Fix wrong number of arguments in `Array#fetch`; fix
@@ -291,7 +291,7 @@ class Array
# #=> "100 is out of bounds"
#
- def fetch(n=nil, ifnone=NONE, &block)
+ def fetch(n, ifnone=NONE, &block)
warn "block supersedes default value argument" if !n.nil? && ifnone != NONE && block
idx = n
