Can't use with* as an input marshaller

[RyanGlScott]

I'm trying to make a function hook that marshals a Storable instance as input. To that end, I want to use the with function (which, according to the c2hs docs, is a default marshaller). I'm using the following code snippets:

-- WithC2hsBug.chs
{-# LANGUAGE EmptyDataDecls, ForeignFunctionInterface #-}
module WithC2hsBug where

import Control.Applicative

import Foreign.C.Types
import Foreign.Marshal.Utils
import Foreign.Storable

#include "with_c2hs_bug.h"

data Foo
data Bar = Bar Int Int

instance Storable Bar where
    sizeOf _ = {#sizeof bar_t #}
    alignment _ = {#alignof bar_t #}
    peek p = Bar
      <$> (fromIntegral <$> {#get bar_t.y #} p)
      <*> (fromIntegral <$> {#get bar_t.z #} p)
    poke p (Bar y z) =
         ({#set bar_t.y #} p $ fromIntegral y)
      *> ({#set bar_t.z #} p $ fromIntegral z)

{#pointer *foo_t as FooPtr -> Foo #}
{#pointer *bar_t as BarPtr -> Bar #}

{#fun unsafe mutate_foo as mutateFoo
  { `FooPtr'
  , with* `Bar'
  } -> `()' #}

// with_c2hs_bug.h
#ifndef WITH_C2HS_BUG_H
#define WITH_C2HS_BUG_H

typedef struct {
    int y;
    int z;
} bar_t;

typedef struct {
    int x;
    bar_t bar;
} foo_t;

void mutate_foo(foo_t *foo, bar_t *bar);

#endif

// with_c2hs_bug.c
#include "with_c2hs_bug.h"

void mutate_foo(foo_t *foo, bar_t *bar) {
    foo->bar = *bar;
}

However, running c2hs WithC2hsBug.chs results in the error:

c2hs: CHS module contains errors:

WithC2hsBug.chs:30: (column 5) [ERROR]  >>> Syntax error!
  The phrase `with' is not allowed here.

A simple workaround is to make a synonym for with:

import Foreign.Ptr

with' :: Storable a => a -> (Ptr a -> IO b) -> IO b
with' = with

{#fun unsafe mutate_foo as mutateFoo
  { `FooPtr'
  , with'* `Bar'
  } -> `()' #}

Then everything works as expected.

[ian-ross]

That's odd, and clearly a bug. Not sure what's happening there, but I'll investigate.

[ian-ross]

@RyanGlScott Heh. This was kind of silly. The keyword with is a reserved identifier in the CHS syntax (used for defining aliases on enum hooks) so it doesn't get passed through as a normal identifier in this case. I've changed things so that with gets treated specially so that it can appear both an input marshaller identifier and a keyword.