The `resolveRef` function exists to turn a *reference* into a *keypath*, given a particular *contextStack*. I.e. if you have `{{#foo}}{{bar}}{{/foo}}`, the `{{bar}}` could resolve to `bar` or `foo.bar`, depending on the model.

There wasn't a way of validating a keypath but I've added one - see [here](https://github.com/RactiveJS/Ractive/blob/c040824b36d67e1adb77498e351958926a1973ed/src/render/shared/ExpressionResolver.js#L138-L153)