Bug #13237: Behavior for #dup and #clone on Rational/Complex/BigDecimal differs from Integer/Float

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.4.0p0 (2016-12-24 revision 57164) [x86_64-linux]
• Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN

[stomar (Marcus Stollsteimer)]

Since the implementation of feature #12979, #dup and #clone on Integer and Float do not raise a TypeError anymore, and silently return self. Rational and Complex still raise an exception.

I'm not sure whether this inconsistent behavior is intended or only an oversight. I guess all Numeric classes should behave in a similar way?

Additionally, what is the intention regarding the returned object for non-immediate numeric values, should they return self or a new object?
At the time being, BigDecimal (which already did allow #dup/#clone before the change) returns a new object, while Bignum integers return self.

Current behavior:

RUBY_VERSION  # => "2.4.0"

1.dup      # => 1
1.clone    # => 1
1.5.dup    # => 1.5
1.5.clone  # => 1.5

Rational(1).dup    rescue $!  # => #<TypeError: can't copy Rational>
Rational(1).clone  rescue $!  # => #<TypeError: can't copy Rational>
Complex(1).dup     rescue $!  # => #<TypeError: can't copy Complex>
Complex(1).clone   rescue $!  # => #<TypeError: can't copy Complex>

require "bigdecimal"
BigDecimal(1).dup    # => 0.1e1
BigDecimal(1).clone  # => 0.1e1

d = (1<<64)
[d.object_id, d.dup.object_id, d.clone.object_id]  # => [5134140, 5134140, 5134140]

d = BigDecimal(1)
[d.object_id, d.dup.object_id, d.clone.object_id]  # => [5133040, 5132900, 5132840]

Old behavior:

RUBY_VERSION  # => "2.3.3"

1.dup      rescue $!  # => #<TypeError: can't dup Fixnum>
1.clone    rescue $!  # => #<TypeError: can't clone Fixnum>
1.5.dup    rescue $!  # => #<TypeError: can't dup Float>
1.5.clone  rescue $!  # => #<TypeError: can't clone Float>

Rational(1).dup    rescue $!  # => #<TypeError: can't copy Rational>
Rational(1).clone  rescue $!  # => #<TypeError: can't copy Rational>
Complex(1).dup     rescue $!  # => #<TypeError: can't copy Complex>
Complex(1).clone   rescue $!  # => #<TypeError: can't copy Complex>

require "bigdecimal"
BigDecimal(1).dup    # => #<BigDecimal:101e270,'0.1E1',9(27)>
BigDecimal(1).clone  # => #<BigDecimal:101dfa0,'0.1E1',9(27)>

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset r57682.

---

numeric.c: Numeric#clone and #dup

• numeric.c (num_clone, num_dup): no longer raises TypeError,
  returns the receiver instead as well as Integer and Float.
  [ruby-core:79636] [Bug #13237]

• object.c (rb_immutable_obj_clone): immutable object clone with
  freeze optional keyword argument.

[matsuda (Akira Matsuda)]

Will this be backported to 2.4? (IOW is this 2.4.0 bug or 2.5 new feature?)

[nobu (Nobuyoshi Nakada)]

• Has duplicate Feature #13985: Avoid exception for #dup/#clone on Rational and Complex added