tests: add tests for is_function/2

Test both `is_function/2` guard opcode and BIF.

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

tests/erlang_tests/CMakeLists.txt

@@ -194,6 +194,7 @@ compile_erlang(test_funs8)
 compile_erlang(test_funs9)
 compile_erlang(test_funs10)
 compile_erlang(test_funs11)
+compile_erlang(test_funs12)
 
 compile_erlang(test_make_fun3)
 
@@ -668,6 +669,7 @@ add_custom_target(erlang_test_modules DEPENDS
     test_funs9.beam
     test_funs10.beam
     test_funs11.beam
+    test_funs12.beam
 
     test_make_fun3.beam
 

tests/erlang_tests/test_funs12.erl

@@ -0,0 +1,61 @@
+%
+% This file is part of AtomVM.
+%
+% Copyright 2025 Davide Bettio <davide@uninstall.it>
+%
+% Licensed under the Apache License, Version 2.0 (the "License");
+% you may not use this file except in compliance with the License.
+% You may obtain a copy of the License at
+%
+%    http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+% See the License for the specific language governing permissions and
+% limitations under the License.
+%
+% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+%
+
+-module(test_funs12).
+-export([start/0, check_guard/3, check_bool/3, discard/1, get_fun/0]).
+
+start() ->
+    CheckGuardFun = fun ?MODULE:check_guard/3,
+    SelfFun = fun erlang:self/0,
+    {A, F} = ?MODULE:get_fun(),
+    true = ?MODULE:check_guard(3, CheckGuardFun, 3),
+    false = ?MODULE:check_guard([], CheckGuardFun, []),
+    true = ?MODULE:check_bool(SelfFun, F, 1),
+    false = ?MODULE:check_bool([], {}, 1),
+    ok = expect_error(fun() -> ?MODULE:check_bool({}, [], not_integer) end, error, badarg),
+    ok = expect_error(fun() -> ?MODULE:check_bool(SelfFun, F, not_integer) end, error, badarg),
+    ok = expect_error(fun() -> ?MODULE:check_bool(SelfFun, F, -20) end, error, badarg),
+    1 = ?MODULE:check_guard(A, F, A),
+    ?MODULE:check_guard(0, SelfFun, 0).
+
+check_guard(A, B, A) when A > 1 andalso is_function(B, A) ->
+    discard(B);
+check_guard(A, B, A) when is_function(B, A) ->
+    A;
+check_guard(A, _B, A) when A < 0 ->
+    error;
+check_guard(_A, _B, _A) ->
+    false.
+
+discard(_X) ->
+    true.
+
+check_bool(A, B, C) ->
+    is_function(A, C) or is_function(B, C).
+
+get_fun() ->
+    {1, fun(X) -> X + 1 end}.
+
+expect_error(Fun, A, B) ->
+    try Fun() of
+        Result -> {error, Result}
+    catch
+        A:B -> ok
+    end.

tests/test.c

@@ -233,6 +233,7 @@ struct Test tests[] = {
     TEST_CASE_EXPECTED(test_funs9, 3555),
     TEST_CASE_EXPECTED(test_funs10, 6817),
     TEST_CASE_EXPECTED(test_funs11, 817),
+    TEST_CASE(test_funs12),
     TEST_CASE(test_make_fun3),
     TEST_CASE(fun_call_bif),