rspec/rspec-expectations — comment on commit d3e53109d36d1fef17b70e26e5b2adeeaf3aa078
File:  line 0
By dchelimsky:

Agreed that breaking changes in minor releases is a no-no, but `Matcher.new` was ever intended to be a public API. This is where versioning gets a bit gray until we're officially SemVer compliant (which we're not yet - we still need to formalize the distinction between public API and stuff that happens to be there).

My guess is you're in a small minority of people who use it and the risk is low, so I'm not really worried about it being a breaking change. If there's an easy way to support both, I'm OK with that, but it's not high priority for me.