Warn unused trait imports

13 files changed, 169 insertions, 25 deletions

diff --git a/src/librustc/dep_graph/dep_node.rs b/src/librustc/dep_graph/dep_node.rs
index 536c739bf16..8732df14371 100644
--- a/src/librustc/dep_graph/dep_node.rs
+++ b/src/librustc/dep_graph/dep_node.rs
@@ -59,6 +59,7 @@ pub enum DepNode<D: Clone + Debug> {
     TypeckItemBody(D),
     Dropck,
     DropckImpl(D),
+    UnusedTraitCheck,
     CheckConst(D),
     Privacy,
     IntrinsicCheck(D),
@@ -163,6 +164,7 @@ impl<D: Clone + Debug> DepNode<D> {
             CheckEntryFn => Some(CheckEntryFn),
             Variance => Some(Variance),
             Dropck => Some(Dropck),
+            UnusedTraitCheck => Some(UnusedTraitCheck),
             Privacy => Some(Privacy),
             Reachability => Some(Reachability),
             DeadCheck => Some(DeadCheck),
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index 7eaace91ae9..68e3e742d03 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -1639,8 +1639,13 @@ pub type FreevarMap = NodeMap<Vec<Freevar>>;
 
 pub type CaptureModeMap = NodeMap<CaptureClause>;
 
+pub struct TraitCandidate {
+    pub def_id: DefId,
+    pub import_id: Option<NodeId>,
+}
+
 // Trait method resolution
-pub type TraitMap = NodeMap<Vec<DefId>>;
+pub type TraitMap = NodeMap<Vec<TraitCandidate>>;
 
 // Map from the NodeId of a glob import to a list of items which are actually
 // imported.
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 5bde6df5123..c7ae038eb7a 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -289,6 +289,8 @@ pub struct TyCtxt<'tcx> {
     // scratch every time.
     pub freevars: RefCell<FreevarMap>,
 
+    pub maybe_unused_trait_imports: NodeSet,
+
     // Records the type of every item.
     pub tcache: RefCell<DepTrackingMap<maps::Tcache<'tcx>>>,
 
@@ -338,6 +340,10 @@ pub struct TyCtxt<'tcx> {
     /// about.
     pub used_mut_nodes: RefCell<NodeSet>,
 
+    /// Set of trait imports actually used in the method resolution.
+    /// This is used for warning unused imports.
+    pub used_trait_imports: RefCell<NodeSet>,
+
     /// The set of external nominal types whose implementations have been read.
     /// This is used for lazy resolution of methods.
     pub populated_external_types: RefCell<DefIdSet>,
@@ -543,6 +549,7 @@ impl<'tcx> TyCtxt<'tcx> {
                                  named_region_map: resolve_lifetime::NamedRegionMap,
                                  map: ast_map::Map<'tcx>,
                                  freevars: FreevarMap,
+                                 maybe_unused_trait_imports: NodeSet,
                                  region_maps: RegionMaps,
                                  lang_items: middle::lang_items::LanguageItems,
                                  stability: stability::Index<'tcx>,
@@ -581,6 +588,7 @@ impl<'tcx> TyCtxt<'tcx> {
             fulfilled_predicates: RefCell::new(fulfilled_predicates),
             map: map,
             freevars: RefCell::new(freevars),
+            maybe_unused_trait_imports: maybe_unused_trait_imports,
             tcache: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
             rcache: RefCell::new(FnvHashMap()),
             tc_cache: RefCell::new(FnvHashMap()),
@@ -595,6 +603,7 @@ impl<'tcx> TyCtxt<'tcx> {
             impl_items: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
             used_unsafe: RefCell::new(NodeSet()),
             used_mut_nodes: RefCell::new(NodeSet()),
+            used_trait_imports: RefCell::new(NodeSet()),
             populated_external_types: RefCell::new(DefIdSet()),
             populated_external_primitive_impls: RefCell::new(DefIdSet()),
             extern_const_statics: RefCell::new(DefIdMap()),
diff --git a/src/librustc_driver/driver.rs b/src/librustc_driver/driver.rs
index 2b56366f1c6..53b914936f5 100644
--- a/src/librustc_driver/driver.rs
+++ b/src/librustc_driver/driver.rs
@@ -795,6 +795,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
     let resolve::CrateMap {
         def_map,
         freevars,
+        maybe_unused_trait_imports,
         export_map,
         trait_map,
         glob_map,
@@ -844,6 +845,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
                              named_region_map,
                              hir_map,
                              freevars,
+                             maybe_unused_trait_imports,
                              region_map,
                              lang_items,
                              index,
diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index 37f7b31b69c..53c0e1f7992 100644
--- a/src/librustc_driver/test.rs
+++ b/src/librustc_driver/test.rs
@@ -132,7 +132,7 @@ fn test_env<F>(source_string: &str,
 
