Summary:
Primitive types are not annotated. Because of that, we used to implicitly derive
`DeclaredNonnull` type for them. This worked fine, but this leads to errors in Strict mode, which does
not believe DeclaredNonnull type.
Now lets offifically teach nullsafe that primitive types are
non-nullable.
Reviewed By: jvillard
Differential Revision: D18114623
fbshipit-source-id: 227217931