905 lines
40 KiB
Rust
905 lines
40 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use super::{
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FulfillmentError,
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FulfillmentErrorCode,
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MismatchedProjectionTypes,
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Obligation,
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ObligationCause,
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ObligationCauseCode,
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OutputTypeParameterMismatch,
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TraitNotObjectSafe,
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PredicateObligation,
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SelectionContext,
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SelectionError,
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ObjectSafetyViolation,
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MethodViolationCode,
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};
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use fmt_macros::{Parser, Piece, Position};
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use hir::def_id::DefId;
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use infer::{InferCtxt};
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use ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
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use ty::fast_reject;
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use ty::fold::TypeFolder;
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use ty::subst::{self, Subst};
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use util::nodemap::{FnvHashMap, FnvHashSet};
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use std::cmp;
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use std::fmt;
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use syntax::ast;
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use syntax::attr::{AttributeMethods, AttrMetaMethods};
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use syntax::codemap::Span;
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use syntax::errors::DiagnosticBuilder;
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#[derive(Debug, PartialEq, Eq, Hash)]
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pub struct TraitErrorKey<'tcx> {
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span: Span,
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warning_node_id: Option<ast::NodeId>,
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predicate: ty::Predicate<'tcx>
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}
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impl<'a, 'gcx, 'tcx> TraitErrorKey<'tcx> {
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fn from_error(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
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e: &FulfillmentError<'tcx>,
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warning_node_id: Option<ast::NodeId>) -> Self {
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let predicate =
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infcx.resolve_type_vars_if_possible(&e.obligation.predicate);
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TraitErrorKey {
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span: e.obligation.cause.span,
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predicate: infcx.tcx.erase_regions(&predicate),
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warning_node_id: warning_node_id
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}
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}
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}
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impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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pub fn report_fulfillment_errors(&self, errors: &Vec<FulfillmentError<'tcx>>) {
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for error in errors {
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self.report_fulfillment_error(error, None);
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}
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}
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pub fn report_fulfillment_errors_as_warnings(&self,
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errors: &Vec<FulfillmentError<'tcx>>,
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node_id: ast::NodeId) {
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for error in errors {
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self.report_fulfillment_error(error, Some(node_id));
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}
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}
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fn report_fulfillment_error(&self,
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error: &FulfillmentError<'tcx>,
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warning_node_id: Option<ast::NodeId>) {
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let error_key = TraitErrorKey::from_error(self, error, warning_node_id);
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debug!("report_fulfillment_errors({:?}) - key={:?}",
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error, error_key);
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if !self.reported_trait_errors.borrow_mut().insert(error_key) {
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debug!("report_fulfillment_errors: skipping duplicate");
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return;
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}
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match error.code {
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FulfillmentErrorCode::CodeSelectionError(ref e) => {
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self.report_selection_error(&error.obligation, e, warning_node_id);
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}
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FulfillmentErrorCode::CodeProjectionError(ref e) => {
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self.report_projection_error(&error.obligation, e, warning_node_id);
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}
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FulfillmentErrorCode::CodeAmbiguity => {
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self.maybe_report_ambiguity(&error.obligation);
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}
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}
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}
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fn report_projection_error(&self,
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obligation: &PredicateObligation<'tcx>,
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error: &MismatchedProjectionTypes<'tcx>,
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warning_node_id: Option<ast::NodeId>)
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{
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let predicate =
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self.resolve_type_vars_if_possible(&obligation.predicate);
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if !predicate.references_error() {
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if let Some(warning_node_id) = warning_node_id {
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self.tcx.sess.add_lint(
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::lint::builtin::UNSIZED_IN_TUPLE,
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warning_node_id,
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obligation.cause.span,
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format!("type mismatch resolving `{}`: {}",
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predicate,
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error.err));
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} else {
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let mut err = struct_span_err!(self.tcx.sess, obligation.cause.span, E0271,
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"type mismatch resolving `{}`: {}",
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predicate,
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error.err);
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self.note_obligation_cause(&mut err, obligation);
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err.emit();
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}
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}
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}