     // run just enough stuff to build a tcx:
     let lang_items = lang_items::collect_language_items(&sess, &ast_map);
-    let resolve::CrateMap { def_map, freevars, .. } =
+    let resolve::CrateMap { def_map, freevars, maybe_unused_trait_imports, .. } =
         resolve::resolve_crate(&sess, &ast_map, resolve::MakeGlobMap::No);
     let named_region_map = resolve_lifetime::krate(&sess, &ast_map, &def_map.borrow());
     let region_map = region::resolve_crate(&sess, &ast_map);
@@ -143,6 +143,7 @@ fn test_env<F>(source_string: &str,
                                named_region_map.unwrap(),
                                ast_map,
                                freevars,
+                               maybe_unused_trait_imports,
                                region_map,
                                lang_items,
                                index,
diff --git a/src/librustc_resolve/check_unused.rs b/src/librustc_resolve/check_unused.rs
index 9135b656736..e213a51fb38 100644
--- a/src/librustc_resolve/check_unused.rs
+++ b/src/librustc_resolve/check_unused.rs
@@ -16,6 +16,8 @@
 // resolve data structures and because it finalises the privacy information for
 // `use` directives.
 //
+// Unused trait imports can't be checked until the method resolution. We save
+// candidates here, and do the acutal check in librustc_typeck/check_unused.rs.
 
 use std::ops::{Deref, DerefMut};
 
@@ -55,10 +57,18 @@ impl<'a, 'b, 'tcx> UnusedImportCheckVisitor<'a, 'b, 'tcx> {
     fn check_import(&mut self, id: ast::NodeId, span: Span) {
         if !self.used_imports.contains(&(id, TypeNS)) &&
            !self.used_imports.contains(&(id, ValueNS)) {
+            if self.maybe_unused_trait_imports.contains(&id) {
+                // Check later.
+                return;
+            }
             self.session.add_lint(lint::builtin::UNUSED_IMPORTS,
                                   id,
                                   span,
                                   "unused import".to_string());
+        } else {
+            // This trait import is definitely used, in a way other than
+            // method resolution.
+            self.maybe_unused_trait_imports.remove(&id);
         }
     }
 }
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 9ef927b6610..2e2b40fec4b 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -52,8 +52,8 @@ use rustc::hir::def_id::DefId;
 use rustc::hir::pat_util::pat_bindings;
 use rustc::ty;
 use rustc::ty::subst::{ParamSpace, FnSpace, TypeSpace};
-use rustc::hir::{Freevar, FreevarMap, TraitMap, GlobMap};
-use rustc::util::nodemap::{NodeMap, FnvHashMap, FnvHashSet};
+use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
+use rustc::util::nodemap::{NodeMap, NodeSet, FnvHashMap, FnvHashSet};
 
 use syntax::ast::{self, FloatTy};
 use syntax::ast::{CRATE_NODE_ID, Name, NodeId, CrateNum, IntTy, UintTy};
@@ -1042,6 +1042,7 @@ pub struct Resolver<'a, 'tcx: 'a> {
 
