Auto merge of #35894 - jseyfried:new_import_semantics, r=nrc

Implement RFC 1560 behind `#![feature(item_like_imports)]`

This implements https://github.com/rust-lang/rfcs/pull/1560 (cc #35120) behind the `item_like_imports` feature gate.

The [RFC text](https://github.com/rust-lang/rfcs/blob/master/text/1560-name-resolution.md#changes-to-name-resolution-rules) describes the changes to name resolution enabled by `#![feature(item_like_imports)` in detail. To summarize,
 - Items and named imports shadow glob imports.
 - Multiple globs can import the same name if the name is unused or the imports are shadowed.
 - Multiple globs can import the same name if the imports are of the same item (following re-exports).
  - The visibility of such a name is the maximum visibility of the imports.
  - Equivalently, adding a glob import will never reduce the visibility of a name, nor will removing one increase it.
 - Non-prelude private imports can be used wherever we currently allow private items to be used.
  - Prelude-imported names are unaffected, i.e. they continue to be usable only in lexical scopes.
 - Globs import all visible names, not just public names.
  - Equivalently, glob importing from an ancestor module imports all of the ancestor's names, and glob importing from other modules is unchanged.

r? @nrc

src/librustc_resolve/build_reduced_graph.rs

@@ -26,6 +26,8 @@
 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
 use rustc::ty::{self, VariantKind};
 
+use std::cell::Cell;
+
 use syntax::ast::Name;
 use syntax::attr;
 use syntax::parse::token;
@@ -81,7 +83,6 @@ fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
     /// Constructs the reduced graph for one item.
     fn build_reduced_graph_for_item(&mut self, item: &Item) {
         let parent = self.current_module;
-        let parent_vis = self.current_vis;
         let name = item.ident.name;
         let sp = item.span;
         let vis = self.resolve_visibility(&item.vis);
@@ -177,7 +178,10 @@ fn build_reduced_graph_for_item(&mut self, item: &Item) {
                         }
                     }
                     ViewPathGlob(_) => {
-                        let subclass = GlobImport { is_prelude: is_prelude };
+                        let subclass = GlobImport {
+                            is_prelude: is_prelude,
+                            max_vis: Cell::new(ty::Visibility::PrivateExternal),
+                        };
                         let span = view_path.span;
                         self.add_import_directive(module_path, subclass, span, item.id, vis);
                     }
@@ -204,7 +208,7 @@ fn build_reduced_graph_for_item(&mut self, item: &Item) {
             ItemKind::Mod(..) => {
                 let parent_link = ModuleParentLink(parent, name);
                 let def = Def::Mod(self.definitions.local_def_id(item.id));
-                let module = self.new_module(parent_link, Some(def), false);
+                let module = self.new_module(parent_link, Some(def), Some(item.id));
                 module.no_implicit_prelude.set({
                     parent.no_implicit_prelude.get() ||
                         attr::contains_name(&item.attrs, "no_implicit_prelude")
@@ -214,7 +218,6 @@ fn build_reduced_graph_for_item(&mut self, item: &Item) {
 
                 // Descend into the module.
                 self.current_module = module;
-                self.current_vis = ty::Visibility::Restricted(item.id);
             }
 
             ItemKind::ForeignMod(..) => {}
@@ -243,7 +246,7 @@ fn build_reduced_graph_for_item(&mut self, item: &Item) {
             ItemKind::Enum(ref enum_definition, _) => {
                 let parent_link = ModuleParentLink(parent, name);
                 let def = Def::Enum(self.definitions.local_def_id(item.id));
-                let module = self.new_module(parent_link, Some(def), false);
+                let module = self.new_module(parent_link, Some(def), parent.normal_ancestor_id);
                 self.define(parent, name, TypeNS, (module, sp, vis));
 
                 for variant in &(*enum_definition).variants {
@@ -285,7 +288,8 @@ fn build_reduced_graph_for_item(&mut self, item: &Item) {
                 // Add all the items within to a new module.
                 let parent_link = ModuleParentLink(parent, name);
                 let def = Def::Trait(def_id);
-                let module_parent = self.new_module(parent_link, Some(def), false);
+                let module_parent =
+                    self.new_module(parent_link, Some(def), parent.normal_ancestor_id);
                 self.define(parent, name, TypeNS, (module_parent, sp, vis));
 
                 // Add the names of all the items to the trait info.
@@ -312,7 +316,6 @@ fn build_reduced_graph_for_item(&mut self, item: &Item) {
 
         visit::walk_item(&mut BuildReducedGraphVisitor { resolver: self }, item);
         self.current_module = parent;
-        self.current_vis = parent_vis;
     }
 
