Suggest next when trying to break from captured block

[wooster0]

When doing this:

def method(&block)
  block.call
end

method do
  break
end

then you get Error in line 6: can't break from captured block.
Now this makes the error message suggest next because when using break in a captured block you most likely tried to escape from the captured block and next makes that possible.
Also when you instead try to return from a captured block, it gives you a helpful error message: Error in line 6: can't return from captured block, use next so why not suggest next in case of break too?

This also downcases next's and break's error message just like all the other error messages.

[straight-shoota]

In general, this is probably a good feature. But I'm not sure if "use next" is the best advice. It's not always as simple as that, because next and break/return have different semantics. If the block is called multiple times, next might not give you what you want. So I think it should be a more relaxed suggestion.

[asterite]

@straight-shoota Right on! I was thinking about did you mean 'next'? But that doesn't give much info either.

In general, I think we should improve all of our error messages to look a bit more like Elm, where they take a lot of time to explain what went wrong and suggestions with their explanations.

[wooster0]

What about sometimes linking to the docs?

can't break from captured block.
If you want to exit the captured block, use `next`, however `next` will have behave differently when used in a block or a loop inside of the captured block.
For more information see https://crystal-lang.org/reference/syntax_and_semantics/next.html.

[Sija]

Actually, why it's not possible to use break in captured blocks?

[asterite]

@Sija break in non-captured blocks means "exit the enclosing method". For a capture block it can't work.

def capture(&block)
  block
end

def foo
  # This break looks like it will exit foo, but that can't happen
  block = capture { break }
  puts 1
  block
end

block = foo
block.call

[wooster0]

I hope this is clear enough now. I don't think it needs to be as long as I proposed. In the end it might rather confuse the user.

[straight-shoota]

Indeed, that is way to long and too much detail. A simple "Maybe you can use next instead?`" would suffice.

[Sija]

@asterite Now it makes sense, thanks for explanation!

[sdogruyol]

Thank you @r00ster91 👍