Incorrect type inference for array rest assignment and inability to add annotation

TypeScript Version: 2.7.1-insiders.20180127

Search Terms: array destructuring rest assignment

Code

// A *self-contained* demonstration of the problem follows...
// Test this by running `tsc` on the command-line, rather than through another build tool such as Gulp, Webpack, etc.
const [stringA, ...numbers] = ['string', 1, 2];
// const [stringA, ...numbers] = <[string, number, number]>['string', 1, 2];
// const [stringA, ...numbers]: [string, number[]] = ['string', 1, 2];
// const [stringA, ...numbers]: [string, [number, number]] = ['string', 1, 2];

Expected behavior: Expect numbers to be of type number[] rather than (string | number)[]. TS also does not allow annotating as a tuple

Actual behavior: const numbers: (string | number)[]

Playground Link: http://www.typescriptlang.org/play/index.html#src=const [stringA%2C ...numbers] %3D [‘string’%2C 1%2C 2]%3B %2F%2F const [stringA%2C ...numbers] %3D <[string%2C number%2C number]>[‘string’%2C 1%2C 2]%3B %2F%2F const [stringA%2C ...numbers]%3A [string%2C number[]] %3D [‘string’%2C 1%2C 2]%3B %2F%2F const [stringA%2C ...numbers]%3A [string%2C [number%2C number]] %3D [‘string’%2C 1%2C 2]%3B

Related Issues:

[mhegazy]

The right type should be const [stringA, ...numbers]: [string, number, number]. and numbers should be inferred correctly. that is a bug we should fix.

[ajafff]

The issue in the opening post is fixed in typescript@next, maybe even 3.0.0-rc. numbers is now of type number[].