Debug support on for guards?

[Henning Diedrich]

Hi folks,

is there a way to add detail to a function_clause error messages? Be it 
guards or patterns that don't match?

On a crash, I would like to clarify what guard failed, or even warn the 
programmer that this guard exists when it may not be intuitive.

1

This is written, I believe, as it should:

milli_epoch({Mega, Sec, Micro}) when
    is_integer(Mega), is_integer(Sec), is_integer(Micro),
    Mega >= 0, Sec >= 0, Micro >= 0 ->
  
    Mega * ?BILLION + Sec * 1000 + trunc(Micro / 1000).

2

This fails the way I would like it to, giving "negative_input" as reason.

But it is written wrong for two (2) counts I believe (I am NOT trying to 
sneak in a point about ifs):

milli_epoch({Mega, Sec, Micro}) when is_integer(Mega), is_integer(Sec), 
is_integer(Micro) ->

    if (Mega >= 0), (Sec >= 0), (Micro >= 0) -> ok;
    true -> throw(negative_input) end,
   
    Mega * ?BILLION + Sec * 1000 + trunc(Micro / 1000).

Thank you very much for taking a look,

Henning