Formatter dedents pasted union

[mjbvz]

From @andy-ms on July 11, 2017 22:10

TypeScript Version: nightly (2.5.0-dev.20170707)

Code

type T =
    | number
    | string;

Run "Format Document" and there is no change.
Cut this and paste it back, and it will be dedented to:

type T =
| number
| string;

Copied from original issue: microsoft/TypeScript#17108

[mjbvz]

From @mhegazy on November 20, 2017 23:0

The cut+past issue seems to be VSCode specific. @mjbvz do you have any insights here?

[rebornix]

#36294, #29896, #38833 share the same root cause: empty lines are not handled gracefully. I pushed a fix which makes this specific case work but it may not work for all cases ;)