| use super::MethodError; |
| use super::NoMatchData; |
| use super::{CandidateSource, ImplSource, TraitSource}; |
| use super::suggest; |
| |
| use crate::check::autoderef::{self, Autoderef}; |
| use crate::check::FnCtxt; |
| use crate::hir::def_id::DefId; |
| use crate::hir::def::DefKind; |
| use crate::namespace::Namespace; |
| |
| use rustc_data_structures::sync::Lrc; |
| use rustc::hir; |
| use rustc::lint; |
| use rustc::session::config::nightly_options; |
| use rustc::ty::subst::{Subst, InternalSubsts, SubstsRef}; |
| use rustc::traits::{self, ObligationCause}; |
| use rustc::traits::query::{CanonicalTyGoal}; |
| use rustc::traits::query::method_autoderef::{CandidateStep, MethodAutoderefStepsResult}; |
| use rustc::traits::query::method_autoderef::{MethodAutoderefBadTy}; |
| use rustc::ty::{self, ParamEnvAnd, Ty, TyCtxt, ToPolyTraitRef, ToPredicate, TraitRef, TypeFoldable}; |
| use rustc::ty::GenericParamDefKind; |
| use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; |
| use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind}; |
| use rustc::util::nodemap::FxHashSet; |
| use rustc::infer::{self, InferOk}; |
| use rustc::infer::canonical::{Canonical, QueryResponse}; |
| use rustc::infer::canonical::{OriginalQueryValues}; |
| use rustc::middle::stability; |
| use syntax::ast; |
| use syntax::util::lev_distance::{lev_distance, find_best_match_for_name}; |
| use syntax_pos::{DUMMY_SP, Span, symbol::Symbol}; |
| use std::iter; |
| use std::mem; |
| use std::ops::Deref; |
| use std::cmp::max; |
| |
| use rustc_error_codes::*; |
| |
| use smallvec::{smallvec, SmallVec}; |
| |
| use self::CandidateKind::*; |
| pub use self::PickKind::*; |
| |
| /// Boolean flag used to indicate if this search is for a suggestion |
| /// or not. If true, we can allow ambiguity and so forth. |
| #[derive(Clone, Copy)] |
| pub struct IsSuggestion(pub bool); |
| |
| struct ProbeContext<'a, 'tcx> { |
| fcx: &'a FnCtxt<'a, 'tcx>, |
| span: Span, |
| mode: Mode, |
| method_name: Option<ast::Ident>, |
| return_type: Option<Ty<'tcx>>, |
| |
| /// This is the OriginalQueryValues for the steps queries |
| /// that are answered in steps. |
| orig_steps_var_values: OriginalQueryValues<'tcx>, |
| steps: Lrc<Vec<CandidateStep<'tcx>>>, |
| |
| inherent_candidates: Vec<Candidate<'tcx>>, |
| extension_candidates: Vec<Candidate<'tcx>>, |
| impl_dups: FxHashSet<DefId>, |
| |
| /// Collects near misses when the candidate functions are missing a `self` keyword and is only |
| /// used for error reporting |
| static_candidates: Vec<CandidateSource>, |
| |
| /// When probing for names, include names that are close to the |
| /// requested name (by Levensthein distance) |
| allow_similar_names: bool, |
| |
| /// Some(candidate) if there is a private candidate |
| private_candidate: Option<(DefKind, DefId)>, |
| |
| /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used |
| /// for error reporting |
| unsatisfied_predicates: Vec<TraitRef<'tcx>>, |
| |
| is_suggestion: IsSuggestion, |
| } |
| |
| impl<'a, 'tcx> Deref for ProbeContext<'a, 'tcx> { |
| type Target = FnCtxt<'a, 'tcx>; |
| fn deref(&self) -> &Self::Target { |
| &self.fcx |
| } |
| } |
| |
| #[derive(Debug)] |
| struct Candidate<'tcx> { |
| // Candidates are (I'm not quite sure, but they are mostly) basically |
| // some metadata on top of a `ty::AssocItem` (without substs). |
| // |
| // However, method probing wants to be able to evaluate the predicates |
| // for a function with the substs applied - for example, if a function |
| // has `where Self: Sized`, we don't want to consider it unless `Self` |
| // is actually `Sized`, and similarly, return-type suggestions want |
| // to consider the "actual" return type. |
| // |
| // The way this is handled is through `xform_self_ty`. It contains |
| // the receiver type of this candidate, but `xform_self_ty`, |
| // `xform_ret_ty` and `kind` (which contains the predicates) have the |
| // generic parameters of this candidate substituted with the *same set* |
| // of inference variables, which acts as some weird sort of "query". |
| // |
| // When we check out a candidate, we require `xform_self_ty` to be |
| // a subtype of the passed-in self-type, and this equates the type |
| // variables in the rest of the fields. |
| // |
| // For example, if we have this candidate: |
| // ``` |
| // trait Foo { |
| // fn foo(&self) where Self: Sized; |
| // } |
| // ``` |
| // |
| // Then `xform_self_ty` will be `&'erased ?X` and `kind` will contain |
| // the predicate `?X: Sized`, so if we are evaluating `Foo` for a |
| // the receiver `&T`, we'll do the subtyping which will make `?X` |
| // get the right value, then when we evaluate the predicate we'll check |
| // if `T: Sized`. |
| xform_self_ty: Ty<'tcx>, |
| xform_ret_ty: Option<Ty<'tcx>>, |
| item: ty::AssocItem, |
| kind: CandidateKind<'tcx>, |
| import_ids: SmallVec<[hir::HirId; 1]>, |
| } |
| |
| #[derive(Debug)] |
| enum CandidateKind<'tcx> { |
| InherentImplCandidate(SubstsRef<'tcx>, |
| // Normalize obligations |
| Vec<traits::PredicateObligation<'tcx>>), |
| ObjectCandidate, |
| TraitCandidate(ty::TraitRef<'tcx>), |
| WhereClauseCandidate(// Trait |
| ty::PolyTraitRef<'tcx>), |
| } |
| |
| #[derive(Debug, PartialEq, Eq, Copy, Clone)] |
| enum ProbeResult { |
| NoMatch, |
| BadReturnType, |
| Match, |
| } |
| |
| #[derive(Debug, PartialEq, Clone)] |
| pub struct Pick<'tcx> { |
| pub item: ty::AssocItem, |
| pub kind: PickKind<'tcx>, |
| pub import_ids: SmallVec<[hir::HirId; 1]>, |
| |
| // Indicates that the source expression should be autoderef'd N times |
| // |
| // A = expr | *expr | **expr | ... |
| pub autoderefs: usize, |
| |
| // Indicates that an autoref is applied after the optional autoderefs |
| // |
| // B = A | &A | &mut A |
| pub autoref: Option<hir::Mutability>, |
| |
| // Indicates that the source expression should be "unsized" to a |
| // target type. This should probably eventually go away in favor |
| // of just coercing method receivers. |
| // |
| // C = B | unsize(B) |
| pub unsize: Option<Ty<'tcx>>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq)] |
| pub enum PickKind<'tcx> { |
| InherentImplPick, |
| ObjectPick, |
| TraitPick, |
| WhereClausePick(// Trait |
| ty::PolyTraitRef<'tcx>), |
| } |
| |
| pub type PickResult<'tcx> = Result<Pick<'tcx>, MethodError<'tcx>>; |
| |
| #[derive(PartialEq, Eq, Copy, Clone, Debug)] |
| pub enum Mode { |
| // An expression of the form `receiver.method_name(...)`. |
| // Autoderefs are performed on `receiver`, lookup is done based on the |
| // `self` argument of the method, and static methods aren't considered. |
| MethodCall, |
| // An expression of the form `Type::item` or `<T>::item`. |
| // No autoderefs are performed, lookup is done based on the type each |
| // implementation is for, and static methods are included. |
| Path, |
| } |
| |
| #[derive(PartialEq, Eq, Copy, Clone, Debug)] |
| pub enum ProbeScope { |
