Add refinements support to method/instance_method.

[Fix GH-2034]

From: manga_osyo <manga.osyo@gmail.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66935 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/core/module/refine_spec.rb

@@ -526,20 +526,78 @@ describe "Module#refine" do
       result.should == "hello from refinement"
     end
 
-    it "is not honored by Kernel#method" do
-      klass = Class.new
-      refinement = Module.new do
-        refine klass do
-          def foo; end
+    ruby_version_is "" ... "2.7" do
+      it "is not honored by Kernel#method" do
+        klass = Class.new
+        refinement = Module.new do
+          refine klass do
+            def foo; end
+          end
         end
-      end
 
-      -> {
+        -> {
+          Module.new do
+            using refinement
+            klass.new.method(:foo)
+          end
+        }.should raise_error(NameError, /undefined method `foo'/)
+      end
+    end
+
+    ruby_version_is "2.7" do
+      it "is honored by Kernel#method" do
+        klass = Class.new
+        refinement = Module.new do
+          refine klass do
+            def foo; end
+          end
+        end
+
+        result = nil
         Module.new do
           using refinement
-          klass.new.method(:foo)
+          result = klass.new.method(:foo).class
         end
-      }.should raise_error(NameError, /undefined method `foo'/)
+
+        result.should == Method
+      end
+    end
+
+    ruby_version_is "" ... "2.7" do
+      it "is not honored by Kernel#instance_method" do
+        klass = Class.new
+        refinement = Module.new do
+          refine klass do
+            def foo; end
+          end
+        end
+
+        -> {
+          Module.new do
+            using refinement
+            klass.instance_method(:foo)
+          end
+        }.should raise_error(NameError, /undefined method `foo'/)
+      end
+    end
+
+    ruby_version_is "2.7" do
+      it "is honored by Kernel#method" do
+        klass = Class.new
+        refinement = Module.new do
+          refine klass do
+            def foo; end
+          end
+        end
+
+        result = nil
+        Module.new do
+          using refinement
+          result = klass.instance_method(:foo).class
+        end
+
+        result.should == UnboundMethod
+      end
     end
 
     ruby_version_is "" ... "2.6" do