Issue #11519 has been updated by Usaku NAKAMURA.

Backport changed from 2.0.0: WONTFIX, 2.1: REQUIRED, 2.2: REQUIRED to 2.0.0: WONTFIX, 2.1: DONE, 2.2: REQUIRED

ruby_2_1 r51978 merged revision(s) 51820.

----------------------------------------
Bug #11519: "#{nil}" produces string as US-ASCII rather than current encoding
https://bugs.ruby-lang.org/issues/11519#change-54309

* Author: Perry Smith
* Status: Closed
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-darwin14]
* Backport: 2.0.0: WONTFIX, 2.1: DONE, 2.2: REQUIRED
----------------------------------------
~~~ruby
#! /usr/bin/env ruby
# encoding: utf-8

puts "Ruby version: #{RUBY_VERSION}"
puts "__ENCODING__ = #{__ENCODING__}"
puts "hello".encoding
foo = "hello"
puts "#{foo}".encoding
puts "#{"hello"}".encoding
bar = nil
puts "#{bar}".encoding
puts "#{nil}".encoding
puts "#{bar}#{foo}".encoding
~~~

The output for this on all versions of ruby that I have except 1.9.1 is this:

~~~
Ruby version: 2.2.3
__ENCODING__ = UTF-8
UTF-8
UTF-8
UTF-8
US-ASCII
US-ASCII
US-ASCII
~~~

It is the last part that gave me grief.  Rails `content_for` used such a construct so all my content was being converted to US-ASCII and sometimes were error off.

It seems to me the `"#{ ... }"` string should be utf-8 and so anything inserted into it should be converted to utf-8 so `"#{nil}"` should be utf-8 -- not US-ASCII.




-- 
https://bugs.ruby-lang.org/