Code not properly colorized in Typescript with conditional return types

[h-Reser]

• VSCode Version: 1.33.1 & 1.34.0 (Insiders)
• OS Version: Windows 10 x64

Steps to Reproduce:
Write the following code in a new Typescript file:

type X = A | B;
type A = string;
type B = number;
function foo<T extends X>(arg: T): T extends B ? number : string {
  if (arg === "A") return <T extends B ? number : never>111;
  return <T extends B ? never : string>"returning a string";
}
foo("A");
foo(1);

In my project, I need to use a function with the typing described in the code above. This is of course a simplified version of my code. The code passes the Typescript 3.4.3 without errors, and also works at run time.
However, the colorization of the code bugs after the if statement.

If I remove the parameters from the return statements, then the colorization works. But the code doesn't pass the type-check anymore.

I get the same result with and without extensions. Also with the latest insiders build of VS Code.

[mjbvz]

I confirmed this using the latest grammar version