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Array type gets inferred incorrectly #53380

Closed as not planned
Closed as not planned
Array type gets inferred incorrectly#53380
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Working as IntendedThe behavior described is the intended behavior; this is not a bug

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@tippfelher
tippfelher
opened on Mar 20, 2023

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const var1: string = "";
const var2: number = 0;

// inferred as: const arr: (string | number)[]
//   this is wrong (?) and should be: const arr: [string, number]
const arr = [var1, var2];

const arr3: (typeof arr) = ["not", "ok"]; // not ok

const bettarr: [string, number] = [var1, var2];

const bettarr3: (typeof bettarr) = ["not", "ok"]; // ok

Activity

  1. fatcerberus commented on Mar 20, 2023

    @fatcerberus
    Bruce Pascoe (fatcerberus)
    on Mar 20, 2023

    This is working as intended. To infer tuples from an array literal without a type annotation, you have to use as const.

    const var1: string = "";
const var2: number = 0;

// inferred as: const arr: readonly [string, number]
const arr = [var1, var2] as const;

const arr3: (typeof arr) = ["not", "ok"]; // ok, now an error

    Next time please follow the issue template for bug reports.

  2. Ryan Cavanaugh (RyanCavanaugh)
    added
    Working as IntendedThe behavior described is the intended behavior; this is not a bug
    on Mar 20, 2023
  3. Ryan Cavanaugh (RyanCavanaugh)
    closed this as not plannedon Mar 20, 2023
  4. microsoft
    locked as resolved and limited conversation to collaborators on Oct 22, 2025
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