From: Stefano Mioli <stefano.mioli@...>
Date: 2011-07-17T08:13:55+09:00
Subject: Re: duplicated when clause is ignored

On 7/16/11 11:50 PM, Marc Heiler wrote:

> foobar.rb:156: warning: duplicated when clause is ignored
>
> Is there any way for Ruby to tell me which are duplicated though?

Not that I know of, rb_compile_warning() is invoked from compile.c with 
the line number on which the 'case' statement is.
I agree that it would be a nice feature.

The problem, though, seems to be elsewhere. How many 'when' clauses are 
there in your script? Is it so high to make a manual check too difficult?
If so, that might be a code smell, meaning that you should refactor your 
code.


 From a couple of tests I made, I observed something interesting.

This:

x = 1
case x
when 0
when 1
when 1
end

will cause the warning to appear.

This, on the other hand:

x = 1
case x
when 0
when 1
when 1 + 0
when 1
end

is enough to fool iseq_set_sequence(), making it print out no warnings 
at all, even though we still *do* have a duplicate 'when' clause (let 
alone that there are actually 3 duplicated clauses).

I wonder if I should file a ticket.

-- 
Stefano Mioli