350 lines
16 KiB
Rust
350 lines
16 KiB
Rust
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// 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::{FulfillmentError, FulfillmentErrorCode,
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ObligationCauseCode, SelectionError,
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PredicateObligation, OutputTypeParameterMismatch};
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use middle::infer::InferCtxt;
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use middle::ty::{mod};
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use syntax::codemap::Span;
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use util::ppaux::{Repr, UserString};
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pub fn report_fulfillment_errors<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
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errors: &Vec<FulfillmentError<'tcx>>) {
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for error in errors.iter() {
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report_fulfillment_error(infcx, error);
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}
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}
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fn report_fulfillment_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
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error: &FulfillmentError<'tcx>) {
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match error.code {
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FulfillmentErrorCode::CodeSelectionError(ref e) => {
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report_selection_error(infcx, &error.obligation, e);
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}
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FulfillmentErrorCode::CodeAmbiguity => {
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maybe_report_ambiguity(infcx, &error.obligation);
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}
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}
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}
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pub fn report_selection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
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obligation: &PredicateObligation<'tcx>,
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error: &SelectionError<'tcx>)
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{
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match *error {
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SelectionError::Overflow => {
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// We could track the stack here more precisely if we wanted, I imagine.
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match obligation.trait_ref {
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ty::Predicate::Trait(ref trait_ref) => {
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let trait_ref =
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infcx.resolve_type_vars_if_possible(&**trait_ref);
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"overflow evaluating the trait `{}` for the type `{}`",
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trait_ref.user_string(infcx.tcx),
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trait_ref.self_ty().user_string(infcx.tcx))[]);
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}
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ty::Predicate::Equate(ref predicate) => {
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let predicate = infcx.resolve_type_vars_if_possible(predicate);
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let err = infcx.equality_predicate(obligation.cause.span,
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&predicate).unwrap_err();
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"the requirement `{}` is not satisfied (`{}`)",
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predicate.user_string(infcx.tcx),
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ty::type_err_to_str(infcx.tcx, &err)).as_slice());
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}
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ty::Predicate::TypeOutlives(..) |
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ty::Predicate::RegionOutlives(..) => {
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!("overflow evaluating lifetime predicate").as_slice());
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}
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}
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let current_limit = infcx.tcx.sess.recursion_limit.get();
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let suggested_limit = current_limit * 2;
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infcx.tcx.sess.span_note(
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obligation.cause.span,
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format!(
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"consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
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suggested_limit)[]);
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note_obligation_cause(infcx, obligation);
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}
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SelectionError::Unimplemented => {
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match obligation.trait_ref {
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ty::Predicate::Trait(ref trait_ref) => {
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let trait_ref =
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infcx.resolve_type_vars_if_possible(
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&**trait_ref);
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if !ty::type_is_error(trait_ref.self_ty()) {
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"the trait `{}` is not implemented for the type `{}`",
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trait_ref.user_string(infcx.tcx),
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trait_ref.self_ty().user_string(infcx.tcx)).as_slice());
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note_obligation_cause(infcx, obligation);
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}
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}
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ty::Predicate::Equate(ref predicate) => {
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let predicate = infcx.resolve_type_vars_if_possible(predicate);
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let err = infcx.equality_predicate(obligation.cause.span,
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&predicate).unwrap_err();
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"the requirement `{}` is not satisfied (`{}`)",
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predicate.user_string(infcx.tcx),
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ty::type_err_to_str(infcx.tcx, &err)).as_slice());
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}
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ty::Predicate::TypeOutlives(..) |
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ty::Predicate::RegionOutlives(..) => {
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let predicate = infcx.resolve_type_vars_if_possible(&obligation.trait_ref);
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"the requirement `{}` is not satisfied",
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predicate.user_string(infcx.tcx)).as_slice());
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}
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}
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}
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OutputTypeParameterMismatch(ref expected_trait_ref, ref actual_trait_ref, ref e) => {
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let expected_trait_ref =
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infcx.resolve_type_vars_if_possible(
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&**expected_trait_ref);
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let actual_trait_ref =
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infcx.resolve_type_vars_if_possible(
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&**actual_trait_ref);
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if !ty::type_is_error(actual_trait_ref.self_ty()) {
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"type mismatch: the type `{}` implements the trait `{}`, \
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but the trait `{}` is required ({})",
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expected_trait_ref.self_ty().user_string(infcx.tcx),
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expected_trait_ref.user_string(infcx.tcx),
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actual_trait_ref.user_string(infcx.tcx),
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ty::type_err_to_str(infcx.tcx, e)).as_slice());
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note_obligation_cause(infcx, obligation);
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}
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}
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}
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}
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fn maybe_report_ambiguity<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
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obligation: &PredicateObligation<'tcx>) {
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// Unable to successfully determine, probably means
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// insufficient type information, but could mean
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// ambiguous impls. The latter *ought* to be a
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// coherence violation, so we don't report it here.
