Change:
That file () has almost 3k LOC and just 3 lines of documentation on the file (methods and types are documented though). I'm entirely unsure how to process that file. I think splitting it up into submodules (e.g. start by extracting out all functions just handling error reporting into a separate module). Some of this work can be just mechanical splitting up, but some parts may require you to start understanding at least some of what's going on in the file in order to find a good module structure. cc <!-- TRIAGEBOTSTART --<!-- TRIAGEBOTASSIGNSTART --<!-- TRIAGEBOTASSIGNDATASTARTTRIAGEBOTASSIGNDATAEND --<!-- TRIAGEBOTASSIGNEND --<!-- TRIAGEBOT_END --
I'll do it, although I am not familiar with the . At least the mechanical part is no problem. As to the model structure, I am going to dive into that issue so I can better think of a reasonable structure. If it is a problem that I am not familiar with the topic, I will back down, no worries.
That's awesome. Please wait until is merged though (you can subscribe to it so you see when it does get merged), because otherwise you'll just get loads of conflicts.
If you are unsure about the module structure, you can first post a design suggestion here if you want.
assign
You still working on this?
Not quite, my other PR is not yet through and I thought I wait for it. But if you want to do it, just take it. If not I'll be on it soon.
I would like to claim this, if nobody minds
assign It's all yours!
release-assignment
I'd like to work in this if is not on it anymore
generally it's fine if it's 3 months and there is no pr from the author. you can start working on it
Gotcha, thanks
claim

Discussion:
<del> // 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`. // ignore-tidy-filelength use crate::collect::PlaceholderHirTyCollector; use crate::middle::resolve_lifetime as rl; use crate::require_c_abi_if_c_variadic; use rustc_ast::{util::lev_distance::find_best_match_for_name, ParamKindOrd}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::ErrorReported; use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId, FatalError}; use rustc_hir as hir; use rustc_hir::def::{CtorOf, DefKind, Namespace, Res}; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::{walk_generics, Visitor as _}; use rustc_hir::lang_items::SizedTraitLangItem; use rustc_hir::{Constness, GenericArg, GenericArgs}; use rustc_middle::ty::subst::{self, InternalSubsts, Subst, SubstsRef}; use rustc_middle::ty::{ self, Const, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness, }; use rustc_middle::ty::{GenericParamDef, GenericParamDefKind}; use rustc_session::lint::builtin::{AMBIGUOUS_ASSOCIATED_ITEMS, LATE_BOUND_LIFETIME_ARGUMENTS}; use rustc_session::parse::feature_err; use rustc_session::Session; use rustc_span::symbol::{kw, sym, Ident, Symbol}; use rustc_span::{MultiSpan, Span, DUMMY_SP}; use rustc_target::spec::abi; use rustc_trait_selection::traits; use rustc_trait_selection::traits::astconv_object_safety_violations; use rustc_trait_selection::traits::error_reporting::report_object_safety_error; use rustc_trait_selection::traits::wf::object_region_bounds; use smallvec::SmallVec; use std::collections::BTreeSet; use std::iter; use std::slice; #[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>; fn default_constness_for_trait_bounds(&self) -> Constness; /// 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: Ident, kind: ConvertedBindingKind<'a, 'tcx>, span: Span, } enum ConvertedBindingKind<'a, 'tcx> { Equality(Ty<'tcx>), Constraint(&'a [hir::GenericBound<'a>]), } /// New-typed boolean indicating whether explicit late-bound lifetimes /// are present in a set of generic arguments. /// /// For example if we have some method `fn f<'a>(&'a self)` implemented /// for some type `T`, although `f` is generic in the lifetime `'a`, `'a` /// is late-bound so should not be provided explicitly. Thus, if `f` is /// instantiated with some generic arguments providing `'a` explicitly, /// we taint those arguments with `ExplicitLateBound::Yes` so that we /// can provide an appropriate diagnostic later. #[derive(Copy, Clone, PartialEq)] pub enum ExplicitLateBound { Yes, No, } #[derive(Copy, Clone, PartialEq)] enum GenericArgPosition { Type, Value, // e.g., functions MethodCall, } /// A marker denoting that the generic arguments that were /// provided did not match the respective generic parameters. #[derive(Clone, Default)] pub struct GenericArgCountMismatch { /// Indicates whether a fatal error was reported (`Some`), or just a lint (`None`). pub reported: Option<ErrorReported>, /// A list of spans of arguments provided that were not valid. pub invalid_args: Vec<Span>, } /// Decorates the result of a generic argument count mismatch /// check with whether explicit late bounds were provided. #[derive(Clone)] pub struct GenericArgCountResult { pub explicit_late_bound: ExplicitLateBound, pub correct: Result<(), GenericArgCountMismatch>, } 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().local_def_id_to_hir_id(def_id)); 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.expect_local()); 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.expect_local()); tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion { def_id: id, index, name })) } Some(rl::Region::Free(scope, id)) => { let name = lifetime_name(id.expect_local()); 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, ); if let Some(b) = assoc_bindings.first() { 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, ) -> GenericArgCountResult { 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` ) } /// 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, ) -> GenericArgCountResult { // 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); } let explicit_late_bound = Self::prohibit_explicit_late_bound_lifetimes(tcx, def, args, position); let check_kind_count = |kind, required, permitted, provided, offset, unexpected_spans: &mut Vec<Span>, silent| { 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 Ok(()); } if silent { return Err(true); } // 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 (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(); unexpected_spans.extend(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(); Err(true) }; let mut arg_count_correct = Ok(()); let mut unexpected_spans = vec![]; if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes { arg_count_correct = check_kind_count( "lifetime", param_counts.lifetimes, param_counts.lifetimes, arg_counts.lifetimes, 0, &mut unexpected_spans, explicit_late_bound == ExplicitLateBound::Yes, ) .and(arg_count_correct); } // FIXME(const_generics:defaults) if !infer_args || arg_counts.consts > param_counts.consts { arg_count_correct = check_kind_count( "const", param_counts.consts, param_counts.consts, arg_counts.consts, arg_counts.lifetimes + arg_counts.types, &mut unexpected_spans, false, ) .and(arg_count_correct); } // 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 { arg_count_correct = 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, &mut unexpected_spans, false, ) .and(arg_count_correct); } GenericArgCountResult { explicit_late_bound, correct: arg_count_correct.map_err(|reported_err| GenericArgCountMismatch { reported: if reported_err { Some(ErrorReported) } else { None }, invalid_args: unexpected_spans, }), } } /// Report an error that a generic argument did not match the generic parameter that was /// expected. fn generic_arg_mismatch_err( sess: &Session, arg: &GenericArg<'_>, kind: &'static str, help: Option<&str>, ) { let mut err = struct_span_err!( sess, arg.span(), E0747, "{} provided when a {} was expected", arg.descr(), kind, ); let unordered = sess.features_untracked().const_generics; let kind_ord = match kind { "lifetime" => ParamKindOrd::Lifetime, "type" => ParamKindOrd::Type, "constant" => ParamKindOrd::Const { unordered }, // It's more concise to match on the string representation, though it means // the match is non-exhaustive. _ => bug!("invalid generic parameter kind {}", kind), }; let arg_ord = match arg { GenericArg::Lifetime(_) => ParamKindOrd::Lifetime, GenericArg::Type(_) => ParamKindOrd::Type, GenericArg::Const(_) => ParamKindOrd::Const { unordered }, }; // This note is only true when generic parameters are strictly ordered by their kind. if kind_ord.cmp(&arg_ord) != core::cmp::Ordering::Equal { let (first, last) = if kind_ord < arg_ord { (kind, arg.descr()) } else { (arg.descr(), kind) }; err.note(&format!