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fn impl_substs(&self,
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did: DefId,
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obligation: PredicateObligation<'tcx>)
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-> subst::Substs<'tcx> {
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let tcx = self.tcx;
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let ity = tcx.lookup_item_type(did);
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let (tps, rps, _) =
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(ity.generics.types.get_slice(subst::TypeSpace),
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ity.generics.regions.get_slice(subst::TypeSpace),
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ity.ty);
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let rps = self.region_vars_for_defs(obligation.cause.span, rps);
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let mut substs = subst::Substs::new(
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subst::VecPerParamSpace::empty(),
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subst::VecPerParamSpace::new(rps, Vec::new(), Vec::new()));
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self.type_vars_for_defs(obligation.cause.span,
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subst::ParamSpace::TypeSpace,
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&mut substs,
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tps);
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substs
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}
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fn impl_with_self_type_of(&self,
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trait_ref: ty::PolyTraitRef<'tcx>,
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obligation: &PredicateObligation<'tcx>)
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-> Option<DefId>
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{
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let tcx = self.tcx;
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let mut result = None;
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let mut ambiguous = false;
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let trait_self_ty = tcx.erase_late_bound_regions(&trait_ref).self_ty();
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if trait_self_ty.is_ty_var() {
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return None;
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}
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self.tcx.lookup_trait_def(trait_ref.def_id())
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.for_each_relevant_impl(self.tcx, trait_self_ty, |def_id| {
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let impl_self_ty = tcx
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.impl_trait_ref(def_id)
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.unwrap()
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.self_ty()
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.subst(tcx, &self.impl_substs(def_id, obligation.clone()));
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if !tcx.has_attr(def_id, "rustc_on_unimplemented") {
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return;
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}
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if let Ok(..) = self.can_equate(&trait_self_ty, &impl_self_ty) {
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ambiguous = result.is_some();
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result = Some(def_id);
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}
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});
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if ambiguous {
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None
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} else {
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result
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}
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}
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fn on_unimplemented_note(&self,
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trait_ref: ty::PolyTraitRef<'tcx>,
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obligation: &PredicateObligation<'tcx>) -> Option<String> {
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let def_id = self.impl_with_self_type_of(trait_ref, obligation)
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.unwrap_or(trait_ref.def_id());
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let trait_ref = trait_ref.skip_binder();
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let span = obligation.cause.span;
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let mut report = None;
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for item in self.tcx.get_attrs(def_id).iter() {
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if item.check_name("rustc_on_unimplemented") {
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let err_sp = item.meta().span.substitute_dummy(span);
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let def = self.tcx.lookup_trait_def(trait_ref.def_id);
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let trait_str = def.trait_ref.to_string();
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if let Some(ref istring) = item.value_str() {
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let mut generic_map = def.generics.types.iter_enumerated()
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.map(|(param, i, gen)| {
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(gen.name.as_str().to_string(),
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trait_ref.substs.types.get(param, i)
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.to_string())
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}).collect::<FnvHashMap<String, String>>();
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generic_map.insert("Self".to_string(),
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trait_ref.self_ty().to_string());
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let parser = Parser::new(&istring);
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let mut errored = false;
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let err: String = parser.filter_map(|p| {
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match p {
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Piece::String(s) => Some(s),
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Piece::NextArgument(a) => match a.position {
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Position::ArgumentNamed(s) => match generic_map.get(s) {
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Some(val) => Some(val),
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None => {
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span_err!(self.tcx.sess, err_sp, E0272,
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"the #[rustc_on_unimplemented] \
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attribute on \
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trait definition for {} refers to \
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non-existent type parameter {}",
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trait_str, s);
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errored = true;
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None
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}
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},
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_ => {
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span_err!(self.tcx.sess, err_sp, E0273,
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"the #[rustc_on_unimplemented] attribute \
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on trait definition for {} must have \
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named format arguments, eg \
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`#[rustc_on_unimplemented = \
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\"foo {{T}}\"]`", trait_str);
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errored = true;
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None
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}
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}
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}
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}).collect();
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// Report only if the format string checks out
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if !errored {
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report = Some(err);
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}
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} else {
