Shouldn't empty if .. do ..else blocks give a compilation error instead ?

[Mário Guimarães]

Hello,

I just observed the following cases

iex(3)> if true do
...(3)> else
...(3)> :ok
...(3)> end
nil
iex(4)> if false do
...(4)> :ok
...(4)> else
...(4)> end
nil
iex(5)> if :anything do
...(5)> else
...(5)> end
nil
iex(6)>

Should't they give a compilation error instead due to the empty blocks?

Not only these cases are somewhat harder to read, but it seems that something is missing ...

Thanks

[Andrea Leopardi]

It can't error out on compilation because it would be a breaking change. However, personally I'm not against a compilation warning here, but there's a chance we decided to not emit that for a reason that I can't recall right now 😅

Andrea

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[Mário Guimarães]

Ok, a warning is enough then, in case you cannot remember of a reason to not emit the warning :-)

quarta-feira, 24 de Junho de 2020 às 16:16:12 UTC+1, Andrea Leopardi escreveu:

It can't error out on compilation because it would be a breaking change. However, personally I'm not against a compilation warning here, but there's a chance we decided to not emit that for a reason that I can't recall right now 😅

Andrea

On Wed, 24 Jun 2020 at 13:19, Mário Guimarães <mario.lui...@gmail.com> wrote:

Hello,

I just observed the following cases

iex(3)> if true do
...(3)> else
...(3)> :ok
...(3)> end
nil
iex(4)> if false do
...(4)> :ok
...(4)> else
...(4)> end
nil
iex(5)> if :anything do
...(5)> else
...(5)> end
nil
iex(6)>

Should't they give a compilation error instead due to the empty blocks?

Not only these cases are somewhat harder to read, but it seems that something is missing ...

Thanks

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[Alessio 'Blaster' Biancalana]

Hi!

A warning would be great so one could watch on them using `mix compile --warnings-as-errors` :-)

Alessio

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[José Valim]

There are constructs that rely on this. For example, if you want to have a receive without clauses, only with an after, you would do:

receive do

after 30_000 -> IO.puts "waited 30s"

end

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[Alessio 'Blaster' Biancalana]

Hm, looks legit. Thanks for the explanation!

Alessio

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