("{} arguments must be provided before {} arguments", first, last)); if let Some(help) = help { err.help(help); } } err.emit(); } /// 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>>, arg_count: GenericArgCountResult, args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs<'b>>, bool), mut provided_kind: impl FnMut(&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(&param) = 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(&param) = 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(); // If we encounter a type or const when we expect a lifetime, we infer the lifetimes. // If we later encounter a lifetime, we know that the arguments were provided in the // wrong order. `force_infer_lt` records the type or const that forced lifetimes to be // inferred, so we can use it for diagnostics later. let mut force_infer_lt = None; 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(&param)) => { match (arg, &param.kind, arg_count.explicit_late_bound) { (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime, _) | (GenericArg::Type(_), GenericParamDefKind::Type { .. }, _) | (GenericArg::Const(_), GenericParamDefKind::Const, _) => { substs.push(provided_kind(param, arg)); args.next(); params.next(); } ( GenericArg::Type(_) | 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)); force_infer_lt = Some(arg); params.next(); } (GenericArg::Lifetime(_), _, ExplicitLateBound::Yes) => { // We've come across a lifetime when we expected something else in // the presence of explicit late bounds. This is most likely // due to the presence of the explicit bound so we're just going to // ignore it. args.next(); } (_, kind, _) => { // We expected one kind of parameter, but the user provided // another. This is an error. However, if we already know that // the arguments don't match up with the parameters, we won't issue // an additional error, as the user already knows what's wrong. if arg_count.correct.is_ok() && arg_count.explicit_late_bound == ExplicitLateBound::No { // We're going to iterate over the parameters to sort them out, and // show that order to the user as a possible order for the parameters let mut param_types_present = defs .params .clone() .into_iter() .map(|param| { ( match param.kind { GenericParamDefKind::Lifetime => { ParamKindOrd::Lifetime } GenericParamDefKind::Type { .. } => { ParamKindOrd::Type } GenericParamDefKind::Const => { ParamKindOrd::Const { unordered: tcx .sess .features_untracked() .const_generics, } } }, param, ) }) .collect::<Vec<(ParamKindOrd, GenericParamDef)>>(); param_types_present.sort_by_key(|(ord, _)| *ord); let (mut param_types_present, ordered_params): ( Vec<ParamKindOrd>, Vec<GenericParamDef>, ) = param_types_present.into_iter().unzip(); param_types_present.dedup(); Self::generic_arg_mismatch_err( tcx.sess, arg, kind.descr(), Some(&format!( "reorder the arguments: {}: `<{}>`", param_types_present .into_iter() .map(|ord| format!("{}s", ord.to_string())) .collect::<Vec<String>>() .join(", then "), ordered_params .into_iter() .filter_map(|param| { if param.name == kw::SelfUpper { None } else { Some(param.name.to_string()) } }) .collect::<Vec<String>>() .join(", ") )), ); } // We've reported the error, but we want to make sure that this // problem doesn't bubble down and create additional, irrelevant // errors. In this case, we're simply going to ignore the argument // and any following arguments. The rest of the parameters will be // inferred. while args.next().is_some() {} } } } (Some(&arg), None) => { // We should never be able to reach this point with well-formed input. // There are three situations in which we can encounter this issue. // //  1.  The number of arguments is incorrect. In this case, an error //      will already have been emitted, and we can ignore it. //  2.  There are late-bound lifetime parameters present, yet the //      lifetime arguments have also been explicitly specified by the //      user. //  3.  We've inferred some lifetimes, which have been provided later (i.e. //      after a type or const). We want to throw an error in this case. if arg_count.correct.is_ok() && arg_count.explicit_late_bound == ExplicitLateBound::No { let kind = arg.descr(); assert_eq!(kind, "lifetime"); let provided = force_infer_lt.expect("lifetimes ought to have been inferred"); Self::generic_arg_mismatch_err(tcx.sess, provided, kind, None); } break; } (None, Some(&param)) => { // If there are fewer arguments than parameters, it means // we're inferring the remaining arguments. substs.push(inferred_kind(Some(&substs), param, infer_args)); 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 constraints 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>>, GenericArgCountResult) { // 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 arg_count = 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 default_ty = tcx.at(span).type_of(param.def_id); let self_param = tcx.types.self_param; if default_ty.walk().any(|arg| arg == self_param.into()) { // 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 mut inferred_params = vec![]; let substs = Self::create_substs_for_generic_args( tcx, def_id, parent_substs, self_ty.is_some(), self_ty, arg_count.clone(), // Provide the generic args, and whether types should be inferred. |did| { if did == def_id { (Some(generic_args), infer_args) } else { // The last component of this tuple is unimportant. (None, false) } }, // Provide substitutions for parameters for which (valid) arguments have been provided. |param, arg| match (&param.kind, arg) { (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => { self.ast_region_to_region(&lt, Some(param)).into() } (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => { if let (hir::TyKind::Infer, false) = (&ty.kind, self.allow_ty_infer()) { inferred_params.push(ty.span); tcx.ty_error().into() } else { self.ast_ty_to_ty(&ty).into() } } (GenericParamDefKind::Const, GenericArg::Const(ct)) => { ty::Const::from_opt_const_arg_anon_const( tcx, ty::WithOptConstParam { did: tcx.hir().local_def_id(ct.value.hir_id), const_param_did: Some(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.ty_error().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.ty_error().into() } } GenericParamDefKind::Const => { let ty = tcx.at(span).type_of(param.def_id); // FIXME(const_generics:defaults) if infer_args { // No const parameters were provided, we can infer all. self.ct_infer(ty, Some(param), span).into() } else { // We've already errored above about the mismatch. tcx.const_error(ty).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, arg_count) } 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( "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().unwrap_or_else(|| FatalError.raise()), 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, constness: Constness, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, speculative: bool, ) -> GenericArgCountResult { let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()); debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id); self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1); let (substs, assoc_bindings, arg_count) = self.create_substs_for_ast_trait_ref( 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, constness)); 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, binding.span, ); // Okay to ignore `Err` because of `ErrorReported` (see above). } debug!( "instantiate_poly_trait_ref({:?}, bounds={:?}) -> {:?}", trait_ref, bounds, poly_trait_ref ); arg_count } /// 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<'_>, constness: Constness, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, ) -> GenericArgCountResult { self.instantiate_poly_trait_ref_inner( &poly_trait_ref.trait_ref, poly_trait_ref.span, constness, self_ty, bounds, false, ) } pub fn instantiate_lang_item_trait_ref( &self, lang_item: hir::LangItem, span: Span, hir_id: hir::HirId, args: &GenericArgs<'_>, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, ) { let trait_def_id = self.tcx().require_lang_item(lang_item, Some(span)); let (substs, assoc_bindings, _) = self.create_substs_for_ast_path(span, trait_def_id, &[], args, false, Some(self_ty)); let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs)); bounds.trait_bounds.push((poly_trait_ref, span, Constness::NotConst)); let mut dup_bindings = FxHashMap::default(); for binding in assoc_bindings { let _: Result<_, ErrorReported> = self.add_predicates_for_ast_type_binding( hir_id, poly_trait_ref, &binding, bounds, false, &mut dup_bindings, span, ); } } 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); if let Some(b) = assoc_bindings.first() { 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 { let sess = &self.tcx().sess.parse_sess; // 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) => match ty.kind { hir::TyKind::Tup(t) => t .iter() .map(|e| sess.source_map().span_to_snippet(e.span)) .collect::<Result<Vec<_>, _>>() .map(|a| a.join(", ")), _ => sess.source_map().span_to_snippet(ty.span), } .map(|s| format!