How to write an assertion that two objects are the same shape in Typescript

sameShape.ts

// this worked in Typescript 3.2.4

// It feels like we should be able to say SameShape<Q extends R, R extends Q>, but this triggers circular reference
// detection in Typescript. Somehow going to {[K in keyof Q]: Q[K]} solves this (though maybe this won't catch things
// like symbols?)
type SameShape<Q extends R, R extends { [K in keyof Q]: Q[K] }> = {
    [K in keyof Q]: R[K] // re-asserting every key of Q is present in R with the same type
} & { // anding the types together will catch any conflicts
    [K in keyof R]: Q[K] // re-asserting every key of R is present in Q with the same type
}

// unfortunately I didn't see a good way of avoiding repeating the generic type here, but I think there _is_ a way
// to avoid it with infer or ... something. This isn't superb but it gets the job done and should be limited to
// library code
function assertShape<Shape extends { [K in keyof Data]: Data[K] }, Data extends Shape>(
    s: Shape,
    d: Data
): SameShape<Shape, Data> {
    return d as any;
}

assertShape({a: 1, b: 2}, {a: 3, b: 4});
// the following will fail at typecheck
// missing keys
// assertShape(
//     {a:1, b:2},
//     {a:3, b:4, c:5}
// )
// extra keys
// assertShape(
//     {a: 1, b:2},
//     {a:1},
// )
// type mismatch
// assertShape({a:1}, {a: 'hi'});
// type mismatch in inner keys
// assertShape({
//         a: {a: 3},
//     }, {a: {a: 3, b: 4}}
//)