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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 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, &param_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.sty {
// 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.sty {
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.sty {
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::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::MutImmutable }) => {
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::MutMutable }) => {
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.sty {
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().sty {
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::MutImmutable).or_else(|| {
self.pick_autorefd_method(step, self_ty, hir::MutMutable)
})})})
.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.sty {
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 = if step.unsize {
Some(self_ty)
} else {
None
};
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/run-pass/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::Existential |
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,
}
}
}
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