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span_err!(self.tcx.sess, err_sp, E0274,
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"the #[rustc_on_unimplemented] attribute on \
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trait definition for {} must have a value, \
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eg `#[rustc_on_unimplemented = \"foo\"]`",
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trait_str);
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}
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break;
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}
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}
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report
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}
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fn find_similar_impl_candidates(&self,
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trait_ref: ty::PolyTraitRef<'tcx>)
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-> Vec<ty::TraitRef<'tcx>>
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{
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let simp = fast_reject::simplify_type(self.tcx,
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trait_ref.skip_binder().self_ty(),
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true);
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let mut impl_candidates = Vec::new();
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let trait_def = self.tcx.lookup_trait_def(trait_ref.def_id());
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match simp {
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Some(simp) => trait_def.for_each_impl(self.tcx, |def_id| {
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let imp = self.tcx.impl_trait_ref(def_id).unwrap();
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let imp_simp = fast_reject::simplify_type(self.tcx,
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imp.self_ty(),
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true);
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if let Some(imp_simp) = imp_simp {
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if simp != imp_simp {
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return;
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}
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}
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impl_candidates.push(imp);
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}),
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None => trait_def.for_each_impl(self.tcx, |def_id| {
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impl_candidates.push(
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self.tcx.impl_trait_ref(def_id).unwrap());
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})
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};
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impl_candidates
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}
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fn report_similar_impl_candidates(&self,
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trait_ref: ty::PolyTraitRef<'tcx>,
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err: &mut DiagnosticBuilder)
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{
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let simp = fast_reject::simplify_type(self.tcx,
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trait_ref.skip_binder().self_ty(),
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true);
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let mut impl_candidates = Vec::new();
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let trait_def = self.tcx.lookup_trait_def(trait_ref.def_id());
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match simp {
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Some(simp) => trait_def.for_each_impl(self.tcx, |def_id| {
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let imp = self.tcx.impl_trait_ref(def_id).unwrap();
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let imp_simp = fast_reject::simplify_type(self.tcx,
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imp.self_ty(),
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true);
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if let Some(imp_simp) = imp_simp {
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if simp != imp_simp {
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return;
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}
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}
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impl_candidates.push(imp);
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}),
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None => trait_def.for_each_impl(self.tcx, |def_id| {
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impl_candidates.push(
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self.tcx.impl_trait_ref(def_id).unwrap());
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})
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};
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if impl_candidates.is_empty() {
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return;
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}
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err.help(&format!("the following implementations were found:"));
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let end = cmp::min(4, impl_candidates.len());
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for candidate in &impl_candidates[0..end] {
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err.help(&format!(" {:?}", candidate));
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}
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if impl_candidates.len() > 4 {
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err.help(&format!("and {} others", impl_candidates.len()-4));
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}
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}
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/// Reports that an overflow has occurred and halts compilation. We
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/// halt compilation unconditionally because it is important that
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/// overflows never be masked -- they basically represent computations
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/// whose result could not be truly determined and thus we can't say
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/// if the program type checks or not -- and they are unusual
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/// occurrences in any case.
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pub fn report_overflow_error<T>(&self,
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obligation: &Obligation<'tcx, T>,
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suggest_increasing_limit: bool) -> !
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where T: fmt::Display + TypeFoldable<'tcx>
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{
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let predicate =
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self.resolve_type_vars_if_possible(&obligation.predicate);
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let mut err = struct_span_err!(self.tcx.sess, obligation.cause.span, E0275,
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"overflow evaluating the requirement `{}`",
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predicate);
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if suggest_increasing_limit {
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self.suggest_new_overflow_limit(&mut err);
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}
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self.note_obligation_cause(&mut err, obligation);
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err.emit();
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self.tcx.sess.abort_if_errors();
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bug!();
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}
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/// Reports that a cycle was detected which led to overflow and halts
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/// compilation. This is equivalent to `report_overflow_error` except
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/// that we can give a more helpful error message (and, in particular,
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/// we do not suggest increasing the overflow limit, which is not
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/// going to help).
