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clean the note-reporting code in report_selection_error

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This commit is contained in:
Ariel Ben-Yehuda 2016-04-05 23:19:29 +03:00
parent b23648fe4a
commit 832b7075b6
1 changed files with 62 additions and 39 deletions
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101
src/librustc/traits/error_reporting.rs
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@ -174,6 +174,53 @@ fn on_unimplemented_note<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
report
}
fn find_similar_impl_candidates<'a, 'tcx>(
infcx: &InferCtxt<'a, 'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>)
-> Vec<ty::TraitRef<'tcx>>
{
let simp = fast_reject::simplify_type(infcx.tcx,
trait_ref.skip_binder().self_ty(),
true);
let mut impl_candidates = Vec::new();
let trait_def = infcx.tcx.lookup_trait_def(trait_ref.def_id());
match simp {
Some(simp) => trait_def.for_each_impl(infcx.tcx, |def_id| {
let imp = infcx.tcx.impl_trait_ref(def_id).unwrap();
let imp_simp = fast_reject::simplify_type(infcx.tcx,
imp.self_ty(),
true);
if let Some(imp_simp) = imp_simp {
if simp != imp_simp {
return;
}
}
impl_candidates.push(imp);
}),
None => trait_def.for_each_impl(infcx.tcx, |def_id| {
impl_candidates.push(
infcx.tcx.impl_trait_ref(def_id).unwrap());
})
};
impl_candidates
}
fn report_similar_impl_candidates(span: Span,
err: &mut DiagnosticBuilder,
impl_candidates: &[ty::TraitRef])
{
err.fileline_help(span, &format!("the following implementations were found:"));
let end = cmp::min(4, impl_candidates.len());
for candidate in &impl_candidates[0..end] {
err.fileline_help(span, &format!(" {:?}", candidate));
}
if impl_candidates.len() > 4 {
err.fileline_help(span, &format!("and {} others", impl_candidates.len()-4));
}
}
/// Reports that an overflow has occurred and halts compilation. We
/// halt compilation unconditionally because it is important that
/// overflows never be masked -- they basically represent computations
@ -364,59 +411,35 @@ pub fn report_selection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
"the trait bound `{}` is not satisfied",
trait_ref.to_predicate());
// Try to report a good error message.
// Try to report a help message
if !trait_ref.has_infer_types() &&
predicate_can_apply(infcx, trait_ref)
{
// If a where-clause may be useful, remind the
// user that they can add it.
//
// don't display an on-unimplemented note, as
// these notes will often be of the form
// "the type `T` can't be frobnicated"
// which is somewhat confusing.
err.fileline_help(obligation.cause.span, &format!(
"consider adding a `where {}` bound",
trait_ref.to_predicate()
));
} else if let Some(s) = on_unimplemented_note(infcx, trait_ref,
obligation.cause.span) {
// Otherwise, if there is an on-unimplemented note,
// display it.
err.fileline_note(obligation.cause.span, &s);
} else {
let simp = fast_reject::simplify_type(infcx.tcx,
trait_ref.self_ty(),
true);
let mut impl_candidates = Vec::new();
let trait_def = infcx.tcx.lookup_trait_def(trait_ref.def_id());
match simp {
Some(simp) => trait_def.for_each_impl(infcx.tcx, |def_id| {
let imp = infcx.tcx.impl_trait_ref(def_id).unwrap();
let imp_simp = fast_reject::simplify_type(infcx.tcx,
imp.self_ty(),
true);
if let Some(imp_simp) = imp_simp {
if simp != imp_simp {
return;
}
}
impl_candidates.push(imp);
}),
None => trait_def.for_each_impl(infcx.tcx, |def_id| {
impl_candidates.push(
infcx.tcx.impl_trait_ref(def_id).unwrap());
})
};
// If we can't show anything useful, try to find
// similar impls.
let impl_candidates = find_similar_impl_candidates(infcx, trait_ref);
if impl_candidates.len() > 0 {
err.fileline_help(
obligation.cause.span,
&format!("the following implementations were found:"));
let end = cmp::min(4, impl_candidates.len());
for candidate in &impl_candidates[0..end] {
err.fileline_help(obligation.cause.span,
&format!(" {:?}", candidate));
}
if impl_candidates.len() > 4 {
err.fileline_help(obligation.cause.span,
&format!("and {} others",
impl_candidates.len()-4));
}
report_similar_impl_candidates(obligation.cause.span,
&mut err, &impl_candidates);
}
}
note_obligation_cause(infcx, &mut err, obligation);