parse-error "Expecting then" "Expecting else" DoAndIfThenElse in indentation

[k-bx]

For this code:

main :: IO ()
main = do
    if True
    then putStrLn "True"

when you press enter after "True" – you get an error:

let: No catch for tag: parse-error, "Expecting then"

[k-bx]

Added a PR with a failing test

[gracjan]

This seems to be an instance of DoAndIfThenElse.

[k-bx]

@gracjan yeah, seems like it. All compilers support it now with no flags needed, so would be nice for haskell-mode to support it, since it feels not right when code compiles, while indentation fails to work.

[gracjan]

The way this extension is defined with this semicolons out of nowhere is super strange. How to make indentation use this syntax will require some ingenuity.

[gracjan]

Actually we have this reported already as #321.