Clean up the scopes of expanded #[macro_use] imports.

src/librustc_resolve/build_reduced_graph.rs

@@ -13,7 +13,7 @@
 //! Here we build the "reduced graph": the graph of the module tree without
 //! any imports resolved.
 
-use macros::{InvocationData, LegacyImports, LegacyScope};
+use macros::{InvocationData, LegacyScope};
 use resolve_imports::ImportDirectiveSubclass::{self, GlobImport};
 use {Module, ModuleS, ModuleKind};
 use Namespace::{self, TypeNS, ValueNS};
@@ -84,7 +84,7 @@ impl<'b> Resolver<'b> {
     }
 
     /// Constructs the reduced graph for one item.
-    fn build_reduced_graph_for_item(&mut self, item: &Item, legacy_imports: &mut LegacyImports) {
+    fn build_reduced_graph_for_item(&mut self, item: &Item, expansion: Mark) {
         let parent = self.current_module;
         let name = item.ident.name;
         let sp = item.span;
@@ -202,7 +202,14 @@ impl<'b> Resolver<'b> {
                             if def.use_locally {
                                 let ext =
                                     Rc::new(macro_rules::compile(&self.session.parse_sess, &def));
-                                legacy_imports.insert(name, (ext, loaded_macro.import_site));
+                                if self.builtin_macros.insert(name, ext).is_some() &&
+                                   expansion != Mark::root() {
+                                    let msg = format!("`{}` is already in scope", name);
+                                    self.session.struct_span_err(loaded_macro.import_site, &msg)
+                                        .note("macro-expanded `#[macro_use]`s may not shadow \
+                                               existing macros (see RFC 1560)")
+                                        .emit();
+                                }
                                 self.macro_names.insert(name);
                             }
                             if def.export {
@@ -513,7 +520,7 @@ impl<'b> Resolver<'b> {
 pub struct BuildReducedGraphVisitor<'a, 'b: 'a> {
     pub resolver: &'a mut Resolver<'b>,
     pub legacy_scope: LegacyScope<'b>,
-    pub legacy_imports: LegacyImports,
+    pub expansion: Mark,
 }
 
 impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
@@ -554,7 +561,7 @@ impl<'a, 'b> Visitor for BuildReducedGraphVisitor<'a, 'b> {
         };
 
         let (parent, legacy_scope) = (self.resolver.current_module, self.legacy_scope);
-        self.resolver.build_reduced_graph_for_item(item, &mut self.legacy_imports);
+        self.resolver.build_reduced_graph_for_item(item, self.expansion);
         visit::walk_item(self, item);
         self.resolver.current_module = parent;
         if !macro_use {

src/librustc_resolve/lib.rs

@@ -3389,8 +3389,8 @@ impl<'a> Resolver<'a> {
                reported_errors.insert((name, span)) {
                 let msg = format!("`{}` is already in scope", name);
                 self.session.struct_span_err(span, &msg)
-                    .note("macro-expanded `macro_rules!`s and `#[macro_use]`s \
-                           may not shadow existing macros (see RFC 1560)")
+                    .note("macro-expanded `macro_rules!`s may not shadow \
+                           existing macros (see RFC 1560)")
                     .emit();
             }
         }

src/librustc_resolve/macros.rs

@@ -111,19 +111,10 @@ impl<'a> base::Resolver for Resolver<'a> {
         let mut visitor = BuildReducedGraphVisitor {
             resolver: self,
             legacy_scope: LegacyScope::Invocation(invocation),
-            legacy_imports: FnvHashMap(),
+            expansion: mark,
         };
         expansion.visit_with(&mut visitor);
         invocation.expansion.set(visitor.legacy_scope);
-
-        if !visitor.legacy_imports.is_empty() {
-            invocation.legacy_scope.set({
-                LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
-                    parent: invocation.legacy_scope.get(),
-                    kind: LegacyBindingKind::MacroUse(visitor.legacy_imports),
-                }))
-            });
-        }
     }
 
     fn add_macro(&mut self, scope: Mark, mut def: ast::MacroDef) {
@@ -173,7 +164,7 @@ impl<'a> base::Resolver for Resolver<'a> {
         None
     }
 
-    fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation, _force: bool)
+    fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation, force: bool)
                      -> Result<Rc<SyntaxExtension>, Determinacy> {
         let (name, span) = match invoc.kind {
             InvocationKind::Bang { ref mac, .. } => {
@@ -194,11 +185,15 @@ impl<'a> base::Resolver for Resolver<'a> {
             invocation.legacy_scope.set(LegacyScope::simplify_expansion(parent));
         }
         self.resolve_macro_name(invocation.legacy_scope.get(), name, true).ok_or_else(|| {
-            let mut err =
-                self.session.struct_span_err(span, &format!("macro undefined: '{}!'", name));
-            self.suggest_macro_name(&name.as_str(), &mut err);
-            err.emit();
-            Determinacy::Determined
+            if force {
+                let mut err =
+                    self.session.struct_span_err(span, &format!("macro undefined: '{}!'", name));
+                self.suggest_macro_name(&name.as_str(), &mut err);
+                err.emit();
+                Determinacy::Determined
+            } else {
+                Determinacy::Undetermined
+            }
         })
     }
 

src/test/compile-fail/macro-shadowing.rs

@@ -12,31 +12,28 @@
 
 macro_rules! foo { () => {} }
 macro_rules! macro_one { () => {} }
+#[macro_use(macro_two)] extern crate two_macros;
 
 macro_rules! m1 { () => {
     macro_rules! foo { () => {} } //~ ERROR `foo` is already in scope
-    //~^ NOTE macro-expanded `macro_rules!`s and `#[macro_use]`s may not shadow existing macros
+    //~^ NOTE macro-expanded `macro_rules!`s may not shadow existing macros
 
-    #[macro_use] //~ ERROR `macro_one` is already in scope
-    //~^ NOTE macro-expanded `macro_rules!`s and `#[macro_use]`s may not shadow existing macros
-    extern crate two_macros;
+    #[macro_use] //~ ERROR `macro_two` is already in scope
+    //~^ NOTE macro-expanded `#[macro_use]`s may not shadow existing macros
+    extern crate two_macros as __;
 }}
 m1!(); //~ NOTE in this expansion
        //~| NOTE in this expansion
        //~| NOTE in this expansion
        //~| NOTE in this expansion
 
-fn f() { macro_one!(); }
 foo!();
 
 macro_rules! m2 { () => {
     macro_rules! foo { () => {} }
-    #[macro_use] extern crate two_macros as __;
-
-    fn g() { macro_one!(); }
     foo!();
 }}
 m2!();
-//^ Since `foo` and `macro_one` are not used outside this expansion, they are not shadowing errors.
+//^ Since `foo` is not used outside this expansion, it is not a shadowing error.
 
 fn main() {}