Discriminated union narrowing fails when use template literal types as tag

TypeScript Version: 4.2.0-dev.20201211

Search Terms: narrowing, discriminated union, template literal types

Code

type Types<T extends string> = {
  one: `${T}/one`;
  two: `${T}/two`;
}
type OneObj<T extends string> = {
  type: Types<T>["one"];
  one: string;
}
type TwoObj<T extends string> = {
  type: Types<T>["two"];
  two: string;
}
type OneOrTwoObj<T extends string> = OneObj<T> | TwoObj<T>

declare function acceptsOneObj<T extends string>(oneObj: OneObj<T>): void;
declare function acceptsTwoObj<T extends string>(twoObj: TwoObj<T>): void;

function f<T extends string>(oneOrTwoObj: OneOrTwoObj<T>, types: Types<T>){
  switch(oneOrTwoObj.type){
    case types.one:
     return acceptsOneObj(oneOrTwoObj); // Error: Argument of type 'OneOrTwoObj<T>' is not assignable to parameter of type 'OneObj<T>'.
    case types.two:
     return acceptsTwoObj(oneOrTwoObj); // Error: Argument of type 'OneOrTwoObj<T>' is not assignable to parameter of type 'OneObj<T>'.
  }
}

Expected behavior:
oneOrTwoObj should be narrowed to OneObj or TwoObj in function f

Actual behavior:
narrowing fails

Playground Link:
playground

Related Issues:

Comienza con la reproducción vinculada de TypeScript Playground y la función genérica f, centrándote en cómo el switch sobre oneOrTwoObj.type gestiona los tipos de literales de plantilla. Confirma el comportamiento actual y, después, sigue el recorrido de comprobación de tipos para el narrowing de uniones discriminadas. Se considera terminado cuando cada rama del switch restringe oneOrTwoObj al OneObj o TwoObj correspondiente, de modo que las llamadas a acceptsOneObj y acceptsTwoObj pasen la comprobación de tipos.