Ruby compatibility: UnboundMethod#hash is the same for the same metho…

…d in subclass and superclass

oracle#2728

CHANGELOG.md

@@ -59,6 +59,7 @@ Compatibility:
 * Fix exception for `Fiddle::Handle.new` with a missing library (#2714, @eregon).
 * Fix arguments implicit type conversion for `BasicObject#instance_eval`, `Module#class_eval`, `Module#module_eval`, `Module#define_method` (@andrykonchin).
 * Raise `ArgumentError` unconditionally when `Proc.new` is called without a block argument (@andrykonchin).
+* Fix `UnboundMethod#hash` to not depend on a module it was retrieved from (#2728, @andrykonchin).
 
 Performance:
 

spec/ruby/core/unboundmethod/fixtures/classes.rb

@@ -84,4 +84,14 @@ def overridden; end
   class C < B
     def overridden; end
   end
+
+  module HashSpecs
+    class SuperClass
+      def foo
+      end
+    end
+
+    class SubClass < SuperClass
+    end
+  end
 end

spec/ruby/core/unboundmethod/hash_spec.rb

@@ -12,4 +12,11 @@
     to_s, inspect = Array.instance_method(:to_s), Array.instance_method(:inspect)
     to_s.hash.should == inspect.hash
   end
+
+  it "equals a hash of the same method in the superclass" do
+    foo_in_superclass = UnboundMethodSpecs::HashSpecs::SuperClass.instance_method(:foo)
+    foo = UnboundMethodSpecs::HashSpecs::SubClass.instance_method(:foo)
+
+    foo.hash.should == foo_in_superclass.hash
+  end
 end

src/main/java/org/truffleruby/core/method/UnboundMethodNodes.java

@@ -121,7 +121,6 @@ public abstract static class HashNode extends CoreMethodArrayArgumentsNode {
         protected long hash(RubyUnboundMethod rubyMethod) {
             final InternalMethod method = rubyMethod.method;
             long h = getContext().getHashing(this).start(method.getDeclaringModule().hashCode());
-            h = Hashing.update(h, rubyMethod.origin.hashCode());
             h = Hashing.update(h, MethodNodes.hashInternalMethod(method));
             return Hashing.end(h);
         }