty) = binding.kind { |
| let late_bound_in_trait_ref = |
| tcx.collect_constrained_late_bound_regions(&trait_ref); |
| let late_bound_in_ty = |
| tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(ty)); |
| debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref); |
| debug!("late_bound_in_ty = {:?}", late_bound_in_ty); |
| for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) { |
| let br_name = match *br { |
| ty::BrNamed(_, name) => name, |
| _ => { |
| span_bug!( |
| binding.span, |
| "anonymous bound region {:?} in binding but not trait ref", |
| br |
| ); |
| } |
| }; |
| struct_span_err!( |
| tcx.sess, |
| binding.span, |
| E0582, |
| "binding for associated type `{}` references lifetime `{}`, \ |
| which does not appear in the trait input types", |
| binding.item_name, |
| br_name |
| ) |
| .emit(); |
| } |
| } |
| } |
| |
| let candidate = |
| if self.trait_defines_associated_type_named(trait_ref.def_id(), binding.item_name) { |
| // Simple case: X is defined in the current trait. |
| trait_ref |
| } else { |
| // Otherwise, we have to walk through the supertraits to find |
| // those that do. |
| self.one_bound_for_assoc_type( |
| || traits::supertraits(tcx, trait_ref), |
| || trait_ref.print_only_trait_path().to_string(), |
| binding.item_name, |
| path_span, |
| || match binding.kind { |
| ConvertedBindingKind::Equality(ty) => Some(ty.to_string()), |
| _ => None, |
| }, |
| )? |
| }; |
| |
| let (assoc_ident, def_scope) = |
| tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id); |
| let assoc_ty = tcx |
| .associated_items(candidate.def_id()) |
| .find(|i| i.kind == ty::AssocKind::Type && i.ident.modern() == assoc_ident) |
| .expect("missing associated type"); |
| |
| if !assoc_ty.vis.is_accessible_from(def_scope, tcx) { |
| let msg = format!("associated type `{}` is private", binding.item_name); |
| tcx.sess.span_err(binding.span, &msg); |
| } |
| tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span); |
| |
| if !speculative { |
| dup_bindings |
| .entry(assoc_ty.def_id) |
| .and_modify(|prev_span| { |
| struct_span_err!( |
| self.tcx().sess, |
| binding.span, |
| E0719, |
| "the value of the associated type `{}` (from trait `{}`) \ |
| is already specified", |
| binding.item_name, |
| tcx.def_path_str(assoc_ty.container.id()) |
| ) |
| .span_label(binding.span, "re-bound here") |
| .span_label(*prev_span, format!("`{}` bound here first", binding.item_name)) |
| .emit(); |
| }) |
| .or_insert(binding.span); |
| } |
| |
| match binding.kind { |
| ConvertedBindingKind::Equality(ref ty) => { |
| // "Desugar" a constraint like `T: Iterator<Item = u32>` this to |
| // the "projection predicate" for: |
| // |
| // `<T as Iterator>::Item = u32` |
| bounds.projection_bounds.push(( |
| candidate.map_bound(|trait_ref| ty::ProjectionPredicate { |
| projection_ty: ty::ProjectionTy::from_ref_and_name( |
| tcx, |
| trait_ref, |
| binding.item_name, |
| ), |
| ty, |
| }), |
| binding.span, |
| )); |
| } |
| ConvertedBindingKind::Constraint(ast_bounds) => { |
| // "Desugar" a constraint like `T: Iterator<Item: Debug>` to |
| // |
| // `<T as Iterator>::Item: Debug` |
| // |
| // Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty` |
| // parameter to have a skipped binder. |
| let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs); |
| self.add_bounds(param_ty, ast_bounds, bounds); |
| } |
| } |
| Ok(()) |
| } |
| |
| fn ast_path_to_ty( |
| &self, |
| span: Span, |
| did: DefId, |
| item_segment: &hir::PathSegment<'_>, |
| ) -> Ty<'tcx> { |
| let substs = self.ast_path_substs_for_ty(span, did, item_segment); |
| self.normalize_ty(span, self.tcx().at(span).type_of(did).subst(self.tcx(), substs)) |
| } |
| |
| fn conv_object_ty_poly_trait_ref( |
| &self, |
| span: Span, |
| trait_bounds: &[hir::PolyTraitRef<'_>], |
| lifetime: &hir::Lifetime, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx(); |
| |
| let mut bounds = Bounds::default(); |
| let mut potential_assoc_types = Vec::new(); |
| let dummy_self = self.tcx().types.trait_object_dummy_self; |
| for trait_bound in trait_bounds.iter().rev() { |
| let cur_potential_assoc_types = |
| self.instantiate_poly_trait_ref(trait_bound, dummy_self, &mut bounds); |
| potential_assoc_types.extend(cur_potential_assoc_types.into_iter().flatten()); |
| } |
| |
| // Expand trait aliases recursively and check that only one regular (non-auto) trait |
| // is used and no 'maybe' bounds are used. |
| let expanded_traits = |
| traits::expand_trait_aliases(tcx, bounds.trait_bounds.iter().cloned()); |
| let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) = |
| expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id())); |
| if regular_traits.len() > 1 { |
| let first_trait = ®ular_traits[0]; |
| let additional_trait = ®ular_traits[1]; |
| let mut err = struct_span_err!( |
| tcx.sess, |
| additional_trait.bottom().1, |
| E0225, |
| "only auto traits can be used as additional traits in a trait object" |
| ); |
| additional_trait.label_with_exp_info( |
| &mut err, |
| "additional non-auto trait", |
| "additional use", |
| ); |
| first_trait.label_with_exp_info(&mut err, "first non-auto trait", "first use"); |
| err.emit(); |
| } |
| |
| if regular_traits.is_empty() && auto_traits.is_empty() { |
| struct_span_err!( |
| tcx.sess, |
| span, |
| E0224, |
| "at least one trait is required for an object type" |
| ) |
| .emit(); |
| return tcx.types.err; |
| } |
| |
| // Check that there are no gross object safety violations; |
| // most importantly, that the supertraits don't contain `Self`, |
| // to avoid ICEs. |
| for item in ®ular_traits { |
| let object_safety_violations = |
| astconv_object_safety_violations(tcx, item.trait_ref().def_id()); |
| if !object_safety_violations.is_empty() { |
| report_object_safety_error( |
| tcx, |
| span, |
| item.trait_ref().def_id(), |
| object_safety_violations, |
| ) |
| .emit(); |
| return tcx.types.err; |
| } |
| } |
| |
| // Use a `BTreeSet` to keep output in a more consistent order. |
| let mut associated_types: FxHashMap<Span, BTreeSet<DefId>> = FxHashMap::default(); |
| |
| let regular_traits_refs_spans = bounds |
| .trait_bounds |
| .into_iter() |
| .filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id())); |
| |
| for (base_trait_ref, span) in regular_traits_refs_spans { |
| for trait_ref in traits::elaborate_trait_ref(tcx, base_trait_ref) { |
| debug!( |
| "conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", |
| trait_ref |
| ); |
| match trait_ref { |
| ty::Predicate::Trait(pred) => { |
| associated_types.entry(span).or_default().extend( |
| tcx.associated_items(pred.def_id()) |
| .filter(|item| item.kind == ty::AssocKind::Type) |
| .map(|item| item.def_id), |
| ); |
| } |
| ty::Predicate::Projection(pred) => { |
| // A `Self` within the original bound will be substituted with a |
| // `trait_object_dummy_self`, so check for that. |
| let references_self = pred.skip_binder().ty.walk().any(|t| t == dummy_self); |
| |
| // If the projection output contains `Self`, force the user to |