| // Assemble candidates coming only from traits in scope. |
| TraitsInScope, |
| |
| // Assemble candidates coming from all traits. |
| AllTraits, |
| } |
| |
| impl<'a, 'tcx> FnCtxt<'a, 'tcx> { |
| /// This is used to offer suggestions to users. It returns methods |
| /// that could have been called which have the desired return |
| /// type. Some effort is made to rule out methods that, if called, |
| /// would result in an error (basically, the same criteria we |
| /// would use to decide if a method is a plausible fit for |
| /// ambiguity purposes). |
| pub fn probe_for_return_type(&self, |
| span: Span, |
| mode: Mode, |
| return_type: Ty<'tcx>, |
| self_ty: Ty<'tcx>, |
| scope_expr_id: hir::HirId) |
| -> Vec<ty::AssocItem> { |
| debug!("probe(self_ty={:?}, return_type={}, scope_expr_id={})", |
| self_ty, |
| return_type, |
| scope_expr_id); |
| let method_names = |
| self.probe_op(span, mode, None, Some(return_type), IsSuggestion(true), |
| self_ty, scope_expr_id, ProbeScope::AllTraits, |
| |probe_cx| Ok(probe_cx.candidate_method_names())) |
| .unwrap_or(vec![]); |
| method_names |
| .iter() |
| .flat_map(|&method_name| { |
| self.probe_op( |
| span, mode, Some(method_name), Some(return_type), |
| IsSuggestion(true), self_ty, scope_expr_id, |
| ProbeScope::AllTraits, |probe_cx| probe_cx.pick() |
| ).ok().map(|pick| pick.item) |
| }) |
| .collect() |
| } |
| |
| pub fn probe_for_name(&self, |
| span: Span, |
| mode: Mode, |
| item_name: ast::Ident, |
| is_suggestion: IsSuggestion, |
| self_ty: Ty<'tcx>, |
| scope_expr_id: hir::HirId, |
| scope: ProbeScope) |
| -> PickResult<'tcx> { |
| debug!("probe(self_ty={:?}, item_name={}, scope_expr_id={})", |
| self_ty, |
| item_name, |
| scope_expr_id); |
| self.probe_op(span, |
| mode, |
| Some(item_name), |
| None, |
| is_suggestion, |
| self_ty, |
| scope_expr_id, |
| scope, |
| |probe_cx| probe_cx.pick()) |
| } |
| |
| fn probe_op<OP, R>( |
| &'a self, |
| span: Span, |
| mode: Mode, |
| method_name: Option<ast::Ident>, |
| return_type: Option<Ty<'tcx>>, |
| is_suggestion: IsSuggestion, |
| self_ty: Ty<'tcx>, |
| scope_expr_id: hir::HirId, |
| scope: ProbeScope, |
| op: OP, |
| ) -> Result<R, MethodError<'tcx>> |
| where |
| OP: FnOnce(ProbeContext<'a, 'tcx>) -> Result<R, MethodError<'tcx>>, |
| { |
| let mut orig_values = OriginalQueryValues::default(); |
| let param_env_and_self_ty = |
| self.infcx.canonicalize_query( |
| &ParamEnvAnd { |
| param_env: self.param_env, |
| value: self_ty |
| }, &mut orig_values); |
| |
| let steps = if mode == Mode::MethodCall { |
| self.tcx.method_autoderef_steps(param_env_and_self_ty) |
| } else { |
| self.infcx.probe(|_| { |
| // Mode::Path - the deref steps is "trivial". This turns |
| // our CanonicalQuery into a "trivial" QueryResponse. This |
| // is a bit inefficient, but I don't think that writing |
| // special handling for this "trivial case" is a good idea. |
| |
| let infcx = &self.infcx; |
| let (ParamEnvAnd { |
| param_env: _, |
| value: self_ty |
| }, canonical_inference_vars) = |
| infcx.instantiate_canonical_with_fresh_inference_vars( |
| span, ¶m_env_and_self_ty); |
| debug!("probe_op: Mode::Path, param_env_and_self_ty={:?} self_ty={:?}", |
| param_env_and_self_ty, self_ty); |
| MethodAutoderefStepsResult { |
| steps: Lrc::new(vec![CandidateStep { |
| self_ty: self.make_query_response_ignoring_pending_obligations( |
| canonical_inference_vars, self_ty), |
| autoderefs: 0, |
| from_unsafe_deref: false, |
| unsize: false, |
| }]), |
| opt_bad_ty: None, |
| reached_recursion_limit: false |
| } |
| }) |
| }; |
| |
| // If our autoderef loop had reached the recursion limit, |
| // report an overflow error, but continue going on with |
| // the truncated autoderef list. |
| if steps.reached_recursion_limit { |
| self.probe(|_| { |
| let ty = &steps.steps.last().unwrap_or_else(|| { |
| span_bug!(span, "reached the recursion limit in 0 steps?") |
| }).self_ty; |
| let ty = self.probe_instantiate_query_response(span, &orig_values, ty) |
| .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty)); |
| autoderef::report_autoderef_recursion_limit_error(self.tcx, span, |
| ty.value); |
| }); |
| } |
| |
| |
| // If we encountered an `_` type or an error type during autoderef, this is |
| // ambiguous. |
| if let Some(bad_ty) = &steps.opt_bad_ty { |
| if is_suggestion.0 { |
| // Ambiguity was encountered during a suggestion. Just keep going. |
| debug!("ProbeContext: encountered ambiguity in suggestion"); |
| } else if bad_ty.reached_raw_pointer && !self.tcx.features().arbitrary_self_types { |
| // this case used to be allowed by the compiler, |
| // so we do a future-compat lint here for the 2015 edition |
| // (see https://github.com/rust-lang/rust/issues/46906) |
| if self.tcx.sess.rust_2018() { |
| span_err!(self.tcx.sess, span, E0699, |
| "the type of this value must be known \ |
| to call a method on a raw pointer on it"); |
| } else { |
| self.tcx.lint_hir( |
| lint::builtin::TYVAR_BEHIND_RAW_POINTER, |
| scope_expr_id, |
| span, |
| "type annotations needed"); |
| } |
| } else { |
| // Encountered a real ambiguity, so abort the lookup. If `ty` is not |
| // an `Err`, report the right "type annotations needed" error pointing |
| // to it. |
| let ty = &bad_ty.ty; |
| let ty = self.probe_instantiate_query_response(span, &orig_values, ty) |
| .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty)); |
| let ty = self.structurally_resolved_type(span, ty.value); |
| assert_eq!(ty, self.tcx.types.err); |
| return Err(MethodError::NoMatch(NoMatchData::new(Vec::new(), |
| Vec::new(), |
| Vec::new(), |
| None, |
| mode))); |
| } |
| } |
| |
| debug!("ProbeContext: steps for self_ty={:?} are {:?}", |
| self_ty, |
| steps); |
| |
| |
| // this creates one big transaction so that all type variables etc |
| // that we create during the probe process are removed later |
| self.probe(|_| { |
| let mut probe_cx = ProbeContext::new( |
| self, span, mode, method_name, return_type, orig_values, |
| steps.steps, is_suggestion, |
| ); |
| |
| probe_cx.assemble_inherent_candidates(); |
| match scope { |
| ProbeScope::TraitsInScope => |
| probe_cx.assemble_extension_candidates_for_traits_in_scope(scope_expr_id)?, |
| ProbeScope::AllTraits => |
| probe_cx.assemble_extension_candidates_for_all_traits()?, |
| }; |
| op(probe_cx) |
| }) |
| } |
| } |
| |
| pub fn provide(providers: &mut ty::query::Providers<'_>) { |
| providers.method_autoderef_steps = method_autoderef_steps; |
| } |
| |
| fn method_autoderef_steps<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| goal: CanonicalTyGoal<'tcx>, |
| ) -> MethodAutoderefStepsResult<'tcx> { |
| debug!("method_autoderef_steps({:?})", goal); |
| |
| tcx.infer_ctxt().enter_with_canonical(DUMMY_SP, &goal, |ref infcx, goal, inference_vars| { |
| let ParamEnvAnd { param_env, value: self_ty } = goal; |
| |
| let mut autoderef = Autoderef::new(infcx, param_env, hir::DUMMY_HIR_ID, DUMMY_SP, self_ty) |