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let trait_ref = match obligation.trait_ref {
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ty::Predicate::Trait(ref trait_ref) => {
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infcx.resolve_type_vars_if_possible(&**trait_ref)
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}
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_ => {
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infcx.tcx.sess.span_bug(
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obligation.cause.span,
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format!("ambiguity from something other than a trait: {}",
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obligation.trait_ref.repr(infcx.tcx)).as_slice());
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}
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};
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let self_ty = trait_ref.self_ty();
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debug!("maybe_report_ambiguity(trait_ref={}, self_ty={}, obligation={})",
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trait_ref.repr(infcx.tcx),
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self_ty.repr(infcx.tcx),
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obligation.repr(infcx.tcx));
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let all_types = &trait_ref.substs().types;
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if all_types.iter().any(|&t| ty::type_is_error(t)) {
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} else if all_types.iter().any(|&t| ty::type_needs_infer(t)) {
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// This is kind of a hack: it frequently happens that some earlier
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// error prevents types from being fully inferred, and then we get
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// a bunch of uninteresting errors saying something like "<generic
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// #0> doesn't implement Sized". It may even be true that we
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// could just skip over all checks where the self-ty is an
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// inference variable, but I was afraid that there might be an
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// inference variable created, registered as an obligation, and
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// then never forced by writeback, and hence by skipping here we'd
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// be ignoring the fact that we don't KNOW the type works
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// out. Though even that would probably be harmless, given that
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// we're only talking about builtin traits, which are known to be
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// inhabited. But in any case I just threw in this check for
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// has_errors() to be sure that compilation isn't happening
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// anyway. In that case, why inundate the user.
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if !infcx.tcx.sess.has_errors() {
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if infcx.tcx.lang_items.sized_trait()
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.map_or(false, |sized_id| sized_id == trait_ref.def_id()) {
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"unable to infer enough type information about `{}`; type annotations \
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required",
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self_ty.user_string(infcx.tcx)).as_slice());
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} else {
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infcx.tcx.sess.span_err(
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obligation.cause.span,
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format!(
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"unable to infer enough type information to \
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locate the impl of the trait `{}` for \
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the type `{}`; type annotations required",
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trait_ref.user_string(infcx.tcx),
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self_ty.user_string(infcx.tcx))[]);
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note_obligation_cause(infcx, obligation);
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}
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}
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} else if !infcx.tcx.sess.has_errors() {
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// Ambiguity. Coherence should have reported an error.
