fix Issue 16460 - ICE for package visibility check in function literal

- fixed by skipping symbol-less scopes when establishing scope for
  FuncDeclaration
- symbol-less scopes like Scope.startCTFE and FuncExp scopes don't
  require a symbol table (and thus don't create a scopesym)

src/func.d

@@ -1397,7 +1397,15 @@ public:
             localsymtab = new DsymbolTable();
             // Establish function scope
             auto ss = new ScopeDsymbol();
-            ss.parent = sc.scopesym;
+            // find enclosing scope symbol, might skip symbol-less CTFE and/or FuncExp scopes
+            for (auto scx = sc; ; scx = scx.enclosing)
+            {
+                if (scx.scopesym)
+                {
+                    ss.parent = scx.scopesym;
+                    break;
+                }
+            }
             Scope* sc2 = sc.push(ss);
             sc2.func = this;
             sc2.parent = this;

test/compilable/imports/imp16460.d

@@ -0,0 +1,3 @@
+module imports.imp16460;
+
+package enum val = 0;

test/compilable/test16460.d

@@ -0,0 +1,13 @@
+module imports.test16460;
+
+void bug()
+{
+    auto d1 = (){
+        import imports.imp16460;
+        return val;
+    };
+    enum d2 = (){
+        import imports.imp16460;
+        return val;
+    };
+}