| .include_raw_pointers() |
| .silence_errors(); |
| let mut reached_raw_pointer = false; |
| let mut steps: Vec<_> = autoderef.by_ref() |
| .map(|(ty, d)| { |
| let step = CandidateStep { |
| self_ty: infcx.make_query_response_ignoring_pending_obligations( |
| inference_vars.clone(), ty), |
| autoderefs: d, |
| from_unsafe_deref: reached_raw_pointer, |
| unsize: false, |
| }; |
| if let ty::RawPtr(_) = ty.kind { |
| // all the subsequent steps will be from_unsafe_deref |
| reached_raw_pointer = true; |
| } |
| step |
| }) |
| .collect(); |
| |
| let final_ty = autoderef.maybe_ambiguous_final_ty(); |
| let opt_bad_ty = match final_ty.kind { |
| ty::Infer(ty::TyVar(_)) | |
| ty::Error => { |
| Some(MethodAutoderefBadTy { |
| reached_raw_pointer, |
| ty: infcx.make_query_response_ignoring_pending_obligations( |
| inference_vars, final_ty) |
| }) |
| } |
| ty::Array(elem_ty, _) => { |
| let dereferences = steps.len() - 1; |
| |
| steps.push(CandidateStep { |
| self_ty: infcx.make_query_response_ignoring_pending_obligations( |
| inference_vars, infcx.tcx.mk_slice(elem_ty)), |
| autoderefs: dereferences, |
| // this could be from an unsafe deref if we had |
| // a *mut/const [T; N] |
| from_unsafe_deref: reached_raw_pointer, |
| unsize: true, |
| }); |
| |
| None |
| } |
| _ => None |
| }; |
| |
| debug!("method_autoderef_steps: steps={:?} opt_bad_ty={:?}", steps, opt_bad_ty); |
| |
| MethodAutoderefStepsResult { |
| steps: Lrc::new(steps), |
| opt_bad_ty: opt_bad_ty.map(Lrc::new), |
| reached_recursion_limit: autoderef.reached_recursion_limit() |
| } |
| }) |
| } |
| |
| impl<'a, 'tcx> ProbeContext<'a, 'tcx> { |
| fn new( |
| fcx: &'a FnCtxt<'a, 'tcx>, |
| span: Span, |
| mode: Mode, |
| method_name: Option<ast::Ident>, |
| return_type: Option<Ty<'tcx>>, |
| orig_steps_var_values: OriginalQueryValues<'tcx>, |
| steps: Lrc<Vec<CandidateStep<'tcx>>>, |
| is_suggestion: IsSuggestion, |
| ) -> ProbeContext<'a, 'tcx> { |
| ProbeContext { |
| fcx, |
| span, |
| mode, |
| method_name, |
| return_type, |
| inherent_candidates: Vec::new(), |
| extension_candidates: Vec::new(), |
| impl_dups: FxHashSet::default(), |
| orig_steps_var_values, |
| steps, |
| static_candidates: Vec::new(), |
| allow_similar_names: false, |
| private_candidate: None, |
| unsatisfied_predicates: Vec::new(), |
| is_suggestion, |
| } |
| } |
| |
| fn reset(&mut self) { |
| self.inherent_candidates.clear(); |
| self.extension_candidates.clear(); |
| self.impl_dups.clear(); |
| self.static_candidates.clear(); |
| self.private_candidate = None; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // CANDIDATE ASSEMBLY |
| |
| fn push_candidate(&mut self, |
| candidate: Candidate<'tcx>, |
| is_inherent: bool) |
| { |
| let is_accessible = if let Some(name) = self.method_name { |
| let item = candidate.item; |
| let def_scope = |
| self.tcx.adjust_ident_and_get_scope(name, item.container.id(), self.body_id).1; |
| item.vis.is_accessible_from(def_scope, self.tcx) |
| } else { |
| true |
| }; |
| if is_accessible { |
| if is_inherent { |
| self.inherent_candidates.push(candidate); |
| } else { |
| self.extension_candidates.push(candidate); |
| } |
| } else if self.private_candidate.is_none() { |
| self.private_candidate = |
| Some((candidate.item.def_kind(), candidate.item.def_id)); |
| } |
| } |
| |
| fn assemble_inherent_candidates(&mut self) { |
| let steps = self.steps.clone(); |
| for step in steps.iter() { |
| self.assemble_probe(&step.self_ty); |
| } |
| } |
| |
| fn assemble_probe(&mut self, self_ty: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>) { |
| debug!("assemble_probe: self_ty={:?}", self_ty); |
| let lang_items = self.tcx.lang_items(); |
| |
| match self_ty.value.value.kind { |
| ty::Dynamic(ref data, ..) => { |
| if let Some(p) = data.principal() { |
| // Subtle: we can't use `instantiate_query_response` here: using it will |
| // commit to all of the type equalities assumed by inference going through |
| // autoderef (see the `method-probe-no-guessing` test). |
| // |
| // However, in this code, it is OK if we end up with an object type that is |
| // "more general" than the object type that we are evaluating. For *every* |
| // object type `MY_OBJECT`, a function call that goes through a trait-ref |
| // of the form `<MY_OBJECT as SuperTraitOf(MY_OBJECT)>::func` is a valid |
| // `ObjectCandidate`, and it should be discoverable "exactly" through one |
| // of the iterations in the autoderef loop, so there is no problem with it |
| // being discoverable in another one of these iterations. |
| // |
| // Using `instantiate_canonical_with_fresh_inference_vars` on our |
| // `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the |
| // `CanonicalVarValues` will exactly give us such a generalization - it |
| // will still match the original object type, but it won't pollute our |
| // type variables in any form, so just do that! |
| let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) = |
| self.fcx.instantiate_canonical_with_fresh_inference_vars( |
| self.span, &self_ty); |
| |
| self.assemble_inherent_candidates_from_object(generalized_self_ty); |
| self.assemble_inherent_impl_candidates_for_type(p.def_id()); |
| } |
| } |
| ty::Adt(def, _) => { |
| self.assemble_inherent_impl_candidates_for_type(def.did); |
| } |
| ty::Foreign(did) => { |
| self.assemble_inherent_impl_candidates_for_type(did); |
| } |
| ty::Param(p) => { |
| self.assemble_inherent_candidates_from_param(p); |
| } |
| ty::Bool => { |
| let lang_def_id = lang_items.bool_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Char => { |
| let lang_def_id = lang_items.char_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Str => { |
| let lang_def_id = lang_items.str_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| |
| let lang_def_id = lang_items.str_alloc_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Slice(_) => { |
| let lang_def_id = lang_items.slice_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| |
| let lang_def_id = lang_items.slice_u8_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| |
| let lang_def_id = lang_items.slice_alloc_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| |
| let lang_def_id = lang_items.slice_u8_alloc_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::Mutability::Immutable }) => { |
| let lang_def_id = lang_items.const_ptr_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::Mutability::Mutable }) => { |
| let lang_def_id = lang_items.mut_ptr_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Int(ast::IntTy::I8) => { |
| let lang_def_id = lang_items.i8_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Int(ast::IntTy::I16) => { |
| let lang_def_id = lang_items.i16_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Int(ast::IntTy::I32) => { |
| let lang_def_id = lang_items.i32_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Int(ast::IntTy::I64) => { |