     used_imports: HashSet<(NodeId, Namespace)>,
     used_crates: HashSet<CrateNum>,
+    maybe_unused_trait_imports: NodeSet,
 
     privacy_errors: Vec<PrivacyError<'a>>,
 
@@ -1137,13 +1138,15 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             export_map: NodeMap(),
             trait_map: NodeMap(),
             module_map: module_map,
-            used_imports: HashSet::new(),
-            used_crates: HashSet::new(),
 
             emit_errors: true,
             make_glob_map: make_glob_map == MakeGlobMap::Yes,
             glob_map: NodeMap(),
 
+            used_imports: HashSet::new(),
+            used_crates: HashSet::new(),
+            maybe_unused_trait_imports: NodeSet(),
+
             privacy_errors: Vec::new(),
 
             arenas: arenas,
@@ -1177,7 +1180,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
     }
 
     #[inline]
-    fn record_use(&mut self, name: Name, ns: Namespace, binding: &'a NameBinding<'a>) {
+    fn record_use(&mut self, name: Name, binding: &'a NameBinding<'a>) {
         // track extern crates for unused_extern_crate lint
         if let Some(DefId { krate, .. }) = binding.module().and_then(ModuleS::def_id) {
             self.used_crates.insert(krate);
@@ -1189,7 +1192,6 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             _ => return,
         };
 
-        self.used_imports.insert((directive.id, ns));
         if let Some(error) = privacy_error.as_ref() {
             self.privacy_errors.push((**error).clone());
         }
@@ -1492,7 +1494,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             false => module.resolve_name(name, namespace, false),
         }.and_then(|binding| {
             if record_used {
-                self.record_use(name, namespace, binding);
+                if let NameBindingKind::Import { directive, .. } = binding.kind {
+                    self.used_imports.insert((directive.id, namespace));
+                }
+                self.record_use(name, binding);
             }
             Success(binding)
         })
@@ -3094,21 +3099,27 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
     }
 
-    fn get_traits_containing_item(&mut self, name: Name) -> Vec<DefId> {
+    fn get_traits_containing_item(&mut self, name: Name) -> Vec<TraitCandidate> {
         debug!("(getting traits containing item) looking for '{}'", name);
 
-        fn add_trait_info(found_traits: &mut Vec<DefId>, trait_def_id: DefId, name: Name) {
+        fn add_trait_info(found_traits: &mut Vec<TraitCandidate>,
+                          trait_def_id: DefId,
+                          import_id: Option<NodeId>,
+                          name: Name) {
             debug!("(adding trait info) found trait {:?} for method '{}'",
                    trait_def_id,
                    name);
-            found_traits.push(trait_def_id);
+            found_traits.push(TraitCandidate {
+                def_id: trait_def_id,
+                import_id: import_id,
+            });
         }
 
         let mut found_traits = Vec::new();
         // Look for the current trait.
         if let Some((trait_def_id, _)) = self.current_trait_ref {
             if self.trait_item_map.contains_key(&(name, trait_def_id)) {
-                add_trait_info(&mut found_traits, trait_def_id, name);
+                add_trait_info(&mut found_traits, trait_def_id, None, name);
             }
         }
 