     // Constructs the reduced graph for one variant. Variants exist in the
@@ -363,7 +366,7 @@ fn build_reduced_graph_for_block(&mut self, block: &Block) {
                    block_id);
 
             let parent_link = BlockParentLink(parent, block_id);
-            let new_module = self.new_module(parent_link, None, false);
+            let new_module = self.new_module(parent_link, None, parent.normal_ancestor_id);
             self.module_map.insert(block_id, new_module);
             self.current_module = new_module; // Descend into the block.
         }
@@ -395,7 +398,7 @@ fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'b>, xcd
                 debug!("(building reduced graph for external crate) building module {} {:?}",
                        name, vis);
                 let parent_link = ModuleParentLink(parent, name);
-                let module = self.new_module(parent_link, Some(def), true);
+                let module = self.new_module(parent_link, Some(def), None);
                 let _ = self.try_define(parent, name, TypeNS, (module, DUMMY_SP, vis));
             }
             Def::Variant(_, variant_id) => {
@@ -437,7 +440,7 @@ fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'b>, xcd
                 }
 
                 let parent_link = ModuleParentLink(parent, name);
-                let module = self.new_module(parent_link, Some(def), true);
+                let module = self.new_module(parent_link, Some(def), None);
                 let _ = self.try_define(parent, name, TypeNS, (module, DUMMY_SP, vis));
             }
             Def::TyAlias(..) | Def::AssociatedTy(..) => {

src/librustc_resolve/resolve_imports.rs

@@ -27,7 +27,7 @@
 
 use syntax::ast::{NodeId, Name};
 use syntax::util::lev_distance::find_best_match_for_name;
-use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::Span;
 
 use std::cell::{Cell, RefCell};
 
@@ -52,7 +52,11 @@ pub enum ImportDirectiveSubclass<'a> {
         value_result: Cell<Result<&'a NameBinding<'a>, Determinacy>>,
         type_result: Cell<Result<&'a NameBinding<'a>, Determinacy>>,
     },
-    GlobImport { is_prelude: bool },
+    GlobImport {
+        is_prelude: bool,
+        max_vis: Cell<ty::Visibility>, // The visibility of the greatest reexport.
+        // n.b. `max_vis` is only used in `finalize_import` to check for reexport errors.
+    },
 }
 
 impl<'a> ImportDirectiveSubclass<'a> {
@@ -167,8 +171,10 @@ pub fn resolve_name_in_module(&mut self,
             _ => return Failed(None), // This happens when there is a cycle of imports
         };
 
+        let new_import_semantics = self.new_import_semantics;
         let is_disallowed_private_import = |binding: &NameBinding| {
-            !allow_private_imports && !binding.is_pseudo_public() && binding.is_import()
+            !new_import_semantics && !allow_private_imports && // disallowed
+            binding.vis != ty::Visibility::Public && binding.is_import() // non-`pub` import
         };
 
         if let Some(span) = record_used {
@@ -176,7 +182,9 @@ pub fn resolve_name_in_module(&mut self,
                 if is_disallowed_private_import(binding) {
                     return Failed(None);
                 }
-                self.record_use(name, ns, binding);
+                if self.record_use(name, ns, binding, span) {
+                    return Success(self.dummy_binding);
+                }
                 if !self.is_accessible(binding.vis) {
                     self.privacy_errors.push(PrivacyError(span, name, binding));
                 }
@@ -274,7 +282,7 @@ pub fn add_import_directive(&mut self,
             }
             // We don't add prelude imports to the globs since they only affect lexical scopes,
             // which are not relevant to import resolution.
-            GlobImport { is_prelude: true } => {}
+            GlobImport { is_prelude: true, .. } => {}
             GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
         }
     }
@@ -283,13 +291,26 @@ pub fn add_import_directive(&mut self,
     // return the corresponding binding defined by the import directive.
     fn import(&mut self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
               -> NameBinding<'a> {
+        let vis = if binding.pseudo_vis().is_at_least(directive.vis.get(), self) ||
+                     !directive.is_glob() && binding.is_extern_crate() { // c.f. `PRIVATE_IN_PUBLIC`
+            directive.vis.get()
+        } else {
+            binding.pseudo_vis()
+        };
+
+        if let GlobImport { ref max_vis, .. } = directive.subclass {
+            if vis == directive.vis.get() || vis.is_at_least(max_vis.get(), self) {
+                max_vis.set(vis)
+            }
+        }
+
         NameBinding {
             kind: NameBindingKind::Import {
                 binding: binding,
                 directive: directive,
             },
             span: directive.span,
-            vis: directive.vis.get(),
+            vis: vis,
         }
     }
 
