[ruby-core:99034] [Ruby master Feature#17004] Provide a way for methods to omit their return value

Issue #17004 has been updated by soulcutter (Bradley Schaefer).


jeremyevans0 (Jeremy Evans) wrote in #note-16:
> soulcutter (Bradley Schaefer) wrote in #note-15:
> > Also, how would you test this behavior?
> 
> ```ruby
> # return value not discarded case
> some_method.must_equal :expected_return_value
> check_for.must_equal :some_side_effect
> 
> # return value discarded case
> some_method
> check_for.must_equal :some_side_effect
> ```

That's fair. There's still a warning flag in my head that there's some subtle case where it is trickier to test, but I might be struggling to wrap my head  around all the implications. Given that I can't come up with that example at the moment, I retract that problem-statement.

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Feature #17004: Provide a way for methods to omit their return value
https://bugs.ruby-lang.org/issues/17004#change-86409

* Author: shyouhei (Shyouhei Urabe)
* Status: Open
* Priority: Normal
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In ruby, it often is the case for a method's return value to not be used by its caller.  Even when a method returns something meaningful, its caller is free to ignore it.

Why not provide a way for a method to know if its return value is needed or not?  That adds a room for methods to be optimized, by for instance skipping creation of complex return values.

The following pull request implements `RubyVM.return_value_is_used?` method, which does that: https://github.com/ruby/ruby/pull/3271



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