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infcx.tcx.sess.span_bug(
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obligation.cause.span,
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format!(
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"coherence failed to report ambiguity: \
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cannot locate the impl of the trait `{}` for \
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the type `{}`",
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trait_ref.user_string(infcx.tcx),
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self_ty.user_string(infcx.tcx))[]);
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}
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}
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fn note_obligation_cause<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
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obligation: &PredicateObligation<'tcx>)
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{
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let trait_ref = match obligation.trait_ref {
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ty::Predicate::Trait(ref trait_ref) => {
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infcx.resolve_type_vars_if_possible(&**trait_ref)
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}
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_ => {
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infcx.tcx.sess.span_bug(
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obligation.cause.span,
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format!("ambiguity from something other than a trait: {}",
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obligation.trait_ref.repr(infcx.tcx)).as_slice());
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}
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};
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note_obligation_cause_code(infcx,
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&trait_ref,
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obligation.cause.span,
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&obligation.cause.code)
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}
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fn note_obligation_cause_code<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
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trait_ref: &ty::PolyTraitRef<'tcx>,
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cause_span: Span,
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cause_code: &ObligationCauseCode<'tcx>)
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{
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let tcx = infcx.tcx;
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let trait_name = ty::item_path_str(tcx, trait_ref.def_id());
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match *cause_code {
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ObligationCauseCode::MiscObligation => { }
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ObligationCauseCode::ItemObligation(item_def_id) => {
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let item_name = ty::item_path_str(tcx, item_def_id);
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tcx.sess.span_note(
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cause_span,
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format!(
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"the trait `{}` must be implemented because it is required by `{}`",
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trait_name,
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item_name).as_slice());
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}
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ObligationCauseCode::ObjectCastObligation(object_ty) => {
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tcx.sess.span_note(
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cause_span,
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format!(
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"the trait `{}` must be implemented for the cast \
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to the object type `{}`",
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trait_name,
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infcx.ty_to_string(object_ty)).as_slice());
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}
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ObligationCauseCode::RepeatVec => {
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tcx.sess.span_note(
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cause_span,
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"the `Copy` trait is required because the \
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repeated element will be copied");
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}
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ObligationCauseCode::VariableType(_) => {
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tcx.sess.span_note(
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cause_span,
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"all local variables must have a statically known size");
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}
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ObligationCauseCode::ReturnType => {
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tcx.sess.span_note(
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cause_span,
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"the return type of a function must have a \
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statically known size");
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}
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ObligationCauseCode::AssignmentLhsSized => {
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tcx.sess.span_note(
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cause_span,
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"the left-hand-side of an assignment must have a statically known size");
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}
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ObligationCauseCode::StructInitializerSized => {
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tcx.sess.span_note(
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cause_span,
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"structs must have a statically known size to be initialized");
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}
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ObligationCauseCode::ClosureCapture(var_id, closure_span, builtin_bound) => {
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let def_id = tcx.lang_items.from_builtin_kind(builtin_bound).unwrap();
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let trait_name = ty::item_path_str(tcx, def_id);
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let name = ty::local_var_name_str(tcx, var_id);
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span_note!(tcx.sess, closure_span,
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"the closure that captures `{}` requires that all captured variables \
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implement the trait `{}`",
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name,
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trait_name);
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}
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ObligationCauseCode::FieldSized => {
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span_note!(tcx.sess, cause_span,
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"only the last field of a struct or enum variant \
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may have a dynamically sized type")
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}
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ObligationCauseCode::ObjectSized => {
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span_note!(tcx.sess, cause_span,
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"only sized types can be made into objects");
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}
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ObligationCauseCode::SharedStatic => {
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span_note!(tcx.sess, cause_span,
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"shared static variables must have a type that implements `Sync`");
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}
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ObligationCauseCode::BuiltinDerivedObligation(ref root_trait_ref, ref root_cause_code) => {
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let root_trait_ref =
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infcx.resolve_type_vars_if_possible(&**root_trait_ref);
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span_note!(tcx.sess, cause_span,
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"the type `{}` must implement `{}` because it appears within the type `{}`",
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trait_ref.self_ty().user_string(infcx.tcx),
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trait_ref.user_string(infcx.tcx),
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root_trait_ref.self_ty().user_string(infcx.tcx));
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note_obligation_cause_code(infcx, &root_trait_ref, cause_span, &**root_cause_code);
|
||
|
|
}
|
||
|
|
ObligationCauseCode::ImplDerivedObligation(ref root_trait_ref, ref root_cause_code) => {
|
||
|
|
let root_trait_ref =
|
||
|
|
infcx.resolve_type_vars_if_possible(&**root_trait_ref);
|
||
|
|
span_note!(tcx.sess, cause_span,
|
||
|
|
"the type `{}` must implement `{}` due to the requirements \
|
||
|
|
on the impl of `{}` for the type `{}`",
|
||
|
|
trait_ref.self_ty().user_string(infcx.tcx),
|
||
|
|
trait_ref.user_string(infcx.tcx),
|
||
|
|
root_trait_ref.user_string(infcx.tcx),
|
||
|
|
root_trait_ref.self_ty().user_string(infcx.tcx));
|
||
|
|
note_obligation_cause_code(infcx, &root_trait_ref, cause_span, &**root_cause_code);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|