@@ -299,10 +320,28 @@ pub fn try_define<T>(&mut self, module: Module<'a>, name: Name, ns: Namespace, b
         where T: ToNameBinding<'a>
     {
         let binding = self.arenas.alloc_name_binding(binding.to_name_binding());
-        self.update_resolution(module, name, ns, |_, resolution| {
+        self.update_resolution(module, name, ns, |this, resolution| {
             if let Some(old_binding) = resolution.binding {
                 if binding.is_glob_import() {
-                    resolution.duplicate_globs.push(binding);
+                    if !this.new_import_semantics || !old_binding.is_glob_import() {
+                        resolution.duplicate_globs.push(binding);
+                    } else if binding.def() != old_binding.def() {
+                        resolution.binding = Some(this.arenas.alloc_name_binding(NameBinding {
+                            kind: NameBindingKind::Ambiguity {
+                                b1: old_binding,
+                                b2: binding,
+                            },
+                            vis: if old_binding.vis.is_at_least(binding.vis, this) {
+                                old_binding.vis
+                            } else {
+                                binding.vis
+                            },
+                            span: old_binding.span,
+                        }));
+                    } else if !old_binding.vis.is_at_least(binding.vis, this) {
+                        // We are glob-importing the same item but with greater visibility.
+                        resolution.binding = Some(binding);
+                    }
                 } else if old_binding.is_glob_import() {
                     resolution.duplicate_globs.push(old_binding);
                     resolution.binding = Some(binding);
@@ -324,23 +363,29 @@ fn update_resolution<T, F>(&mut self, module: Module<'a>, name: Name, ns: Namesp
     {
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
         // during which the resolution might end up getting re-defined via a glob cycle.
-        let (new_binding, t) = {
+        let (binding, t) = {
             let mut resolution = &mut *self.resolution(module, name, ns).borrow_mut();
-            let was_known = resolution.binding().is_some();
+            let old_binding = resolution.binding();
 
             let t = f(self, resolution);
 
-            if was_known { return t; }
             match resolution.binding() {
-                Some(binding) => (binding, t),
+                _ if !self.new_import_semantics && old_binding.is_some() => return t,
                 None => return t,
+                Some(binding) => match old_binding {
+                    Some(old_binding) if old_binding as *const _ == binding as *const _ => return t,
+                    _ => (binding, t),
+                }
             }
         };
 
-        // Define `new_binding` in `module`s glob importers.
-        if new_binding.is_importable() && new_binding.is_pseudo_public() {
-            for directive in module.glob_importers.borrow_mut().iter() {
-                let imported_binding = self.import(new_binding, directive);
+        // Define `binding` in `module`s glob importers.
+        for directive in module.glob_importers.borrow_mut().iter() {
+            if match self.new_import_semantics {
+                true => self.is_accessible_from(binding.vis, directive.parent),
+                false => binding.vis == ty::Visibility::Public,
+            } {
+                let imported_binding = self.import(binding, directive);
                 let _ = self.try_define(directive.parent, name, ns, imported_binding);
             }
         }
@@ -381,14 +426,6 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
     // remain or unsuccessfully when no forward progress in resolving imports
     // is made.
 
-    fn set_current_module(&mut self, module: Module<'b>) {
-        self.current_module = module;
-        self.current_vis = ty::Visibility::Restricted({
-            let normal_module = self.get_nearest_normal_module_parent_or_self(module);
-            self.definitions.as_local_node_id(normal_module.def_id().unwrap()).unwrap()
-        });
-    }
-
     /// Resolves all imports for the crate. This method performs the fixed-
     /// point iteration.
     fn resolve_imports(&mut self) {
@@ -424,7 +461,7 @@ fn resolve_imports(&mut self) {
                 errors = true;
                 let (span, help) = match err {
                     Some((span, msg)) => (span, msg),
-                    None => (import.span, String::new()),
+                    None => continue,
                 };
 