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pub fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
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let cycle = self.resolve_type_vars_if_possible(&cycle.to_owned());
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assert!(cycle.len() > 0);
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debug!("report_overflow_error_cycle: cycle={:?}", cycle);
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self.report_overflow_error(&cycle[0], false);
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}
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pub fn report_selection_error(&self,
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obligation: &PredicateObligation<'tcx>,
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error: &SelectionError<'tcx>,
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warning_node_id: Option<ast::NodeId>)
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{
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let span = obligation.cause.span;
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let mut err = match *error {
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SelectionError::Unimplemented => {
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if let ObligationCauseCode::CompareImplMethodObligation = obligation.cause.code {
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span_err!(
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self.tcx.sess, span, E0276,
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"the requirement `{}` appears on the impl \
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method but not on the corresponding trait method",
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obligation.predicate);
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return;
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} else {
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match obligation.predicate {
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ty::Predicate::Trait(ref trait_predicate) => {
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let trait_predicate =
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self.resolve_type_vars_if_possible(trait_predicate);
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if self.tcx.sess.has_errors() && trait_predicate.references_error() {
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return;
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} else {
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let trait_ref = trait_predicate.to_poly_trait_ref();
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if let Some(warning_node_id) = warning_node_id {
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self.tcx.sess.add_lint(
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::lint::builtin::UNSIZED_IN_TUPLE,
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warning_node_id,
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obligation.cause.span,
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format!("the trait bound `{}` is not satisfied",
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trait_ref.to_predicate()));
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return;
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}
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let mut err = struct_span_err!(
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self.tcx.sess, span, E0277,
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"the trait bound `{}` is not satisfied",
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trait_ref.to_predicate());
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// Try to report a help message
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if !trait_ref.has_infer_types() &&
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self.predicate_can_apply(trait_ref) {
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// If a where-clause may be useful, remind the
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// user that they can add it.
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//
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// don't display an on-unimplemented note, as
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// these notes will often be of the form
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// "the type `T` can't be frobnicated"
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// which is somewhat confusing.
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err.help(&format!("consider adding a `where {}` bound",
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trait_ref.to_predicate()));
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} else if let Some(s) = self.on_unimplemented_note(trait_ref,
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obligation) {
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// If it has a custom "#[rustc_on_unimplemented]"
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// error message, let's display it!
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err.note(&s);
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} else {
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// If we can't show anything useful, try to find
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// similar impls.
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let impl_candidates =
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self.find_similar_impl_candidates(trait_ref);
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if impl_candidates.len() > 0 {
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self.report_similar_impl_candidates(trait_ref, &mut err);
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}
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}
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err
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}
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}
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ty::Predicate::Equate(ref predicate) => {
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let predicate = self.resolve_type_vars_if_possible(predicate);
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let err = self.equality_predicate(span,
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&predicate).err().unwrap();
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struct_span_err!(self.tcx.sess, span, E0278,
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"the requirement `{}` is not satisfied (`{}`)",
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predicate, err)
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}
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ty::Predicate::RegionOutlives(ref predicate) => {
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let predicate = self.resolve_type_vars_if_possible(predicate);
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let err = self.region_outlives_predicate(span,
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&predicate).err().unwrap();
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struct_span_err!(self.tcx.sess, span, E0279,
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"the requirement `{}` is not satisfied (`{}`)",
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predicate, err)
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}
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|
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ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
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let predicate =
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self.resolve_type_vars_if_possible(&obligation.predicate);
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struct_span_err!(self.tcx.sess, span, E0280,
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"the requirement `{}` is not satisfied",
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predicate)
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}
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ty::Predicate::ObjectSafe(trait_def_id) => {
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let violations = self.tcx.object_safety_violations(trait_def_id);
|
|
let err = self.tcx.report_object_safety_error(span,
|
|
trait_def_id,
|
|
warning_node_id,
|
|
violations);
|
|
if let Some(err) = err {
|
|
err
|
|
} else {
|
|
return;
|
|
}
|
|
}
|
|
|
|
ty::Predicate::ClosureKind(closure_def_id, kind) => {
|
|
let found_kind = self.closure_kind(closure_def_id).unwrap();
|
|
let closure_span = self.tcx.map.span_if_local(closure_def_id).unwrap();
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess, closure_span, E0525,
|
|
"expected a closure that implements the `{}` trait, \
|
|
but this closure only implements `{}`",
|
|
kind,
|
|
found_kind);
|
|
err.span_note(
|
|
obligation.cause.span,
|
|
&format!("the requirement to implement \
|
|
`{}` derives from here", kind));
|
|
err.emit();
|
|
return;
|
|
}
|
|
|
|
ty::Predicate::WellFormed(ty) => {
|
|
// WF predicates cannot themselves make
|
|
// errors. They can only block due to
|
|
// ambiguity; otherwise, they always
|
|
// degenerate into other obligations
|
|
// (which may fail).
