Add regression test for trivia at the head of tokenlist

tests/input/regression/test_trivia_head.asm

@@ -0,0 +1,5 @@
+; sample program with trivia on the head of the tokenlist
+
+_start:
+    xor rax, rax
+    call exit

tests/main.c

@@ -2,9 +2,11 @@
 
 extern MunitTest ast_tests[];
 extern MunitTest lexer_tests[];
+extern MunitTest regression_tests[];
 
 int main(int argc, char *argv[MUNIT_ARRAY_PARAM(argc + 1)]) {
     MunitSuite suites[] = {
+        {"/regression", regression_tests, nullptr, 1, MUNIT_SUITE_OPTION_NONE},
         {"/ast",        ast_tests,        nullptr, 1, MUNIT_SUITE_OPTION_NONE},
         {"/lexer",      lexer_tests,      nullptr, 1, MUNIT_SUITE_OPTION_NONE},
         {nullptr,       nullptr,          nullptr, 0, MUNIT_SUITE_OPTION_NONE},

tests/regression.c

@@ -0,0 +1,31 @@
+#include "../src/ast.h"
+#include "../src/parser/parser.h"
+#include "munit.h"
+
+MunitResult test_regression_trivia_head(const MunitParameter params[], void *data) {
+    (void)params;
+    (void)data;
+
+    lexer_t *lex = &(lexer_t){};
+    error_t *err = lexer_open(lex, "tests/input/regression/test_trivia_head.asm");
+    munit_assert_null(err);
+
+    tokenlist_t *list;
+    err = tokenlist_alloc(&list);
+    munit_assert_null(err);
+
+    err = tokenlist_fill(list, lex);
+    munit_assert_null(err);
+
+    parse_result_t result = parse(list->head);
+    munit_assert_null(result.err);
+    munit_assert_null(result.next);
+
+    ast_node_free(result.node);
+    tokenlist_free(list);
+}
+
+MunitTest regression_tests[] = {
+    {"/trivia_head", test_regression_trivia_head, nullptr, nullptr, MUNIT_TEST_OPTION_NONE, nullptr},
+    {nullptr,        nullptr,                     nullptr, nullptr, MUNIT_TEST_OPTION_NONE, nullptr}
+};