                 // If the error is a single failed import then create a "fake" import
@@ -450,13 +487,8 @@ fn resolve_imports(&mut self) {
     // failed resolution
     fn import_dummy_binding(&mut self, directive: &'b ImportDirective<'b>) {
         if let SingleImport { target, .. } = directive.subclass {
-            let dummy_binding = self.arenas.alloc_name_binding(NameBinding {
-                kind: NameBindingKind::Def(Def::Err),
-                span: DUMMY_SP,
-                vis: ty::Visibility::Public,
-            });
+            let dummy_binding = self.dummy_binding;
             let dummy_binding = self.import(dummy_binding, directive);
-
             let _ = self.try_define(directive.parent, target, ValueNS, dummy_binding.clone());
             let _ = self.try_define(directive.parent, target, TypeNS, dummy_binding);
         }
@@ -472,7 +504,7 @@ fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResul
                names_to_string(&directive.module_path),
                module_to_string(self.current_module));
 
-        self.set_current_module(directive.parent);
+        self.current_module = directive.parent;
 
         let module = if let Some(module) = directive.imported_module.get() {
             module
@@ -548,7 +580,7 @@ fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResul
     }
 
     fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
-        self.set_current_module(directive.parent);
+        self.current_module = directive.parent;
 
         let ImportDirective { ref module_path, span, .. } = *directive;
         let module_result = self.resolve_module_path(&module_path, DontUseLexicalScope, Some(span));
@@ -566,12 +598,23 @@ fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResu
                 let msg = "Cannot glob-import a module into itself.".into();
                 return Failed(Some((directive.span, msg)));
             }
-            GlobImport { .. } => return Success(()),
+            GlobImport { is_prelude, ref max_vis } => {
+                if !is_prelude &&
+                   max_vis.get() != ty::Visibility::PrivateExternal && // Allow empty globs.
+                   !max_vis.get().is_at_least(directive.vis.get(), self) {
+                    let msg = "A non-empty glob must import something with the glob's visibility";
+                    self.session.span_err(directive.span, msg);
+                }
+                return Success(());
+            }
         };
 
         for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
             if let Ok(binding) = result {
-                self.record_use(name, ns, binding);
+                if self.record_use(name, ns, binding, directive.span) {
+                    self.resolution(module, name, ns).borrow_mut().binding =
+                        Some(self.dummy_binding);
+                }
             }
         }
 
@@ -608,22 +651,44 @@ fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResu
             }
         }
 
+        let session = self.session;
+        let reexport_error = || {
+            let msg = format!("`{}` is private, and cannot be reexported", name);
+            let note_msg =
+                format!("consider marking `{}` as `pub` in the imported module", name);
+            struct_span_err!(session, directive.span, E0364, "{}", &msg)
+                .span_note(directive.span, &note_msg)
+                .emit();
+        };
+
+        let extern_crate_lint = || {
+            let msg = format!("extern crate `{}` is private, and cannot be reexported \
+                               (error E0364), consider declaring with `pub`",
+                               name);
+            session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
+        };
+
         match (value_result, type_result) {
+            // With `#![feature(item_like_imports)]`, all namespaces
+            // must be re-exported with extra visibility for an error to occur.
+            (Ok(value_binding), Ok(type_binding)) if self.new_import_semantics => {
+                let vis = directive.vis.get();
+                if !value_binding.pseudo_vis().is_at_least(vis, self) &&
+                   !type_binding.pseudo_vis().is_at_least(vis, self) {
+                    reexport_error();
+                } else if type_binding.is_extern_crate() &&
+                          !type_binding.vis.is_at_least(vis, self) {
+                    extern_crate_lint();
+                }
+            }
+
             (Ok(binding), _) if !binding.pseudo_vis().is_at_least(directive.vis.get(), self) => {
-                let msg = format!("`{}` is private, and cannot be reexported", name);
-                let note_msg =
-                    format!("consider marking `{}` as `pub` in the imported module", name);
-                struct_span_err!(self.session, directive.span, E0364, "{}", &msg)
-                    .span_note(directive.span, &note_msg)
-                    .emit();
+                reexport_error();
             }
 
             (_, Ok(binding)) if !binding.pseudo_vis().is_at_least(directive.vis.get(), self) => {
                 if binding.is_extern_crate() {
-                    let msg = format!("extern crate `{}` is private, and cannot be reexported \
-                                       (error E0364), consider declaring with `pub`",
-                                       name);
-                    self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
+                    extern_crate_lint();
                 } else {
                     struct_span_err!(self.session, directive.span, E0365,
                                      "`{}` is private, and cannot be reexported", name)
@@ -639,9 +704,9 @@ fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResu
         // Record what this import resolves to for later uses in documentation,
         // this may resolve to either a value or a type, but for documentation
         // purposes it's good enough to just favor one over the other.
-        let def = match type_result.ok().and_then(NameBinding::def) {
+        let def = match type_result.ok().map(NameBinding::def) {
             Some(def) => def,
-            None => value_result.ok().and_then(NameBinding::def).unwrap(),
+            None => value_result.ok().map(NameBinding::def).unwrap(),
         };
         let path_resolution = PathResolution::new(def);
         self.def_map.insert(directive.id, path_resolution);
@@ -656,11 +721,10 @@ fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
 
