v0.35.0

Likely to cause new Flow errors:

• Flow now knows that calling addEventListener() with 'click' and 'dblclick' will pass a MouseEvent to the listener. This means you might need to update foo.addEventListener('click', (e) => bar()) to foo.addEventListener('click', (e: MouseEvent) => bar()).

New Features:

• Better error messages in a bunch of situations
• flowtype.org/try now has an AST tab that shows the parsed AST of the example

Notable bug fixes:

• Bindings that come from imports are now treated as const
• Found and fixed a few situations where Flow was emitting redundant errors
• Some if statement refinements were sticking around after the if statement in some situations when they should not have.

Misc:

• Various libdef fixes and improvements
• Various docs fixes and improvements
• If foo has the typed mixed, we now allow foo.bar if you check that foo is not null or undefined.

Parser:

• Better error message if you try to make a class property optional (currently unsupported)
• Dropped support for let statements, which never made it into the spec (thanks @andreypopp)