New Rule: If a type is a record, it should be either opaque or not exported

[elbrujohalcon]

No Exported Record Types

Brief Description

If your module defines a record and it also defines a type for it, that type should not be exported/accessible from the outside.

Should be on by default?

YES

Reasoning

Since the record is defined within the module, nobody from outside the module should know how to build an instance of that record. That means that the type associated with the record should not be public.
It can be an opaque type, so that other modules can pass around record instances but not [de]construct them. Or it can just be not exported so no modules other than the current one have knowledge about the record.

Examples

-module bad.
-record my_rec, {a, b, c}.

-type my_rec() :: #my_rec{}.
-export_type [my_rec/0].

-module good.
-record my_rec, {a, b, c}.

-opaque my_rec() :: #my_rec{}.
-export_type [my_rec/0].

-module also_good.
-record my_rec, {a, b, c}.

-type my_rec() :: #my_rec{}.

[paulo-ferraz-oliveira]

No maps? Or simply tuples instead of records?

[paulo-ferraz-oliveira]

It could even be part of the options: applies_to: [maps, records, tuples] where the default would be records (and/or tuples too).