|
|
span_bug!(span, "WF predicate not satisfied for {:?}", ty);
|
|
}
|
|
|
|
ty::Predicate::Rfc1592(ref data) => {
|
|
span_bug!(
|
|
obligation.cause.span,
|
|
"RFC1592 predicate not satisfied for {:?}",
|
|
data);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
OutputTypeParameterMismatch(ref expected_trait_ref, ref actual_trait_ref, ref e) => {
|
|
let expected_trait_ref = self.resolve_type_vars_if_possible(&*expected_trait_ref);
|
|
let actual_trait_ref = self.resolve_type_vars_if_possible(&*actual_trait_ref);
|
|
if actual_trait_ref.self_ty().references_error() {
|
|
return;
|
|
}
|
|
struct_span_err!(self.tcx.sess, span, E0281,
|
|
"type mismatch: the type `{}` implements the trait `{}`, \
|
|
but the trait `{}` is required ({})",
|
|
expected_trait_ref.self_ty(),
|
|
expected_trait_ref,
|
|
actual_trait_ref,
|
|
e)
|
|
}
|
|
|
|
TraitNotObjectSafe(did) => {
|
|
let violations = self.tcx.object_safety_violations(did);
|
|
let err = self.tcx.report_object_safety_error(span, did,
|
|
warning_node_id,
|
|
violations);
|
|
if let Some(err) = err {
|
|
err
|
|
} else {
|
|
return;
|
|
}
|
|
}
|
|
};
|
|
self.note_obligation_cause(&mut err, obligation);
|
|
err.emit();
|
|
}
|
|
}
|
|
|
|
impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
|
|
pub fn recursive_type_with_infinite_size_error(self,
|
|
type_def_id: DefId)
|
|
-> DiagnosticBuilder<'tcx>
|
|
{
|
|
assert!(type_def_id.is_local());
|
|
let span = self.map.span_if_local(type_def_id).unwrap();
|
|
let mut err = struct_span_err!(self.sess, span, E0072,
|
|
"recursive type `{}` has infinite size",
|
|
self.item_path_str(type_def_id));
|
|
err.help(&format!("insert indirection (e.g., a `Box`, `Rc`, or `&`) \
|
|
at some point to make `{}` representable",
|
|
self.item_path_str(type_def_id)));
|
|
err
|
|
}
|
|
|
|
pub fn report_object_safety_error(self,
|
|
span: Span,
|
|
trait_def_id: DefId,
|
|
warning_node_id: Option<ast::NodeId>,
|
|
violations: Vec<ObjectSafetyViolation>)
|
|
-> Option<DiagnosticBuilder<'tcx>>
|
|
{
|
|
let mut err = match warning_node_id {
|
|
Some(_) => None,
|
|
None => {
|
|
Some(struct_span_err!(
|
|
self.sess, span, E0038,
|
|
"the trait `{}` cannot be made into an object",
|
|
self.item_path_str(trait_def_id)))
|
|
}
|
|
};
|
|
|
|
let mut reported_violations = FnvHashSet();
|
|
for violation in violations {
|
|
if !reported_violations.insert(violation.clone()) {
|
|
continue;
|
|
}
|
|
let buf;
|
|
let note = match violation {
|
|
ObjectSafetyViolation::SizedSelf => {
|
|
"the trait cannot require that `Self : Sized`"
|
|
}
|
|
|
|
ObjectSafetyViolation::SupertraitSelf => {
|
|
"the trait cannot use `Self` as a type parameter \
|
|
in the supertrait listing"
|
|
}
|
|
|
|
ObjectSafetyViolation::Method(method,
|
|
MethodViolationCode::StaticMethod) => {
|
|
buf = format!("method `{}` has no receiver",
|
|
method.name);
|
|
&buf
|
|
}
|
|
|
|
ObjectSafetyViolation::Method(method,
|
|
MethodViolationCode::ReferencesSelf) => {
|
|
