Feature #10499
Eliminate implicit magic in Proc.new and Kernel#proc
Description
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?
Related issues
History
Updated by marcandre (Marc-Andre Lafortune) about 5 years ago
- Category set to core
- Assignee set to matz (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.
Updated by headius (Charles Nutter) about 5 years ago
Adding a deprecation warning would be easy if we can get buy-in from matz.
matz: ball's in your court, I think!
Updated by k0kubun (Takashi Kokubun) 7 months ago
- Copied to Feature #15554: warn/error passing a block to a method which never use a block added