| let lang_def_id = lang_items.i64_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Int(ast::IntTy::I128) => { |
| let lang_def_id = lang_items.i128_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Int(ast::IntTy::Isize) => { |
| let lang_def_id = lang_items.isize_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Uint(ast::UintTy::U8) => { |
| let lang_def_id = lang_items.u8_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Uint(ast::UintTy::U16) => { |
| let lang_def_id = lang_items.u16_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Uint(ast::UintTy::U32) => { |
| let lang_def_id = lang_items.u32_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Uint(ast::UintTy::U64) => { |
| let lang_def_id = lang_items.u64_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Uint(ast::UintTy::U128) => { |
| let lang_def_id = lang_items.u128_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Uint(ast::UintTy::Usize) => { |
| let lang_def_id = lang_items.usize_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Float(ast::FloatTy::F32) => { |
| let lang_def_id = lang_items.f32_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| |
| let lang_def_id = lang_items.f32_runtime_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| ty::Float(ast::FloatTy::F64) => { |
| let lang_def_id = lang_items.f64_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| |
| let lang_def_id = lang_items.f64_runtime_impl(); |
| self.assemble_inherent_impl_for_primitive(lang_def_id); |
| } |
| _ => {} |
| } |
| } |
| |
| fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id: Option<DefId>) { |
| if let Some(impl_def_id) = lang_def_id { |
| self.assemble_inherent_impl_probe(impl_def_id); |
| } |
| } |
| |
| fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) { |
| let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id); |
| for &impl_def_id in impl_def_ids.iter() { |
| self.assemble_inherent_impl_probe(impl_def_id); |
| } |
| } |
| |
| fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) { |
| if !self.impl_dups.insert(impl_def_id) { |
| return; // already visited |
| } |
| |
| debug!("assemble_inherent_impl_probe {:?}", impl_def_id); |
| |
| for item in self.impl_or_trait_item(impl_def_id) { |
| if !self.has_applicable_self(&item) { |
| // No receiver declared. Not a candidate. |
| self.record_static_candidate(ImplSource(impl_def_id)); |
| continue |
| } |
| |
| let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id); |
| let impl_ty = impl_ty.subst(self.tcx, impl_substs); |
| |
| // Determine the receiver type that the method itself expects. |
| let xform_tys = self.xform_self_ty(&item, impl_ty, impl_substs); |
| |
| // We can't use normalize_associated_types_in as it will pollute the |
| // fcx's fulfillment context after this probe is over. |
| let cause = traits::ObligationCause::misc(self.span, self.body_id); |
| let selcx = &mut traits::SelectionContext::new(self.fcx); |
| let traits::Normalized { value: (xform_self_ty, xform_ret_ty), obligations } = |
| traits::normalize(selcx, self.param_env, cause, &xform_tys); |
| debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}/{:?}", |
| xform_self_ty, xform_ret_ty); |
| |
| self.push_candidate(Candidate { |
| xform_self_ty, xform_ret_ty, item, |
| kind: InherentImplCandidate(impl_substs, obligations), |
| import_ids: smallvec![] |
| }, true); |
| } |
| } |
| |
| fn assemble_inherent_candidates_from_object(&mut self, |
| self_ty: Ty<'tcx>) { |
| debug!("assemble_inherent_candidates_from_object(self_ty={:?})", |
| self_ty); |
| |
| let principal = match self_ty.kind { |
| ty::Dynamic(ref data, ..) => Some(data), |
| _ => None |
| }.and_then(|data| data.principal()).unwrap_or_else(|| { |
| span_bug!(self.span, "non-object {:?} in assemble_inherent_candidates_from_object", |
| self_ty) |
| }); |
| |
| // It is illegal to invoke a method on a trait instance that |
| // refers to the `Self` type. An error will be reported by |
| // `enforce_object_limitations()` if the method refers to the |
| // `Self` type anywhere other than the receiver. Here, we use |
| // a substitution that replaces `Self` with the object type |
| // itself. Hence, a `&self` method will wind up with an |
| // argument type like `&Trait`. |
| let trait_ref = principal.with_self_ty(self.tcx, self_ty); |
| self.elaborate_bounds(iter::once(trait_ref), |this, new_trait_ref, item| { |
| let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref); |
| |
| let (xform_self_ty, xform_ret_ty) = |
| this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs); |
| this.push_candidate(Candidate { |
| xform_self_ty, xform_ret_ty, item, |
| kind: ObjectCandidate, |
| import_ids: smallvec![] |
| }, true); |
| }); |
| } |
| |
| fn assemble_inherent_candidates_from_param(&mut self, param_ty: ty::ParamTy) { |
| // FIXME: do we want to commit to this behavior for param bounds? |
| |
| let bounds = self.param_env |
| .caller_bounds |
| .iter() |
| .filter_map(|predicate| { |
| match *predicate { |
| ty::Predicate::Trait(ref trait_predicate) => { |
| match trait_predicate.skip_binder().trait_ref.self_ty().kind { |
| ty::Param(ref p) if *p == param_ty => { |
| Some(trait_predicate.to_poly_trait_ref()) |
| } |
| _ => None, |
| } |
| } |
| ty::Predicate::Subtype(..) | |
| ty::Predicate::Projection(..) | |
| ty::Predicate::RegionOutlives(..) | |
| ty::Predicate::WellFormed(..) | |
| ty::Predicate::ObjectSafe(..) | |
| ty::Predicate::ClosureKind(..) | |
| ty::Predicate::TypeOutlives(..) | |
| ty::Predicate::ConstEvaluatable(..) => None, |
| } |
| }); |
| |
| self.elaborate_bounds(bounds, |this, poly_trait_ref, item| { |
| let trait_ref = this.erase_late_bound_regions(&poly_trait_ref); |
| |
| let (xform_self_ty, xform_ret_ty) = |
| this.xform_self_ty(&item, trait_ref.self_ty(), trait_ref.substs); |
| |
| // Because this trait derives from a where-clause, it |
| // should not contain any inference variables or other |
| // artifacts. This means it is safe to put into the |
| // `WhereClauseCandidate` and (eventually) into the |
| // `WhereClausePick`. |
| assert!(!trait_ref.substs.needs_infer()); |
| |
| this.push_candidate(Candidate { |
| xform_self_ty, xform_ret_ty, item, |
| kind: WhereClauseCandidate(poly_trait_ref), |
| import_ids: smallvec![] |
| }, true); |
| }); |
| } |
| |
| // Do a search through a list of bounds, using a callback to actually |
| // create the candidates. |
| fn elaborate_bounds<F>( |
| &mut self, |
| bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>, |
| mut mk_cand: F, |
| ) where |
| F: for<'b> FnMut(&mut ProbeContext<'b, 'tcx>, ty::PolyTraitRef<'tcx>, ty::AssocItem), |
| { |
| let tcx = self.tcx; |
| for bound_trait_ref in traits::transitive_bounds(tcx, bounds) { |
| debug!("elaborate_bounds(bound_trait_ref={:?})", bound_trait_ref); |
| for item in self.impl_or_trait_item(bound_trait_ref.def_id()) { |
| if !self.has_applicable_self(&item) { |
| self.record_static_candidate(TraitSource(bound_trait_ref.def_id())); |