| // elaborate it explicitly to avoid a lot of complexity. |
| // |
| // The "classicaly useful" case is the following: |
| // ``` |
| // trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput { |
| // type MyOutput; |
| // } |
| // ``` |
| // |
| // Here, the user could theoretically write `dyn MyTrait<Output = X>`, |
| // but actually supporting that would "expand" to an infinitely-long type |
| // `fix $ τ → dyn MyTrait<MyOutput = X, Output = <τ as MyTrait>::MyOutput`. |
| // |
| // Instead, we force the user to write |
| // `dyn MyTrait<MyOutput = X, Output = X>`, which is uglier but works. See |
| // the discussion in #56288 for alternatives. |
| if !references_self { |
| // Include projections defined on supertraits. |
| bounds.projection_bounds.push((pred, span)); |
| } |
| } |
| _ => (), |
| } |
| } |
| } |
| |
| for (projection_bound, _) in &bounds.projection_bounds { |
| for (_, def_ids) in &mut associated_types { |
| def_ids.remove(&projection_bound.projection_def_id()); |
| } |
| } |
| |
| self.complain_about_missing_associated_types( |
| associated_types, |
| potential_assoc_types, |
| trait_bounds, |
| ); |
| |
| // De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as |
| // `dyn Trait + Send`. |
| auto_traits.sort_by_key(|i| i.trait_ref().def_id()); |
| auto_traits.dedup_by_key(|i| i.trait_ref().def_id()); |
| debug!("regular_traits: {:?}", regular_traits); |
| debug!("auto_traits: {:?}", auto_traits); |
| |
| // Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by |
| // removing the dummy `Self` type (`trait_object_dummy_self`). |
| let trait_ref_to_existential = |trait_ref: ty::TraitRef<'tcx>| { |
| if trait_ref.self_ty() != dummy_self { |
| // FIXME: There appears to be a missing filter on top of `expand_trait_aliases`, |
| // which picks up non-supertraits where clauses - but also, the object safety |
| // completely ignores trait aliases, which could be object safety hazards. We |
| // `delay_span_bug` here to avoid an ICE in stable even when the feature is |
| // disabled. (#66420) |
| tcx.sess.delay_span_bug( |
| DUMMY_SP, |
| &format!( |
| "trait_ref_to_existential called on {:?} with non-dummy Self", |
| trait_ref, |
| ), |
| ); |
| } |
| ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref) |
| }; |
| |
| // Erase the `dummy_self` (`trait_object_dummy_self`) used above. |
| let existential_trait_refs = regular_traits |
| .iter() |
| .map(|i| i.trait_ref().map_bound(|trait_ref| trait_ref_to_existential(trait_ref))); |
| let existential_projections = bounds.projection_bounds.iter().map(|(bound, _)| { |
| bound.map_bound(|b| { |
| let trait_ref = trait_ref_to_existential(b.projection_ty.trait_ref(tcx)); |
| ty::ExistentialProjection { |
| ty: b.ty, |
| item_def_id: b.projection_ty.item_def_id, |
| substs: trait_ref.substs, |
| } |
| }) |
| }); |
| |
| // Calling `skip_binder` is okay because the predicates are re-bound. |
| let regular_trait_predicates = existential_trait_refs |
| .map(|trait_ref| ty::ExistentialPredicate::Trait(*trait_ref.skip_binder())); |
| let auto_trait_predicates = auto_traits |
| .into_iter() |
| .map(|trait_ref| ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id())); |
| let mut v = regular_trait_predicates |
| .chain(auto_trait_predicates) |
| .chain( |
| existential_projections |
| .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())), |
| ) |
| .collect::<SmallVec<[_; 8]>>(); |
| v.sort_by(|a, b| a.stable_cmp(tcx, b)); |
| v.dedup(); |
| let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter())); |
| |
| // Use explicitly-specified region bound. |
| let region_bound = if !lifetime.is_elided() { |
| self.ast_region_to_region(lifetime, None) |
| } else { |
| self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| { |
| if tcx.named_region(lifetime.hir_id).is_some() { |
| self.ast_region_to_region(lifetime, None) |
| } else { |
| self.re_infer(None, span).unwrap_or_else(|| { |
| struct_span_err!( |
| tcx.sess, |
| span, |
| E0228, |
| "the lifetime bound for this object type cannot be deduced \ |
| from context; please supply an explicit bound" |
| ) |
| .emit(); |
| tcx.lifetimes.re_static |
| }) |
| } |
| }) |
| }; |
| debug!("region_bound: {:?}", region_bound); |
| |
| let ty = tcx.mk_dynamic(existential_predicates, region_bound); |
| debug!("trait_object_type: {:?}", ty); |
| ty |
| } |
| |
| /// When there are any missing associated types, emit an E0191 error and attempt to supply a |
| /// reasonable suggestion on how to write it. For the case of multiple associated types in the |
| /// same trait bound have the same name (as they come from different super-traits), we instead |
| /// emit a generic note suggesting using a `where` clause to constraint instead. |
| fn complain_about_missing_associated_types( |
| &self, |
| associated_types: FxHashMap<Span, BTreeSet<DefId>>, |
| potential_assoc_types: Vec<Span>, |
| trait_bounds: &[hir::PolyTraitRef<'_>], |
| ) { |
| if !associated_types.values().any(|v| v.len() > 0) { |
| return; |
| } |
| let tcx = self.tcx(); |
| // FIXME: Marked `mut` so that we can replace the spans further below with a more |
| // appropriate one, but this should be handled earlier in the span assignment. |
| let mut associated_types: FxHashMap<Span, Vec<_>> = associated_types |
| .into_iter() |
| .map(|(span, def_ids)| { |
| (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect()) |
| }) |
| .collect(); |
| let mut names = vec![]; |
| |
| // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and |
| // `issue-22560.rs`. |
| let mut trait_bound_spans: Vec<Span> = vec![]; |
| for (span, items) in &associated_types { |
| if !items.is_empty() { |
| trait_bound_spans.push(*span); |
| } |
| for assoc_item in items { |
| let trait_def_id = assoc_item.container.id(); |
| names.push(format!( |
| "`{}` (from trait `{}`)", |
| assoc_item.ident, |
| tcx.def_path_str(trait_def_id), |
| )); |
| } |
| } |
| |
| match (&potential_assoc_types[..], &trait_bounds) { |
| ([], [bound]) => match &bound.trait_ref.path.segments[..] { |
| // FIXME: `trait_ref.path.span` can point to a full path with multiple |
| // segments, even though `trait_ref.path.segments` is of length `1`. Work |
| // around that bug here, even though it should be fixed elsewhere. |
| // This would otherwise cause an invalid suggestion. For an example, look at |
| // `src/test/ui/issues/issue-28344.rs` where instead of the following: |
| // |
| // error[E0191]: the value of the associated type `Output` |
| // (from trait `std::ops::BitXor`) must be specified |
| // --> $DIR/issue-28344.rs:4:17 |
| // | |
| // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8); |
| // | ^^^^^^ help: specify the associated type: |
| // | `BitXor<Output = Type>` |
| // |
| // we would output: |
| // |
| // error[E0191]: the value of the associated type `Output` |
| // (from trait `std::ops::BitXor`) must be specified |
| // --> $DIR/issue-28344.rs:4:17 |
| // | |
| // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8); |
| // | ^^^^^^^^^^^^^ help: specify the associated type: |
