From: "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
Date: 2012-12-11T01:44:21+09:00
Subject: [ruby-core:50739] [ruby-trunk - Bug #7539] Misleading error message "can't convert nil into string"


Issue #7539 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


kosaki (Motohiro KOSAKI) wrote:
> I support "can't append nil to string" error.

I'd prefer a more descriptive message like:

"can't append nil to string (object doesn't respond to `to_str`)"

This way someone would know that this would work:

> nil.class.module_eval{alias to_str to_s}; '' + nil
----------------------------------------
Bug #7539: Misleading error message "can't convert nil into string"
https://bugs.ruby-lang.org/issues/7539#change-34591

Author: connec (Chris Connelly)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 1.9.3
ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux]


When trying to call `String#+` with `nil` as an argument, you get the error "can't convert nil into String", which does not make sense (in fact seeming blatantly false) as `nil.to_s`, `String(nil)` etc. all return `''` without errors.

Ideally, this method should use `to_s` to convert the argument, or else report an error along the lines of "can't append nil to string".

Minimal test case:



Actual:
    > '' + nil
    TypeError: can't convert nil into String

Expected:
    > '' + nil
    ''



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