("({})", s)) .ok(), _ => None, }) .unwrap_or_else(|| "()".to_string()), trait_segment .generic_args() .bindings .iter() .find_map(|b| match (b.ident.name == sym::Output, &b.kind) { (true, hir::TypeBindingKind::Equality { ty }) => { sess.source_map().span_to_snippet(ty.span).ok() } _ => None, }) .unwrap_or_else(|| "()".to_string()), )), ) } else { ("parenthetical notation is only stable when used with `Fn`-family traits", None) }; 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>>, GenericArgCountResult) { 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: Ident) -> bool { self.tcx() .associated_items(trait_def_id) .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, trait_def_id) .is_some() } // 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: /// /// ```text /// 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(); let constness = self.default_constness_for_trait_bounds(); for ast_bound in ast_bounds { match *ast_bound { hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) => { trait_bounds.push((b, constness)) } hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::MaybeConst) => { trait_bounds.push((b, Constness::NotConst)) } hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {} hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => self .instantiate_lang_item_trait_ref( lang_item, span, hir_id, args, param_ty, bounds, ), hir::GenericBound::Outlives(ref l) => region_bounds.push(l), } } for (bound, constness) in trait_bounds { let _ = self.instantiate_poly_trait_ref(bound, constness, 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<i32> { } // trait SuperTrait<A> { type T; } // // ... B: SubTrait<T = foo> ... // ``` // // We want to produce `<B as SuperTrait<i32>>::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); // FIXME: point at the type params that don't have appropriate lifetimes: // struct S1<F: for<'a> Fn(&i32, &i32) -> &'a i32>(F); //                         ----  ----     ^^^^^^^ self.validate_late_bound_regions( late_bound_in_trait_ref, late_bound_in_ty, |br_name| { struct_span_err!( tcx.sess, binding.span, E0582, "binding for associated type `{}` references {},  which does not appear in the trait input types", binding.item_name, br_name ) }, ); } } 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); // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead // of calling `filter_by_name_and_kind`. let assoc_ty = tcx .associated_items(candidate.def_id()) .filter_by_name_unhygienic(assoc_ident.name) .find(|i| { i.kind == ty::AssocKind::Type && i.ident.normalize_to_macros_2_0() == assoc_ident }) .expect("missing associated type"); if !assoc_ty.vis.is_accessible_from(def_scope, tcx) { tcx.sess .struct_span_err( binding.span, &format!("associated type `{}` is private", binding.item_name), ) .span_label(binding.span, "private associated type") .emit(); } 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, borrowed: bool, ) -> 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() { if let GenericArgCountResult { correct: Err(GenericArgCountMismatch { invalid_args: cur_potential_assoc_types, .. }), .. } = self.instantiate_poly_trait_ref( trait_bound, Constness::NotConst, dummy_self, &mut bounds, ) { potential_assoc_types.extend(cur_potential_assoc_types.into_iter()); } } // 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().map(|&(a, b, _)| (a, b))); 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 = &regular_traits[0]; let additional_trait = &regular_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.help(&format!( "consider creating a new trait with all of these as super-traits and using that  trait here instead: `trait NewTrait: {} {{}}`", regular_traits .iter() .map(|t| t.trait_ref().print_only_trait_path().to_string()) .collect::<Vec<_>>() .join(" + "), )); err.note( "auto-traits like `Send` and `Sync` are traits that have special properties;  for more information on them, visit  <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>", ); 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.ty_error(); } // Check that there are no gross object safety violations; // most importantly, that the supertraits don't contain `Self`, // to avoid ICEs. for item in &regular_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.ty_error(); } } // 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, constness) in regular_traits_refs_spans { assert_eq!(constness, Constness::NotConst); for obligation in traits::elaborate_trait_ref(tcx, base_trait_ref) { debug!( "conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", obligation.predicate ); match obligation.predicate.skip_binders() { ty::PredicateAtom::Trait(pred, _) => { let pred = ty::Binder::bind(pred); associated_types.entry(span).or_default().extend( tcx.associated_items(pred.def_id()) .in_definition_order() .filter(|item| item.kind == ty::AssocKind::Type) .map(|item| item.def_id), ); } ty::PredicateAtom::Projection(pred) => { let pred = ty::Binder::bind(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(|arg| arg == dummy_self.into()); // 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 associated_types.values_mut() { 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_to_existential)); 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(|| { let mut err = struct_span_err!( tcx.sess, span, E0228, "the lifetime bound for this object type cannot be deduced  from context; please supply an explicit bound" ); if borrowed { // We will have already emitted an error E0106 complaining about a // missing named lifetime in `&dyn Trait`, so we elide this one. err.delay_as_bug(); } else { err.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().all(|v| v.is_empty()) { 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), )); } } if let ([], [bound]) = (&potential_assoc_types[..], &trait_bounds) { 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: Symbol, ) { 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: LocalDefId, assoc_name: 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.to_def_id()).predicates; debug!("find_bound_for_assoc_item: predicates={:#?}", predicates); let param_hir_id = tcx.hir().local_def_id_to_hir_id(ty_param_def_id); 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: 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_id = bound.def_id(); let bound_span = self .tcx() .associated_items(bound_id) .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_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    wheren        T: {},n{}", ty_param_name(), where_bounds.join(",n"), )); } err.emit(); if !where_bounds.is_empty() { return Err(ErrorReported); } } Ok(bound) } fn complain_about_assoc_type_not_found<I>( &self, all_candidates: impl Fn() -> I, ty_param_name: &str, assoc_name: 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()).in_definition_order()) .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.name, 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) | Res::Def(DefKind::TyParam, param_did), ) => self.find_bound_for_assoc_item(param_did.expect_local(), 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.name, 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().guess_head_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); // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead // of calling `filter_by_name_and_kind`. let item = tcx .associated_items(trait_did) .in_definition_order() .find(|i| { i.kind.namespace() == Namespace::TypeNS && i.ident.normalize_to_macros_2_0() == 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 kind = kind.descr(item.def_id); let msg = format!("{} `{}` is private", kind, assoc_ident); tcx.sess .struct_span_err(span, &msg) .span_label(span, &format!