         if let Some(Def::Trait(_)) = module.def {
             self.session.span_err(directive.span, "items in traits are not importable.");
-        }
-
-        if module.def_id() == directive.parent.def_id()  {
             return;
-        } else if let GlobImport { is_prelude: true } = directive.subclass {
+        } else if module.def_id() == directive.parent.def_id()  {
+            return;
+        } else if let GlobImport { is_prelude: true, .. } = directive.subclass {
             self.prelude = Some(module);
             return;
         }
@@ -674,7 +738,8 @@ fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
             resolution.borrow().binding().map(|binding| (*name, binding))
         }).collect::<Vec<_>>();
         for ((name, ns), binding) in bindings {
-            if binding.is_importable() && binding.is_pseudo_public() {
+            if binding.pseudo_vis() == ty::Visibility::Public ||
+               self.new_import_semantics && self.is_accessible(binding.vis) {
                 let imported_binding = self.import(binding, directive);
                 let _ = self.try_define(directive.parent, name, ns, imported_binding);
             }
@@ -702,20 +767,23 @@ fn finalize_resolutions_in(&mut self, module: Module<'b>) {
             };
 
             // Report conflicts
-            for duplicate_glob in resolution.duplicate_globs.iter() {
-                // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
-                if !binding.is_import() {
-                    if let NameBindingKind::Import { binding, .. } = duplicate_glob.kind {
-                        if binding.is_import() { continue }
+            if !self.new_import_semantics {
+                for duplicate_glob in resolution.duplicate_globs.iter() {
+                    // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
+                    if !binding.is_import() {
+                        if let NameBindingKind::Import { binding, .. } = duplicate_glob.kind {
+                            if binding.is_import() { continue }
+                        }
                     }
-                }
 
-                self.report_conflict(module, name, ns, duplicate_glob, binding);
+                    self.report_conflict(module, name, ns, duplicate_glob, binding);
+                }
             }
 
             if binding.vis == ty::Visibility::Public &&
                (binding.is_import() || binding.is_extern_crate()) {
-                if let Some(def) = binding.def() {
+                let def = binding.def();
+                if def != Def::Err {
                     reexports.push(Export { name: name, def_id: def.def_id() });
                 }
             }

src/libsyntax/feature_gate.rs

@@ -285,7 +285,10 @@ pub fn new() -> Features {
 
     // Allows the sysV64 ABI to be specified on all platforms
     // instead of just the platforms on which it is the C ABI
-    (active, abi_sysv64, "1.13.0", Some(36167))
+    (active, abi_sysv64, "1.13.0", Some(36167)),
+
+    // Use the import semantics from RFC 1560.
+    (active, item_like_imports, "1.13.0", Some(35120))
 );
 
 declare_features! (

src/test/compile-fail/bad-module.rs

@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: failed to resolve. Use of undeclared type or module `thing`
+fn main() {
+    let foo = thing::len(Vec::new());
+    //~^ ERROR failed to resolve. Use of undeclared type or module `thing`
 
-fn main() { let foo = thing::len(Vec::new()); }
+    let foo = foo::bar::baz();
+    //~^ ERROR failed to resolve. Use of undeclared type or module `foo`
+}