| } else { |
| mk_cand(self, bound_trait_ref, item); |
| } |
| } |
| } |
| } |
| |
| fn assemble_extension_candidates_for_traits_in_scope(&mut self, |
| expr_hir_id: hir::HirId) |
| -> Result<(), MethodError<'tcx>> { |
| if expr_hir_id == hir::DUMMY_HIR_ID { |
| return Ok(()) |
| } |
| let mut duplicates = FxHashSet::default(); |
| let opt_applicable_traits = self.tcx.in_scope_traits(expr_hir_id); |
| if let Some(applicable_traits) = opt_applicable_traits { |
| for trait_candidate in applicable_traits.iter() { |
| let trait_did = trait_candidate.def_id; |
| if duplicates.insert(trait_did) { |
| let import_ids = trait_candidate.import_ids.iter().map(|node_id| |
| self.fcx.tcx.hir().node_to_hir_id(*node_id)).collect(); |
| let result = self.assemble_extension_candidates_for_trait(import_ids, |
| trait_did); |
| result?; |
| } |
| } |
| } |
| Ok(()) |
| } |
| |
| fn assemble_extension_candidates_for_all_traits(&mut self) -> Result<(), MethodError<'tcx>> { |
| let mut duplicates = FxHashSet::default(); |
| for trait_info in suggest::all_traits(self.tcx) { |
| if duplicates.insert(trait_info.def_id) { |
| self.assemble_extension_candidates_for_trait(smallvec![], trait_info.def_id)?; |
| } |
| } |
| Ok(()) |
| } |
| |
| pub fn matches_return_type(&self, |
| method: &ty::AssocItem, |
| self_ty: Option<Ty<'tcx>>, |
| expected: Ty<'tcx>) -> bool { |
| match method.kind { |
| ty::AssocKind::Method => { |
| let fty = self.tcx.fn_sig(method.def_id); |
| self.probe(|_| { |
| let substs = self.fresh_substs_for_item(self.span, method.def_id); |
| let fty = fty.subst(self.tcx, substs); |
| let (fty, _) = self.replace_bound_vars_with_fresh_vars( |
| self.span, |
| infer::FnCall, |
| &fty |
| ); |
| |
| if let Some(self_ty) = self_ty { |
| if self.at(&ObligationCause::dummy(), self.param_env) |
| .sup(fty.inputs()[0], self_ty) |
| .is_err() |
| { |
| return false |
| } |
| } |
| self.can_sub(self.param_env, fty.output(), expected).is_ok() |
| }) |
| } |
| _ => false, |
| } |
| } |
| |
| fn assemble_extension_candidates_for_trait(&mut self, |
| import_ids: SmallVec<[hir::HirId; 1]>, |
| trait_def_id: DefId) |
| -> Result<(), MethodError<'tcx>> { |
| debug!("assemble_extension_candidates_for_trait(trait_def_id={:?})", |
| trait_def_id); |
| let trait_substs = self.fresh_item_substs(trait_def_id); |
| let trait_ref = ty::TraitRef::new(trait_def_id, trait_substs); |
| |
| if self.tcx.is_trait_alias(trait_def_id) { |
| // For trait aliases, assume all super-traits are relevant. |
| let bounds = iter::once(trait_ref.to_poly_trait_ref()); |
| self.elaborate_bounds(bounds, |this, new_trait_ref, item| { |
| let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref); |
| |
| let (xform_self_ty, xform_ret_ty) = |
| this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs); |
| this.push_candidate(Candidate { |
| xform_self_ty, xform_ret_ty, item, import_ids: import_ids.clone(), |
| kind: TraitCandidate(new_trait_ref), |
| }, true); |
| }); |
| } else { |
| debug_assert!(self.tcx.is_trait(trait_def_id)); |
| for item in self.impl_or_trait_item(trait_def_id) { |
| // Check whether `trait_def_id` defines a method with suitable name. |
| if !self.has_applicable_self(&item) { |
| debug!("method has inapplicable self"); |
| self.record_static_candidate(TraitSource(trait_def_id)); |
| continue; |
| } |
| |
| let (xform_self_ty, xform_ret_ty) = |
| self.xform_self_ty(&item, trait_ref.self_ty(), trait_substs); |
| self.push_candidate(Candidate { |
| xform_self_ty, xform_ret_ty, item, import_ids: import_ids.clone(), |
| kind: TraitCandidate(trait_ref), |
| }, false); |
| } |
| } |
| Ok(()) |
| } |
| |
| fn candidate_method_names(&self) -> Vec<ast::Ident> { |
| let mut set = FxHashSet::default(); |
| let mut names: Vec<_> = self.inherent_candidates |
| .iter() |
| .chain(&self.extension_candidates) |
| .filter(|candidate| { |
| if let Some(return_ty) = self.return_type { |
| self.matches_return_type(&candidate.item, None, return_ty) |
| } else { |
| true |
| } |
| }) |
| .map(|candidate| candidate.item.ident) |
| .filter(|&name| set.insert(name)) |
| .collect(); |
| |
| // Sort them by the name so we have a stable result. |
| names.sort_by_cached_key(|n| n.as_str()); |
| names |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // THE ACTUAL SEARCH |
| |
| fn pick(mut self) -> PickResult<'tcx> { |
| assert!(self.method_name.is_some()); |
| |
| if let Some(r) = self.pick_core() { |
| return r; |
| } |
| |
| debug!("pick: actual search failed, assemble diagnotics"); |
| |
| let static_candidates = mem::take(&mut self.static_candidates); |
| let private_candidate = self.private_candidate.take(); |
| let unsatisfied_predicates = mem::take(&mut self.unsatisfied_predicates); |
| |
| // things failed, so lets look at all traits, for diagnostic purposes now: |
| self.reset(); |
| |
| let span = self.span; |
| let tcx = self.tcx; |
| |
| self.assemble_extension_candidates_for_all_traits()?; |
| |
| let out_of_scope_traits = match self.pick_core() { |
| Some(Ok(p)) => vec![p.item.container.id()], |
| //Some(Ok(p)) => p.iter().map(|p| p.item.container().id()).collect(), |
| Some(Err(MethodError::Ambiguity(v))) => { |
| v.into_iter() |
| .map(|source| { |
| match source { |
| TraitSource(id) => id, |
| ImplSource(impl_id) => { |
| match tcx.trait_id_of_impl(impl_id) { |
| Some(id) => id, |
| None => { |
| span_bug!(span, |
| "found inherent method when looking at traits") |
| } |
| } |
| } |
| } |
| }) |
| .collect() |
| } |
| Some(Err(MethodError::NoMatch(NoMatchData { out_of_scope_traits: others, .. }))) => { |
| assert!(others.is_empty()); |
| vec![] |
| } |
| _ => vec![], |
| }; |
| |
| if let Some((kind, def_id)) = private_candidate { |
| return Err(MethodError::PrivateMatch(kind, def_id, out_of_scope_traits)); |
| } |
| let lev_candidate = self.probe_for_lev_candidate()?; |
| |
| Err(MethodError::NoMatch(NoMatchData::new(static_candidates, |
| unsatisfied_predicates, |
| out_of_scope_traits, |
| lev_candidate, |
| self.mode))) |
| } |
| |
| fn pick_core(&mut self) -> Option<PickResult<'tcx>> { |
| let steps = self.steps.clone(); |
| |
| // find the first step that works |
| steps |
| .iter() |
| .filter(|step| { |
| debug!("pick_core: step={:?}", step); |
| // skip types that are from a type error or that would require dereferencing |
| // a raw pointer |
| !step.self_ty.references_error() && !step.from_unsafe_deref |
| }).flat_map(|step| { |
| let InferOk { value: self_ty, obligations: _ } = |
| self.fcx.probe_instantiate_query_response( |
| self.span, &self.orig_steps_var_values, &step.self_ty |
| ).unwrap_or_else(|_| { |
| span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty) |
| }); |
| self.pick_by_value_method(step, self_ty).or_else(|| { |
| self.pick_autorefd_method(step, self_ty, hir::Mutability::Immutable).or_else(|| { |
| self.pick_autorefd_method(step, self_ty, hir::Mutability::Mutable) |
| })})}) |
| .next() |
| } |
| |