("private {}", kind)) .emit(); } tcx.check_stability(item.def_id, Some(hir_ref_id), span); if let Some(variant_def_id) = variant_resolution { tcx.struct_span_lint_hir(AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, |lint| { let mut err = lint.build("ambiguous associated item"); let mut could_refer_to = |kind: DefKind, def_id, also| { let note_msg = format!( "`{}` could{} refer to the {} defined here", assoc_ident, also, kind.descr(def_id) ); err.span_note(tcx.def_span(def_id), &note_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, ); err.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| { def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id)) }) .map(|hir_id| tcx.hir().get_parent_did(hir_id).to_def_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.ty_error(); }; 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; has_err = 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; } } // Only emit the first error to avoid overloading the user with error messages. if let [binding, ..] = segment.generic_args().bindings { has_err = true; Self::prohibit_assoc_ty_binding(self.tcx(), binding.span); } } 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(); } /// Prohibits explicit lifetime arguments if late-bound lifetime parameters /// are present. This is used both for datatypes and function calls. fn prohibit_explicit_late_bound_lifetimes( tcx: TyCtxt<'_>, def: &ty::Generics, args: &hir::GenericArgs<'_>, position: GenericArgPosition, ) -> ExplicitLateBound { let param_counts = def.own_counts(); let arg_counts = args.own_counts(); let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0; if infer_lifetimes { ExplicitLateBound::No } else 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(); } else { let mut multispan = MultiSpan::from_span(span); multispan.push_span_label(span_late, note.to_string()); tcx.struct_span_lint_hir( LATE_BOUND_LIFETIME_ARGUMENTS, args.args[0].id(), multispan, |lint| lint.build(msg).emit(), ); } ExplicitLateBound::Yes } else { ExplicitLateBound::No } } // 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::AssocFn | 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 | DefKind::TyAlias | DefKind::Struct | DefKind::Union | 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().local_def_id_to_hir_id(def_id.expect_local()); 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.types.str_, } } Res::Err => { self.set_tainted_by_errors(); self.tcx().ty_error() } _ => 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> { self.ast_ty_to_ty_inner(ast_ty, false) } /// Turns a `hir::Ty` into a `Ty`. For diagnostics' purposes we keep track of whether trait /// objects are borrowed like `&dyn Trait` to avoid emitting redundant errors. fn ast_ty_to_ty_inner(&self, ast_ty: &hir::Ty<'_>, borrowed: bool) -> 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_inner(&mt.ty, true); 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, &hir::Generics::empty(), None, )) } hir::TyKind::TraitObject(ref bounds, ref lifetime) => { self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime, borrowed) } 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::OpaqueDef(item_id, ref lifetimes) => { let opaque_ty = tcx.hir().expect_item(item_id.id); let def_id = tcx.hir().local_def_id(item_id.id).to_def_id(); match opaque_ty.kind { hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => { self.impl_trait_ty_to_ty(def_id, lifetimes, impl_trait_fn.is_some()) } ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i), } } 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_else(|_| tcx.ty_error()) } hir::TyKind::Path(hir::QPath::LangItem(lang_item, span)) => { let def_id = tcx.require_lang_item(lang_item, Some(span)); let (substs, _, _) = self.create_substs_for_ast_path( span, def_id, &[], &GenericArgs::none(), true, None, ); self.normalize_ty(span, tcx.at(span).type_of(def_id).subst(tcx, substs)) } hir::TyKind::Array(ref ty, ref length) => { let length_def_id = tcx.hir().local_def_id(length.hir_id); let length = ty::Const::from_anon_const(tcx, length_def_id); 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.ty_error() } 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.ty_error(), }; debug!("ast_ty_to_ty: result_ty={:?}", result_ty); self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span); result_ty } pub fn impl_trait_ty_to_ty( &self, def_id: DefId, lifetimes: &[hir::GenericArg<'_>], replace_parent_lifetimes: bool, ) -> 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 { match param.kind { // For RPIT (return position impl trait), only lifetimes // mentioned in the impl Trait predicate are captured by // the opaque type, so the lifetime parameters from the // parent item need to be replaced with `'static`. // // For `impl Trait` in the types of statics, constants, // locals and type aliases. These capture all parent // lifetimes, so they can use their identity subst. GenericParamDefKind::Lifetime if replace_parent_lifetimes => { 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<'_>, generics: &hir::Generics<'_>, ident_span: Option<Span>, ) -> ty::PolyFnSig<'tcx> { debug!("ty_of_fn"); let tcx = self.tcx(); // We proactively collect all the inferred type params to emit a single error per fn def. let mut visitor = PlaceholderHirTyCollector::default(); for ty in decl.inputs { visitor.visit_ty(ty); } walk_generics(&mut visitor, generics); let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None)); let output_ty = match decl.output { hir::FnRetTy::Return(ref output) => { visitor.visit_ty(output); self.ast_ty_to_ty(output) } hir::FnRetTy::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. We check for the presence of // `ident_span` to not emit an error twice when we have `fn foo(_: fn() -> _)`. crate::collect::placeholder_type_error( tcx, ident_span.map(|sp| sp.shrink_to_hi()), &generics.params[..], visitor.0, true, ); } // 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); self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| { struct_span_err!( tcx.sess, decl.output.span(), E0581, "return type references {}, which is not constrained by the fn input types", br_name ) }); bare_fn_ty } fn validate_late_bound_regions( &self, constrained_regions: FxHashSet<ty::BoundRegion>, referenced_regions: FxHashSet<ty::BoundRegion>, generate_err: impl Fn(&str) -> rustc_errors::DiagnosticBuilder<'tcx>, ) { for br in referenced_regions.difference(&constrained_regions) { let br_name = match *br { ty::BrNamed(_, name) => format!("lifetime `{}`", name), ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(), }; let mut err = generate_err(&br_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 and #62200 for examples. 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(); } } /// 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(); } 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: /// /// ```text /// 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, Constness)>, /// 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.without_const().to_predicate(tcx), 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(tcx), span) }) .chain(self.trait_bounds.iter().map(|&(bound_trait_ref, span, constness)| { let predicate = bound_trait_ref.with_constness(constness).to_predicate(tcx); (predicate, span) })) .chain( self.projection_bounds .iter() .map(|&(projection, span)| (projection.to_predicate(tcx), span)), ), ) .collect() } } </del>

