Suggest associated type when the specified one cannot be found
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Ohad Ravid
parent
99b89533d4
commit
a4a2fc0af3
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@ -1145,11 +1145,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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} else {
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// Otherwise, we have to walk through the supertraits to find
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// those that do.
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let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
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self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
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});
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self.one_bound_for_assoc_type(
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candidates,
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|| traits::supertraits(tcx, trait_ref),
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&trait_ref.print_only_trait_path().to_string(),
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binding.item_name,
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binding.span
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@ -1531,50 +1528,48 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
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let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
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// Check that there is exactly one way to find an associated type with the
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// correct name.
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let suitable_bounds = traits::transitive_bounds(tcx, bounds)
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.filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
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let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
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let param_name = tcx.hir().ty_param_name(param_hir_id);
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self.one_bound_for_assoc_type(suitable_bounds,
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¶m_name.as_str(),
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assoc_name,
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span)
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self.one_bound_for_assoc_type(
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|| traits::transitive_bounds(tcx, predicates
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.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref())),
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¶m_name.as_str(),
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assoc_name,
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span,
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)
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}
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// Checks that `bounds` contains exactly one element and reports appropriate
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// errors otherwise.
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fn one_bound_for_assoc_type<I>(&self,
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mut bounds: I,
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all_candidates: impl Fn() -> I,
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ty_param_name: &str,
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assoc_name: ast::Ident,
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span: Span)
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-> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
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where I: Iterator<Item = ty::PolyTraitRef<'tcx>>
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{
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let bound = match bounds.next() {
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let mut matching_candidates = all_candidates().filter(|r| {
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self.trait_defines_associated_type_named(r.def_id(), assoc_name)
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});
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let bound = match matching_candidates.next() {
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Some(bound) => bound,
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None => {
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struct_span_err!(self.tcx().sess, span, E0220,
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"associated type `{}` not found for `{}`",
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assoc_name,
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ty_param_name)
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.span_label(span, format!("associated type `{}` not found", assoc_name))
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.emit();
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self.complain_about_assoc_type_not_found(
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all_candidates,
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ty_param_name,
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assoc_name,
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span
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);
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return Err(ErrorReported);
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}
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};
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debug!("one_bound_for_assoc_type: bound = {:?}", bound);
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if let Some(bound2) = bounds.next() {
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if let Some(bound2) = matching_candidates.next() {
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debug!("one_bound_for_assoc_type: bound2 = {:?}", bound2);
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let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
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let bounds = iter::once(bound).chain(iter::once(bound2)).chain(matching_candidates);
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let mut err = struct_span_err!(
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self.tcx().sess, span, E0221,
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"ambiguous associated type `{}` in bounds of `{}`",
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@ -1606,6 +1601,50 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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return Ok(bound);
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}
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fn complain_about_assoc_type_not_found<I>(&self,
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all_candidates: impl Fn() -> I,
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ty_param_name: &str,
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assoc_name: ast::Ident,
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span: Span)
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where I: Iterator<Item = ty::PolyTraitRef<'tcx>> {
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let mut err = struct_span_err!(self.tcx().sess, span, E0220,
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"associated type `{}` not found for `{}`",
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assoc_name,
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ty_param_name);
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let all_candidate_names: Vec<_> = all_candidates()
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.map(|r| self.tcx().associated_items(r.def_id()))
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.flatten()
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.filter_map(|item|
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if item.kind == ty::AssocKind::Type {
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Some(item.ident.name)
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} else {
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None
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}
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)
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.collect();
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if let Some(suggested_name) = find_best_match_for_name(
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all_candidate_names.iter(),
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&assoc_name.as_str(),
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None,
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) {
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err.span_suggestion(
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span,
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"there is an associated type with a similar name",
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suggested_name.to_string(),
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Applicability::MaybeIncorrect,
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);
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} else {
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err.span_label(
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span,
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format!("associated type `{}` not found", assoc_name)
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);
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}
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err.emit();
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}
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// Create a type from a path to an associated type.
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// For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
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// and item_segment is the path segment for `D`. We return a type and a def for
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@ -1660,10 +1699,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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}
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};
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let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
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.filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_ident));
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self.one_bound_for_assoc_type(candidates, "Self", assoc_ident, span)?
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self.one_bound_for_assoc_type(
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|| traits::supertraits(tcx, ty::Binder::bind(trait_ref)),
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"Self",
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assoc_ident,
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span
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)?
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}
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(&ty::Param(_), Res::SelfTy(Some(param_did), None)) |
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(&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
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@ -2,7 +2,7 @@ error[E0220]: associated type `Trget` not found for `std::ops::Deref`
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--> $DIR/type-binding.rs:6:20
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LL | fn homura<T: Deref<Trget = i32>>(_: T) {}
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| ^^^^^^^^^^^ associated type `Trget` not found
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| ^^^^^^^^^^^ help: there is an associated type with a similar name: `Target`
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error: aborting due to previous error
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