diff --git a/src/librustc/middle/traits/error_reporting.rs b/src/librustc/middle/traits/error_reporting.rs index ef8982219563b..f4235f3df21c6 100644 --- a/src/librustc/middle/traits/error_reporting.rs +++ b/src/librustc/middle/traits/error_reporting.rs @@ -27,6 +27,7 @@ use fmt_macros::{Parser, Piece, Position}; use middle::def_id::DefId; use middle::infer::InferCtxt; use middle::ty::{self, ToPredicate, HasTypeFlags, ToPolyTraitRef, TraitRef, Ty}; +use middle::ty::fast_reject; use middle::ty::fold::TypeFoldable; use util::nodemap::{FnvHashMap, FnvHashSet}; @@ -233,20 +234,38 @@ pub fn report_selection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>, if let Some(s) = custom_note { err.fileline_note(obligation.cause.span, &s); } else { - let mut impl_candidates = Vec::new(); - infcx.tcx.lookup_trait_def(trait_ref.def_id()) - .for_each_relevant_impl( - infcx.tcx, - trait_ref.self_ty(), - |impl_def_id| { - match infcx.tcx.impl_trait_ref(impl_def_id) { - Some(ref imp) => { - impl_candidates.push(format!(" {}", imp)); - }, - None => (), + infcx.tcx.populate_implementations_for_trait_if_necessary( + trait_ref.def_id()); + + let trait_def = infcx.tcx.lookup_trait_def(trait_ref.def_id()); + let blanket_impls = trait_def.blanket_impls.borrow(); + let impl_iter = blanket_impls.iter() + .filter_map(|&id| + infcx.tcx.impl_trait_ref(id)); + + let nonblanket = trait_def.nonblanket_impls.borrow(); + let nonblanket_iter = nonblanket.values() + .flat_map(|ids| + ids.iter().filter_map(|&id| + infcx.tcx.impl_trait_ref(id))); + + let simp = fast_reject::simplify_type(infcx.tcx, trait_ref.self_ty(), true); + let nonblanket_iter = nonblanket_iter.filter(|def| { + if let Some(simp) = simp { + let imp_simp = fast_reject::simplify_type(infcx.tcx, def.self_ty(), true); + if let Some(imp_simp) = imp_simp { + simp == imp_simp + } else { + false } + } else { + true } - ); + }); + + let impl_candidates = impl_iter.chain(nonblanket_iter) + .map(|imp| format!(" {}", imp)) + .take(5).collect::>(); if impl_candidates.len() > 0 { err.fileline_help(