<ins> use crate::astconv::AstConv; use rustc_ast::util::lev_distance::find_best_match_for_name; use rustc_data_structures::fx::FxHashMap; use rustc_errors::{pluralize, struct_span_err, Applicability}; use rustc_hir as hir; use rustc_hir::def_id::DefId; use rustc_middle::ty; use rustc_session::parse::feature_err; use rustc_span::symbol::{sym, Ident}; use rustc_span::{Span, DUMMY_SP}; use std::collections::BTreeSet; impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { /// On missing type parameters, emit an E0393 error and provide a structured suggestion using /// the type parameter's name as a placeholder. pub(crate) 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( "because of the default `Self` reference, type parameters must be  specified on object types", ); err.emit(); } /// 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. pub(crate) 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 { let sess = &self.tcx().sess.parse_sess; // 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) => match ty.kind { hir::TyKind::Tup(t) => t .iter() .map(|e| sess.source_map().span_to_snippet(e.span)) .collect::<Result<Vec<_>, _>>() .map(|a| a.join(", ")), _ => sess.source_map().span_to_snippet(ty.span), } .map(|s| format!("({})", s)) .ok(), _ => None, }) .unwrap_or_else(|| "()".to_string()), trait_segment .generic_args() .bindings .iter() .find_map(|b| match (b.ident.name == sym::Output, &b.kind) { (true, hir::TypeBindingKind::Equality { ty }) => { sess.source_map().span_to_snippet(ty.span).ok() } _ => None, }) .unwrap_or_else(|| "()".to_string()), )), ) } else { ("parenthetical notation is only stable when used with `Fn`-family traits", None) }; 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(); } } pub(crate) fn complain_about_assoc_type_not_found<I>( &self, all_candidates: impl Fn() -> I, ty_param_name: &str, assoc_name: 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()).in_definition_order()) .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.name, 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(); } /// 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. pub(crate) 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().all(|v| v.is_empty()) { 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), )); } } if let ([], [bound]) = (&potential_assoc_types[..], &trait_bounds) { 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(); } } </ins>

<ins> use crate::astconv::{ AstConv, ExplicitLateBound, GenericArgCountMismatch, GenericArgCountResult, GenericArgPosition, }; use rustc_ast::ast::ParamKindOrd; use rustc_errors::{pluralize, struct_span_err, DiagnosticId, ErrorReported}; use rustc_hir as hir; use rustc_hir::def_id::DefId; use rustc_hir::{GenericArg, GenericArgs}; use rustc_middle::ty::{ self, subst, subst::SubstsRef, GenericParamDef, GenericParamDefKind, Ty, TyCtxt, }; use rustc_session::{lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS, Session}; use rustc_span::{symbol::kw, MultiSpan, Span}; use smallvec::SmallVec; impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { /// Report an error that a generic argument did not match the generic parameter that was /// expected. fn generic_arg_mismatch_err( sess: &Session, arg: &GenericArg<'_>, kind: &'static str, help: Option<&str>, ) { let mut err = struct_span_err!( sess, arg.span(), E0747, "{} provided when a {} was expected", arg.descr(), kind, ); let unordered = sess.features_untracked().const_generics; let kind_ord = match kind { "lifetime" => ParamKindOrd::Lifetime, "type" => ParamKindOrd::Type, "constant" => ParamKindOrd::Const { unordered }, // It's more concise to match on the string representation, though it means // the match is non-exhaustive. _ => bug!("invalid generic parameter kind {}", kind), }; let arg_ord = match arg { GenericArg::Lifetime(_) => ParamKindOrd::Lifetime, GenericArg::Type(_) => ParamKindOrd::Type, GenericArg::Const(_) => ParamKindOrd::Const { unordered }, }; // This note is only true when generic parameters are strictly ordered by their kind. if kind_ord.cmp(&arg_ord) != core::cmp::Ordering::Equal { let (first, last) = if kind_ord < arg_ord { (kind, arg.descr()) } else { (arg.descr(), kind) }; err.note(&format!("{} arguments must be provided before {} arguments", first, last)); if let Some(help) = help { err.help(help); } } err.emit(); } /// 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>>, arg_count: GenericArgCountResult, args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs<'b>>, bool), mut provided_kind: impl FnMut(&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(&param) = 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(&param) = 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(); // If we encounter a type or const when we expect a lifetime, we infer the lifetimes. // If we later encounter a lifetime, we know that the arguments were provided in the // wrong order. `force_infer_lt` records the type or const that forced lifetimes to be // inferred, so we can use it for diagnostics later. let mut force_infer_lt = None; 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(&param)) => { match (arg, &param.kind, arg_count.explicit_late_bound) { (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime, _) | (GenericArg::Type(_), GenericParamDefKind::Type { .. }, _) | (GenericArg::Const(_), GenericParamDefKind::Const, _) => { substs.push(provided_kind(param, arg)); args.next(); params.next(); } ( GenericArg::Type(_) | 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)); force_infer_lt = Some(arg); params.next(); } (GenericArg::Lifetime(_), _, ExplicitLateBound::Yes) => { // We've come across a lifetime when we expected something else in // the presence of explicit late bounds. This is most likely // due to the presence of the explicit bound so we're just going to // ignore it. args.next(); } (_, kind, _) => { // We expected one kind of parameter, but the user provided // another. This is an error. However, if we already know that // the arguments don't match up with the parameters, we won't issue // an additional error, as the user already knows what's wrong. if arg_count.correct.is_ok() && arg_count.explicit_late_bound == ExplicitLateBound::No { // We're going to iterate over the parameters to sort them out, and // show that order to the user as a possible order for the parameters let mut param_types_present = defs .params .clone() .into_iter() .map(|param| { ( match param.kind { GenericParamDefKind::Lifetime => { ParamKindOrd::Lifetime } GenericParamDefKind::Type { .. } => { ParamKindOrd::Type } GenericParamDefKind::Const => { ParamKindOrd::Const { unordered: tcx .sess .features_untracked() .const_generics, } } }, param, ) }) .collect::<Vec<(ParamKindOrd, GenericParamDef)>>(); param_types_present.sort_by_key(|(ord, _)| *ord); let (mut param_types_present, ordered_params): ( Vec<ParamKindOrd>, Vec<GenericParamDef>, ) = param_types_present.into_iter().unzip(); param_types_present.dedup(); Self::generic_arg_mismatch_err( tcx.sess, arg, kind.descr(), Some(&format!( "reorder the arguments: {}: `<{}>`", param_types_present .into_iter() .map(|ord| format!("{}s", ord.to_string())) .collect::<Vec<String>>() .join(", then "), ordered_params .into_iter() .filter_map(|param| { if param.name == kw::SelfUpper { None } else { Some(param.name.to_string()) } }) .collect::<Vec<String>>() .join(", ") )), ); } // We've reported the error, but we want to make sure that this // problem doesn't bubble down and create additional, irrelevant // errors. In this case, we're simply going to ignore the argument // and any following arguments. The rest of the parameters will be // inferred. while args.next().is_some() {} } } } (Some(&arg), None) => { // We should never be able to reach this point with well-formed input. // There are three situations in which we can encounter this issue. // //  1.  The number of arguments is incorrect. In this case, an error //      will already have been emitted, and we can ignore it. //  2.  There are late-bound lifetime parameters present, yet the //      lifetime arguments have also been explicitly specified by the //      user. //  3.  We've inferred some lifetimes, which have been provided later (i.e. //      after a type or const). We want to throw an error in this case. if arg_count.correct.is_ok() && arg_count.explicit_late_bound == ExplicitLateBound::No { let kind = arg.descr(); assert_eq!