rspec/rspec-expectations — comment on commit f4efada6c86b840802a18e3de12ea68279f9030f
File: lib/rspec/matchers/matcher.rb line 38
By dchelimsky:

It was a convenience in order to not differentiate between user ivars and internal ivars that need to be reset (but present) between invocations. I'll change it so it resets the internally resettable ivars but removes the user ivars.