[ruby/prism] Check circular references in default values of params

Fix https://github.com/ruby/prism/pull/1637

https://github.com/ruby/prism/commit/0172d69cba

1 files changed, 16 insertions, 0 deletions

diff --git a/test/prism/errors_test.rb b/test/prism/errors_test.rb
index bcc9629622..9c96725463 100644
--- a/test/prism/errors_test.rb
+++ b/test/prism/errors_test.rb
@@ -1829,6 +1829,22 @@ module Prism
       ]
     end
 
+    def test_circular_param
+      source = <<~RUBY
+        def foo(bar = bar) = 42
+        def foo(bar: bar) = 42
+        proc { |foo = foo| }
+        proc { |foo: foo| }
+      RUBY
+      message = 'Invalid circular reference in a default parameter'
+      assert_errors expression(source), source, [
+        [message, 14..17],
+        [message, 37..40],
+        [message, 61..64],
+        [message, 81..84],
+      ], compare_ripper: false # Ripper does not check 'circular reference'.
+    end
+
     private
 
     def assert_errors(expected, source, errors, compare_ripper: RUBY_ENGINE == "ruby")