@@ -3131,8 +3142,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
                     let trait_def_id = binding.def().unwrap().def_id();
                     if self.trait_item_map.contains_key(&(name, trait_def_id)) {
-                        add_trait_info(&mut found_traits, trait_def_id, name);
-                        self.record_use(trait_name, TypeNS, binding);
+                        let mut import_id = None;
+                        if let NameBindingKind::Import { directive, .. } = binding.kind {
+                            let id = directive.id;
+                            self.maybe_unused_trait_imports.insert(id);
+                            import_id = Some(id);
+                        }
+                        add_trait_info(&mut found_traits, trait_def_id, import_id, name);
+                        self.record_use(trait_name, binding);
                     }
                 }
             };
@@ -3506,6 +3523,7 @@ fn err_path_resolution() -> PathResolution {
 pub struct CrateMap {
     pub def_map: RefCell<DefMap>,
     pub freevars: FreevarMap,
+    pub maybe_unused_trait_imports: NodeSet,
     pub export_map: ExportMap,
     pub trait_map: TraitMap,
     pub glob_map: Option<GlobMap>,
@@ -3543,6 +3561,7 @@ pub fn resolve_crate<'a, 'tcx>(session: &'a Session,
     CrateMap {
         def_map: resolver.def_map,
         freevars: resolver.freevars,
+        maybe_unused_trait_imports: resolver.maybe_unused_trait_imports,
         export_map: resolver.export_map,
         trait_map: resolver.trait_map,
         glob_map: if resolver.make_glob_map {
diff --git a/src/librustc_typeck/check/method/mod.rs b/src/librustc_typeck/check/method/mod.rs
index 367cac68509..26d1f50f8c5 100644
--- a/src/librustc_typeck/check/method/mod.rs
+++ b/src/librustc_typeck/check/method/mod.rs
@@ -128,6 +128,11 @@ pub fn lookup<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
     let mode = probe::Mode::MethodCall;
     let self_ty = fcx.infcx().resolve_type_vars_if_possible(&self_ty);
     let pick = probe::probe(fcx, span, mode, method_name, self_ty, call_expr.id)?;
+
+    if let Some(import_id) = pick.import_id {
+        fcx.tcx().used_trait_imports.borrow_mut().insert(import_id);
+    }
+
     Ok(confirm::confirm(fcx, span, self_expr, call_expr, self_ty, pick, supplied_method_types))
 }
 
@@ -339,8 +344,12 @@ pub fn resolve_ufcs<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
 {
     let mode = probe::Mode::Path;
     let pick = probe::probe(fcx, span, mode, method_name, self_ty, expr_id)?;
-    let def = pick.item.def();
 
+    if let Some(import_id) = pick.import_id {
+        fcx.tcx().used_trait_imports.borrow_mut().insert(import_id);
+    }
+
+    let def = pick.item.def();
     if let probe::InherentImplPick = pick.kind {
         if !pick.item.vis().is_accessible_from(fcx.body_id, &fcx.tcx().map) {
             let msg = format!("{} `{}` is private", def.kind_name(), &method_name.as_str());
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index 2defbf0d33e..4716bab71bf 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -42,6 +42,7 @@ struct ProbeContext<'a, 'tcx:'a> {
     inherent_candidates: Vec<Candidate<'tcx>>,
     extension_candidates: Vec<Candidate<'tcx>>,
     impl_dups: HashSet<DefId>,
+    import_id: Option<ast::NodeId>,
 
     /// Collects near misses when the candidate functions are missing a `self` keyword and is only
     /// used for error reporting
@@ -67,6 +68,7 @@ struct Candidate<'tcx> {
     xform_self_ty: Ty<'tcx>,
     item: ty::ImplOrTraitItem<'tcx>,
     kind: CandidateKind<'tcx>,
+    import_id: Option<ast::NodeId>,
 }
 
 #[derive(Debug)]
@@ -84,6 +86,7 @@ enum CandidateKind<'tcx> {
 pub struct Pick<'tcx> {
     pub item: ty::ImplOrTraitItem<'tcx>,
     pub kind: PickKind<'tcx>,
+    pub import_id: Option<ast::NodeId>,
 
     // Indicates that the source expression should be autoderef'd N times
     //
@@ -247,6 +250,7 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
             inherent_candidates: Vec::new(),
             extension_candidates: Vec::new(),
             impl_dups: HashSet::new(),
+            import_id: None,
             steps: Rc::new(steps),
             opt_simplified_steps: opt_simplified_steps,
             static_candidates: Vec::new(),
@@ -435,7 +439,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
         self.inherent_candidates.push(Candidate {
             xform_self_ty: xform_self_ty,
             item: item,
-            kind: InherentImplCandidate(impl_substs, obligations)
+            kind: InherentImplCandidate(impl_substs, obligations),
+            import_id: self.import_id,
         });
     }
 
