-main-is flag in {-# OPTIONS #-} pragma not fully supported

[Stephan202]

The -main-is flag is dynamic an may therefore be placed inside the {-# OPTIONS #-} pragma. Version 6.8.3 of runghc respects this flag (that is, runghc works as expected), but this cannot be said of ghc.

Example file T.hs

{-# OPTIONS -main-is T.main #-}

module T where

main :: IO ()
main = putStrLn "Hello world"

Example execution

$ ghc --make -o t T.hs
[1 of 1] Compiling T                ( T.hs, T.o )
Warning: output was redirected with -o, but no output will be generated
because there is no Main module.

Additional notes

This bug is related to ticket #1312, but the difference is that ticket #1312 only addressed runghc, not ghc.

[igloo]

Thanks for the report!

[Stephan202]

This bug is still present in version 6.12.3. I set the type of failure to Incorrect warning at compile-time, though arguably the compiler's output is simply incorrect: it should produce an executable but doesn't.

[dterei]

oops sorry, I only meant to add myself to the cc, not change the failure type.