Issue with maybe expr #55
Description
This simplified code:
-module(t).
-feature(maybe_expr, enable).
-export([mult2/1]).
-spec mult2(string()) -> {ok, string()} | {error, bad_int}.
mult2(Str) ->
maybe
{ok, Int} ?= convert_to_int(Str),
{ok, integer_to_list(Int*2)}
end.
-spec convert_to_int(string()) -> {ok, integer()} | {error, bad_int}.
convert_to_int(Str) ->
try list_to_integer(Str) of Int ->
{ok, Int}
catch _:_ -> {error, bad_int}
end.leads to issue:
error: incompatible_types
┌─ src/t.erl:9:22
│
9 │ {ok, Int} ?= convert_to_int(Str),
│ ^^^^^^^^^^^^^^^^^^^
│ │
│ convert_to_int(Str).
Expression has type: {'ok', number()} | {'error', 'bad_int'}
Context expected type: {'ok', string()} | {'error', 'bad_int'}
See https://fb.me/eqwalizer_errors#incompatible_types
│
{'ok', number()} | {'error', 'bad_int'} is not compatible with {'ok', string()} | {'error', 'bad_int'}
because
{'ok', number()} is not compatible with {'ok', string()} | {'error', 'bad_int'}
because
at tuple index 2:
{'ok', number()} is not compatible with {'ok', string()}
because
number() is not compatible with string()
Everything works well If i replace it with equivalent case expression:
-spec mult2(string()) -> {ok, string()} | {error, bad_int}.
mult2(Str) ->
case convert_to_int(Str) of
{ok, Int} ->
{ok, integer_to_list(Int*2)};
Other ->
Other
end.