@@ -463,7 +468,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
             this.inherent_candidates.push(Candidate {
                 xform_self_ty: xform_self_ty,
                 item: item,
-                kind: ObjectCandidate
+                kind: ObjectCandidate,
+                import_id: this.import_id,
             });
         });
     }
@@ -533,7 +539,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
             this.inherent_candidates.push(Candidate {
                 xform_self_ty: xform_self_ty,
                 item: item,
-                kind: WhereClauseCandidate(poly_trait_ref)
+                kind: WhereClauseCandidate(poly_trait_ref),
+                import_id: this.import_id,
             });
         });
     }
@@ -577,9 +584,13 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
         let mut duplicates = HashSet::new();
         let opt_applicable_traits = self.fcx.ccx.trait_map.get(&expr_id);
         if let Some(applicable_traits) = opt_applicable_traits {
-            for &trait_did in applicable_traits {
+            for trait_candidate in applicable_traits {
+                let trait_did = trait_candidate.def_id;
                 if duplicates.insert(trait_did) {
-                    self.assemble_extension_candidates_for_trait(trait_did)?;
+                    self.import_id = trait_candidate.import_id;
+                    let result = self.assemble_extension_candidates_for_trait(trait_did);
+                    self.import_id = None;
+                    result?;
                 }
             }
         }
@@ -679,7 +690,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
             self.extension_candidates.push(Candidate {
                 xform_self_ty: xform_self_ty,
                 item: item.clone(),
-                kind: ExtensionImplCandidate(impl_def_id, impl_substs, obligations)
+                kind: ExtensionImplCandidate(impl_def_id, impl_substs, obligations),
+                import_id: self.import_id,
             });
         });
     }
@@ -754,7 +766,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
             self.inherent_candidates.push(Candidate {
                 xform_self_ty: xform_self_ty,
                 item: item.clone(),
-                kind: TraitCandidate
+                kind: TraitCandidate,
+                import_id: self.import_id,
             });
         }
 
