Merge pull request #5330 from WalterBright/fix15389

fix Issue 15389 - extern(C++) forward referencing problem

src/nspace.d

@@ -159,6 +159,21 @@ public:
         return Dsymbol.oneMember(ps, ident);
     }
 
+    override final Dsymbol search(Loc loc, Identifier ident, int flags = IgnoreNone)
+    {
+        //printf("%s.Nspace.search('%s')\n", toChars(), ident.toChars());
+        if (_scope && !symtab)
+            semantic(_scope);
+
+        if (!members || !symtab) // opaque or semantic() is not yet called
+        {
+            error("is forward referenced when looking for '%s'", ident.toChars());
+            return null;
+        }
+
+        return ScopeDsymbol.search(loc, ident, flags);
+    }
+
     override int apply(Dsymbol_apply_ft_t fp, void* param)
     {
         if (members)

test/compilable/test15389_x.d

@@ -0,0 +1,7 @@
+import test15389_y;
+
+//struct ns
+extern (C++, ns)
+{
+    class X { test15389_y.ns.Y a; }
+}

test/compilable/test15389_y.d

@@ -0,0 +1,8 @@
+import test15389_x;
+
+//struct ns
+extern (C++, ns)
+{
+    class Y { test15389_x.ns.X b; }
+}
+