Issue #5694 has been updated by akr (Akira Tanaka).

Assignee changed from matz (Yukihiro Matsumoto) to nobu (Nobuyoshi Nakada)

We discussed this issue at a developer meeting.
We have consensus that lambda {...}.arity should behave as Method#arity.

Note that we should not change proc {...}.arity.


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Bug #5694: Proc#arity doesn't take optional arguments into account. 
https://bugs.ruby-lang.org/issues/5694#change-28044

Author: marcandre (Marc-Andre Lafortune)
Status: Assigned
Priority: Normal
Assignee: nobu (Nobuyoshi Nakada)
Category: core
Target version: 
ruby -v: -


Currently:

    ->(foo = 42){}.arity # => 0, should be -1

This is contrary to the documentation and to what we should expect from the equivalent method definition.

Fixed in trunk, requesting backport for the 1.9 line.



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