| // | `BitXor::bitor<Output = Type>` |
| [segment] if segment.args.is_none() => { |
| trait_bound_spans = vec![segment.ident.span]; |
| associated_types = associated_types |
| .into_iter() |
| .map(|(_, items)| (segment.ident.span, items)) |
| .collect(); |
| } |
| _ => {} |
| }, |
| _ => {} |
| } |
| names.sort(); |
| trait_bound_spans.sort(); |
| let mut err = struct_span_err!( |
| tcx.sess, |
| trait_bound_spans, |
| E0191, |
| "the value of the associated type{} {} must be specified", |
| pluralize!(names.len()), |
| names.join(", "), |
| ); |
| let mut suggestions = vec![]; |
| let mut types_count = 0; |
| let mut where_constraints = vec![]; |
| for (span, assoc_items) in &associated_types { |
| let mut names: FxHashMap<_, usize> = FxHashMap::default(); |
| for item in assoc_items { |
| types_count += 1; |
| *names.entry(item.ident.name).or_insert(0) += 1; |
| } |
| let mut dupes = false; |
| for item in assoc_items { |
| let prefix = if names[&item.ident.name] > 1 { |
| let trait_def_id = item.container.id(); |
| dupes = true; |
| format!("{}::", tcx.def_path_str(trait_def_id)) |
| } else { |
| String::new() |
| }; |
| if let Some(sp) = tcx.hir().span_if_local(item.def_id) { |
| err.span_label(sp, format!("`{}{}` defined here", prefix, item.ident)); |
| } |
| } |
| if potential_assoc_types.len() == assoc_items.len() { |
| // Only suggest when the amount of missing associated types equals the number of |
| // extra type arguments present, as that gives us a relatively high confidence |
| // that the user forgot to give the associtated type's name. The canonical |
| // example would be trying to use `Iterator<isize>` instead of |
| // `Iterator<Item = isize>`. |
| for (potential, item) in potential_assoc_types.iter().zip(assoc_items.iter()) { |
| if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(*potential) { |
| suggestions.push((*potential, format!("{} = {}", item.ident, snippet))); |
| } |
| } |
| } else if let (Ok(snippet), false) = |
| (tcx.sess.source_map().span_to_snippet(*span), dupes) |
| { |
| let types: Vec<_> = |
| assoc_items.iter().map(|item| format!("{} = Type", item.ident)).collect(); |
| let code = if snippet.ends_with(">") { |
| // The user wrote `Trait<'a>` or similar and we don't have a type we can |
| // suggest, but at least we can clue them to the correct syntax |
| // `Trait<'a, Item = Type>` while accounting for the `<'a>` in the |
| // suggestion. |
| format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", ")) |
| } else { |
| // The user wrote `Iterator`, so we don't have a type we can suggest, but at |
| // least we can clue them to the correct syntax `Iterator<Item = Type>`. |
| format!("{}<{}>", snippet, types.join(", ")) |
| }; |
| suggestions.push((*span, code)); |
| } else if dupes { |
| where_constraints.push(*span); |
| } |
| } |
| let where_msg = "consider introducing a new type parameter, adding `where` constraints \ |
| using the fully-qualified path to the associated types"; |
| if !where_constraints.is_empty() && suggestions.is_empty() { |
| // If there are duplicates associated type names and a single trait bound do not |
| // use structured suggestion, it means that there are multiple super-traits with |
| // the same associated type name. |
| err.help(where_msg); |
| } |
| if suggestions.len() != 1 { |
| // We don't need this label if there's an inline suggestion, show otherwise. |
| for (span, assoc_items) in &associated_types { |
| let mut names: FxHashMap<_, usize> = FxHashMap::default(); |
| for item in assoc_items { |
| types_count += 1; |
| *names.entry(item.ident.name).or_insert(0) += 1; |
| } |
| let mut label = vec![]; |
| for item in assoc_items { |
| let postfix = if names[&item.ident.name] > 1 { |
| let trait_def_id = item.container.id(); |
| format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id)) |
| } else { |
| String::new() |
| }; |
| label.push(format!("`{}`{}", item.ident, postfix)); |
| } |
| if !label.is_empty() { |
| err.span_label( |
| *span, |
| format!( |
| "associated type{} {} must be specified", |
| pluralize!(label.len()), |
| label.join(", "), |
| ), |
| ); |
| } |
| } |
| } |
| if !suggestions.is_empty() { |
| err.multipart_suggestion( |
| &format!("specify the associated type{}", pluralize!(types_count)), |
| suggestions, |
| Applicability::HasPlaceholders, |
| ); |
| if !where_constraints.is_empty() { |
| err.span_help(where_constraints, where_msg); |
| } |
| } |
| err.emit(); |
| } |
| |
| fn report_ambiguous_associated_type( |
| &self, |
| span: Span, |
| type_str: &str, |
| trait_str: &str, |
| name: ast::Name, |
| ) { |
| let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type"); |
| if let (Some(_), Ok(snippet)) = ( |
| self.tcx().sess.confused_type_with_std_module.borrow().get(&span), |
| self.tcx().sess.source_map().span_to_snippet(span), |
| ) { |
| err.span_suggestion( |
| span, |
| "you are looking for the module in `std`, not the primitive type", |
| format!("std::{}", snippet), |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| err.span_suggestion( |
| span, |
| "use fully-qualified syntax", |
| format!("<{} as {}>::{}", type_str, trait_str, name), |
| Applicability::HasPlaceholders, |
| ); |
| } |
| err.emit(); |
| } |
| |
| // Search for a bound on a type parameter which includes the associated item |
| // given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter |
| // This function will fail if there are no suitable bounds or there is |
| // any ambiguity. |
| fn find_bound_for_assoc_item( |
| &self, |
| ty_param_def_id: DefId, |
| assoc_name: ast::Ident, |
| span: Span, |
| ) -> Result<ty::PolyTraitRef<'tcx>, ErrorReported> { |
| let tcx = self.tcx(); |
| |
| debug!( |
| "find_bound_for_assoc_item(ty_param_def_id={:?}, assoc_name={:?}, span={:?})", |
| ty_param_def_id, assoc_name, span, |
| ); |
| |
| let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates; |
| |
| debug!("find_bound_for_assoc_item: predicates={:#?}", predicates); |
| |
| let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap(); |
| let param_name = tcx.hir().ty_param_name(param_hir_id); |
| self.one_bound_for_assoc_type( |
| || { |
| traits::transitive_bounds( |
| tcx, |
| predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref()), |
| ) |
| }, |
| || param_name.to_string(), |
| assoc_name, |
| span, |
| || None, |
| ) |
| } |
| |
| // Checks that `bounds` contains exactly one element and reports appropriate |
| // errors otherwise. |
| fn one_bound_for_assoc_type<I>( |
| &self, |
| all_candidates: impl Fn() -> I, |
| ty_param_name: impl Fn() -> String, |
| assoc_name: ast::Ident, |
| span: Span, |
| is_equality: impl Fn() -> Option<String>, |
| ) -> Result<ty::PolyTraitRef<'tcx>, ErrorReported> |
| where |
| I: Iterator<Item = ty::PolyTraitRef<'tcx>>, |
| { |
| let mut matching_candidates = all_candidates() |
| .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name)); |
| |
| let bound = match matching_candidates.next() { |
| Some(bound) => bound, |
| None => { |
| self.complain_about_assoc_type_not_found( |
