fix Issue 9578 - "is a nested function and cannot be accessed from" problem

Author: 9rnsr

src/template.c

@@ -6197,9 +6197,17 @@ int TemplateInstance::hasNestedArgs(Objects *args)
           Lsa:
             sa = sa->toAlias();
             TemplateDeclaration *td = sa->isTemplateDeclaration();
+            if (td)
+            {
+                TemplateInstance *ti = sa->toParent()->isTemplateInstance();
+                if (ti && ti->enclosing)
+                    sa = ti;
+            }
+            TemplateInstance *ti = sa->isTemplateInstance();
             AggregateDeclaration *ad = sa->isAggregateDeclaration();
             Declaration *d = sa->isDeclaration();
             if ((td && td->literal) ||
+                (ti && ti->enclosing) ||
 #if FIXBUG8863
                 (ad && ad->isNested()) ||
 #endif

test/runnable/template9.d

@@ -2173,6 +2173,23 @@ void test9536()
     assert(s.bar() == 84);
 }
 
+/**********************************/
+// 9578
+
+template t9578(alias f) { void tf()() { f(); } }
+
+void g9578a(alias f)()  { f(); }        // Error -> OK
+void g9578b(alias ti)() { ti.tf(); }    // Error -> OK
+
+void test9578()
+{
+    int i = 0;
+    int m() { return i; }
+
+    g9578a!(t9578!m.tf)();
+    g9578b!(t9578!m)();
+}
+
 /**********************************/
 // 9596
 
@@ -2801,6 +2818,7 @@ int main()
     test9143();
     test9266();
     test9536();
+    test9578();
     test9596();
     test9837();
     test9874();