Summary:
Overall plan to modify Future<T>::then to be r-value qualified and use Future<T>::thenTry or Future<T>::thenValue.
The goal is to disambiguate folly::Future and to improve type and lifetime safety of Future and its methods.
4/n: Codemod:
* rvalue-future<T>.then(callable with operator()(not-a-try)) to rvalue-future<T>.thenValue(callable with operator()(not-a-try)).
* rvalue-future<T>.then(callable with operator()()) to rvalue-future<T>.thenValue(callable with operator()(auto&&)).
* rvalue-future<T>.then(callable with operator()(auto)) to rvalue-future<T>.thenValue(callable with operator()(auto)).
Applied to xplat.
Reviewed By: marshallcline
Differential Revision: D9133114
fbshipit-source-id: 30cc4f0480ca04b3abda54af3aafd9fc4dfdf0e0
092484e255