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Assigning values from tuple. #9874
Description
TypeScript Version: 1.8.10
Code
const someTuple: [string, number] = ['someString', 1];
const first: string = someTuple.shift();Expected behavior:
TypeScript lets me assign the result of shift() to first: string, or assign the result of pop() to first: number.
Actual behavior:
error TS2322: Type 'string | number' is not assignable to type 'string'.
If I hint first as any, or access someTuple[0], both of those work.
Activity
yulianovdey commentedon Jul 21, 2016
I guess the problem is I'm not supposed to be modifying my "immutable" tuple ;).
DanielRosenwasser commentedon Jul 21, 2016
The type system doesn't have a way to track the relationship between the first numeric property of a tuple and the behavior of
shift(especially whenshiftchanges the contents of the containing array), and I don't think doing so is very realistic.yulianovdey commentedon Jul 21, 2016
Daniel Rosenwasser (@DanielRosenwasser) understood, thanks. What about making
slicework, since it copies and you could infer types based on each resulting index?