Hi,

In message "Bug? String literal %s{#{a}} cause irb to abort"
    on 04/07/17, Alexey Verkhovsky <alex / verk.info> writes:

|irb(main):002:0> s = %s{#{aaa}}
|/usr/local/lib/ruby/1.9/irb/ruby-token.rb:101:in `Token': undefined
|method `ancestors' for nil:NilClass (NoMethodError)
|        from /usr/local/lib/ruby/1.9/irb/ruby-lex.rb:995:in
|`identify_string'
|        from /usr/local/lib/ruby/1.9/irb/ruby-lex.rb:914:in
|`identify_quotation'

It's a bug in irb.  Thank you for the report.

							matz.