src/test/compile-fail/imports/duplicate.rs

+// 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.
+
+#![feature(item_like_imports)]
+
+mod a {
+    pub fn foo() {}
+}
+
+mod b {
+    pub fn foo() {}
+}
+
+mod c {
+    pub use a::foo;
+}
+
+mod d {
+    use a::foo; //~ NOTE previous import
+    use a::foo; //~ ERROR `foo` has already been imported
+                //~| NOTE already imported
+}
+
+mod e {
+    pub use a::*;
+    pub use c::*; // ok
+}
+
+mod f {
+    pub use a::*; //~ NOTE `foo` could resolve to the name imported here
+    pub use b::*; //~ NOTE `foo` could also resolve to the name imported here
+}
+
+mod g {
+    pub use a::*; //~ NOTE `foo` could resolve to the name imported here
+    pub use f::*; //~ NOTE `foo` could also resolve to the name imported here
+}
+
+fn main() {
+    e::foo();
+    f::foo(); //~ ERROR `foo` is ambiguous
+              //~| NOTE Consider adding an explicit import of `foo` to disambiguate
+    g::foo(); //~ ERROR `foo` is ambiguous
+              //~| NOTE Consider adding an explicit import of `foo` to disambiguate
+}
+
+mod ambiguous_module_errors {
+    pub mod m1 { pub use super::m1 as foo; }
+    pub mod m2 { pub use super::m2 as foo; }
+
+    use self::m1::*; //~ NOTE
+                     //~| NOTE
+    use self::m2::*; //~ NOTE
+                     //~| NOTE
+
+    use self::foo::bar; //~ ERROR `foo` is ambiguous
+                        //~| NOTE
+
+    fn f() {
+        foo::bar(); //~ ERROR `foo` is ambiguous
+                    //~| NOTE
+    }
+}

src/test/compile-fail/imports/reexports.rs

+// 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.
+
+#![feature(item_like_imports)]
+
+mod a {
+    fn foo() {}
+    mod foo {}
+
+    mod a {
+        pub use super::foo; //~ ERROR cannot be reexported
+        pub use super::*; //~ ERROR must import something with the glob's visibility
+    }
+}
+
+mod b {
+    pub fn foo() {}
+    mod foo { pub struct S; }
+
+    pub mod a {
+        pub use super::foo; // This is OK since the value `foo` is visible enough.
+        fn f(_: foo::S) {} // `foo` is imported in the type namespace (but not `pub` reexported).
+    }
+
+    pub mod b {
+        pub use super::*; // This is also OK since the value `foo` is visible enough.
+        fn f(_: foo::S) {} // Again, the module `foo` is imported (but not `pub` reexported).
+    }
+}
+
+mod c {
+    // Test that `foo` is not reexported.
+    use b::a::foo::S; //~ ERROR `foo`
+    use b::b::foo::S as T; //~ ERROR `foo`
+}
+
+fn main() {}

src/test/compile-fail/task-rng-isnt-sendable.rs

@@ -10,10 +10,10 @@
 
 // ensure that the ThreadRng isn't/doesn't become accidentally sendable.
 
-use std::rand; //~ ERROR: module `rand` is private
+use std::__rand::ThreadRng;
 
 fn test_send<S: Send>() {}
 
 pub fn main() {
-    test_send::<rand::ThreadRng>();
+    test_send::<ThreadRng>(); //~ ERROR std::marker::Send` is not satisfied
 }

src/test/run-pass/imports.rs

+// 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.
+
+// ignore-pretty : (#23623) problems when ending with // comments
+
+#![feature(item_like_imports)]
+#![allow(unused)]
+
+// Like other items, private imports can be imported and used non-lexically in paths.
+mod a {
+    use a as foo;
+    use self::foo::foo as bar;
+
+    mod b {
+        use super::bar;
+    }
+}
+
+mod foo { pub fn f() {} }
+mod bar { pub fn f() {} }
+
+pub fn f() -> bool { true }
+
+// Items and explicit imports shadow globs.
+fn g() {
+    use foo::*;
+    use bar::*;
+    fn f() -> bool { true }
+    let _: bool = f();
+}
+
+fn h() {
+    use foo::*;
+    use bar::*;
+    use f;
+    let _: bool = f();
+}
+
+// Here, there appears to be shadowing but isn't because of namespaces.
+mod b {
+    use foo::*; // This imports `f` in the value namespace.
+    use super::b as f; // This imports `f` only in the type namespace,
+    fn test() { self::f(); } // so the glob isn't shadowed.
+}
+
+// Here, there is shadowing in one namespace, but not the other.
+mod c {
+    mod test {
+        pub fn f() {}
+        pub mod f {}
+    }
+    use self::test::*; // This glob-imports `f` in both namespaces.
+    mod f { pub fn f() {} } // This shadows the glob only in the value namespace.
+
+    fn test() {
+        self::f(); // Check that the glob-imported value isn't shadowed.
+        self::f::f(); // Check that the glob-imported module is shadowed.
+    }
+}
+
+// Unused names can be ambiguous.
+mod d {
+    pub use foo::*; // This imports `f` in the value namespace.
+    pub use bar::*; // This also imports `f` in the value namespace.
+}
+
+mod e {
+    pub use d::*; // n.b. Since `e::f` is not used, this is not considered to be a use of `d::f`.
+}
+
+fn main() {}