Bug #20401: Duplicated when clause warning line number

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

[kddnewton (Kevin Newton)]

When you have a duplicated when clause, you get a warning for it. For example:

case foo
when :bar
when :baz
when :bar
end

you get warning: duplicated `when' clause with line 2 is ignored.

But the when clause that is ignored is the one on line 4, not line 2. It seems like it's warning for the wrong line.

[kddnewton (Kevin Newton)]

On the otherhand, if you have duplicated hash keys you get:

{
  bar: 1,
  baz: 1,
  bar: 1
}

For the warning: warning: key :bar is duplicated and overwritten on line 4. So this seems correct.

[mame (Yusuke Endoh)]

This behavior was discovered and briefly discussed during the previous dev meeting. The actual warning is

test.rb:4: warning: duplicated 'when' clause with line 2 is ignored

According to @nobu (Nobuyoshi Nakada), this reads "The 'when' clause at line 4 duplicates (conflicts) with (a 'when' clause at) line 2. This is ignored."

Anyway I agree that it is too confusing. I think it would be good if they could improve the English.

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[kddnewton (Kevin Newton)]

I've updated the message to say:

'when' clause on line 4 duplicates 'when' clause on line 2 and is ignored

I hope this is okay, I believe it is much more clear. The PR is here: https://github.com/ruby/ruby/pull/10776. @nobu (Nobuyoshi Nakada) or @mame (Yusuke Endoh) could you review?