From: Doug Glidden <41mortimer@...>
Date: 2008-08-28T00:28:39+09:00
Subject: Re: assert_raise question

Brian Candler wrote:
>> def test_raise
>>   assert_raise ArgumentError {raise ArgumentError.new("basic argument  issue")}
>> end
>> 
>> Now there's suddenly an Exception: undefined method 'ArgumentError'... 
>> I was more than a little surprised to discover that the parens make a 
>> difference here?  Can anyone explain to me _why_ there's a difference?
> 
> I believe that x y z is parsed as x(y(z)):
> 
>   irb(main):013:0> puts ArgumentError
>   ArgumentError
>   => nil
>   irb(main):014:0> puts ArgumentError 123
>   (irb):14: warning: parenthesize argument(s) for future version
>   NoMethodError: undefined method `ArgumentError' for main:Object
>           from (irb):14
>           from :0
>   irb(main):015:0> puts ArgumentError(123)
>   NoMethodError: undefined method `ArgumentError' for main:Object
>           from (irb):15
>           from :0
>   irb(main):016:0>
> 
> and x y {block} is parsed as x(y() {block}), i.e. y is forced to be a 
> method
> call as that's the only meaningful thing next to a block.
> 
[snip]

Well, now that you explained it, it makes perfect sense!  Thanks.

I guess in the future I'll double-check a little more carefully that my 
code is doing what I expect when I leave out parens.

Doug
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