buf = format!("method `{}` references the `Self` type \
|
|
in its arguments or return type",
|
|
method.name);
|
|
&buf
|
|
}
|
|
|
|
ObjectSafetyViolation::Method(method,
|
|
MethodViolationCode::Generic) => {
|
|
buf = format!("method `{}` has generic type parameters",
|
|
method.name);
|
|
&buf
|
|
}
|
|
};
|
|
match (warning_node_id, &mut err) {
|
|
(Some(node_id), &mut None) => {
|
|
self.sess.add_lint(
|
|
::lint::builtin::OBJECT_UNSAFE_FRAGMENT,
|
|
node_id,
|
|
span,
|
|
note.to_string());
|
|
}
|
|
(None, &mut Some(ref mut err)) => {
|
|
err.note(note);
|
|
}
|
|
_ => unreachable!()
|
|
}
|
|
}
|
|
err
|
|
}
|
|
}
|
|
|
|
impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
|
|
fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>) {
|
|
// Unable to successfully determine, probably means
|
|
// insufficient type information, but could mean
|
|
// ambiguous impls. The latter *ought* to be a
|
|
// coherence violation, so we don't report it here.
|
|
|
|
let predicate = self.resolve_type_vars_if_possible(&obligation.predicate);
|
|
|
|
debug!("maybe_report_ambiguity(predicate={:?}, obligation={:?})",
|
|
predicate,
|
|
obligation);
|
|
|
|
// Ambiguity errors are often caused as fallout from earlier
|
|
// errors. So just ignore them if this infcx is tainted.
|
|
if self.is_tainted_by_errors() {
|
|
return;
|
|
}
|
|
|
|
match predicate {
|
|
ty::Predicate::Trait(ref data) => {
|
|
let trait_ref = data.to_poly_trait_ref();
|
|
let self_ty = trait_ref.self_ty();
|
|
let all_types = &trait_ref.substs().types;
|
|
if all_types.references_error() {
|
|
} else {
|
|
// Typically, this ambiguity should only happen if
|
|
// there are unresolved type inference variables
|
|
// (otherwise it would suggest a coherence
|
|
// failure). But given #21974 that is not necessarily
|
|
// the case -- we can have multiple where clauses that
|
|
// are only distinguished by a region, which results
|
|
// in an ambiguity even when all types are fully
|
|
// known, since we don't dispatch based on region
|
|
// relationships.
|
|
|
|
// This is kind of a hack: it frequently happens that some earlier
|
|
// error prevents types from being fully inferred, and then we get
|
|
// a bunch of uninteresting errors saying something like "<generic
|
|
// #0> doesn't implement Sized". It may even be true that we
|
|
// could just skip over all checks where the self-ty is an
|
|
// inference variable, but I was afraid that there might be an
|
|
// inference variable created, registered as an obligation, and
|
|
// then never forced by writeback, and hence by skipping here we'd
|
|
// be ignoring the fact that we don't KNOW the type works
|
|
// out. Though even that would probably be harmless, given that
|
|
// we're only talking about builtin traits, which are known to be
|
|
// inhabited. But in any case I just threw in this check for
|
|
// has_errors() to be sure that compilation isn't happening
|
|
// anyway. In that case, why inundate the user.
