hack for RustEmbed with updated test

Author: LorrensP-2158466

compiler/rustc_resolve/src/imports.rs

@@ -454,6 +454,17 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             module.underscore_disambiguator.update_unchecked(|d| d + 1);
             module.underscore_disambiguator.get()
         });
+        // "Same res different import" ambiguity hack for macros introduced in #145108.
+        // See related discussion for more info:
+        // https://rust-lang.zulipchat.com/#narrow/channel/421156-gsoc/topic/Project.3A.20Parallel.20Macro.20Expansion/near/542057918.
+        if ns == MacroNS
+            && decl.is_glob_import()
+            && decl.vis.get().is_public() // is a glob that reexports a macro
+            && self.macro_use_prelude.contains_key(&ident.name) // which also lives in macro_use world
+            && let Some(def_id) = res.opt_def_id()
+        {
+            self.macro_vis_hack_map.insert((module, def_id));
+        }
         self.update_local_resolution(module, key, warn_ambiguity, |this, resolution| {
             if let Some(old_decl) = resolution.best_decl() {
                 assert_ne!(decl, old_decl);
@@ -642,7 +653,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         for (import, side_effect) in import_resolutions {
             let SideEffect { imported_module, decls: side_effect_bindings } = side_effect;
             let parent = import.parent_scope.module;
-
             match (&import.kind, side_effect_bindings) {
                 (
                     ImportKind::Single { target, decls, .. },
@@ -1677,12 +1687,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         module.for_each_child(self, |this, ident, _, binding| {
             let res = binding.res().expect_non_local();
             if res != def::Res::Err {
-                let child = |reexport_chain| ModChild {
-                    ident: ident.0,
-                    res,
-                    vis: binding.vis(),
-                    reexport_chain,
+                let vis = match res.opt_def_id() {
+                    Some(def_id) if self.macro_vis_hack_map.contains(&(module, def_id)) => {
+                        Visibility::Public
+                    }
+                    Some(_) | None => binding.vis.get(),
                 };
+                let child = |reexport_chain| ModChild { ident: ident.0, res, vis, reexport_chain };
                 if let Some((ambig_binding1, ambig_binding2)) = binding.descent_to_ambiguity() {
                     let main = child(ambig_binding1.reexport_chain(this));
                     let second = ModChild {

compiler/rustc_resolve/src/lib.rs

@@ -1219,6 +1219,7 @@ pub struct Resolver<'ra, 'tcx> {
     /// Crate-local macro expanded `macro_export` referred to by a module-relative path.
     macro_expanded_macro_export_errors: BTreeSet<(Span, Span)> = BTreeSet::new(),
 
+    macro_vis_hack_map: FxIndexSet<(Module<'ra>, DefId)>,
     /// When a type is re-exported that has an inaccessible constructor because it has fields that
     /// are inaccessible from the import's scope, we mark that as the type won't be able to be built
     /// through the re-export. We use this information to extend the existing diagnostic.
@@ -1616,6 +1617,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
             glob_map: Default::default(),
             maybe_unused_trait_imports: Default::default(),
+            macro_vis_hack_map: Default::default(),
 
             arenas,
             dummy_decl: arenas.new_pub_def_decl(Res::Err, DUMMY_SP, LocalExpnId::ROOT),

tests/ui/imports/same-res-ambigious.fail.stderr

@@ -1,10 +1,11 @@
+//@ check-pass
 //@ edition: 2018
 //@ revisions: fail pass
 //@[pass] aux-crate: ambigious_extern=same-res-ambigious-extern.rs
 //@[fail] aux-crate: ambigious_extern=same-res-ambigious-extern-fail.rs
 // see https://github.com/rust-lang/rust/pull/147196
 
-#[derive(ambigious_extern::Embed)] //~ ERROR: derive macro `Embed` is private
+#[derive(ambigious_extern::Embed)]
 struct Foo{}
 
 fn main(){}