Issue #7539 has been updated by drbrain (Eric Hodel).


I am worried about implying that the user should add to_str, to_ary, etc. to fix this problem.  Rarely is implementing these methods appropriate since they are used for objects that are intended to behave exactly as a String, Array, etc.

An error message that omitted mention of these methods can help prevent users from accidentally shooting themselves in the foot.
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Bug #7539: Misleading error message "can't convert nil into string"
https://bugs.ruby-lang.org/issues/7539#change-34599

Author: connec (Chris Connelly)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: next minor
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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