Do not reexport macros that are already at the crate root.

Author: cjgillot

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1102,9 +1102,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
                     let def_id = self.local_def_id(child_index);
                     let res = Res::Def(kind, def_id);
 
-                    if !kind.is_macro() {
-                        callback(Export { res, ident, vis, span });
-                    }
+                    callback(Export { res, ident, vis, span });
 
                     // For non-re-export structs and variants add their constructors to children.
                     // Re-export lists automatically contain constructors when necessary.

compiler/rustc_resolve/src/imports.rs

@@ -16,7 +16,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::ptr_key::PtrKey;
 use rustc_errors::{pluralize, struct_span_err, Applicability};
 use rustc_hir::def::{self, PartialRes};
-use rustc_hir::def_id::DefId;
+use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
 use rustc_middle::hir::exports::Export;
 use rustc_middle::span_bug;
 use rustc_middle::ty;
@@ -1392,9 +1392,23 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
             // FIXME: Implement actual cross-crate hygiene.
             let is_good_import =
                 binding.is_import() && !binding.is_ambiguity() && !ident.span.from_expansion();
-            if is_good_import || binding.is_macro_def() {
-                let res = binding.res().map_id(|id| this.local_def_id(id));
-                if res != def::Res::Err {
+            let res = binding.res();
+            if res == Res::Err {
+                // Do not insert failed resolutions.
+                return;
+            } else if is_good_import {
+                let res = res.map_id(|id| this.local_def_id(id));
+                reexports.push(Export { ident, res, span: binding.span, vis: binding.vis });
+            } else if let NameBindingKind::Res(Res::Def(def_kind, macro_def_id), true) =
+                binding.kind
+            {
+                let macro_is_at_root = macro_def_id
+                    .as_local()
+                    .and_then(|macro_def_id| this.definitions.def_key(macro_def_id).parent)
+                    == Some(CRATE_DEF_INDEX);
+                // Insert a re-export at crate root for exported macro_rules defined elsewhere.
+                if module.parent.is_none() && !macro_is_at_root {
+                    let res = def::Res::Def(def_kind, macro_def_id);
                     reexports.push(Export { ident, res, span: binding.span, vis: binding.vis });
                 }
             }

compiler/rustc_resolve/src/lib.rs

@@ -815,10 +815,6 @@ impl<'a> NameBinding<'a> {
         )
     }
 
-    fn is_macro_def(&self) -> bool {
-        matches!(self.kind, NameBindingKind::Res(Res::Def(DefKind::Macro(..), _), _))
-    }
-
     fn macro_kind(&self) -> Option<MacroKind> {
         self.res().macro_kind()
     }