Lexical this not captured for super element accessed calls

[weswigham]

TypeScript Version: 2.7.0-dev.201xxxxx

Code

class A { x() {} }

class B extends A {
    constructor() {
        super();
    }
    foo() {
        return () => {
            super["x"]();
        }
    }
}

Expected behavior:

var A = /** @class */ (function () {
    function A() {
    }
    A.prototype.x = function () { };
    return A;
}());
var B = /** @class */ (function (_super) {
    __extends(B, _super);
    function B() {
        return _super.call(this) || this;
    }
    B.prototype.foo = function () {
        var _this = this;
        return function () {
            _super.prototype["x"].call(_this);
        };
    };
    return B;
}(A));

Actual behavior:

var A = /** @class */ (function () {
    function A() {
    }
    A.prototype.x = function () { };
    return A;
}());
var B = /** @class */ (function (_super) {
    __extends(B, _super);
    function B() {
        return _super.call(this) || this;
    }
    B.prototype.foo = function () {
        return function () {
            _super.prototype["x"].call(this);
        };
    };
    return B;
}(A));

Related:
Found while working on #20125; will likely be included in the fix.

[weswigham]

In the same vein, a super property reference that is never called causes an unused lexical this capture:

class A { x() {} }

class B extends A {
    constructor() {
        super();
    }
    foo() {
        return () => {
            super.x;
        }
    }
}

yields

var A = /** @class */ (function () {
    function A() {
    }
    A.prototype.x = function () { };
    return A;
}());
var B = /** @class */ (function (_super) {
    __extends(B, _super);
    function B() {
        return _super.call(this) || this;
    }
    B.prototype.foo = function () {
        var _this = this;
        return function () {
            _super.prototype.x;
        };
    };
    return B;
}(A));

but should yield

var A = /** @class */ (function () {
    function A() {
    }
    A.prototype.x = function () { };
    return A;
}());
var B = /** @class */ (function (_super) {
    __extends(B, _super);
    function B() {
        return _super.call(this) || this;
    }
    B.prototype.foo = function () {
        return function () {
            _super.prototype.x;
        };
    };
    return B;
}(A));