(kind, "lifetime"); let provided = force_infer_lt.expect("lifetimes ought to have been inferred"); Self::generic_arg_mismatch_err(tcx.sess, provided, kind, None); } break; } (None, Some(&param)) => { // If there are fewer arguments than parameters, it means // we're inferring the remaining arguments. substs.push(inferred_kind(Some(&substs), param, infer_args)); params.next(); } (None, None) => break, } } } tcx.intern_substs(&substs) } /// 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, ) -> GenericArgCountResult { 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` ) } /// Checks that the correct number of generic arguments have been provided. /// This is used both for datatypes and function calls. pub(crate) fn check_generic_arg_count( tcx: TyCtxt<'_>, span: Span, def: &ty::Generics, args: &hir::GenericArgs<'_>, position: GenericArgPosition, has_self: bool, infer_args: bool, ) -> GenericArgCountResult { // 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() { Self::prohibit_assoc_ty_binding(tcx, args.bindings[0].span); } let explicit_late_bound = Self::prohibit_explicit_late_bound_lifetimes(tcx, def, args, position); let check_kind_count = |kind, required, permitted, provided, offset, unexpected_spans: &mut Vec<Span>, silent| { 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 Ok(()); } if silent { return Err(true); } // 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 (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(); unexpected_spans.extend(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(); Err(true) }; let mut arg_count_correct = Ok(()); let mut unexpected_spans = vec![]; if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes { arg_count_correct = check_kind_count( "lifetime", param_counts.lifetimes, param_counts.lifetimes, arg_counts.lifetimes, 0, &mut unexpected_spans, explicit_late_bound == ExplicitLateBound::Yes, ) .and(arg_count_correct); } // FIXME(const_generics:defaults) if !infer_args || arg_counts.consts > param_counts.consts { arg_count_correct = check_kind_count( "const", param_counts.consts, param_counts.consts, arg_counts.consts, arg_counts.lifetimes + arg_counts.types, &mut unexpected_spans, false, ) .and(arg_count_correct); } // 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 { arg_count_correct = 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, &mut unexpected_spans, false, ) .and(arg_count_correct); } GenericArgCountResult { explicit_late_bound, correct: arg_count_correct.map_err(|reported_err| GenericArgCountMismatch { reported: if reported_err { Some(ErrorReported) } else { None }, invalid_args: unexpected_spans, }), } } /// Report error if there is an explicit type parameter when using `impl Trait`. pub(crate) 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 } /// Emits an error regarding forbidden type binding associations 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(); } /// Prohibits explicit lifetime arguments if late-bound lifetime parameters /// are present. This is used both for datatypes and function calls. pub(crate) fn prohibit_explicit_late_bound_lifetimes( tcx: TyCtxt<'_>, def: &ty::Generics, args: &hir::GenericArgs<'_>, position: GenericArgPosition, ) -> ExplicitLateBound { let param_counts = def.own_counts(); let arg_counts = args.own_counts(); let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0; if infer_lifetimes { ExplicitLateBound::No } else 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(); } else { let mut multispan = MultiSpan::from_span(span); multispan.push_span_label(span_late, note.to_string()); tcx.struct_span_lint_hir( LATE_BOUND_LIFETIME_ARGUMENTS, args.args[0].id(), multispan, |lint| lint.build(msg).emit(), ); } ExplicitLateBound::Yes } else { ExplicitLateBound::No } } } </ins>

<ins> //! 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`. mod errors; mod generics; use crate::bounds::Bounds; use crate::collect::PlaceholderHirTyCollector; use crate::middle::resolve_lifetime as rl; use crate::require_c_abi_if_c_variadic; use rustc_ast::util::lev_distance::find_best_match_for_name; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::{struct_span_err, Applicability, ErrorReported, FatalError}; use rustc_hir as hir; use rustc_hir::def::{CtorOf, DefKind, Namespace, Res}; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::{walk_generics, Visitor as _}; use rustc_hir::lang_items::SizedTraitLangItem; use rustc_hir::{Constness, GenericArg, GenericArgs}; use rustc_middle::ty::subst::{self, InternalSubsts, Subst, SubstsRef}; use rustc_middle::ty::GenericParamDefKind; use rustc_middle::ty::{self, Const, DefIdTree, Ty, TyCtxt, TypeFoldable}; use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS; use rustc_span::symbol::{Ident, Symbol}; use rustc_span::{Span, DUMMY_SP}; use rustc_target::spec::abi; use rustc_trait_selection::traits; use rustc_trait_selection::traits::astconv_object_safety_violations; use rustc_trait_selection::traits::error_reporting::report_object_safety_error; use rustc_trait_selection::traits::wf::object_region_bounds; use smallvec::SmallVec; use std::collections::BTreeSet; use std::iter; use std::slice; #[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>; fn default_constness_for_trait_bounds(&self) -> Constness; /// 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: Ident, kind: ConvertedBindingKind<'a, 'tcx>, span: Span, } enum ConvertedBindingKind<'a, 'tcx> { Equality(Ty<'tcx>), Constraint(&'a [hir::GenericBound<'a>]), } /// New-typed boolean indicating whether explicit late-bound lifetimes /// are present in a set of generic arguments. /// /// For example if we have some method `fn f<'a>(&'a self)` implemented /// for some type `T`, although `f` is generic in the lifetime `'a`, `'a` /// is late-bound so should not be provided explicitly. Thus, if `f` is /// instantiated with some generic arguments providing `'a` explicitly, /// we taint those arguments with `ExplicitLateBound::Yes` so that we /// can provide an appropriate diagnostic later. #[derive(Copy, Clone, PartialEq)] pub enum ExplicitLateBound { Yes, No, } /// Denotes the "position" of a generic argument, indicating if it is a generic type, /// generic function or generic method call. #[derive(Copy, Clone, PartialEq)] pub(crate) enum GenericArgPosition { Type, Value, // e.g., functions MethodCall, } /// A marker denoting that the generic arguments that were /// provided did not match the respective generic parameters. #[derive(Clone, Default)] pub struct GenericArgCountMismatch { /// Indicates whether a fatal error was reported (`Some`), or just a lint (`None`). pub reported: Option<ErrorReported>, /// A list of spans of arguments provided that were not valid. pub invalid_args: Vec<Span>, } /// Decorates the result of a generic argument count mismatch /// check with whether explicit late bounds were provided. #[derive(Clone)] pub struct GenericArgCountResult { pub explicit_late_bound: ExplicitLateBound, pub correct: Result<(), GenericArgCountMismatch>, } 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().local_def_id_to_hir_id(def_id)); 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.expect_local()); 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.expect_local()); tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion { def_id: id, index, name })) } Some(rl::Region::Free(scope, id)) => { let name = lifetime_name(id.expect_local()); 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, ); if let Some(b) = assoc_bindings.first() { Self::prohibit_assoc_ty_binding(self.tcx(), b.span); } 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 constraints 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>>, GenericArgCountResult) { // 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 arg_count = 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 default_ty = tcx.at(span).type_of(param.def_id); let self_param = tcx.types.self_param; if default_ty.walk().any(|arg| arg == self_param.into()) { // 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 mut inferred_params = vec![]; let substs = Self::create_substs_for_generic_args( tcx, def_id, parent_substs, self_ty.is_some(), self_ty, arg_count.clone(), // Provide the generic args, and whether types should be inferred. |did| { if did == def_id { (Some(generic_args), infer_args) } else { // The last component of this tuple is unimportant. (None, false) } }, // Provide substitutions for parameters for which (valid) arguments have been provided. |param, arg| match (&param.kind, arg) { (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => { self.ast_region_to_region(&lt, Some(param)).into() } (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => { if let (hir::TyKind::Infer, false) = (&ty.kind, self.allow_ty_infer()) { inferred_params.push(ty.span); tcx.ty_error().into() } else { self.ast_ty_to_ty(&ty).into() } } (GenericParamDefKind::Const, GenericArg::Const(ct)) => { ty::Const::from_opt_const_arg_anon_const( tcx, ty::WithOptConstParam { did: tcx.hir().local_def_id(ct.value.hir_id), const_param_did: Some(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.ty_error().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.ty_error().into() } } GenericParamDefKind::Const => { let ty = tcx.at(span).type_of(param.def_id); // FIXME(const_generics:defaults) if infer_args { // No const parameters were provided, we can infer all. self.ct_infer(ty, Some(param), span).into() } else { // We've already errored above about the mismatch. tcx.const_error(ty).