| all_candidates, |
| &ty_param_name(), |
| assoc_name, |
| span, |
| ); |
| return Err(ErrorReported); |
| } |
| }; |
| |
| debug!("one_bound_for_assoc_type: bound = {:?}", bound); |
| |
| if let Some(bound2) = matching_candidates.next() { |
| debug!("one_bound_for_assoc_type: bound2 = {:?}", bound2); |
| |
| let is_equality = is_equality(); |
| let bounds = iter::once(bound).chain(iter::once(bound2)).chain(matching_candidates); |
| let mut err = if is_equality.is_some() { |
| // More specific Error Index entry. |
| struct_span_err!( |
| self.tcx().sess, |
| span, |
| E0222, |
| "ambiguous associated type `{}` in bounds of `{}`", |
| assoc_name, |
| ty_param_name() |
| ) |
| } else { |
| struct_span_err!( |
| self.tcx().sess, |
| span, |
| E0221, |
| "ambiguous associated type `{}` in bounds of `{}`", |
| assoc_name, |
| ty_param_name() |
| ) |
| }; |
| err.span_label(span, format!("ambiguous associated type `{}`", assoc_name)); |
| |
| let mut where_bounds = vec![]; |
| for bound in bounds { |
| let bound_span = self |
| .tcx() |
| .associated_items(bound.def_id()) |
| .find(|item| { |
| item.kind == ty::AssocKind::Type |
| && self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id()) |
| }) |
| .and_then(|item| self.tcx().hir().span_if_local(item.def_id)); |
| |
| if let Some(bound_span) = bound_span { |
| err.span_label( |
| bound_span, |
| format!( |
| "ambiguous `{}` from `{}`", |
| assoc_name, |
| bound.print_only_trait_path(), |
| ), |
| ); |
| if let Some(constraint) = &is_equality { |
| where_bounds.push(format!( |
| " T: {trait}::{assoc} = {constraint}", |
| trait=bound.print_only_trait_path(), |
| assoc=assoc_name, |
| constraint=constraint, |
| )); |
| } else { |
| err.span_suggestion( |
| span, |
| "use fully qualified syntax to disambiguate", |
| format!( |
| "<{} as {}>::{}", |
| ty_param_name(), |
| bound.print_only_trait_path(), |
| assoc_name, |
| ), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } else { |
| err.note(&format!( |
| "associated type `{}` could derive from `{}`", |
| ty_param_name(), |
| bound.print_only_trait_path(), |
| )); |
| } |
| } |
| if !where_bounds.is_empty() { |
| err.help(&format!( |
| "consider introducing a new type parameter `T` and adding `where` constraints:\ |
| \n where\n T: {},\n{}", |
| ty_param_name(), |
| where_bounds.join(",\n"), |
| )); |
| } |
| err.emit(); |
| if !where_bounds.is_empty() { |
| return Err(ErrorReported); |
| } |
| } |
| return Ok(bound); |
| } |
| |
| fn complain_about_assoc_type_not_found<I>( |
| &self, |
| all_candidates: impl Fn() -> I, |
| ty_param_name: &str, |
| assoc_name: ast::Ident, |
| span: Span, |
| ) where |
| I: Iterator<Item = ty::PolyTraitRef<'tcx>>, |
| { |
| // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a |
| // valid span, so we point at the whole path segment instead. |
| let span = if assoc_name.span != DUMMY_SP { assoc_name.span } else { span }; |
| let mut err = struct_span_err!( |
| self.tcx().sess, |
| span, |
| E0220, |
| "associated type `{}` not found for `{}`", |
| assoc_name, |
| ty_param_name |
| ); |
| |
| let all_candidate_names: Vec<_> = all_candidates() |
| .map(|r| self.tcx().associated_items(r.def_id())) |
| .flatten() |
| .filter_map( |
| |item| if item.kind == ty::AssocKind::Type { Some(item.ident.name) } else { None }, |
| ) |
| .collect(); |
| |
| if let (Some(suggested_name), true) = ( |
| find_best_match_for_name(all_candidate_names.iter(), &assoc_name.as_str(), None), |
| assoc_name.span != DUMMY_SP, |
| ) { |
| err.span_suggestion( |
| assoc_name.span, |
| "there is an associated type with a similar name", |
| suggested_name.to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| } else { |
| err.span_label(span, format!("associated type `{}` not found", assoc_name)); |
| } |
| |
| err.emit(); |
| } |
| |
| // Create a type from a path to an associated type. |
| // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C` |
| // and item_segment is the path segment for `D`. We return a type and a def for |
| // the whole path. |
| // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type |
| // parameter or `Self`. |
| pub fn associated_path_to_ty( |
| &self, |
| hir_ref_id: hir::HirId, |
| span: Span, |
| qself_ty: Ty<'tcx>, |
| qself_res: Res, |
| assoc_segment: &hir::PathSegment<'_>, |
| permit_variants: bool, |
| ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> { |
| let tcx = self.tcx(); |
| let assoc_ident = assoc_segment.ident; |
| |
| debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident); |
| |
| // Check if we have an enum variant. |
| let mut variant_resolution = None; |
| if let ty::Adt(adt_def, _) = qself_ty.kind { |
| if adt_def.is_enum() { |
| let variant_def = adt_def |
| .variants |
| .iter() |
| .find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did)); |
| if let Some(variant_def) = variant_def { |
| if permit_variants { |
| tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span); |
| self.prohibit_generics(slice::from_ref(assoc_segment)); |
| return Ok((qself_ty, DefKind::Variant, variant_def.def_id)); |
| } else { |
| variant_resolution = Some(variant_def.def_id); |
| } |
| } |
| } |
| } |
| |
| // Find the type of the associated item, and the trait where the associated |
| // item is declared. |
| let bound = match (&qself_ty.kind, qself_res) { |
| (_, Res::SelfTy(Some(_), Some(impl_def_id))) => { |
| // `Self` in an impl of a trait -- we have a concrete self type and a |
| // trait reference. |
| let trait_ref = match tcx.impl_trait_ref(impl_def_id) { |
| Some(trait_ref) => trait_ref, |
| None => { |
| // A cycle error occurred, most likely. |
| return Err(ErrorReported); |
| } |
| }; |
| |
| self.one_bound_for_assoc_type( |
| || traits::supertraits(tcx, ty::Binder::bind(trait_ref)), |
| || "Self".to_string(), |
| assoc_ident, |
| span, |
| || None, |
| )? |
| } |
| (&ty::Param(_), Res::SelfTy(Some(param_did), None)) |
| | (&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => { |
| self.find_bound_for_assoc_item(param_did, assoc_ident, span)? |
| } |
| _ => { |
| if variant_resolution.is_some() { |
| // Variant in type position |
| let msg = format!("expected type, found variant `{}`", assoc_ident); |
| tcx.sess.span_err(span, &msg); |
| } else if qself_ty.is_enum() { |
| let mut err = struct_span_err!( |
| tcx.sess, |
| assoc_ident.span, |
| E0599, |
| "no variant named `{}` found for enum `{}`", |
| assoc_ident, |
| qself_ty, |
| ); |
| |
| let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT"); |
| if let Some(suggested_name) = find_best_match_for_name( |
| adt_def.variants.iter().map(|variant| &variant.ident.name), |
| &assoc_ident.as_str(), |
| None, |
| ) { |
| err.span_suggestion( |
| assoc_ident.span, |
| "there is a variant with a similar name", |
| suggested_name.to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| } else { |
| err.span_label( |
| assoc_ident.span, |
| format!("variant not found in `{}`", qself_ty), |
| ); |
| } |
| |
| if let Some(sp) = tcx.hir().span_if_local(adt_def.did) { |
