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object getters return type error #58483

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object getters return type error#58483
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@lqzhgood
lqzhgood
opened on May 9, 2024
type T = {
  data: {
    a: number;
  };
};

const b: T = {
  data: {
    a: 123123,
    b: 3444,    // throw type error
  },
};

const c: T = {
  get data() {
    return {
      a: 123,
      b: 333, // not throw type error
    };
  },
};


const d = {
  get data() {
    return {
      a: 123,
      b: 333 
    };
  },
};

type td = typeof  d; // { a:number, b:number }

c.data.b not throw type error seems to be a mistake ?

Activity

  1. lqzhgood
    added
    DuplicateAn existing issue was already created
    on May 9, 2024

  2. whzx5byb commented on May 9, 2024

    @whzx5byb
    whzx5byb
    on May 9, 2024

    See https://github.com/microsoft/TypeScript/wiki/FAQ#indirect-excess-properties-are-ok

  3. lqzhgood commented on May 9, 2024

    @lqzhgood
    lqzhgood
    on May 9, 2024
    Author

    See https://github.com/microsoft/TypeScript/wiki/FAQ#indirect-excess-properties-are-ok

    bug b.data.b throw type error. and in c.data no type prompt like any,

    see typescirpt palay

    https://www.typescriptlang.org/play/?#code/C4TwDgpgBAKlC8UDeAoKUAmBDYWBcya6U+UAdgK4C2ARhAE4DcRAvs2yigMYD2ZAzsCg0CcRKnTZcBCcVIBGAEwBmJcoA0RdCKjKALAfXEoAehNRgAC3o8A7hfDQGN+q00dufQVC6iEhdABzCCEpLAAKAEoA4noQinoyGOMFFU1jbQJlbKMzch4hKxt7UEgoZx5XYw50FndmTl4BUP9ZYNCcCOjZdDjgBKSeuQI1dIydbOUoLSga2frOUuhgDH8lngAzSUZTcyQSPEpaBiMRI7p6WaA

  4. fatcerberus commented on May 9, 2024

    @fatcerberus
    Bruce Pascoe (fatcerberus)
    on May 9, 2024

    Sigh... I really wish the wording of this error message would be changed.

    This isn't a bug. The excess property check error is not a type error, it's a lint check. You can't rely on it to prevent extra properties from being put on an object because it won't always trigger (which is by design). If that's what you need, see #12936.

    The other issue you linked to this (#49511) is unrelated - there is nothing like an any involved here. { a: number, b: number } is a legal subtype of and assignable to { a: number }.

  5. snarbies commented on May 9, 2024

    @snarbies
    snarbies
    on May 9, 2024

    Indirect excess properties are not an error. Examples of indirect excess properties would be:

    • values returned by functions
    • values stored in intermediate variables

    b is direct. You go straight from value→property.

    c in indirect because it is one step removed. You have a getter, which is a function that returns a value.

    From the linked FAQ, excess property checks are to defend against things like typos:

    const p: Dimensions = {
    width: 32,
    height: 14,
    depht: 11 // <-- typo!!
}

    But there are plenty of situations where you want or need to allow extra properties.

  6. whzx5byb commented on May 9, 2024

    @whzx5byb
    whzx5byb
    on May 9, 2024

    When inspecting the code I do find something looks like a bug: #58484.
    lqzhgood , is it what you are talking about?

  7. lqzhgood commented on May 9, 2024

    @lqzhgood
    lqzhgood
    on May 9, 2024
    Author

    Sigh... I really wish the wording of this error message would be changed.

    This isn't a bug. The excess property check error is not a type error, it's a lint check. You can't rely on it to prevent extra properties from being put on an object because it won't always trigger (which is by design). If that's what you need, see #12936.

    The other issue you linked to this (#49511) is unrelated - there is nothing like an any involved here. { a: number, b: number } is a legal subtype of and assignable to { a: number }.

    The focus of this issue is not on whether additional attributes can be added,
    Is difference types of b.data and c.data by use getters
    b.data and c.data should throw errors simultaneously or not

  8. lqzhgood commented on May 9, 2024

    @lqzhgood
    lqzhgood
    on May 9, 2024
    Author

    When inspecting the code I do find something looks like a bug: #58484. lqzhgood , is it what you are talking about?

    yes,
    d.data and c.data (getter) Inconsistent types returned,(from the perspective of throwing exceptions)
    and c.data looks like any in autocomplete

  9. lqzhgood commented on May 9, 2024

    @lqzhgood
    lqzhgood
    on May 9, 2024
    Author

    Indirect excess properties are not an error. Examples of indirect excess properties would be:

    • values returned by functions
    • values stored in intermediate variables

    b is direct. You go straight from value→property.

    c in indirect because it is one step removed. You have a getter, which is a function that returns a value.

    From the linked FAQ, excess property checks are to defend against things like typos:

    const p: Dimensions = {
    width: 32,
    height: 14,
    depht: 11 // <-- typo!!
}

    But there are plenty of situations where you want or need to allow extra properties.

    Thank you for your answer, but c.data look like any in autocomplete.

    https://www.typescriptlang.org/play/?#code/C4TwDgpgBAKlC8UDeAoKUAmBDYWBcya6U+UAdgK4C2ARhAE4DcR6AXuwZbQ8+gL7MBKFAGMA9mQDOwKDQJxEqdNlwElxUgEYATAGYdugDQtZBXQBZLh4lAD0tqMAAW9MQHdH4aA1f0T7VgIDIj5jIVEJaSgReQRCdABzCBkVLAAKAEp44npkinoybJstPWMbdDkoXWrre3IxGWdXD1BIKB8xP3KodhMhfjDmYXEpFLj1JJScdKz1dFzgfMK5jSDSkwqzaqg+3ihQlHDW6GAMOOOxADNlRjsHJBI8Ljp6azlnhn2gA

    image

  10. fatcerberus commented on May 9, 2024

    @fatcerberus
    Bruce Pascoe (fatcerberus)
    on May 9, 2024

    You are conflating two different things. The autocomplete thing is unrelated to the type checking of c.data.

    b.data and c.data should throw errors simultaneously or not

    No, they shouldn't; it's already been explained several times why c.data doesn't have an error. The excess property check doesn't apply to it, but it's still type-checked properly. For example if you change the code to

    const c: T = {
  get data() {
    return 42;
  },
};

    then you get a type error.

  11. lqzhgood commented on May 9, 2024

    @lqzhgood
    lqzhgood
    on May 9, 2024
    Author

    You are conflating two different things. The autocomplete thing is unrelated to the type checking of c.data.

    b.data and c.data should throw errors simultaneously or not

    No, they shouldn't; it's already been explained several times why c.data doesn't have an error. The excess property check doesn't apply to it, but it's still type-checked properly. For example if you change the code to

    const c: T = {
  get data() {
    return 42;
  },
};

    then you get a type error.

    Thank you, I understand my mistake
    The real problem should be automatic completion
    The problem of automatic completion made me think that c.data had changed to any type, resulting in the loss of type checking

  12. fatcerberus commented on May 9, 2024

    @fatcerberus
    Bruce Pascoe (fatcerberus)
    on May 9, 2024

    In that case, this is a retroactive duplicate of #58484 😄

  13. lqzhgood commented on May 9, 2024

    @lqzhgood
    lqzhgood
    on May 9, 2024
    Author

    the real problem is #58484. I will close this issue

  14. lqzhgood
    closed this as completedon May 9, 2024
  15. microsoft
    locked as resolved and limited conversation to collaborators on Oct 22, 2025
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