Let's say we have this module:
defmodule MyModule do
> defguard is_some_complex_item(item) when is_struct(item) or is_atom(item)
>
> def id(%{a: a, b: b} = item) when is_some_complex_item(a) and
> is_some_complex_item(b) do
> item
> end
> end
>
then invoking MyModule.id(1) produces the following error:
** (FunctionClauseError) no function clause matching in MyModule.id/1
>
> The following arguments were given to MyModule.id/1:
>
> # 1
> 1
>
> Attempted function clauses (showing 1 out of 1):
>
> def id(%{a: a, b: b} = item) when (is_map(a) and
> is_map_key(:__struct__, a) and is_atom(map_get(:__struct__, a)) or
> is_atom(a)) and (is_map(b) and is_map_key(:__struct__, b) and
> is_atom(map_get(:__struct__, b)) or is_atom(b))
>
The issue here is that internal implementation of my custom guard and even
built-in is_struct is shown.
It is not easy to debug this kind of messages. My expectation is to see not
expanded macro in guards.
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