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, arg_count) } 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 } } /// 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().unwrap_or_else(|| FatalError.raise()), 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, constness: Constness, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, speculative: bool, ) -> GenericArgCountResult { let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()); debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id); self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1); let (substs, assoc_bindings, arg_count) = self.create_substs_for_ast_trait_ref( 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, constness)); 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, binding.span, ); // Okay to ignore `Err` because of `ErrorReported` (see above). } debug!( "instantiate_poly_trait_ref({:?}, bounds={:?}) -> {:?}", trait_ref, bounds, poly_trait_ref ); arg_count } /// 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<'_>, constness: Constness, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, ) -> GenericArgCountResult { self.instantiate_poly_trait_ref_inner( &poly_trait_ref.trait_ref, poly_trait_ref.span, constness, self_ty, bounds, false, ) } pub fn instantiate_lang_item_trait_ref( &self, lang_item: hir::LangItem, span: Span, hir_id: hir::HirId, args: &GenericArgs<'_>, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, ) { let trait_def_id = self.tcx().require_lang_item(lang_item, Some(span)); let (substs, assoc_bindings, _) = self.create_substs_for_ast_path(span, trait_def_id, &[], args, false, Some(self_ty)); let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs)); bounds.trait_bounds.push((poly_trait_ref, span, Constness::NotConst)); let mut dup_bindings = FxHashMap::default(); for binding in assoc_bindings { let _: Result<_, ErrorReported> = self.add_predicates_for_ast_type_binding( hir_id, poly_trait_ref, &binding, bounds, false, &mut dup_bindings, span, ); } } 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); if let Some(b) = assoc_bindings.first() { Self::prohibit_assoc_ty_binding(self.tcx(), b.span); } ty::TraitRef::new(trait_def_id, substs) } 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>>, GenericArgCountResult) { 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: Ident) -> bool { self.tcx() .associated_items(trait_def_id) .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, trait_def_id) .is_some() } // 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: /// /// ```text /// 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(); let constness = self.default_constness_for_trait_bounds(); for ast_bound in ast_bounds { match *ast_bound { hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) => { trait_bounds.push((b, constness)) } hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::MaybeConst) => { trait_bounds.push((b, Constness::NotConst)) } hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {} hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => self .instantiate_lang_item_trait_ref( lang_item, span, hir_id, args, param_ty, bounds, ), hir::GenericBound::Outlives(ref l) => region_bounds.push(l), } } for (bound, constness) in trait_bounds { let _ = self.instantiate_poly_trait_ref(bound, constness, 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<i32> { } // trait SuperTrait<A> { type T; } // // ... B: SubTrait<T = foo> ... // ``` // // We want to produce `<B as SuperTrait<i32>>::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); // FIXME: point at the type params that don't have appropriate lifetimes: // struct S1<F: for<'a> Fn(&i32, &i32) -> &'a i32>(F); //                         ----  ----     ^^^^^^^ self.validate_late_bound_regions( late_bound_in_trait_ref, late_bound_in_ty, |br_name| { struct_span_err!( tcx.sess, binding.span, E0582, "binding for associated type `{}` references {},  which does not appear in the trait input types", binding.item_name, br_name ) }, ); } } 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); // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead // of calling `filter_by_name_and_kind`. let assoc_ty = tcx .associated_items(candidate.def_id()) .filter_by_name_unhygienic(assoc_ident.name) .find(|i| { i.kind == ty::AssocKind::Type && i.ident.normalize_to_macros_2_0() == assoc_ident }) .expect("missing associated type"); if !assoc_ty.vis.is_accessible_from(def_scope, tcx) { tcx.sess .struct_span_err( binding.span, &format!("associated type `{}` is private", binding.item_name), ) .span_label(binding.span, "private associated type") .emit(); } 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, borrowed: bool, ) -> 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() { if let GenericArgCountResult { correct: Err(GenericArgCountMismatch { invalid_args: cur_potential_assoc_types, .. }), .. } = self.instantiate_poly_trait_ref( trait_bound, Constness::NotConst, dummy_self, &mut bounds, ) { potential_assoc_types.extend(cur_potential_assoc_types.into_iter()); } } // 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().map(|&(a, b, _)| (a, b))); 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 = &regular_traits[0]; let additional_trait = &regular_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.help(&format!( "consider creating a new trait with all of these as super-traits and using that  trait here instead: `trait NewTrait: {} {{}}`", regular_traits .iter() .map(|t| t.trait_ref().print_only_trait_path().to_string()) .collect::<Vec<_>>() .join(" + "), )); err.note( "auto-traits like `Send` and `Sync` are traits that have special properties;  for more information on them, visit  <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>", ); 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.ty_error(); } // Check that there are no gross object safety violations; // most importantly, that the supertraits don't contain `Self`, // to avoid ICEs. for item in &regular_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.ty_error(); } } // 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, constness) in regular_traits_refs_spans { assert_eq!(constness, Constness::NotConst); for obligation in traits::elaborate_trait_ref(tcx, base_trait_ref) { debug!( "conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", obligation.predicate ); match obligation.predicate.skip_binders() { ty::PredicateAtom::Trait(pred, _) => { let pred = ty::Binder::bind(pred); associated_types.entry(span).or_default().extend( tcx.associated_items(pred.def_id()) .in_definition_order() .filter(|item| item.kind == ty::AssocKind::Type) .map(|item| item.def_id), ); } ty::PredicateAtom::Projection(pred) => { let pred = ty::Binder::bind(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(|arg| arg == dummy_self.into()); // 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 associated_types.values_mut() { 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_to_existential)); 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(|| { let mut err = struct_span_err!( tcx.sess, span, E0228, "the lifetime bound for this object type cannot be deduced  from context; please supply an explicit bound" ); if borrowed { // We will have already emitted an error E0106 complaining about a // missing named lifetime in `&dyn Trait`, so we elide this one. err.delay_as_bug(); } else { err.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 } fn report_ambiguous_associated_type( &self, span: Span, type_str: &str, trait_str: &str, name: Symbol, ) { 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: LocalDefId, assoc_name: 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.to_def_id()).predicates; debug!("find_bound_for_assoc_item: predicates={:#?}", predicates); let param_hir_id = tcx.hir().local_def_id_to_hir_id(ty_param_def_id); 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: 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_id = bound.def_id(); let bound_span = self .tcx() .associated_items(bound_id) .