| let sp = tcx.sess.source_map().def_span(sp); |
| err.span_label(sp, format!("variant `{}` not found here", assoc_ident)); |
| } |
| |
| err.emit(); |
| } else if !qself_ty.references_error() { |
| // Don't print `TyErr` to the user. |
| self.report_ambiguous_associated_type( |
| span, |
| &qself_ty.to_string(), |
| "Trait", |
| assoc_ident.name, |
| ); |
| } |
| return Err(ErrorReported); |
| } |
| }; |
| |
| let trait_did = bound.def_id(); |
| let (assoc_ident, def_scope) = |
| tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id); |
| let item = tcx |
| .associated_items(trait_did) |
| .find(|i| Namespace::from(i.kind) == Namespace::Type && i.ident.modern() == assoc_ident) |
| .expect("missing associated type"); |
| |
| let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, assoc_segment, bound); |
| let ty = self.normalize_ty(span, ty); |
| |
| let kind = DefKind::AssocTy; |
| if !item.vis.is_accessible_from(def_scope, tcx) { |
| let msg = format!("{} `{}` is private", kind.descr(item.def_id), assoc_ident); |
| tcx.sess.span_err(span, &msg); |
| } |
| tcx.check_stability(item.def_id, Some(hir_ref_id), span); |
| |
| if let Some(variant_def_id) = variant_resolution { |
| let mut err = tcx.struct_span_lint_hir( |
| AMBIGUOUS_ASSOCIATED_ITEMS, |
| hir_ref_id, |
| span, |
| "ambiguous associated item", |
| ); |
| |
| let mut could_refer_to = |kind: DefKind, def_id, also| { |
| let note_msg = format!( |
| "`{}` could{} refer to {} defined here", |
| assoc_ident, |
| also, |
| kind.descr(def_id) |
| ); |
| err.span_note(tcx.def_span(def_id), ¬e_msg); |
| }; |
| could_refer_to(DefKind::Variant, variant_def_id, ""); |
| could_refer_to(kind, item.def_id, " also"); |
| |
| err.span_suggestion( |
| span, |
| "use fully-qualified syntax", |
| format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident), |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| |
| Ok((ty, kind, item.def_id)) |
| } |
| |
| fn qpath_to_ty( |
| &self, |
| span: Span, |
| opt_self_ty: Option<Ty<'tcx>>, |
| item_def_id: DefId, |
| trait_segment: &hir::PathSegment<'_>, |
| item_segment: &hir::PathSegment<'_>, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx(); |
| |
| let trait_def_id = tcx.parent(item_def_id).unwrap(); |
| |
| debug!("qpath_to_ty: trait_def_id={:?}", trait_def_id); |
| |
| let self_ty = if let Some(ty) = opt_self_ty { |
| ty |
| } else { |
| let path_str = tcx.def_path_str(trait_def_id); |
| |
| let def_id = self.item_def_id(); |
| |
| debug!("qpath_to_ty: self.item_def_id()={:?}", def_id); |
| |
| let parent_def_id = def_id |
| .and_then(|def_id| tcx.hir().as_local_hir_id(def_id)) |
| .map(|hir_id| tcx.hir().get_parent_did(hir_id)); |
| |
| debug!("qpath_to_ty: parent_def_id={:?}", parent_def_id); |
| |
| // If the trait in segment is the same as the trait defining the item, |
| // use the `<Self as ..>` syntax in the error. |
| let is_part_of_self_trait_constraints = def_id == Some(trait_def_id); |
| let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id); |
| |
| let type_name = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait { |
| "Self" |
| } else { |
| "Type" |
| }; |
| |
| self.report_ambiguous_associated_type( |
| span, |
| type_name, |
| &path_str, |
| item_segment.ident.name, |
| ); |
| return tcx.types.err; |
| }; |
| |
| debug!("qpath_to_ty: self_type={:?}", self_ty); |
| |
| let trait_ref = self.ast_path_to_mono_trait_ref(span, trait_def_id, self_ty, trait_segment); |
| |
| let item_substs = self.create_substs_for_associated_item( |
| tcx, |
| span, |
| item_def_id, |
| item_segment, |
| trait_ref.substs, |
| ); |
| |
| debug!("qpath_to_ty: trait_ref={:?}", trait_ref); |
| |
| self.normalize_ty(span, tcx.mk_projection(item_def_id, item_substs)) |
| } |
| |
| pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment<'a>>>( |
| &self, |
| segments: T, |
| ) -> bool { |
| let mut has_err = false; |
| for segment in segments { |
| let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false); |
| for arg in segment.generic_args().args { |
| let (span, kind) = match arg { |
| hir::GenericArg::Lifetime(lt) => { |
| if err_for_lt { |
| continue; |
| } |
| err_for_lt = true; |
| has_err = true; |
| (lt.span, "lifetime") |
| } |
| hir::GenericArg::Type(ty) => { |
| if err_for_ty { |
| continue; |
| } |
| err_for_ty = true; |
| has_err = true; |
| (ty.span, "type") |
| } |
| hir::GenericArg::Const(ct) => { |
| if err_for_ct { |
| continue; |
| } |
| err_for_ct = true; |
| (ct.span, "const") |
| } |
| }; |
| let mut err = struct_span_err!( |
| self.tcx().sess, |
| span, |
| E0109, |
| "{} arguments are not allowed for this type", |
| kind, |
| ); |
| err.span_label(span, format!("{} argument not allowed", kind)); |
| err.emit(); |
| if err_for_lt && err_for_ty && err_for_ct { |
| break; |
| } |
| } |
| for binding in segment.generic_args().bindings { |
| has_err = true; |
| Self::prohibit_assoc_ty_binding(self.tcx(), binding.span); |
| break; |
| } |
| } |
| has_err |
| } |
| |
| pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_>, span: Span) { |
| let mut err = struct_span_err!( |
| tcx.sess, |
| span, |
| E0229, |
| "associated type bindings are not allowed here" |
| ); |
| err.span_label(span, "associated type not allowed here").emit(); |
| } |
| |
| // FIXME(eddyb, varkor) handle type paths here too, not just value ones. |
| pub fn def_ids_for_value_path_segments( |
| &self, |
| segments: &[hir::PathSegment<'_>], |
| self_ty: Option<Ty<'tcx>>, |
| kind: DefKind, |
| def_id: DefId, |
| ) -> Vec<PathSeg> { |
| // We need to extract the type parameters supplied by the user in |
| // the path `path`. Due to the current setup, this is a bit of a |
| // tricky-process; the problem is that resolve only tells us the |
| // end-point of the path resolution, and not the intermediate steps. |
| // Luckily, we can (at least for now) deduce the intermediate steps |
| // just from the end-point. |
| // |
| // There are basically five cases to consider: |
| // |
| // 1. Reference to a constructor of a struct: |
| // |
| // struct Foo<T>(...) |
| // |
| // In this case, the parameters are declared in the type space. |
| // |
| // 2. Reference to a constructor of an enum variant: |
| // |
| // enum E<T> { Foo(...) } |
| // |
| // In this case, the parameters are defined in the type space, |
| // but may be specified either on the type or the variant. |
| // |
| // 3. Reference to a fn item or a free constant: |
| // |
| // fn foo<T>() { } |
| // |
| // In this case, the path will again always have the form |
| // `a::b::foo::<T>` where only the final segment should have |
| // type parameters. However, in this case, those parameters are |
| // declared on a value, and hence are in the `FnSpace`. |
| // |
| // 4. Reference to a method or an associated constant: |
| // |
| // impl<A> SomeStruct<A> { |
| // fn foo<B>(...) |
| // } |
| // |
| // Here we can have a path like |
| // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters |
| // may appear in two places. The penultimate segment, |
