[ruby-core:90118] [Ruby trunk Feature#15352] Mandatory block parameters

[sawadatsuyoshi@gmail.com]

Issue #15352 has been updated by sawa (Tsuyoshi Sawada).


I don't find this feature useful. If you wanted to raise an error when no block is given, all you have to do is call `yield` within the method body, which will not be an extra code if you are going to use the block somewhere in the method body.

```ruby
def foo
  yield
end

foo
#  >> `foo': no block given (yield) (LocalJumpError)
```

And in case you want to return an error with a different message, then that is when you want to implement your custom validation clause in your code like the ones found in the examples that you have searched.

----------------------------------------
Feature #15352: Mandatory block parameters
https://bugs.ruby-lang.org/issues/15352#change-75239

* Author: gfx (Goro FUJI)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
There are too many block parameter assertions (it's kind of idioms: [`raise NoBlockGiven unless glock_given?`](https://github.com/search?q=raise+NoBlockGiven+unless+block_given&type=Code)).

It's very useful if there's a syntax to declare mandatory block parameters, such as:

```ruby
def foo(&!block)
  block.call
end

foo() # raises ArgumentError "in `foo`: no block given"

```





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