|
|
if !self.tcx.sess.has_errors() {
|
|
if
|
|
self.tcx.lang_items.sized_trait()
|
|
.map_or(false, |sized_id| sized_id == trait_ref.def_id())
|
|
{
|
|
self.need_type_info(obligation.cause.span, self_ty);
|
|
} else {
|
|
let mut err = struct_span_err!(self.tcx.sess,
|
|
obligation.cause.span, E0283,
|
|
"type annotations required: \
|
|
cannot resolve `{}`",
|
|
predicate);
|
|
self.note_obligation_cause(&mut err, obligation);
|
|
err.emit();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
ty::Predicate::WellFormed(ty) => {
|
|
// Same hacky approach as above to avoid deluging user
|
|
// with error messages.
|
|
if !ty.references_error() && !self.tcx.sess.has_errors() {
|
|
self.need_type_info(obligation.cause.span, ty);
|
|
}
|
|
}
|
|
|
|
_ => {
|
|
if !self.tcx.sess.has_errors() {
|
|
let mut err = struct_span_err!(self.tcx.sess,
|
|
obligation.cause.span, E0284,
|
|
"type annotations required: \
|
|
cannot resolve `{}`",
|
|
predicate);
|
|
self.note_obligation_cause(&mut err, obligation);
|
|
err.emit();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Returns whether the trait predicate may apply for *some* assignment
|
|
/// to the type parameters.
|
|
fn predicate_can_apply(&self, pred: ty::PolyTraitRef<'tcx>) -> bool {
|
|
struct ParamToVarFolder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
|
|
infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
|
|
var_map: FnvHashMap<Ty<'tcx>, Ty<'tcx>>
|
|
}
|
|
|
|
impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ParamToVarFolder<'a, 'gcx, 'tcx> {
|
|
fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.infcx.tcx }
|
|
|
|
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
|
|
if let ty::TyParam(..) = ty.sty {
|
|
let infcx = self.infcx;
|
|
self.var_map.entry(ty).or_insert_with(|| infcx.next_ty_var())
|
|
} else {
|
|
ty.super_fold_with(self)
|
|
}
|
|
}
|
|
}
|
|
|
|
self.probe(|_| {
|
|
let mut selcx = SelectionContext::new(self);
|
|
|
|
let cleaned_pred = pred.fold_with(&mut ParamToVarFolder {
|
|
infcx: self,
|
|
var_map: FnvHashMap()
|
|
});
|
|
|
|
let cleaned_pred = super::project::normalize(
|
|
&mut selcx,
|
|
ObligationCause::dummy(),
|
|
&cleaned_pred
|
|
).value;
|
|
|
|
let obligation = Obligation::new(
|
|
ObligationCause::dummy(),
|
|
cleaned_pred.to_predicate()
|
|
);
|
|
|
|
selcx.evaluate_obligation(&obligation)
|
|
})
|
|
}
|
|
|
|
|
|
fn need_type_info(&self, span: Span, ty: Ty<'tcx>) {
|
|
span_err!(self.tcx.sess, span, E0282,
|
|
"unable to infer enough type information about `{}`; \
|
|
type annotations or generic parameter binding required",
|
|
ty);
|
|
}
|
|
|
|
fn note_obligation_cause<T>(&self,
|
|
err: &mut DiagnosticBuilder,
|
|
obligation: &Obligation<'tcx, T>)
|
|
where T: fmt::Display
|
|
{
|
|
self.note_obligation_cause_code(err,
|
|
&obligation.predicate,
|
|
&obligation.cause.code);
|
|
}
|
|
|
|
fn note_obligation_cause_code<T>(&self,
|
|
err: &mut DiagnosticBuilder,
|
|
predicate: &T,
|
|
cause_code: &ObligationCauseCode<'tcx>)
|
|
where T: fmt::Display
|
|
{
|
|
let tcx = self.tcx;
|
|
match *cause_code {
|
|
ObligationCauseCode::MiscObligation => { }
|
|
ObligationCauseCode::SliceOrArrayElem => {
|
|
err.note("slice and array elements must have `Sized` type");
|
|
}
|
|
ObligationCauseCode::TupleElem => {
|
|
err.note("tuple elements must have `Sized` type");
