https://github.com/ruby/ruby/pull/15498/commits/74ea62b99ebbaf68343224ba56e3e21892a4cd0c

Author: Earlopain

src/prism.c

@@ -1180,12 +1180,9 @@ pm_check_value_expression(pm_parser_t *parser, pm_node_t *node) {
                 if (parser->version >= PM_OPTIONS_VERSION_CRUBY_4_0) {
                     pm_node_t *body_part;
                     PM_NODE_LIST_FOREACH(&cast->body, index, body_part) {
-                        switch (PM_NODE_TYPE(body_part)) {
-                            case PM_CASE_VOID_VALUE:
-                                if (void_node == NULL) void_node = body_part;
-                                break;
-                            default: break;
-                        }
+                        if (index == cast->body.size - 1) break;
+                        pm_node_t *vn = pm_check_value_expression(parser, body_part);
+                        if (vn) return vn;
                     }
                 }
 

…errors/singleton_method_for_literals.txt ….3-3.4/singleton_method_for_literals.txttest/prism/errors/singleton_method_for_literals.txt renamed to test/prism/errors/3.3-3.4/singleton_method_for_literals.txt test/prism/errors/singleton_method_for_literals.txt renamed to test/prism/errors/3.3-3.4/singleton_method_for_literals.txt

@@ -0,0 +1,40 @@
+def (1).g; end
+     ^ cannot define singleton method for literals
+def ((a; 1)).foo; end
+         ^ cannot define singleton method for literals
+def ((return; 1)).bar; end
+      ^~~~~~ unexpected void value expression
+              ^ cannot define singleton method for literals
+def (((1))).foo; end
+       ^ cannot define singleton method for literals
+def (__FILE__).foo; end
+     ^~~~~~~~ cannot define singleton method for literals
+def (__ENCODING__).foo; end
+     ^~~~~~~~~~~~ cannot define singleton method for literals
+def (__LINE__).foo; end
+     ^~~~~~~~ cannot define singleton method for literals
+def ("foo").foo; end
+     ^~~~~ cannot define singleton method for literals
+def (3.14).foo; end
+     ^~~~ cannot define singleton method for literals
+def (3.14i).foo; end
+     ^~~~~ cannot define singleton method for literals
+def (:foo).foo; end
+     ^~~~ cannot define singleton method for literals
+def (:'foo').foo; end
+     ^~~~~~ cannot define singleton method for literals
+def (:'f{o}').foo; end
+     ^~~~~~~ cannot define singleton method for literals
+def ('foo').foo; end
+     ^~~~~ cannot define singleton method for literals
+def ("foo").foo; end
+     ^~~~~ cannot define singleton method for literals
+def ("#{fo}o").foo; end
+     ^~~~~~~~ cannot define singleton method for literals
+def (/foo/).foo; end
+     ^~~~~ cannot define singleton method for literals
+def (/f#{oo}/).foo; end
+     ^~~~~~~~ cannot define singleton method for literals
+def ([1]).foo; end
+     ^~~ cannot define singleton method for literals
+