Issue #9593 has been updated by Nobuyoshi Nakada. Yes, it's a very old bug. Optional arguments have same semantics as assignments. ---------------------------------------- Bug #9593: Keyword arguments default argument assignment behaviour not consistent with optional argument https://bugs.ruby-lang.org/issues/9593#change-45765 * Author: Jack Chen * Status: Closed * Priority: Normal * Assignee: Yukihiro Matsumoto * Category: syntax * Target version: current: 2.2.0 * ruby -v: 2.1.1 * Backport: 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED ---------------------------------------- Given the following code: def var 100 end def foo(var: var + 1) puts "var: #{var.inspect}" end def bar(var = var + 1) puts "var: #{var.inspect}" end foo(var: 1) foo rescue p $! bar(1) bar Ruby 2.0.0: var: 1 var: 101 var: 1 var: 101 Ruby 2.1.1: var: 1 #<NoMethodError: undefined method `+' for nil:NilClass> var: 1 var: 101 What appears to be happening is that since 2.1.1, the keyword argument defines `var` as a variable before evaluating the default argument. Personally, I prefer 2.0.0 behaviour, but the way 2.1.1 handles default arguments in non keyword arguments is inconsistent. -- http://bugs.ruby-lang.org/