Bug #13222: Array#sum inconsistency when init value is non-numeric

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.5.0dev (2017-02-17 trunk 57644) [x86_64-darwin15]
• Backport: 2.2: DONTNEED, 2.3: DONTNEED, 2.4: DONE

[matsuda (Akira Matsuda)]

Since Array#sum skips calling plus for 0 https://github.com/ruby/ruby/blob/c85a58d/array.c#L5831-L5832, it doesn't raise when the receiver array consists of 0 only, even when the "init" value is non-numeric.

% ruby -e "p [1].sum('a')"
-e:1:in `sum': String can't be coerced into Integer (TypeError)

% ruby -e "p [0].sum('a')"
"a"

% ruby -e "p [0, 0, 0].sum('a')"
"a"

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset r57651.

---

array.c: check if numeric

• array.c (finish_exact_sum): add 0 and the initial value to check
  if the latter is numeric. [ruby-core:79572] [Bug #13222]

[mtsmfm (Fumiaki Matsushima)]

I confirmed this behavior appears not only 2.5.0dev but also 2.4.x.

$ docker run ruby:2.4.1 ruby -e "p [0].sum('a')"
"a"

$ docker run ruby:2.4.0 ruby -e "p [0].sum('a')"
"a"

Should we backport the patch?

[usa (Usaku NAKAMURA)]

• Backport changed from 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN to 2.2: DONTNEED, 2.3: DONTNEED, 2.4: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.2: DONTNEED, 2.3: DONTNEED, 2.4: REQUIRED to 2.2: DONTNEED, 2.3: DONTNEED, 2.4: DONE

ruby_2_4 r61361 merged revision(s) 57649,57651.