Can not use nested object method in expression for binding

Environment

• CLI: 5.0.1
• Cross-platform modules: 5.0.5
• Android Runtime: 5.0.0
• iOS Runtime: not installed

To Reproduce

class ViewModel extends Observable {
    public obj = {
        fun: function () {
            return "It's fun()"
        }
    }
}

const vm = new ViewModel();

<Label text="{{ obj.fun() }}"/>

Binding: Run-time error occured in file: undefined at line: undefined and column: undefined

Same result if it used, as ListView item bindingContext.

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Start by reproducing the binding failure with the provided ViewModel and Label expression, then trace the expression-binding handling for nested object method calls. Verify the fix against both the Label example and the ListView item bindingContext case; done means obj.fun() evaluates without a runtime binding error.