Fix SimpleDelegator respond_to? regression

In 2.6, SimpleDelegator would always use the target `respond_to?`

In 2.7.0 it doesn't if the target does not inherit from Object.

This breaks compatibility for delegated objects that inherit
from BasicObject and redefine `respond_to?`. [Bug #16606]

(cherry picked from commit f2552216d43040cd42bbb9fd484eab6c70856fe6)

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/delegate.rb b/lib/delegate.rb
index 63657646e1..1587c7e3bb 100644
--- a/lib/delegate.rb
+++ b/lib/delegate.rb
@@ -103,13 +103,20 @@ class Delegator < BasicObject
     r
   end
 
+  KERNEL_RESPOND_TO = ::Kernel.instance_method(:respond_to?)
+  private_constant :KERNEL_RESPOND_TO
+
   # Handle BasicObject instances
   private def target_respond_to?(target, m, include_private)
     case target
     when Object
       target.respond_to?(m, include_private)
     else
-      ::Kernel.instance_method(:respond_to?).bind_call(target, m, include_private)
+      if KERNEL_RESPOND_TO.bind_call(target, :respond_to?)
+        target.respond_to?(m, include_private)
+      else
+        KERNEL_RESPOND_TO.bind_call(target, m, include_private)
+      end
     end
   end