2.1 compile error: "Unexpected token , fo

[unional]

function (m: string) {
    [1, 2, 3].map(i => {
        return true? { [m]: i } : false
    })
}

produces:

function (m) {
    [1, 2, 3].map(function (i) {
        return true ? _a = {}, _a[m] = i, _a : false;   // <-- unexpected token ,
        var _a;
    });
}

instead of:

function (m) {
    [1, 2, 3].map(function (i) {
        return true ? (_a = {}, _a[m] = i, _a) : false;
        var _a;
    });
}