| // `SomeStruct::<A>`, contains parameters in TypeSpace, and the |
| // final segment, `foo::<B>` contains parameters in fn space. |
| // |
| // The first step then is to categorize the segments appropriately. |
| |
| let tcx = self.tcx(); |
| |
| assert!(!segments.is_empty()); |
| let last = segments.len() - 1; |
| |
| let mut path_segs = vec![]; |
| |
| match kind { |
| // Case 1. Reference to a struct constructor. |
| DefKind::Ctor(CtorOf::Struct, ..) => { |
| // Everything but the final segment should have no |
| // parameters at all. |
| let generics = tcx.generics_of(def_id); |
| // Variant and struct constructors use the |
| // generics of their parent type definition. |
| let generics_def_id = generics.parent.unwrap_or(def_id); |
| path_segs.push(PathSeg(generics_def_id, last)); |
| } |
| |
| // Case 2. Reference to a variant constructor. |
| DefKind::Ctor(CtorOf::Variant, ..) | DefKind::Variant => { |
| let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap()); |
| let (generics_def_id, index) = if let Some(adt_def) = adt_def { |
| debug_assert!(adt_def.is_enum()); |
| (adt_def.did, last) |
| } else if last >= 1 && segments[last - 1].args.is_some() { |
| // Everything but the penultimate segment should have no |
| // parameters at all. |
| let mut def_id = def_id; |
| |
| // `DefKind::Ctor` -> `DefKind::Variant` |
| if let DefKind::Ctor(..) = kind { |
| def_id = tcx.parent(def_id).unwrap() |
| } |
| |
| // `DefKind::Variant` -> `DefKind::Enum` |
| let enum_def_id = tcx.parent(def_id).unwrap(); |
| (enum_def_id, last - 1) |
| } else { |
| // FIXME: lint here recommending `Enum::<...>::Variant` form |
| // instead of `Enum::Variant::<...>` form. |
| |
| // Everything but the final segment should have no |
| // parameters at all. |
| let generics = tcx.generics_of(def_id); |
| // Variant and struct constructors use the |
| // generics of their parent type definition. |
| (generics.parent.unwrap_or(def_id), last) |
| }; |
| path_segs.push(PathSeg(generics_def_id, index)); |
| } |
| |
| // Case 3. Reference to a top-level value. |
| DefKind::Fn | DefKind::Const | DefKind::ConstParam | DefKind::Static => { |
| path_segs.push(PathSeg(def_id, last)); |
| } |
| |
| // Case 4. Reference to a method or associated const. |
| DefKind::Method | DefKind::AssocConst => { |
| if segments.len() >= 2 { |
| let generics = tcx.generics_of(def_id); |
| path_segs.push(PathSeg(generics.parent.unwrap(), last - 1)); |
| } |
| path_segs.push(PathSeg(def_id, last)); |
| } |
| |
| kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id), |
| } |
| |
| debug!("path_segs = {:?}", path_segs); |
| |
| path_segs |
| } |
| |
| // Check a type `Path` and convert it to a `Ty`. |
| pub fn res_to_ty( |
| &self, |
| opt_self_ty: Option<Ty<'tcx>>, |
| path: &hir::Path<'_>, |
| permit_variants: bool, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx(); |
| |
| debug!( |
| "res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})", |
| path.res, opt_self_ty, path.segments |
| ); |
| |
| let span = path.span; |
| match path.res { |
| Res::Def(DefKind::OpaqueTy, did) => { |
| // Check for desugared `impl Trait`. |
| assert!(ty::is_impl_trait_defn(tcx, did).is_none()); |
| let item_segment = path.segments.split_last().unwrap(); |
| self.prohibit_generics(item_segment.1); |
| let substs = self.ast_path_substs_for_ty(span, did, item_segment.0); |
| self.normalize_ty(span, tcx.mk_opaque(did, substs)) |
| } |
| Res::Def(DefKind::Enum, did) |
| | Res::Def(DefKind::TyAlias, did) |
| | Res::Def(DefKind::Struct, did) |
| | Res::Def(DefKind::Union, did) |
| | Res::Def(DefKind::ForeignTy, did) => { |
| assert_eq!(opt_self_ty, None); |
| self.prohibit_generics(path.segments.split_last().unwrap().1); |
| self.ast_path_to_ty(span, did, path.segments.last().unwrap()) |
| } |
| Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => { |
| // Convert "variant type" as if it were a real type. |
| // The resulting `Ty` is type of the variant's enum for now. |
| assert_eq!(opt_self_ty, None); |
| |
| let path_segs = |
| self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id); |
| let generic_segs: FxHashSet<_> = |
| path_segs.iter().map(|PathSeg(_, index)| index).collect(); |
| self.prohibit_generics(path.segments.iter().enumerate().filter_map( |
| |(index, seg)| { |
| if !generic_segs.contains(&index) { Some(seg) } else { None } |
| }, |
| )); |
| |
| let PathSeg(def_id, index) = path_segs.last().unwrap(); |
| self.ast_path_to_ty(span, *def_id, &path.segments[*index]) |
| } |
| Res::Def(DefKind::TyParam, def_id) => { |
| assert_eq!(opt_self_ty, None); |
| self.prohibit_generics(path.segments); |
| |
| let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| let item_id = tcx.hir().get_parent_node(hir_id); |
| let item_def_id = tcx.hir().local_def_id(item_id); |
| let generics = tcx.generics_of(item_def_id); |
| let index = generics.param_def_id_to_index[&def_id]; |
| tcx.mk_ty_param(index, tcx.hir().name(hir_id)) |
| } |
| Res::SelfTy(Some(_), None) => { |
| // `Self` in trait or type alias. |
| assert_eq!(opt_self_ty, None); |
| self.prohibit_generics(path.segments); |
| tcx.types.self_param |
| } |
| Res::SelfTy(_, Some(def_id)) => { |
| // `Self` in impl (we know the concrete type). |
| assert_eq!(opt_self_ty, None); |
| self.prohibit_generics(path.segments); |
| // Try to evaluate any array length constants. |
| self.normalize_ty(span, tcx.at(span).type_of(def_id)) |
| } |
| Res::Def(DefKind::AssocTy, def_id) => { |
| debug_assert!(path.segments.len() >= 2); |
| self.prohibit_generics(&path.segments[..path.segments.len() - 2]); |
| self.qpath_to_ty( |
| span, |
| opt_self_ty, |
| def_id, |
| &path.segments[path.segments.len() - 2], |
| path.segments.last().unwrap(), |
| ) |
| } |
| Res::PrimTy(prim_ty) => { |
| assert_eq!(opt_self_ty, None); |
| self.prohibit_generics(path.segments); |
| match prim_ty { |
| hir::PrimTy::Bool => tcx.types.bool, |
| hir::PrimTy::Char => tcx.types.char, |
| hir::PrimTy::Int(it) => tcx.mk_mach_int(it), |
| hir::PrimTy::Uint(uit) => tcx.mk_mach_uint(uit), |
| hir::PrimTy::Float(ft) => tcx.mk_mach_float(ft), |
| hir::PrimTy::Str => tcx.mk_str(), |
| } |
| } |
| Res::Err => { |
| self.set_tainted_by_errors(); |
| return self.tcx().types.err; |
| } |
| _ => span_bug!(span, "unexpected resolution: {:?}", path.res), |
| } |
| } |
| |
| /// Parses the programmer's textual representation of a type into our |
| /// internal notion of a type. |
| pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> { |
| debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})", ast_ty.hir_id, ast_ty, ast_ty.kind); |
| |
| let tcx = self.tcx(); |
| |
| let result_ty = match ast_ty.kind { |
| hir::TyKind::Slice(ref ty) => tcx.mk_slice(self.ast_ty_to_ty(&ty)), |
| hir::TyKind::Ptr(ref mt) => { |
| tcx.mk_ptr(ty::TypeAndMut { ty: self.ast_ty_to_ty(&mt.ty), mutbl: mt.mutbl }) |
| } |
| hir::TyKind::Rptr(ref region, ref mt) => { |
| let r = self.ast_region_to_region(region, None); |
| debug!("ast_ty_to_ty: r={:?}", r); |
| let t = self.ast_ty_to_ty(&mt.ty); |
