Bug #16406: `(lambda_proc << normal_proc).lambda?` should return false

• Status: Closed
• Assignee: alanwu (Alan Wu)
• Target version: 3.0
• ruby -v: ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-linux]
• Backport: 2.5: DONTNEED, 2.6: REQUIRED, 2.7: DONE
• Tags: core

[alanwu (Alan Wu)]

Consider:

plus = proc { |a, b| a + b }
mult_two = ->(x) { x * 2 }
composed = mult_two << plus
p [composed. lambda?, composed.call([1, 2])]

I think this ought to print [false, 6] instead of [true, 6], as the call composed.call([1, 2]) is clearly not using lambda semantics.
Since composed = f << g calls g first, I think it makes sense to report #lambda? base on whether g has lambda semantics.
I have a pull request at https://github.com/ruby/ruby/pull/2729 to make this change.

[alanwu (Alan Wu)]

• Subject changed from `(lambda_proc << normal_proc).lambda?` returns true to `(lambda_proc << normal_proc).lambda?` should return false

[ko1 (Koichi Sasada)]

It was discussed and Matz approved to fix it after Ruby 2.7 release.

[nobu (Nobuyoshi Nakada)]

• Target version set to 36

[nobu (Nobuyoshi Nakada)]

• Backport changed from 2.5: UNKNOWN, 2.6: UNKNOWN to 2.5: DONTNEED, 2.6: REQUIRED, 2.7: REQUIRED

[alanwu (Alan Wu)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Assigned
• Assignee set to alanwu (Alan Wu)

[alanwu (Alan Wu)]

Should be addressed by https://git.ruby-lang.org/ruby.git/commit/?id=99c7b0b7ea789643bef60085ab59e4b62011ef8b

[alanwu (Alan Wu)]

• Status changed from Assigned to Closed

Applied in changeset git|3264a00958f56e1ba75a95c93e59fc9cccf323e8.

---

Fix Proc#<< spec

[Bug #16406]

[naruse (Yui NARUSE)]

• Backport changed from 2.5: DONTNEED, 2.6: REQUIRED, 2.7: REQUIRED to 2.5: DONTNEED, 2.6: REQUIRED, 2.7: DONE

ruby_2_7 52bb32d6b71365cb24273de3eed5a712206815f3 [Backport #16406].

[hsbt (Hiroshi SHIBATA)]

• Target version changed from 36 to 3.0