rspec/rspec-support — pull request #85 by myronmarston (2014-06-20 17:43:15+00:00)
Title: Remove `proc_to_lambda`.

There's a very odd ruby bug that makes this unsafe to use, as its
usage mutates the behavior of the block:

https://bugs.ruby-lang.org/issues/9967

Unfortunately, this un-fixes rspec/rspec-mocks#714, but we've got to do it.