| tcx.mk_ref(r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl }) |
| } |
| hir::TyKind::Never => tcx.types.never, |
| hir::TyKind::Tup(ref fields) => { |
| tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t))) |
| } |
| hir::TyKind::BareFn(ref bf) => { |
| require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span); |
| tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl, &[], None)) |
| } |
| hir::TyKind::TraitObject(ref bounds, ref lifetime) => { |
| self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime) |
| } |
| hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => { |
| debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path); |
| let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself)); |
| self.res_to_ty(opt_self_ty, path, false) |
| } |
| hir::TyKind::Def(item_id, ref lifetimes) => { |
| let did = tcx.hir().local_def_id(item_id.id); |
| self.impl_trait_ty_to_ty(did, lifetimes) |
| } |
| hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => { |
| debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment); |
| let ty = self.ast_ty_to_ty(qself); |
| |
| let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.kind { |
| path.res |
| } else { |
| Res::Err |
| }; |
| self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false) |
| .map(|(ty, _, _)| ty) |
| .unwrap_or(tcx.types.err) |
| } |
| hir::TyKind::Array(ref ty, ref length) => { |
| let length = self.ast_const_to_const(length, tcx.types.usize); |
| let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length)); |
| self.normalize_ty(ast_ty.span, array_ty) |
| } |
| hir::TyKind::Typeof(ref _e) => { |
| struct_span_err!( |
| tcx.sess, |
| ast_ty.span, |
| E0516, |
| "`typeof` is a reserved keyword but unimplemented" |
| ) |
| .span_label(ast_ty.span, "reserved keyword") |
| .emit(); |
| |
| tcx.types.err |
| } |
| hir::TyKind::Infer => { |
| // Infer also appears as the type of arguments or return |
| // values in a ExprKind::Closure, or as |
| // the type of local variables. Both of these cases are |
| // handled specially and will not descend into this routine. |
| self.ty_infer(None, ast_ty.span) |
| } |
| hir::TyKind::Err => tcx.types.err, |
| }; |
| |
| debug!("ast_ty_to_ty: result_ty={:?}", result_ty); |
| |
| self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span); |
| result_ty |
| } |
| |
| /// Returns the `DefId` of the constant parameter that the provided expression is a path to. |
| pub fn const_param_def_id(&self, expr: &hir::Expr<'_>) -> Option<DefId> { |
| // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments |
| // currently have to be wrapped in curly brackets, so it's necessary to special-case. |
| let expr = match &expr.kind { |
| ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => { |
| block.expr.as_ref().unwrap() |
| } |
| _ => expr, |
| }; |
| |
| match &expr.kind { |
| ExprKind::Path(hir::QPath::Resolved(_, path)) => match path.res { |
| Res::Def(DefKind::ConstParam, did) => Some(did), |
| _ => None, |
| }, |
| _ => None, |
| } |
| } |
| |
| pub fn ast_const_to_const( |
| &self, |
| ast_const: &hir::AnonConst, |
| ty: Ty<'tcx>, |
| ) -> &'tcx ty::Const<'tcx> { |
| debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const); |
| |
| let tcx = self.tcx(); |
| let def_id = tcx.hir().local_def_id(ast_const.hir_id); |
| |
| let expr = &tcx.hir().body(ast_const.body).value; |
| |
| let lit_input = match expr.kind { |
| hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }), |
| hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind { |
| hir::ExprKind::Lit(ref lit) => { |
| Some(LitToConstInput { lit: &lit.node, ty, neg: true }) |
| } |
| _ => None, |
| }, |
| _ => None, |
| }; |
| |
| if let Some(lit_input) = lit_input { |
| // If an error occurred, ignore that it's a literal and leave reporting the error up to |
| // mir. |
| if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) { |
| return c; |
| } |
| } |
| |
| let kind = if let Some(def_id) = self.const_param_def_id(expr) { |
| // Find the name and index of the const parameter by indexing the generics of the |
| // parent item and construct a `ParamConst`. |
| let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| let item_id = tcx.hir().get_parent_node(hir_id); |
| let item_def_id = tcx.hir().local_def_id(item_id); |
| let generics = tcx.generics_of(item_def_id); |
| let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)]; |
| let name = tcx.hir().name(hir_id); |
| ty::ConstKind::Param(ty::ParamConst::new(index, name)) |
| } else { |
| ty::ConstKind::Unevaluated(def_id, InternalSubsts::identity_for_item(tcx, def_id), None) |
| }; |
| tcx.mk_const(ty::Const { val: kind, ty }) |
| } |
| |
| pub fn impl_trait_ty_to_ty( |
| &self, |
| def_id: DefId, |
| lifetimes: &[hir::GenericArg<'_>], |
| ) -> Ty<'tcx> { |
| debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes); |
| let tcx = self.tcx(); |
| |
| let generics = tcx.generics_of(def_id); |
| |
| debug!("impl_trait_ty_to_ty: generics={:?}", generics); |
| let substs = InternalSubsts::for_item(tcx, def_id, |param, _| { |
| if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) { |
| // Our own parameters are the resolved lifetimes. |
| match param.kind { |
| GenericParamDefKind::Lifetime => { |
| if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] { |
| self.ast_region_to_region(lifetime, None).into() |
| } else { |
| bug!() |
| } |
| } |
| _ => bug!(), |
| } |
| } else { |
| // Replace all parent lifetimes with `'static`. |
| match param.kind { |
| GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(), |
| _ => tcx.mk_param_from_def(param), |
| } |
| } |
| }); |
| debug!("impl_trait_ty_to_ty: substs={:?}", substs); |
| |
| let ty = tcx.mk_opaque(def_id, substs); |
| debug!("impl_trait_ty_to_ty: {}", ty); |
| ty |
| } |
| |
| pub fn ty_of_arg(&self, ty: &hir::Ty<'_>, expected_ty: Option<Ty<'tcx>>) -> Ty<'tcx> { |
| match ty.kind { |
| hir::TyKind::Infer if expected_ty.is_some() => { |
| self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span); |
| expected_ty.unwrap() |
| } |
| _ => self.ast_ty_to_ty(ty), |
| } |
| } |
| |
| pub fn ty_of_fn( |
| &self, |
| unsafety: hir::Unsafety, |
| abi: abi::Abi, |
| decl: &hir::FnDecl<'_>, |
| generic_params: &[hir::GenericParam<'_>], |
| ident_span: Option<Span>, |
| ) -> ty::PolyFnSig<'tcx> { |
| debug!("ty_of_fn"); |
| |
| let tcx = self.tcx(); |
| |
| // We proactively collect all the infered type params to emit a single error per fn def. |
| let mut visitor = PlaceholderHirTyCollector::default(); |
| for ty in decl.inputs { |
| visitor.visit_ty(ty); |
| } |
| let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None)); |
| let output_ty = match decl.output { |
| hir::FunctionRetTy::Return(ref output) => { |
| visitor.visit_ty(output); |
| self.ast_ty_to_ty(output) |
| } |
| hir::FunctionRetTy::DefaultReturn(..) => tcx.mk_unit(), |
| }; |
| |
| debug!("ty_of_fn: output_ty={:?}", output_ty); |
| |
| let bare_fn_ty = |
| ty::Binder::bind(tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi)); |
