added tests

interpreter/tests/lox/regression/40.lox

@@ -0,0 +1,22 @@
+fun caller(g) {
+  g();
+  // g should be a function, not nil.
+  print g == nil; // expect: false
+}
+
+fun callCaller() {
+  var capturedVar = "before";
+  var a = "a";
+
+  fun f() {
+    // Commenting the next line out prevents the bug!
+    capturedVar = "after";
+
+    // Returning anything also fixes it, even nil:
+    //return nil;
+  }
+
+  caller(f);
+}
+
+callCaller();