Nested lookuptypes do not inference correctly

While trying to scope certain keys that would point to different types, I stumbled upon a problem when I needed to nest lookup types to lookup what type the key would correspond to. During decleration, this did not seem to be possible to get the compiler to understand. Applying the type does actually give out the correct type inferencing though. A simple example can be observed below.

TypeScript Version: 3.2.0-dev.201xxxxx
Tested with both 3.1.1 and typescript@next

Search Terms:
Lookuptypes, type inference, keyof

Code

interface Y {
  x: {
    x1: "x1";
    x2: "x2";
  }
}

interface Z {
  x1: number;
  x2: string;
  x3: number;
}

type H<K extends keyof Y, J extends keyof Y[K]> = (k: K, j: J) => Z[Y[K][J]]; // <----- Error Incorrectly?!
type T6 = H<"x", "x1">;
type T7 = H<"x", "x2">;
type T8 = H<"x", "x3">; // Errors Correctly!

// @ts-ignore
type L<K extends keyof Y, J extends keyof Y[K]> = (k: K, j: J) => Z[Y[K][J]];
type T3 = L<"x", "x1">;
type T4 = L<"x", "x2">;
type T5 = L<"x", "x3">; // Errors Correctly!

Expected behavior:
For the Z[Y[K][J]] in the example to not give error. Applying the type seems to work correctly.

Actual behavior:
Decleration of the type shows error when it should not.

Playground Link: https://www.typescriptlang.org/play/#src=interface%20Y%20%7B%0D%0A%20%20x%3A%20%7B%0D%0A%20%20%20%20x1%3A%20%22x1%22%3B%0D%0A%20%20%20%20x2%3A%20%22x2%22%3B%0D%0A%20%20%7D%0D%0A%7D%0D%0A%0D%0Ainterface%20Z%20%7B%0D%0A%20%20x1%3A%20number%3B%0D%0A%20%20x2%3A%20string%3B%0D%0A%20%20x3%3A%20number%3B%0D%0A%7D%0D%0A%0D%0A%0D%0Atype%20H%3CK%20extends%20keyof%20Y%2C%20J%20extends%20keyof%20Y%5BK%5D%3E%20%3D%20(k%3A%20K%2C%20j%3A%20J)%20%3D%3E%20Z%5BY%5BK%5D%5BJ%5D%5D%3B%0D%0A%0D%0Atype%20T6%20%3D%20H%3C%22x%22%2C%20%22x1%22%3E%3B%0D%0Atype%20T7%20%3D%20H%3C%22x%22%2C%20%22x2%22%3E%3B%0D%0Atype%20T8%20%3D%20H%3C%22x%22%2C%20%22x3%22%3E%3B%0D%0A%0D%0A%2F%2F%20%40ts-ignore%0D%0Atype%20L%3CK%20extends%20keyof%20Y%2C%20J%20extends%20keyof%20Y%5BK%5D%3E%20%3D%20(k%3A%20K%2C%20j%3A%20J)%20%3D%3E%20Z%5BY%5BK%5D%5BJ%5D%5D%3B%0D%0A%0D%0Atype%20T3%20%3D%20L%3C%22x%22%2C%20%22x1%22%3E%3B%0D%0Atype%20T4%20%3D%20L%3C%22x%22%2C%20%22x2%22%3E%3B%0D%0Atype%20T5%20%3D%20L%3C%22x%22%2C%20%22x3%22%3E%3B%0D%0A

Commencez par l’exemple TypeScript Playground lié et reproduisez le diagnostic sur l’accès indexé imbriqué dans le type H. Suivez le traitement par le compilateur de Z[Y[K][J]] pour les types de recherche génériques ; le travail est terminé lorsque la déclaration est acceptée, tandis que le cas invalide T8 signale toujours une erreur.