* Remove whitespace generation and rely on default printing
Changes to printing:
* Add newline after last empty SwitchCase
* Add newlines around block comments if they are non-flow comments or contain newlines
* Fix a few more fixtures
* Add variance node type and generate property variance annotations
babel/babylon#161 adds parsing support for property variance
annotations. This PR adds the necessary node type for the new Variance
node and generate support for all the positions where variance can now
appear.
* Variance is no longer a separate node type
This diff also adds tests to class properties and to the
flow-strip-types transform.
* Add test + fix for edge case with variance and class proeprties
This fixes an issue where optional properties would get transformed to
an invalid syntax. The easiest solution was to make all FunctionTypes
get transformed to the arrow syntax (previously everything went the
other way).
This syntax allows you to specify whether a type variable can appear in
a covariant or contravariant position, and is super useful for, say,
Promise.
Right now this is hacked in jankily, but in the next major release we
should stop using Identifier nodes for type parameters.
An interface export is just like a type export. In fact, it's a syntax affordance which makes the following equivalent:
```javascript
interface I_ { ... }
export type I = I_;
```
```javascript
export interface I { ... }
```
See facebook/flow#1145
This has been a feature in Flow for a long time (couldn't easily find a
specific commit adding this). Interfaces are basically undocumented, though, so
it's easy to see how this was missed.
