Fix () -> (void) being rejected as SyntaxError

`void_allowed` was hardcoded to `false` when parsing a parenthesized
type, causing `(void)` to be rejected even in return type positions
where `void` is valid.

Author: ksss

src/parser.c

@@ -1120,7 +1120,7 @@ static bool parse_simple(rbs_parser_t *parser, rbs_node_t **type, bool void_allo
     switch (parser->current_token.type) {
     case pLPAREN: {
         rbs_node_t *lparen_type;
-        CHECK_PARSE(rbs_parse_type(parser, &lparen_type, false, self_allowed, classish_allowed));
+        CHECK_PARSE(rbs_parse_type(parser, &lparen_type, void_allowed, self_allowed, classish_allowed));
         ADVANCE_ASSERT(parser, pRPAREN);
         *type = lparen_type;
         return true;

test/rbs/method_type_parsing_test.rb

@@ -32,6 +32,12 @@ def test_method_type
     Parser.parse_method_type("(?foo?: Integer, ?bar!: String)->void")
   end
 
+  def test_method_type__void_in_paren
+    Parser.parse_method_type("() -> (void)").tap do |type|
+      assert_instance_of Types::Bases::Void, type.type.return_type
+    end
+  end
+
   def test_method_param
     Parser.parse_method_type("(untyped _, top __, Object _2, String _abc_123)->void").yield_self do |type|
       assert_equal "(untyped _, top __, Object _2, String _abc_123) -> void", type.to_s

test/rbs/type_parsing_test.rb

@@ -925,6 +925,11 @@ def test_parse__void__return_types
     Parser.parse_type("^() { () -> void } -> void").tap do |type|
       assert_instance_of Types::Proc, type
     end
+
+    Parser.parse_type("^() -> (void)").tap do |type|
+      assert_instance_of Types::Proc, type
+      assert_instance_of Types::Bases::Void, type.type.return_type
+    end
   end
 
   def test_parse__void__prohibited