| fn pick_by_value_method( |
| &mut self, |
| step: &CandidateStep<'tcx>, |
| self_ty: Ty<'tcx>, |
| ) -> Option<PickResult<'tcx>> { |
| //! For each type `T` in the step list, this attempts to find a |
| //! method where the (transformed) self type is exactly `T`. We |
| //! do however do one transformation on the adjustment: if we |
| //! are passing a region pointer in, we will potentially |
| //! *reborrow* it to a shorter lifetime. This allows us to |
| //! transparently pass `&mut` pointers, in particular, without |
| //! consuming them for their entire lifetime. |
| |
| if step.unsize { |
| return None; |
| } |
| |
| self.pick_method(self_ty).map(|r| { |
| r.map(|mut pick| { |
| pick.autoderefs = step.autoderefs; |
| |
| // Insert a `&*` or `&mut *` if this is a reference type: |
| if let ty::Ref(_, _, mutbl) = step.self_ty.value.value.kind { |
| pick.autoderefs += 1; |
| pick.autoref = Some(mutbl); |
| } |
| |
| pick |
| }) |
| }) |
| } |
| |
| fn pick_autorefd_method( |
| &mut self, |
| step: &CandidateStep<'tcx>, |
| self_ty: Ty<'tcx>, |
| mutbl: hir::Mutability, |
| ) -> Option<PickResult<'tcx>> { |
| let tcx = self.tcx; |
| |
| // In general, during probing we erase regions. See |
| // `impl_self_ty()` for an explanation. |
| let region = tcx.lifetimes.re_erased; |
| |
| let autoref_ty = tcx.mk_ref(region, |
| ty::TypeAndMut { |
| ty: self_ty, mutbl |
| }); |
| self.pick_method(autoref_ty).map(|r| { |
| r.map(|mut pick| { |
| pick.autoderefs = step.autoderefs; |
| pick.autoref = Some(mutbl); |
| pick.unsize = step.unsize.then_some(self_ty); |
| pick |
| }) |
| }) |
| } |
| |
| fn pick_method(&mut self, self_ty: Ty<'tcx>) -> Option<PickResult<'tcx>> { |
| debug!("pick_method(self_ty={})", self.ty_to_string(self_ty)); |
| |
| let mut possibly_unsatisfied_predicates = Vec::new(); |
| let mut unstable_candidates = Vec::new(); |
| |
| for (kind, candidates) in &[ |
| ("inherent", &self.inherent_candidates), |
| ("extension", &self.extension_candidates), |
| ] { |
| debug!("searching {} candidates", kind); |
| let res = self.consider_candidates( |
| self_ty, |
| candidates.iter(), |
| &mut possibly_unsatisfied_predicates, |
| Some(&mut unstable_candidates), |
| ); |
| if let Some(pick) = res { |
| if !self.is_suggestion.0 && !unstable_candidates.is_empty() { |
| if let Ok(p) = &pick { |
| // Emit a lint if there are unstable candidates alongside the stable ones. |
| // |
| // We suppress warning if we're picking the method only because it is a |
| // suggestion. |
| self.emit_unstable_name_collision_hint(p, &unstable_candidates); |
| } |
| } |
| return Some(pick); |
| } |
| } |
| |
| debug!("searching unstable candidates"); |
| let res = self.consider_candidates( |
| self_ty, |
| unstable_candidates.into_iter().map(|(c, _)| c), |
| &mut possibly_unsatisfied_predicates, |
| None, |
| ); |
| if res.is_none() { |
| self.unsatisfied_predicates.extend(possibly_unsatisfied_predicates); |
| } |
| res |
| } |
| |
| fn consider_candidates<'b, ProbesIter>( |
| &self, |
| self_ty: Ty<'tcx>, |
| probes: ProbesIter, |
| possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>, |
| unstable_candidates: Option<&mut Vec<(&'b Candidate<'tcx>, Symbol)>>, |
| ) -> Option<PickResult<'tcx>> |
| where |
| ProbesIter: Iterator<Item = &'b Candidate<'tcx>> + Clone, |
| { |
| let mut applicable_candidates: Vec<_> = probes.clone() |
| .map(|probe| { |
| (probe, self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates)) |
| }) |
| .filter(|&(_, status)| status != ProbeResult::NoMatch) |
| .collect(); |
| |
| debug!("applicable_candidates: {:?}", applicable_candidates); |
| |
| if applicable_candidates.len() > 1 { |
| if let Some(pick) = self.collapse_candidates_to_trait_pick(&applicable_candidates[..]) { |
| return Some(Ok(pick)); |
| } |
| } |
| |
| if let Some(uc) = unstable_candidates { |
| applicable_candidates.retain(|&(p, _)| { |
| if let stability::EvalResult::Deny { feature, .. } = |
| self.tcx.eval_stability(p.item.def_id, None, self.span) |
| { |
| uc.push((p, feature)); |
| return false; |
| } |
| true |
| }); |
| } |
| |
| if applicable_candidates.len() > 1 { |
| let sources = probes |
| .map(|p| self.candidate_source(p, self_ty)) |
| .collect(); |
| return Some(Err(MethodError::Ambiguity(sources))); |
| } |
| |
| applicable_candidates.pop().map(|(probe, status)| { |
| if status == ProbeResult::Match { |
| Ok(probe.to_unadjusted_pick()) |
| } else { |
| Err(MethodError::BadReturnType) |
| } |
| }) |
| } |
| |
| fn emit_unstable_name_collision_hint( |
| &self, |
| stable_pick: &Pick<'_>, |
| unstable_candidates: &[(&Candidate<'tcx>, Symbol)], |
| ) { |
| let mut diag = self.tcx.struct_span_lint_hir( |
| lint::builtin::UNSTABLE_NAME_COLLISIONS, |
| self.fcx.body_id, |
| self.span, |
| "a method with this name may be added to the standard library in the future", |
| ); |
| |
| // FIXME: This should be a `span_suggestion` instead of `help` |
| // However `self.span` only |
| // highlights the method name, so we can't use it. Also consider reusing the code from |
| // `report_method_error()`. |
| diag.help(&format!( |
| "call with fully qualified syntax `{}(...)` to keep using the current method", |
| self.tcx.def_path_str(stable_pick.item.def_id), |
| )); |
| |
| if nightly_options::is_nightly_build() { |
| for (candidate, feature) in unstable_candidates { |
| diag.help(&format!( |
| "add `#![feature({})]` to the crate attributes to enable `{}`", |
| feature, |
| self.tcx.def_path_str(candidate.item.def_id), |
| )); |
| } |
| } |
| |
| diag.emit(); |
| } |
| |
| fn select_trait_candidate(&self, trait_ref: ty::TraitRef<'tcx>) |
| -> traits::SelectionResult<'tcx, traits::Selection<'tcx>> |
| { |
| let cause = traits::ObligationCause::misc(self.span, self.body_id); |
| let predicate = |
| trait_ref.to_poly_trait_ref().to_poly_trait_predicate(); |
| let obligation = traits::Obligation::new(cause, self.param_env, predicate); |
| traits::SelectionContext::new(self).select(&obligation) |
| } |
| |
| fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>) |
| -> CandidateSource |
| { |
| match candidate.kind { |
| InherentImplCandidate(..) => ImplSource(candidate.item.container.id()), |
| ObjectCandidate | |
| WhereClauseCandidate(_) => TraitSource(candidate.item.container.id()), |
| TraitCandidate(trait_ref) => self.probe(|_| { |
| let _ = self.at(&ObligationCause::dummy(), self.param_env) |
| .sup(candidate.xform_self_ty, self_ty); |
| match self.select_trait_candidate(trait_ref) { |
| Ok(Some(traits::Vtable::VtableImpl(ref impl_data))) => { |
| // If only a single impl matches, make the error message point |
| // to that impl. |
| ImplSource(impl_data.impl_def_id) |
| } |
| _ => { |
| TraitSource(candidate.item.container.id()) |
| } |
| } |
| }) |
| } |
| } |
| |
| fn consider_probe(&self, |
| self_ty: Ty<'tcx>, |
| probe: &Candidate<'tcx>, |
| possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>) |
| -> ProbeResult { |
| debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe); |
| |
| self.probe(|_| { |
| // First check that the self type can be related. |
| let sub_obligations = match self.at(&ObligationCause::dummy(), self.param_env) |
| .sup(probe.xform_self_ty, self_ty) { |
| Ok(InferOk { obligations, value: () }) => obligations, |
| Err(_) => { |
| debug!("--> cannot relate self-types"); |
| return ProbeResult::NoMatch; |
| } |
| }; |
| |
| let mut result = ProbeResult::Match; |
| let selcx = &mut traits::SelectionContext::new(self); |
| let cause = traits::ObligationCause::misc(self.span, self.body_id); |
| |
| // If so, impls may carry other conditions (e.g., where |
| // clauses) that must be considered. Make sure that those |
| // match as well (or at least may match, sometimes we |
| // don't have enough information to fully evaluate). |
| let candidate_obligations : Vec<_> = match probe.kind { |
| InherentImplCandidate(ref substs, ref ref_obligations) => { |
| // Check whether the impl imposes obligations we have to worry about. |
| let impl_def_id = probe.item.container.id(); |
| let impl_bounds = self.tcx.predicates_of(impl_def_id); |
| let impl_bounds = impl_bounds.instantiate(self.tcx, substs); |
| let traits::Normalized { value: impl_bounds, obligations: norm_obligations } = |
| traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds); |
| |
| // Convert the bounds into obligations. |
| let impl_obligations = traits::predicates_for_generics( |
| cause, self.param_env, &impl_bounds); |
| |
| debug!("impl_obligations={:?}", impl_obligations); |
| impl_obligations.into_iter() |
| .chain(norm_obligations.into_iter()) |
| .chain(ref_obligations.iter().cloned()) |
| .collect() |
| } |
| |
| ObjectCandidate | |
| WhereClauseCandidate(..) => { |
| // These have no additional conditions to check. |
| vec![] |
| } |
| |
| TraitCandidate(trait_ref) => { |
| let predicate = trait_ref.to_predicate(); |
| let obligation = |
| traits::Obligation::new(cause, self.param_env, predicate); |
| if !self.predicate_may_hold(&obligation) { |
| if self.probe(|_| self.select_trait_candidate(trait_ref).is_err()) { |
| // This candidate's primary obligation doesn't even |
| // select - don't bother registering anything in |
| // `potentially_unsatisfied_predicates`. |
| return ProbeResult::NoMatch; |
| } else { |
| // Some nested subobligation of this predicate |
| // failed. |
| // |
| // FIXME: try to find the exact nested subobligation |
| // and point at it rather than reporting the entire |
| // trait-ref? |
| result = ProbeResult::NoMatch; |
| let trait_ref = self.resolve_vars_if_possible(&trait_ref); |
| possibly_unsatisfied_predicates.push(trait_ref); |
| } |
| } |
| vec![] |
| } |
| }; |
| |
| debug!("consider_probe - candidate_obligations={:?} sub_obligations={:?}", |
| candidate_obligations, sub_obligations); |
| |
| // Evaluate those obligations to see if they might possibly hold. |
| for o in candidate_obligations.into_iter().chain(sub_obligations) { |
| let o = self.resolve_vars_if_possible(&o); |
| if !self.predicate_may_hold(&o) { |
| result = ProbeResult::NoMatch; |
| if let &ty::Predicate::Trait(ref pred) = &o.predicate { |
| possibly_unsatisfied_predicates.push(pred.skip_binder().trait_ref); |
| } |
| } |
| } |
| |
| if let ProbeResult::Match = result { |
| if let (Some(return_ty), Some(xform_ret_ty)) = |
| (self.return_type, probe.xform_ret_ty) |
| { |
| let xform_ret_ty = self.resolve_vars_if_possible(&xform_ret_ty); |
| debug!("comparing return_ty {:?} with xform ret ty {:?}", |
| return_ty, |
| probe.xform_ret_ty); |
| if self.at(&ObligationCause::dummy(), self.param_env) |
| .sup(return_ty, xform_ret_ty) |
| .is_err() |
| { |
| return ProbeResult::BadReturnType; |
| } |
| } |
| } |
| |
| result |
| }) |
| } |
| |
| /// Sometimes we get in a situation where we have multiple probes that are all impls of the |
| /// same trait, but we don't know which impl to use. In this case, since in all cases the |
| /// external interface of the method can be determined from the trait, it's ok not to decide. |
| /// We can basically just collapse all of the probes for various impls into one where-clause |
| /// probe. This will result in a pending obligation so when more type-info is available we can |
| /// make the final decision. |
| /// |
| /// Example (`src/test/ui/method-two-trait-defer-resolution-1.rs`): |
| /// |
| /// ``` |
| /// trait Foo { ... } |
| /// impl Foo for Vec<int> { ... } |
| /// impl Foo for Vec<usize> { ... } |
| /// ``` |
| /// |
| /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we |
| /// use, so it's ok to just commit to "using the method from the trait Foo". |
| fn collapse_candidates_to_trait_pick(&self, probes: &[(&Candidate<'tcx>, ProbeResult)]) |
| -> Option<Pick<'tcx>> |
| { |
| // Do all probes correspond to the same trait? |
| let container = probes[0].0.item.container; |
| if let ty::ImplContainer(_) = container { |
| return None |
| } |
| if probes[1..].iter().any(|&(p, _)| p.item.container != container) { |
| return None; |
| } |
| |
| // FIXME: check the return type here somehow. |
| // If so, just use this trait and call it a day. |
| Some(Pick { |
| item: probes[0].0.item.clone(), |
| kind: TraitPick, |
| import_ids: probes[0].0.import_ids.clone(), |
| autoderefs: 0, |
| autoref: None, |
| unsize: None, |
| }) |
| } |
| |
| /// Similarly to `probe_for_return_type`, this method attempts to find the best matching |
| /// candidate method where the method name may have been misspelt. Similarly to other |
| /// Levenshtein based suggestions, we provide at most one such suggestion. |
| fn probe_for_lev_candidate(&mut self) -> Result<Option<ty::AssocItem>, MethodError<'tcx>> { |
| debug!("probing for method names similar to {:?}", |
| self.method_name); |
| |
| let steps = self.steps.clone(); |
| self.probe(|_| { |
| let mut pcx = ProbeContext::new(self.fcx, self.span, self.mode, self.method_name, |
| self.return_type, |
| self.orig_steps_var_values.clone(), |
| steps, IsSuggestion(true)); |
| pcx.allow_similar_names = true; |
| pcx.assemble_inherent_candidates(); |
| pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)?; |
| |
| let method_names = pcx.candidate_method_names(); |
| pcx.allow_similar_names = false; |
| let applicable_close_candidates: Vec<ty::AssocItem> = method_names |
| .iter() |
| .filter_map(|&method_name| { |
| pcx.reset(); |
| pcx.method_name = Some(method_name); |
| pcx.assemble_inherent_candidates(); |
| pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID) |
| .ok().map_or(None, |_| { |
| pcx.pick_core() |
| .and_then(|pick| pick.ok()) |
| .and_then(|pick| Some(pick.item)) |
| }) |
| }) |
| .collect(); |
| |
| if applicable_close_candidates.is_empty() { |
| Ok(None) |
| } else { |
| let best_name = { |
| let names = applicable_close_candidates.iter().map(|cand| &cand.ident.name); |
| find_best_match_for_name(names, |
| &self.method_name.unwrap().as_str(), |