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_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    wheren        T: {},n{}", ty_param_name(), where_bounds.join(",n"), )); } err.emit(); if !where_bounds.is_empty() { return Err(ErrorReported); } } Ok(bound) } // 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) | Res::Def(DefKind::TyParam, param_did), ) => self.find_bound_for_assoc_item(param_did.expect_local(), 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.name, 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().guess_head_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); // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead // of calling `filter_by_name_and_kind`. let item = tcx .associated_items(trait_did) .in_definition_order() .find(|i| { i.kind.namespace() == Namespace::TypeNS && i.ident.normalize_to_macros_2_0() == 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 kind = kind.descr(item.def_id); let msg = format!("{} `{}` is private", kind, assoc_ident); tcx.sess .struct_span_err(span, &msg) .span_label(span, &format!("private {}", kind)) .emit(); } tcx.check_stability(item.def_id, Some(hir_ref_id), span); if let Some(variant_def_id) = variant_resolution { tcx.struct_span_lint_hir(AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, |lint| { let mut err = lint.build("ambiguous associated item"); let mut could_refer_to = |kind: DefKind, def_id, also| { let note_msg = format!( "`{}` could{} refer to the {} defined here", assoc_ident, also, kind.descr(def_id) ); err.span_note(tcx.def_span(def_id), &note_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, ); err.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| { def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id)) }) .map(|hir_id| tcx.hir().get_parent_did(hir_id).to_def_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.ty_error(); }; 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; has_err = 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; } } // Only emit the first error to avoid overloading the user with error messages. if let [binding, ..] = segment.generic_args().bindings { has_err = true; Self::prohibit_assoc_ty_binding(self.tcx(), binding.span); } } has_err } // 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::AssocFn | 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 | DefKind::TyAlias | DefKind::Struct | DefKind::Union | 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().local_def_id_to_hir_id(def_id.expect_local()); 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.types.str_, } } Res::Err => { self.set_tainted_by_errors(); self.tcx().ty_error() } _ => 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> { self.ast_ty_to_ty_inner(ast_ty, false) } /// Turns a `hir::Ty` into a `Ty`. For diagnostics' purposes we keep track of whether trait /// objects are borrowed like `&dyn Trait` to avoid emitting redundant errors. fn ast_ty_to_ty_inner(&self, ast_ty: &hir::Ty<'_>, borrowed: bool) -> 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_inner(&mt.ty, true); 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, &hir::Generics::empty(), None, )) } hir::TyKind::TraitObject(ref bounds, ref lifetime) => { self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime, borrowed) } 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::OpaqueDef(item_id, ref lifetimes) => { let opaque_ty = tcx.hir().expect_item(item_id.id); let def_id = tcx.hir().local_def_id(item_id.id).to_def_id(); match opaque_ty.kind { hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => { self.impl_trait_ty_to_ty(def_id, lifetimes, impl_trait_fn.is_some()) } ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i), } } 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_else(|_| tcx.ty_error()) } hir::TyKind::Path(hir::QPath::LangItem(lang_item, span)) => { let def_id = tcx.require_lang_item(lang_item, Some(span)); let (substs, _, _) = self.create_substs_for_ast_path( span, def_id, &[], &GenericArgs::none(), true, None, ); self.normalize_ty(span, tcx.at(span).type_of(def_id).subst(tcx, substs)) } hir::TyKind::Array(ref ty, ref length) => { let length_def_id = tcx.hir().local_def_id(length.hir_id); let length = ty::Const::from_anon_const(tcx, length_def_id); 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.ty_error() } 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.ty_error(), }; debug!("ast_ty_to_ty: result_ty={:?}", result_ty); self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span); result_ty } pub fn impl_trait_ty_to_ty( &self, def_id: DefId, lifetimes: &[hir::GenericArg<'_>], replace_parent_lifetimes: bool, ) -> 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 { match param.kind { // For RPIT (return position impl trait), only lifetimes // mentioned in the impl Trait predicate are captured by // the opaque type, so the lifetime parameters from the // parent item need to be replaced with `'static`. // // For `impl Trait` in the types of statics, constants, // locals and type aliases. These capture all parent // lifetimes, so they can use their identity subst. GenericParamDefKind::Lifetime if replace_parent_lifetimes => { 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<'_>, generics: &hir::Generics<'_>, ident_span: Option<Span>, ) -> ty::PolyFnSig<'tcx> { debug!("ty_of_fn"); let tcx = self.tcx(); // We proactively collect all the inferred type params to emit a single error per fn def. let mut visitor = PlaceholderHirTyCollector::default(); for ty in decl.inputs { visitor.visit_ty(ty); } walk_generics(&mut visitor, generics); let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None)); let output_ty = match decl.output { hir::FnRetTy::Return(ref output) => { visitor.visit_ty(output); self.ast_ty_to_ty(output) } hir::FnRetTy::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. We check for the presence of // `ident_span` to not emit an error twice when we have `fn foo(_: fn() -> _)`. crate::collect::placeholder_type_error( tcx, ident_span.map(|sp| sp.shrink_to_hi()), &generics.params[..], visitor.0, true, ); } // 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); self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| { struct_span_err!( tcx.sess, decl.output.span(), E0581, "return type references {}, which is not constrained by the fn input types", br_name ) }); bare_fn_ty } fn validate_late_bound_regions( &self, constrained_regions: FxHashSet<ty::BoundRegion>, referenced_regions: FxHashSet<ty::BoundRegion>, generate_err: impl Fn(&str) -> rustc_errors::DiagnosticBuilder<'tcx>, ) { for br in referenced_regions.difference(&constrained_regions) { let br_name = match *br { ty::BrNamed(_, name) => format!("lifetime `{}`", name), ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(), }; let mut err = generate_err(&br_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 and #62200 for examples. 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(); } } /// 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(); } Some(r) } } </ins>

<ins> //! Bounds are restrictions applied to some types after they've been converted into the //! `ty` form from the HIR. use rustc_hir::Constness; use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, WithConstness}; use rustc_span::Span; /// Collects together a list of type bounds. These lists of bounds occur in many places /// in Rust's syntax: /// /// ```text /// 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 not #[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, Constness)>, /// 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.without_const().to_predicate(tcx), 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(tcx), span) }) .chain(self.trait_bounds.iter().map(|&(bound_trait_ref, span, constness)| { let predicate = bound_trait_ref.with_constness(constness).to_predicate(tcx); (predicate, span) })) .chain( self.projection_bounds .iter() .map(|&(projection, span)| (projection.to_predicate(tcx), span)), ), ) .collect() } } </ins>

//! At present, however, we do run collection across all items in the //! crate as a kind of pass. This should eventually be factored away. <del> use crate::astconv::{AstConv, Bounds, SizedByDefault}; </del> <ins> use crate::astconv::{AstConv, SizedByDefault}; use crate::bounds::Bounds; </ins> use crate::check::intrinsic::intrinsic_operation_unsafety; use crate::constrained_generic_params as cgp; use crate::middle::resolve_lifetime as rl;

pub mod expr_use_visitor; mod astconv; <ins> mod bounds; </ins> mod check_unused; mod coherence; mod collect;

use std::iter; <del> use astconv::{AstConv, Bounds}; </del> <ins> use astconv::AstConv; use bounds::Bounds; </ins> fn require_c_abi_if_c_variadic(tcx: TyCtxt<'_>, decl: &hir::FnDecl<'_>, abi: Abi, span: Span) { if decl.c_variadic && !(abi == Abi::C || abi == Abi::Cdecl) {