[ruby/prism] Use `0` for the default valie of `current_param_name`

https://github.com/ruby/prism/commit/896915de24

prism/parser.h

@@ -675,11 +675,7 @@ struct pm_parser {
     /** This flag indicates that we are currently parsing a keyword argument. */
     bool in_keyword_arg;
 
-    /**
-     * The current parameter name id on parsing its default value.
-     * Since this is used for detecting circular references, this is available
-     * only on `PM_CONTEXT_DEFAULT_PARAM`.
-     */
+    /** The current parameter name id on parsing its default value. */
     pm_constant_id_t current_param_name;
 
     /**

prism/prism.c

@@ -4040,8 +4040,6 @@ pm_local_variable_or_write_node_create(pm_parser_t *parser, pm_node_t *target, c
     return node;
 }
 
-static bool context_p(pm_parser_t *parser, pm_context_t context);
-
 /**
  * Allocate a new LocalVariableReadNode node.
  */
@@ -4049,10 +4047,7 @@ static pm_local_variable_read_node_t *
 pm_local_variable_read_node_create(pm_parser_t *parser, const pm_token_t *name, uint32_t depth) {
     pm_constant_id_t name_id = pm_parser_constant_id_token(parser, name);
 
-    if (
-        context_p(parser, PM_CONTEXT_DEFAULT_PARAMS) &&
-        parser->current_param_name == name_id
-    ) {
+    if (parser->current_param_name == name_id) {
         pm_parser_err_token(parser, name, PM_ERR_PARAMETER_CIRCULAR);
     }
 
@@ -16958,6 +16953,7 @@ pm_parser_init(pm_parser_t *parser, const uint8_t *source, size_t size, const pm
         .encoding_changed = false,
         .pattern_matching_newlines = false,
         .in_keyword_arg = false,
+        .current_param_name = 0,
         .semantic_token_seen = false,
         .frozen_string_literal = false,
         .suppress_warnings = false

test/prism/errors_test.rb

@@ -1836,7 +1836,7 @@ module Prism
         proc { |foo = foo| }
         proc { |foo: foo| }
       RUBY
-      message = 'Invalid circular reference in a default parameter'
+      message = 'Parameter default value references itself'
       assert_errors expression(source), source, [
         [message, 14..17],
         [message, 37..40],