| |
| if !self.allow_ty_infer() { |
| // We always collect the spans for placeholder types when evaluating `fn`s, but we |
| // only want to emit an error complaining about them if infer types (`_`) are not |
| // allowed. `allow_ty_infer` gates this behavior. |
| crate::collect::placeholder_type_error( |
| tcx, |
| ident_span.map(|sp| sp.shrink_to_hi()).unwrap_or(DUMMY_SP), |
| generic_params, |
| visitor.0, |
| ident_span.is_some(), |
| ); |
| } |
| |
| // Find any late-bound regions declared in return type that do |
| // not appear in the arguments. These are not well-formed. |
| // |
| // Example: |
| // for<'a> fn() -> &'a str <-- 'a is bad |
| // for<'a> fn(&'a String) -> &'a str <-- 'a is ok |
| let inputs = bare_fn_ty.inputs(); |
| let late_bound_in_args = |
| tcx.collect_constrained_late_bound_regions(&inputs.map_bound(|i| i.to_owned())); |
| let output = bare_fn_ty.output(); |
| let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output); |
| for br in late_bound_in_ret.difference(&late_bound_in_args) { |
| let lifetime_name = match *br { |
| ty::BrNamed(_, name) => format!("lifetime `{}`,", name), |
| ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(), |
| }; |
| let mut err = struct_span_err!( |
| tcx.sess, |
| decl.output.span(), |
| E0581, |
| "return type references {} \ |
| which is not constrained by the fn input types", |
| lifetime_name |
| ); |
| if let ty::BrAnon(_) = *br { |
| // The only way for an anonymous lifetime to wind up |
| // in the return type but **also** be unconstrained is |
| // if it only appears in "associated types" in the |
| // input. See #47511 for an example. In this case, |
| // though we can easily give a hint that ought to be |
| // relevant. |
| err.note( |
| "lifetimes appearing in an associated type \ |
| are not considered constrained", |
| ); |
| } |
| err.emit(); |
| } |
| |
| bare_fn_ty |
| } |
| |
| /// Given the bounds on an object, determines what single region bound (if any) we can |
| /// use to summarize this type. The basic idea is that we will use the bound the user |
| /// provided, if they provided one, and otherwise search the supertypes of trait bounds |
| /// for region bounds. It may be that we can derive no bound at all, in which case |
| /// we return `None`. |
| fn compute_object_lifetime_bound( |
| &self, |
| span: Span, |
| existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>, |
| ) -> Option<ty::Region<'tcx>> // if None, use the default |
| { |
| let tcx = self.tcx(); |
| |
| debug!("compute_opt_region_bound(existential_predicates={:?})", existential_predicates); |
| |
| // No explicit region bound specified. Therefore, examine trait |
| // bounds and see if we can derive region bounds from those. |
| let derived_region_bounds = object_region_bounds(tcx, existential_predicates); |
| |
| // If there are no derived region bounds, then report back that we |
| // can find no region bound. The caller will use the default. |
| if derived_region_bounds.is_empty() { |
| return None; |
| } |
| |
| // If any of the derived region bounds are 'static, that is always |
| // the best choice. |
| if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) { |
| return Some(tcx.lifetimes.re_static); |
| } |
| |
| // Determine whether there is exactly one unique region in the set |
| // of derived region bounds. If so, use that. Otherwise, report an |
| // error. |
| let r = derived_region_bounds[0]; |
| if derived_region_bounds[1..].iter().any(|r1| r != *r1) { |
| struct_span_err!( |
| tcx.sess, |
| span, |
| E0227, |
| "ambiguous lifetime bound, explicit lifetime bound required" |
| ) |
| .emit(); |
| } |
| return Some(r); |
| } |
| } |
| |
| /// Collects together a list of bounds that are applied to some type, |
| /// after they've been converted into `ty` form (from the HIR |
| /// representations). These lists of bounds occur in many places in |
| /// Rust's syntax: |
| /// |
| /// ``` |
| /// trait Foo: Bar + Baz { } |
| /// ^^^^^^^^^ supertrait list bounding the `Self` type parameter |
| /// |
| /// fn foo<T: Bar + Baz>() { } |
| /// ^^^^^^^^^ bounding the type parameter `T` |
| /// |
| /// impl dyn Bar + Baz |
| /// ^^^^^^^^^ bounding the forgotten dynamic type |
| /// ``` |
| /// |
| /// Our representation is a bit mixed here -- in some cases, we |
| /// include the self type (e.g., `trait_bounds`) but in others we do |
| #[derive(Default, PartialEq, Eq, Clone, Debug)] |
| pub struct Bounds<'tcx> { |
| /// A list of region bounds on the (implicit) self type. So if you |
| /// had `T: 'a + 'b` this might would be a list `['a, 'b]` (but |
| /// the `T` is not explicitly included). |
| pub region_bounds: Vec<(ty::Region<'tcx>, Span)>, |
| |
| /// A list of trait bounds. So if you had `T: Debug` this would be |
| /// `T: Debug`. Note that the self-type is explicit here. |
| pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>, |
| |
| /// A list of projection equality bounds. So if you had `T: |
| /// Iterator<Item = u32>` this would include `<T as |
| /// Iterator>::Item => u32`. Note that the self-type is explicit |
| /// here. |
| pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>, |
| |
| /// `Some` if there is *no* `?Sized` predicate. The `span` |
| /// is the location in the source of the `T` declaration which can |
| /// be cited as the source of the `T: Sized` requirement. |
| pub implicitly_sized: Option<Span>, |
| } |
| |
| impl<'tcx> Bounds<'tcx> { |
| /// Converts a bounds list into a flat set of predicates (like |
| /// where-clauses). Because some of our bounds listings (e.g., |
| /// regions) don't include the self-type, you must supply the |
| /// self-type here (the `param_ty` parameter). |
| pub fn predicates( |
| &self, |
| tcx: TyCtxt<'tcx>, |
| param_ty: Ty<'tcx>, |
| ) -> Vec<(ty::Predicate<'tcx>, Span)> { |
| // If it could be sized, and is, add the `Sized` predicate. |
| let sized_predicate = self.implicitly_sized.and_then(|span| { |
| tcx.lang_items().sized_trait().map(|sized| { |
| let trait_ref = ty::Binder::bind(ty::TraitRef { |
| def_id: sized, |
| substs: tcx.mk_substs_trait(param_ty, &[]), |
| }); |
| (trait_ref.to_predicate(), span) |
| }) |
| }); |
| |
| sized_predicate |
| .into_iter() |
| .chain( |
| self.region_bounds |
| .iter() |
| .map(|&(region_bound, span)| { |
| // Account for the binder being introduced below; no need to shift `param_ty` |
| // because, at present at least, it either only refers to early-bound regions, |
| // or it's a generic associated type that deliberately has escaping bound vars. |
| let region_bound = ty::fold::shift_region(tcx, region_bound, 1); |
| let outlives = ty::OutlivesPredicate(param_ty, region_bound); |
| (ty::Binder::bind(outlives).to_predicate(), span) |
| }) |
| .chain( |
| self.trait_bounds |
| .iter() |
| .map(|&(bound_trait_ref, span)| (bound_trait_ref.to_predicate(), span)), |
| ) |
| .chain( |
| self.projection_bounds |
| .iter() |
| .map(|&(projection, span)| (projection.to_predicate(), span)), |
| ), |
| ) |
| .collect() |
| } |
| } |