Incorrect return type when a union type is used by a partial get function

[sebinsua]

Closed as this was the wrong repository... See: microsoft/TypeScript#14400 (comment)

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In situations in which I wish to use a partial get function TypeScript doesn't seem able to work out the return type correctly.

TypeScript 2.5.3

interface Props {
    property: boolean;
    someProperty: string;
    someOtherProperty: number;
}

const obj = {
    property: true,
    someProperty: 'some property',
    someOtherProperty: 9999
}

function get1<T, K extends keyof T = keyof T>(k: K) {
    return (obj: T): T[K] => obj[k]
}

function get2<T, K extends keyof T = keyof T>(k: K, obj: T): T[K] {
    return obj[k]
}

// Why do I need to supply 'someProperty' as the second type argument to get this to work?
const getSomeProperty = get1<Props>('someProperty')
const someProperty = getSomeProperty(obj) // Type is `string | number | boolean`

// The type is worked out correctly here.
const someProperty2 = get2('someProperty', obj); // Type is `string`

Other than calling get1<Props, 'someProperty'>('someProperty') what could I do to dynamically create a getSomeProperty function which returns a string?

// Perhaps it was wrong for me to set a default type for K, but if I remove it completely then
// on usage of `get1` I get an error message: "Expected 2 type arguments, but got 1" which
// as far as I can tell, still has the same problem and forces the same inelegant approach.

function get1<T, K extends keyof T>(k: K) {
    return (obj: T): T[K] => obj[k]
}

Sorry, if this isn't the right place for this. I use this style of coding quite frequently in libraries that I write, and I want to find out whether this feature request is being tracked somewhere so I can follow it. Or if there is already some elegant syntax to do this, I want to know what it is!