Bug: Typescript compiler is confused between Tuple literal and Array Literal

[wongjiahau]

Expected behavior:

No error

Actual behavior:

Type error.

Playground Link:

http://www.typescriptlang.org/play/#src=interface%20OK%3CT%3E%20%7B%0D%0A%20%20%20%20kind%3A%20%22OK%22%3B%0D%0A%20%20%20%20value%3A%20T%3B%0D%0A%7D%0D%0Aexport%20function%20ok%3CT%3E(value%3A%20T)%3A%20OK%3CT%3E%20%7B%0D%0A%20%20%20%20return%20%7B%0D%0A%20%20%20%20%20%20%20%20kind%3A%20%22OK%22%2C%0D%0A%20%20%20%20%20%20%20%20value%3A%20value%0D%0A%20%20%20%20%7D%3B%0D%0A%7D%0D%0A%0D%0Alet%20result%3A%20OK%3C%5Bstring%2C%20number%5D%3E%20%3D%20ok(%5B%22hello%22%2C%2012%5D)%3B

Related Issues:

[ghost]

Duplicate of #11152 -- the problem is that annotating the result as OK<[string, number]> has no effect in the inferred type argument. let result = ok<[string, number]> (["hello", 12]); would work though.

[wongjiahau]

Despite the solution provided by @andy-ms , another workaround is as follows:

let result = ok(["hello", 12] as [string, number]);

[wongjiahau]

Extra notes

This bug arises because ["hello", 12] is inferred as array (string | number)[] instead of tuple [string, number], so, to fix this bug the type inference algorithm must be situational.

[typescript-bot]

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