From e21a444e1cef72b33b80fc07cdb796a95c1a6bb0 Mon Sep 17 00:00:00 2001
From: Sampo Kuokkanen <sampo.kuokkanen@gmail.com>
Date: Fri, 22 May 2026 12:04:36 +0900
Subject: [PATCH] Add specs for defined? on protected methods (MRI Bug #22076)

Covers protected methods accessed via subclass receiver, base-class receiver, and a shared included module. The module case is guarded by ruby_bug "#22076" until 4.1. MRI's defined? returned nil when the call would have succeeded; fix is in master with backports REQUIRED for 3.3, 3.4, 4.0.
---
 language/defined_spec.rb     | 16 ++++++++++++++++
 language/fixtures/defined.rb | 27 +++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/language/defined_spec.rb b/language/defined_spec.rb
index 3fd611d09e..6846179a7c 100644
--- a/language/defined_spec.rb
+++ b/language/defined_spec.rb
@@ -211,6 +211,22 @@
       }.should complain(/warning: possibly useless use of defined\? in void context/, verbose: true)
     end
   end
+
+  describe "for a protected method" do
+    it "returns 'method' when the receiver is a subclass instance" do
+      DefinedSpecs::ProtectedBase.new.defined_on(DefinedSpecs::ProtectedSubclass.new).should == "method"
+    end
+
+    it "returns 'method' when the receiver is the base class instance" do
+      DefinedSpecs::ProtectedSubclass.new.defined_on(DefinedSpecs::ProtectedBase.new).should == "method"
+    end
+
+    ruby_bug "#22076", ""..."4.1" do
+      it "returns 'method' when the receiver is a sibling class instance via a shared included module" do
+        DefinedSpecs::ProtectedIncluderA.new.defined_on(DefinedSpecs::ProtectedIncluderB.new).should == "method"
+      end
+    end
+  end
 end
 
 describe "The defined? keyword for an expression" do
diff --git a/language/fixtures/defined.rb b/language/fixtures/defined.rb
index 3761cfa5bd..15bd7c50cf 100644
--- a/language/fixtures/defined.rb
+++ b/language/fixtures/defined.rb
@@ -299,6 +299,33 @@ def method_no_args
       super
     end
   end
+
+  class ProtectedBase
+    def m; end
+    protected :m
+    def defined_on(o)
+      defined?(o.m)
+    end
+  end
+
+  class ProtectedSubclass < ProtectedBase
+  end
+
+  module ProtectedInModule
+    def m; end
+    protected :m
+    def defined_on(o)
+      defined?(o.m)
+    end
+  end
+
+  class ProtectedIncluderA
+    include ProtectedInModule
+  end
+
+  class ProtectedIncluderB
+    include ProtectedInModule
+  end
 end
 
 class Object