|
|
}
|
|
ObligationCauseCode::ProjectionWf(data) => {
|
|
err.note(&format!("required so that the projection `{}` is well-formed",
|
|
data));
|
|
}
|
|
ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => {
|
|
err.note(&format!("required so that reference `{}` does not outlive its referent",
|
|
ref_ty));
|
|
}
|
|
ObligationCauseCode::ItemObligation(item_def_id) => {
|
|
let item_name = tcx.item_path_str(item_def_id);
|
|
err.note(&format!("required by `{}`", item_name));
|
|
}
|
|
ObligationCauseCode::ObjectCastObligation(object_ty) => {
|
|
err.note(&format!("required for the cast to the object type `{}`",
|
|
self.ty_to_string(object_ty)));
|
|
}
|
|
ObligationCauseCode::RepeatVec => {
|
|
err.note("the `Copy` trait is required because the \
|
|
repeated element will be copied");
|
|
}
|
|
ObligationCauseCode::VariableType(_) => {
|
|
err.note("all local variables must have a statically known size");
|
|
}
|
|
ObligationCauseCode::ReturnType => {
|
|
err.note("the return type of a function must have a \
|
|
statically known size");
|
|
}
|
|
ObligationCauseCode::AssignmentLhsSized => {
|
|
err.note("the left-hand-side of an assignment must have a statically known size");
|
|
}
|
|
ObligationCauseCode::StructInitializerSized => {
|
|
err.note("structs must have a statically known size to be initialized");
|
|
}
|
|
ObligationCauseCode::ClosureCapture(var_id, _, builtin_bound) => {
|
|
let def_id = tcx.lang_items.from_builtin_kind(builtin_bound).unwrap();
|
|
let trait_name = tcx.item_path_str(def_id);
|
|
let name = tcx.local_var_name_str(var_id);
|
|
err.note(
|
|
&format!("the closure that captures `{}` requires that all captured variables \
|
|
implement the trait `{}`",
|
|
name,
|
|
trait_name));
|
|
}
|
|
ObligationCauseCode::FieldSized => {
|
|
err.note("only the last field of a struct or enum variant \
|
|
may have a dynamically sized type");
|
|
}
|
|
ObligationCauseCode::SharedStatic => {
|
|
err.note("shared static variables must have a type that implements `Sync`");
|
|
}
|
|
ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
|
|
let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
|
|
err.note(&format!("required because it appears within the type `{}`",
|
|
parent_trait_ref.0.self_ty()));
|
|
let parent_predicate = parent_trait_ref.to_predicate();
|
|
self.note_obligation_cause_code(err,
|
|
&parent_predicate,
|
|
&data.parent_code);
|
|
}
|
|
ObligationCauseCode::ImplDerivedObligation(ref data) => {
|
|
let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
|
|
err.note(
|
|
&format!("required because of the requirements on the impl of `{}` for `{}`",
|
|
parent_trait_ref,
|
|
parent_trait_ref.0.self_ty()));
|
|
let parent_predicate = parent_trait_ref.to_predicate();
|
|
self.note_obligation_cause_code(err,
|
|
&parent_predicate,
|
|
&data.parent_code);
|
|
}
|
|
ObligationCauseCode::CompareImplMethodObligation => {
|
|
err.note(
|
|
&format!("the requirement `{}` appears on the impl method \
|
|
but not on the corresponding trait method",
|
|
predicate));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder) {
|
|
let current_limit = self.tcx.sess.recursion_limit.get();
|
|
let suggested_limit = current_limit * 2;
|
|
err.note(&format!(
|
|
"consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
|
|
suggested_limit));
|
|
}
|
|
}
|