From: ruby-core@...
Date: 2014-11-12T15:23:58+00:00
Subject: [ruby-core:66228] [ruby-trunk - Feature #10499] Eliminate implicit magic in Proc.new and Kernel#proc

Issue #10499 has been updated by Marc-Andre Lafortune.

Category set to core
Assignee set to Yukihiro Matsumoto

I agree.

Deprecate first (2.2?), remove afterwards.

This would also simplify things if and when we want to warn/raise on unused blocks when calling user methods.


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Feature #10499: Eliminate implicit magic in Proc.new and Kernel#proc
https://bugs.ruby-lang.org/issues/10499#change-49915

* 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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