type inference of nested type property

[kim-jaedeok]

🔎 Search Terms

"type inference", "property deep inside"

🕗 Version & Regression Information

tested at 5.3.3, 4.9.3, 4.6.3

⏯ Playground Link

https://www.typescriptlang.org/play?#code/C4TwDgpgBAglC8AoKUA+UDeUwCcD2YAXJlKJMQEQCGFA3FAG5UA2ArhMVgBYCWxATFAC+w4cjQlcBTqXAcoFAEZ1GLdjK4RmzPMQCMokUNqJEAYzwA7AM7AoVBFAAUVYjACUCAHyZx1gO48wGZczlQAdFJg4WQQnhjiKGZU1tDUFISJKFA4EMCsOJb2kfjRTGwQ4bz0APQ1UAAqclAAkpYAZhC5lmbQ-ng4ANbhWcmpCsqZ2dm5+YXOnvA+EVHh5exVWjq19U2QrR1dED3Qlnh2-UMjKEKIxqYWNnaKjk6Kbos+CUlWtpKlongUEUJj8gWCoScq1i8VGKTSNCm0xyeQKRVW60q1SgdUazTanW6vSgl2GcPGSgyWRQszRC282FKazUWK2eB2eP2BKOJxJAzJNzuQA

💻 Code

type A =
  | { prop: { type: "a"; value: { hi: 2 } } }
  | { prop: { type: "b"; value: { hello: 1 } } };

const a = (a: A) => {
  switch (a.prop.type) {
    case "a":
      return a.prop.value.hi; // Type Inference work.
    case "b":
      return () => a.prop.value.hello; // Type Inference not work.
  }
};

const b = (b: A) => {
  const { prop } = b;

  switch (prop.type) {
    case "a":
      return prop.value.hi; // Type Inference work.
    case "b":
      return () => prop.value.hello; // Type Inference work.
  }
}

🙁 Actual behavior

When a property deep inside an object is entered in a conditional statement, type inference is not made.

🙂 Expected behavior

type error not occur.

Additional information about the issue

No response

[fatcerberus]

#18758

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.