behaviour won't work on a module transformed by pmod_pt

[Tatsuya Kawano]

Related to: rabbitmq/erlando#12 (comment)

It seems a module can't have both -behaviour(..) and -compile({parse_transform, pmod_pt}) at the same time. I think the reason is behaviour tries to validate callback functions after pmot_pt is applied(?)

state_t.erl

-module(state_t, [InnerMonad]).
-compile({parse_transform, do}).
-compile({parse_transform, pmod_pt}).

-behaviour(monad).
-export(['>>='/2, return/1, fail/1]).
...

monad.erl

behaviour_info(callbacks) ->
    [{'>>=',  2},
     {return, 1},
     {fail,   1}];

state_t module doesn't compile:

src/state_t.erl:21: undefined callback function '>>='/2 (behaviour 'monad')
src/state_t.erl:21: undefined callback function fail/1 (behaviour 'monad')
src/state_t.erl:21: undefined callback function return/1 (behaviour 'monad')

If I remove -behaviour(monad), it compiles. Note that each function has an extra parameter (e.g. '>>='/3, not '>>='/2)

Erlang R16B (erts-5.10.1) [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V5.10.1  (abort with ^G)
...
3> state_t:module_info().
[{exports,[{'>>=',3},
           {return,2},
           {fail,2},
           {get,1},
           {put,2},
           {eval,3},
           {exec,3},
           {run,3},
           {modify,2},
           {modify_and_return,2},
           {lift,2},
           {new,1},
           {instance,1},
           {module_info,0},
           {module_info,1}]},

[Carlos Marin]

Noticed the same issue.

[Richard Carlsson]

The problem is not with the parse transform itself, but that the behaviour callback check in the compiler doesn't understand the parameterized module, whose actual functions have an additional parameter. And since the support for parameterized modules has been dropped from the compiler, there is no way this can be added now. In short, you can't combine behaviour declarations and parameterized modules.

[Carlos Marin]

Understood, thanks for clarifying.