Bug #2551: case/when matches literal *[1,2,3] but not variable *ary
http://redmine.ruby-lang.org/issues/show/2551

Author: Jeremy Kemper
Status: Open, Priority: High
Category: core, Target version: Ruby 1.8.8
ruby -v: ruby 1.8.8dev (2010-01-01 revision 26212) [i386-darwin10.2.0]

Matching a splat works with a literal but not a variable:

$ irb188
>> case 42; when *[41..43]; true end
=> true
>> a = [41..43]
=> [41..43]
>> case 42; when *a; true end
=> nil

Behaves correctly on 1.9.2dev and 1.8.7:

$ irb192
>> RUBY_DESCRIPTION
=> "ruby 1.9.2dev (2010-01-03 trunk 26233) [x86_64-darwin10.2.0]"
>> case 42; when *[41..43]; true end
=> true
>> a = [41..43]
=> [41..43]
>> case 42; when *a; true end
=> true

This breaks a lot of code, such as the Builder library which escapes all values as '***' on 1.8.8dev.

A test case:

diff --git a/test/ruby/test_case.rb b/test/ruby/test_case.rb
index af925d1..f996ed6 100644
--- a/test/ruby/test_case.rb
+++ b/test/ruby/test_case.rb
@@ -52,5 +52,13 @@ class TestCase < Test::Unit::TestCase
     else
       assert(false)
     end
+
+    range = [41..43]
+    case 42
+    when *range
+      assert(true)
+    else
+      assert(false)
+    end
   end
 end


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