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Bug #18432
closedcase ... when bug if add a extra comma on the end of condition.
Description
I will describe how this bug happen for me.
- I have code like this at first, it works!
type = 'aaa'
case type
when 'aaa'
x = 100
p x
when 'bbb'
x = 100
p x
end
# => 100
- Because the code in when case 'aaa' or 'bbb', all code same, so, i do some refactor, it still work, like this:
type = 'aaa'
case type
when 'aaa', 'bbb'
x = 100
p x
end
# => 100
- Then, logic is changes, i need split 'aaa' and 'bbb' back to original form, somethings is wrong!
type = 'aaa'
case type
when 'aaa',
x = 100
p x
when 'bbb'
x = 200
p x
end
# => nil
What i expected is raise syntax error, let me find this issue quickly, but, it just ignore silently.
- In fact, it even no syntax error raised when i remove the second when.
type = 'aaa'
case type
when 'aaa',
x = 100
p x
'bbb'
x = 200
p x
# nil
# 200
end
Following is disam ouput for case 3
== disasm: #<ISeq:<main>@1.rb:1 (1,0)-(10,3)> (catch: FALSE)
local table (size: 2, argc: 0 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 2] type@0 [ 1] x@1
0000 putstring "aaa" ( 1)[Li]
0002 setlocal_WC_0 type@0
0004 getlocal_WC_0 type@0 ( 3)[Li]
0006 dup ( 4)
0007 putobject "aaa"
0009 checkmatch 2
0011 branchif 33
0013 dup ( 5)
0014 putobject 100
0016 dup
0017 setlocal_WC_0 x@1
0019 checkmatch 2
0021 branchif 33
0023 dup ( 7)
0024 putobject "bbb"
0026 checkmatch 2
0028 branchif 40
0030 pop ( 3)
0031 putnil
0032 leave ( 9)
0033 pop ( 4)
0034 putself ( 6)[Li]
0035 getlocal_WC_0 x@1
0037 opt_send_without_block <calldata!mid:p, argc:1, FCALL|ARGS_SIMPLE>
0039 leave ( 9)
0040 pop ( 7)
0041 putobject 200 ( 8)[Li]
0043 setlocal_WC_0 x@1
0045 putself ( 9)[Li]
0046 getlocal_WC_0 x@1
0048 opt_send_without_block <calldata!mid:p, argc:1, FCALL|ARGS_SIMPLE>
Updated by mame (Yusuke Endoh) almost 3 years ago
case type
when 'aaa',
x = 100
p x
end
is parsed as
case type
when 'aaa', (x = 100)
p x
end
which is (almost) equivalent to
if 'aaa' === type || ((x = 100) === type)
p x
end
. If 'aaa' === type
evaluates to true, (x = 100)
is not executed. Thus, x
is uninitialized, so it is nil by default.
Updated by zw963 (Wei Zheng) almost 3 years ago
mame (Yusuke Endoh) wrote in #note-1:
case type when 'aaa', x = 100 p x end
is parsed as
case type when 'aaa', (x = 100) p x end
which is (almost) equivalent to
if 'aaa' === type || ((x = 100) === type) p x end
. If
'aaa' === type
evaluates to true,(x = 100)
is not executed. Thus,x
is uninitialized, so it is nil by default.
Yes, i see now, but this behavior is a little oddness, from programming language perspective, this default behavior not good.
e.g. i add a binding.irb, like this, it so strange.
From: 1.rb @ line 7 :
2:
3: case type
4: when 'aaa',
5: x = 100
6: p x
=> 7: binding.irb
8: when 'bbb'
9: x = 200
10: p x
11: end
3.0.3 :001 > x
=> nil
Updated by jeremyevans0 (Jeremy Evans) almost 3 years ago
- Status changed from Open to Rejected
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