Private fields

test/mjsunit/harmony/class-privates-errors.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-private-class-fields
+
+// Adding the same property twice
+// TODO(bakkot) instantiating 'Base' should be an error
+{
+  class Base {
+    constructor() { return new Derived; }
+  }
+
+  class Derived extends Base {
+    #a = 0;
+  }

[Dan Ehrenberg, 2016/09/15 21:26:58]

This test is a little incomplete, as you don't actually instantiate Derived in
this test. This looks like a fun infinite loop to me; you may want to make a
base case so you can actually observe that the check currently doesn't occur.

+}
+
+// Deleting a private field
+// TODO(bakkot) each of these lines should be a syntax error
+{
+  class C { #a; m(){ delete #a; } }
+  class D { #a; m(){ delete this.#a; } }
+}
+
+// Referencing a private field outside a class
+// TODO(bakkot) this is not spec'd to be a syntax error, but should be
+{
+  () => #a;
+  () => this.#a;
+}
+
+// Referencing a private field inside a class which doesn't declare it
+// TODO(bakkot) it is unclear whether or not this will be an error, see
+// https://github.com/tc39/proposal-private-fields/issues/49

[Dan Ehrenberg, 2016/09/15 21:26:58]

I think the only ongoing discussion is whether it should be a syntax error to
list an outer enclosing one on an inner class. If it statically doesn't resolve
to anything at all, I think it should be a SyntaxError, and I haven't heard an
argument the other way.

+{
+  class C {
+    #a;
+    m(){ #b; }
+  }
+}
+
+// Referencing a private field through 'eval'
+// TODO(bakkot) it is unclear whether or not this will be an error, see
+// https://github.com/tc39/proposal-private-fields/issues/47
+{
+  class C {
+    #a = 0;
+    m() { return eval('#a'); }
+  }
+  let c = new C;
+  assertEquals(0, c.m());
+}