[ruby-core:66748] [ruby-trunk - Feature #10499] Eliminate implicit magic in Proc.new and Kernel#proc

Issue #10499 has been updated by Charles Nutter.


Adding a deprecation warning would be easy if we can get buy-in from matz.

matz: ball's in your court, I think!

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Feature #10499: Eliminate implicit magic in Proc.new and Kernel#proc
https://bugs.ruby-lang.org/issues/10499#change-50337

* Author: Charles Nutter
* Status: Open
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Category: core
* Target version: Next Major
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Proc.new and Kernel#proc have a little known feature: if called without a block, they capture whatever block was passed to the current method.

I propose that this feature should be removed, finally, since it:

* Doesn't enhance readability (where is this block coming from?)
* Doesn't reflect any other behavior in Ruby
* Can lead to bugs (call either without a block accidentally and you aren't sure what you'll get)

I believe this was an implementation artifact in MRI, since the most recently-pushed block would still be on global stacks, which is where the logic for proc and Proc.new looked for it.

All argument syntaxes now support &block, which I believe is the correct way to clearly, explicitly capture the incoming block into an object.

Thoughts?



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