super in object literal causes error

[mrac]

The following code should log:

original
new

as it does in ES6. Instead in TypeScript 1.6.2 it causes an error:

'super' can only be referenced in a derived class.

Here's the code:

var obj = {
    __proto__: {
        method() {
            console.log('original');
        }
    },
    method() {
        super.method();
        console.log('new');
    }
};

obj.method();

[mhegazy]

As per the ES6/S2015 spec, super is only allowed in classes. In this sample __proto__ is just a regular poverty and is not treated differently by the typesystem. What works is rewriting this as classes, this should be equivalent:

var obj = class extends class {
    method() {
        console.log('original');
    }
}{
    method() {
        super.method();
        console.log('new');
    }
};

new obj().method();

[mrac]

I didn't decypher the spec document, but the MDN doc says:

The super.prop and super[expr] expressions are valid in any method definition in both classes and object literals.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/super

Chrome, Node, Firefox and Babel all call the prototype method here. No error.
So TypeScript is not compatible with ES6 in this case.

[weswigham]

@mrac seems right - nothing in the super keyword spec indicates that it is only valid within a class, and, in fact, there are even places that call out that you can't user super in places like certain evals and module statement lists. The spec area indicating that any function with a home object can use super would be Function.[[HasSuperBinding]].

[mhegazy]

yes. looking at the final spec that seems the case; though i remember it was not at some point.

[RyanCavanaugh]

Design meeting resolution: super should be allowed only in ES6 in a shorthand method body in an object literal and is of type any