Fix show_source command when obj.method is overrided (#1111)

`method` method is sometimes overridden. (example: Net::HTTPRequest)
To handle this case, use `Object.instance_method(:method).bind_call` instead of `obj.method(name)`

Author: tompng

lib/irb/source_finder.rb

@@ -114,7 +114,7 @@ def method_target(owner_receiver, super_level, method, type)
       when "owner"
         target_method = owner_receiver.instance_method(method)
       when "receiver"
-        target_method = owner_receiver.method(method)
+        target_method = Kernel.instance_method(:method).bind_call(owner_receiver, method)
       end
       super_level.times do |s|
         target_method = target_method.super_method if target_method

test/irb/command/test_show_source.rb

@@ -376,6 +376,23 @@ def test_show_source_shows_binary_source
       assert_match(%r[Defined in binary file:.+io/console], out)
     end
 
+    def test_show_source_method_overrided
+      write_ruby <<~RUBY
+        class Request
+          def method; 'POST'; end
+          def path; '/'; end
+        end
+        request = Request.new
+        binding.irb
+      RUBY
+
+      out = run_ruby_file do
+        type "show_source request.path"
+        type "exit"
+      end
+      assert_match(%r[#{@ruby_file.to_path}:3\s+def path; '/'; end], out)
+    end
+
     def test_show_source_with_constant_lookup
       write_ruby <<~RUBY
         X = 1