Bug #12174: Interpolation ignores `to_s` (and `inspect`) when `to_s` is defined to `nil`.

• Status: Rejected
• Assignee: -
• Target version: -
• Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN

[sawa (Tsuyoshi Sawada)]

When to_s is defined to return nil, interpolation prints the original inspection.

class A
  def to_s; end
end

puts "#{A.new}" # => #<A:0x007f4edf19d720>

It even ignores an overwritten inspect definition.

class A
  def to_s; end
  def inspect; "foo" end
end

puts "#{A.new}" # => #<A:0x007f8176c09050>

[sawa (Tsuyoshi Sawada)]

The description was too specific. Whenever to_s is defined to be not a string, the issue arises.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Rejected

Yes, to be interpolated into a string, to_s must return a string.
Non-string object cannot be concatenated to a string.