topazproject/topaz — pull request #815 by scooter-dangle (2013-07-30 02:14:22+00:00)
Title: Calculate Proc#arity the same way as Method#arity

`Proc#arity` should return `-(n+1)` where `n` is the number of required arguments.

Relevant to this RubySpec pull request: rubyspec/rubyspec#224

For discussion that resulted in the consensus on arity calculation, see https://bugs.ruby-lang.org/issues/5694#change-28156.