@@ -811,7 +824,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
                     self.extension_candidates.push(Candidate {
                         xform_self_ty: xform_self_ty,
                         item: item.clone(),
-                        kind: TraitCandidate
+                        kind: TraitCandidate,
+                        import_id: self.import_id,
                     });
                 }
             }
@@ -842,7 +856,8 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
             self.extension_candidates.push(Candidate {
                 xform_self_ty: xform_self_ty,
                 item: item.clone(),
-                kind: WhereClauseCandidate(poly_bound)
+                kind: WhereClauseCandidate(poly_bound),
+                import_id: self.import_id,
             });
         }
     }
@@ -1140,6 +1155,7 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
         Some(Pick {
             item: probes[0].item.clone(),
             kind: TraitPick,
+            import_id: probes[0].import_id,
             autoderefs: 0,
             autoref: None,
             unsize: None
@@ -1345,6 +1361,7 @@ impl<'tcx> Candidate<'tcx> {
                     WhereClausePick(trait_ref.clone())
                 }
             },
+            import_id: self.import_id,
             autoderefs: 0,
             autoref: None,
             unsize: None
diff --git a/src/librustc_typeck/check_unused.rs b/src/librustc_typeck/check_unused.rs
new file mode 100644
index 00000000000..3c594ebdf0b
--- /dev/null
+++ b/src/librustc_typeck/check_unused.rs
@@ -0,0 +1,64 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use lint;
+use rustc::dep_graph::DepNode;
+use rustc::ty::TyCtxt;
+
+use syntax::ast;
+use syntax::codemap::{Span, DUMMY_SP};
+
+use rustc::hir;
+use rustc::hir::intravisit::Visitor;
+
+struct UnusedTraitImportVisitor<'a, 'tcx: 'a> {
+    tcx: &'a TyCtxt<'tcx>,
+}
+
+impl<'a, 'tcx> UnusedTraitImportVisitor<'a, 'tcx> {
+    fn check_import(&self, id: ast::NodeId, span: Span) {
+        if !self.tcx.maybe_unused_trait_imports.contains(&id) {
+            return;
+        }
+        if self.tcx.used_trait_imports.borrow().contains(&id) {
+            return;
+        }
+        self.tcx.sess.add_lint(lint::builtin::UNUSED_IMPORTS,
+                               id,
+                               span,
+                               "unused import".to_string());
+    }
+}
+
+impl<'a, 'tcx, 'v> Visitor<'v> for UnusedTraitImportVisitor<'a, 'tcx> {
+    fn visit_item(&mut self, item: &hir::Item) {
+        if item.vis == hir::Public || item.span == DUMMY_SP {
+            return;
+        }
+        if let hir::ItemUse(ref path) = item.node {
+            match path.node {
+                hir::ViewPathSimple(..) | hir::ViewPathGlob(..) => {
+                    self.check_import(item.id, path.span);
+                }
+                hir::ViewPathList(_, ref path_list) => {
+                    for path_item in path_list {
+                        self.check_import(path_item.node.id(), path_item.span);
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub fn check_crate(tcx: &TyCtxt) {
+    let _task = tcx.dep_graph.in_task(DepNode::UnusedTraitCheck);
+    let mut visitor = UnusedTraitImportVisitor { tcx: tcx };
+    tcx.map.krate().visit_all_items(&mut visitor);
+}
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index c51304120a8..ed393b54f0e 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -122,6 +122,7 @@ use std::cell::RefCell;
 pub mod diagnostics;
 
 pub mod check;
+pub mod check_unused;
 mod rscope;
 mod astconv;
 pub mod collect;
@@ -363,6 +364,7 @@ pub fn check_crate(tcx: &TyCtxt, trait_map: hir::TraitMap) -> CompileResult {
 
     time(time_passes, "drop-impl checking", || check::check_drop_impls(&ccx))?;
 
+    check_unused::check_crate(tcx);
     check_for_entry_fn(&ccx);
 
     let err_count = tcx.sess.err_count();
diff --git a/src/test/compile-fail/dep-graph-trait-impl-two-traits-same-method.rs b/src/test/compile-fail/dep-graph-trait-impl-two-traits-same-method.rs
index 1afecd80ff5..5e4f43af669 100644
--- a/src/test/compile-fail/dep-graph-trait-impl-two-traits-same-method.rs
+++ b/src/test/compile-fail/dep-graph-trait-impl-two-traits-same-method.rs
@@ -15,6 +15,7 @@
 
 #![feature(rustc_attrs)]
 #![allow(dead_code)]
+#![allow(unused_imports)]
 
 fn main() { }
 
diff --git a/src/test/compile-fail/lint-unused-imports.rs b/src/test/compile-fail/lint-unused-imports.rs
index 3c1f4b04306..40322f5a5b5 100644
--- a/src/test/compile-fail/lint-unused-imports.rs
+++ b/src/test/compile-fail/lint-unused-imports.rs
@@ -24,6 +24,8 @@ use test::A;       //~ ERROR unused import
 // Be sure that if we just bring some methods into scope that they're also
 // counted as being used.
 use test::B;
+// But only when actually used: do not get confused by the method with the same name.
+use test::B2; //~ ERROR unused import
 
 // Make sure this import is warned about when at least one of its imported names
 // is unused
@@ -37,6 +39,7 @@ mod test2 {
 mod test {
     pub trait A { fn a(&self) {} }
     pub trait B { fn b(&self) {} }
+    pub trait B2 { fn b(&self) {} }
     pub struct C;
     impl A for C {}
     impl B for C {}