Re: [ ruby-Bugs-3565 ] Method object used as Object#instance_eval block doesn't work (as expected)

On Pr 2006-02-16 at 03:18 +0900, Yukihiro Matsumoto wrote:

> A method object is tightly bound to its receiver.  Even instance_eval
> cannot rebind the bound receiver of a method object, mostly because
> methods simply just don't work well with objects of other types,
> unlike simple Proc objects written in Ruby.  For example, string
> methods like #split expect their receiver to be strings, and no other
> type.  If rebound is allowed they would just crash.

I see. This is the the answer I was expecting. I was just experimenting 
with the language to understand it better.

> Considering above reason, we have three choices: a) disallow invoking
> instance_eval with a proc made from a method at all.  b) abandon
> receiver rebinding for a proc made from a method.  c) add type checks
> for the receivers in every methods, no matter who implemented.  these
> checks could be source of bugs, and could slow down the interpreter a
> lot.
> 
> I'd rather choose option b.  It's safe, fast, and inconsistency is
> small.  As far as I can imagine, not many people try to rebind the
> receiver of the bound method using instance_eval().

I agree, option b would be the optimum solution. I believe, for
consistency, additionally a warning might be generated and this
limitation should be stated in instance_eval documentation, and maybe in
Method#to_proc documentation too.
Thank you,
Regards.