| None) |
| }.unwrap(); |
| Ok(applicable_close_candidates |
| .into_iter() |
| .find(|method| method.ident.name == best_name)) |
| } |
| }) |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // MISCELLANY |
| fn has_applicable_self(&self, item: &ty::AssocItem) -> bool { |
| // "Fast track" -- check for usage of sugar when in method call |
| // mode. |
| // |
| // In Path mode (i.e., resolving a value like `T::next`), consider any |
| // associated value (i.e., methods, constants) but not types. |
| match self.mode { |
| Mode::MethodCall => item.method_has_self_argument, |
| Mode::Path => match item.kind { |
| ty::AssocKind::OpaqueTy | |
| ty::AssocKind::Type => false, |
| ty::AssocKind::Method | ty::AssocKind::Const => true |
| }, |
| } |
| // FIXME -- check for types that deref to `Self`, |
| // like `Rc<Self>` and so on. |
| // |
| // Note also that the current code will break if this type |
| // includes any of the type parameters defined on the method |
| // -- but this could be overcome. |
| } |
| |
| fn record_static_candidate(&mut self, source: CandidateSource) { |
| self.static_candidates.push(source); |
| } |
| |
| fn xform_self_ty(&self, |
| item: &ty::AssocItem, |
| impl_ty: Ty<'tcx>, |
| substs: SubstsRef<'tcx>) |
| -> (Ty<'tcx>, Option<Ty<'tcx>>) { |
| if item.kind == ty::AssocKind::Method && self.mode == Mode::MethodCall { |
| let sig = self.xform_method_sig(item.def_id, substs); |
| (sig.inputs()[0], Some(sig.output())) |
| } else { |
| (impl_ty, None) |
| } |
| } |
| |
| fn xform_method_sig(&self, |
| method: DefId, |
| substs: SubstsRef<'tcx>) |
| -> ty::FnSig<'tcx> |
| { |
| let fn_sig = self.tcx.fn_sig(method); |
| debug!("xform_self_ty(fn_sig={:?}, substs={:?})", |
| fn_sig, |
| substs); |
| |
| assert!(!substs.has_escaping_bound_vars()); |
| |
| // It is possible for type parameters or early-bound lifetimes |
| // to appear in the signature of `self`. The substitutions we |
| // are given do not include type/lifetime parameters for the |
| // method yet. So create fresh variables here for those too, |
| // if there are any. |
| let generics = self.tcx.generics_of(method); |
| assert_eq!(substs.len(), generics.parent_count as usize); |
| |
| // Erase any late-bound regions from the method and substitute |
| // in the values from the substitution. |
| let xform_fn_sig = self.erase_late_bound_regions(&fn_sig); |
| |
| if generics.params.is_empty() { |
| xform_fn_sig.subst(self.tcx, substs) |
| } else { |
| let substs = InternalSubsts::for_item(self.tcx, method, |param, _| { |
| let i = param.index as usize; |
| if i < substs.len() { |
| substs[i] |
| } else { |
| match param.kind { |
| GenericParamDefKind::Lifetime => { |
| // In general, during probe we erase regions. See |
| // `impl_self_ty()` for an explanation. |
| self.tcx.lifetimes.re_erased.into() |
| } |
| GenericParamDefKind::Type { .. } |
| | GenericParamDefKind::Const => { |
| self.var_for_def(self.span, param) |
| } |
| } |
| } |
| }); |
| xform_fn_sig.subst(self.tcx, substs) |
| } |
| } |
| |
| /// Gets the type of an impl and generate substitutions with placeholders. |
| fn impl_ty_and_substs(&self, impl_def_id: DefId) -> (Ty<'tcx>, SubstsRef<'tcx>) { |
| (self.tcx.type_of(impl_def_id), self.fresh_item_substs(impl_def_id)) |
| } |
| |
| fn fresh_item_substs(&self, def_id: DefId) -> SubstsRef<'tcx> { |
| InternalSubsts::for_item(self.tcx, def_id, |param, _| { |
| match param.kind { |
| GenericParamDefKind::Lifetime => self.tcx.lifetimes.re_erased.into(), |
| GenericParamDefKind::Type { .. } => { |
| self.next_ty_var(TypeVariableOrigin { |
| kind: TypeVariableOriginKind::SubstitutionPlaceholder, |
| span: self.tcx.def_span(def_id), |
| }).into() |
| } |
| GenericParamDefKind::Const { .. } => { |
| let span = self.tcx.def_span(def_id); |
| let origin = ConstVariableOrigin { |
| kind: ConstVariableOriginKind::SubstitutionPlaceholder, |
| span, |
| }; |
| self.next_const_var(self.tcx.type_of(param.def_id), origin).into() |
| } |
| } |
| }) |
| } |
| |
| /// Replaces late-bound-regions bound by `value` with `'static` using |
| /// `ty::erase_late_bound_regions`. |
| /// |
| /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of |
| /// method matching. It is reasonable during the probe phase because we don't consider region |
| /// relationships at all. Therefore, we can just replace all the region variables with 'static |
| /// rather than creating fresh region variables. This is nice for two reasons: |
| /// |
| /// 1. Because the numbers of the region variables would otherwise be fairly unique to this |
| /// particular method call, it winds up creating fewer types overall, which helps for memory |
| /// usage. (Admittedly, this is a rather small effect, though measurable.) |
| /// |
| /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any |
| /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound |
| /// regions with actual region variables as is proper, we'd have to ensure that the same |
| /// region got replaced with the same variable, which requires a bit more coordination |
| /// and/or tracking the substitution and |
| /// so forth. |
| fn erase_late_bound_regions<T>(&self, value: &ty::Binder<T>) -> T |
| where T: TypeFoldable<'tcx> |
| { |
| self.tcx.erase_late_bound_regions(value) |
| } |
| |
| /// Finds the method with the appropriate name (or return type, as the case may be). If |
| /// `allow_similar_names` is set, find methods with close-matching names. |
| fn impl_or_trait_item(&self, def_id: DefId) -> Vec<ty::AssocItem> { |
| if let Some(name) = self.method_name { |
| if self.allow_similar_names { |
| let max_dist = max(name.as_str().len(), 3) / 3; |
| self.tcx.associated_items(def_id) |
| .filter(|x| { |
| let dist = lev_distance(&*name.as_str(), &x.ident.as_str()); |
| Namespace::from(x.kind) == Namespace::Value && dist > 0 |
| && dist <= max_dist |
| }) |
| .collect() |
| } else { |
| self.fcx |
| .associated_item(def_id, name, Namespace::Value) |
| .map_or(Vec::new(), |x| vec![x]) |
| } |
| } else { |
| self.tcx.associated_items(def_id).collect() |
| } |
| } |
| } |
| |
| impl<'tcx> Candidate<'tcx> { |
| fn to_unadjusted_pick(&self) -> Pick<'tcx> { |
| Pick { |
| item: self.item.clone(), |
| kind: match self.kind { |
| InherentImplCandidate(..) => InherentImplPick, |
| ObjectCandidate => ObjectPick, |
| TraitCandidate(_) => TraitPick, |
| WhereClauseCandidate(ref trait_ref) => { |
| // Only trait derived from where-clauses should |
| // appear here, so they should not contain any |
| // inference variables or other artifacts. This |
| // means they are safe to put into the |
| // `WhereClausePick`. |
| assert!( |
| !trait_ref.skip_binder().substs.needs_infer() |
| && !trait_ref.skip_binder().substs.has_placeholders() |
| ); |
| |
| WhereClausePick(trait_ref.clone()) |
| } |
| }, |
| import_ids: self.import_ids.clone(), |
| autoderefs: 0, |
| autoref: None, |
| unsize: None, |
| } |
| } |
| } |
