One potential difference between the two is that the current behavior allows the `Main` module to import `main` from another module, while the new behavior would fail in that case.

For example, a file that has only a single line:

import SomeOtherModule(main)

This still seems like a fairly unusual corner case (with an obvious work around), so I don't think it matters much, but I thought I'd mention it so that we are aware of it.

On Tue, May 16, 2017 at 7:18 AM, Joachim Breitner <mail@joachim-breitner.de> wrote:

Hi,

a very small proposal to be considered for Haskell':

Currently, the report states

An abbreviated form of module, consisting only of the module body,
is permitted. If this is used, the header is assumed to be ‘module
Main(main) where’.

I propose to change that to

An abbreviated form of module, consisting only of the module body,
is permitted. If this is used, the header is assumed to be ‘module
Main where’.

The rationale is that a main-less main module is still useful, e.g.
when you are working a lot in GHCi, and offload a few extensions to a
separate file. Currently, tools like hdevtools will complain about a
missing main function when editing such a file.

It would also work better with GHC’s -main-is flag, and avoid problems
like the one described in https://ghc.haskell.org/trac/ghc/ticket/13704

I don’t see any downsides. When compiling to a binary, implementations
are still able to detect that a Main module is not imported by any
other module and only the main function is used, and optimize as if
only main were exported.

Greetings,
Joachim

--
Joachim “nomeata” Breitner
mail@joachim-breitner.de • https://www.joachim-breitner.de/
XMPP: nomeata@joachim-breitner.de • OpenPGP-Key: 0xF0FBF51F
Debian Developer: nomeata@debian.org
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