String indexer is readonly in lib._x_.d.ts

[david-driscoll]

Currently the string indexer is currently set to readonly in lib.d.ts. When trying to swap out characters in a string, you must cast to any to solve. Is this expected behavior, or a side effect of some other issue being solved?

This is not an issue for Array, as it's indexer is mutable.

https://github.com/Microsoft/TypeScript/blob/master/lib/lib.es5.d.ts#L442
https://github.com/Microsoft/TypeScript/blob/master/lib/lib.es6.d.ts#L442
https://github.com/Microsoft/TypeScript/blob/master/lib/lib.d.ts#L442

TypeScript Version: 1.8.0 / nightly (2.0.0-dev.201xxxxx)
2.1.0-dev.20160801
Code

let rangeValue = '1234567890123'
if (rangeValue.length > 1) {
    rangeValue[0] = 'V';
}  

Expected behavior:
Should be able to assign a value to any index of a string;

Actual behavior:
Get compiler error Left-hand side of assignment expression cannot be a constant or a read-only property.

[RyanCavanaugh]

JS strings are immutable. The code you have there doesn't work.

[RyanCavanaugh]

http://stackoverflow.com/questions/1431094/how-do-i-replace-a-character-at-a-particular-index-in-javascript

[david-driscoll]

Yeah I was seeing some strange behavior in chrome, but yeah they're not mutable normally. I'll go back to work. 🐑 Thanks @RyanCavanaugh