ieQu1 / typerefl

Use Erlang typespecs in the runtime

Typerefl

This library reifies dialyzer types as ordinary Erlang functions. It enables e.g. validation of terms against dialyzer typespecs in the runtime.

Talk is cheap, show me the code

Simple example using builtin types:

-include_lib("typerefl/include/types.hrl").

main() ->
  %% Define type (in the term Universe!)
  Type = {foo, non_neg_integer(), #{atom() => integer()}},
  %% Valid term:
  ok = typerefl:typecheck(Type, {foo, 3, #{bar => 42}}),
  %% Invalid term:
  {error,"Expected: {foo, non_neg_integer(), #{atom() => integer()}}\nGot: 1\n"} =
    typerefl:typecheck(Type, 1).

Higher kind recursive types are of course supported too:

-include_lib("typerefl/include/types.hrl").

-type stupid_list(A, B) :: {cons, A, stupid_list(A, B)} | B.

-type stupid_list(A) :: stupid_list(A, nil).

%% Any dialyzer type can be reified:
-reflect_type([stupid_list/1]).

main() ->
  ok = typerefl:typecheck(stupid_list(atom()), {cons, foo, nil}),
  {error, _} = typerefl:typecheck(stupid_list(atom()), {cons, 1, nil}).

Maps:

-include_lib("typerefl/include/types.hrl").

-type foo() :: #{ foo := integer()
                , bar := atom()
                , integer() => list()
                }.

-reflect_type([foo/0]).

main() ->
  ok = typerefl:typecheck(foo(), #{foo => 1, bar => foo, 1 => []}).

This library typechecks pretty much anything that dialyzer does, except for functions. In the future it may support arity check.