jruby · Jul 11, 2018 · Jul 12, 2018 · Jul 12, 2018 · Jul 12, 2018
diff --git a/core/src/main/java/org/jruby/RubyModule.java b/core/src/main/java/org/jruby/RubyModule.java
@@ -2255,7 +2255,9 @@ public IRubyObject initialize_copy(IRubyObject original) {
 
         RubyModule originalModule = (RubyModule)original;
 
-        if (!getMetaClass().isSingleton()) setMetaClass(originalModule.getSingletonClassClone());
+        if (!getMetaClass().isSingleton()) {
+            setMetaClass(originalModule.getSingletonClassCloneAndAttach(this));
+        }
         setSuperClass(originalModule.getSuperClass());
         if (originalModule.hasVariables()) syncVariables(originalModule);
         syncConstants(originalModule);
@@ -2376,7 +2378,12 @@ public RubyString to_s() {
                 if (attached instanceof RubyClass || attached instanceof RubyModule) {
                     buffer.cat19(attached.inspect().convertToString());
                 } else {
-                    buffer.cat19((RubyString) attached.anyToString());
+                    try {
+                        buffer.cat19((RubyString) attached.anyToString());
+                    } catch (NullPointerException npe) {
+                        npe.printStackTrace();
+                        throw npe;
+                    }
                 }
             }
             buffer.cat19(runtime.newString(">"));

diff --git a/core/src/main/java/org/jruby/internal/runtime/methods/PartialDelegatingMethod.java b/core/src/main/java/org/jruby/internal/runtime/methods/PartialDelegatingMethod.java
@@ -112,6 +112,10 @@ public DynamicMethod getRealMethod() {
         return method.getRealMethod();
     }
 
+    public DynamicMethod getDelegate() {
+        return method;
+    }
+
     @Override
     public Arity getArity() {
         return method.getArity();

diff --git a/core/src/main/java/org/jruby/ir/targets/InvokeSite.java b/core/src/main/java/org/jruby/ir/targets/InvokeSite.java
@@ -15,6 +15,7 @@
 import org.jruby.RubySymbol;
 import org.jruby.internal.runtime.methods.AliasMethod;
 import org.jruby.internal.runtime.methods.DynamicMethod;
+import org.jruby.internal.runtime.methods.PartialDelegatingMethod;
 import org.jruby.ir.JIT;
 import org.jruby.runtime.Block;
 import org.jruby.runtime.CallType;
@@ -411,7 +412,9 @@ public static IRubyObject negate(IRubyObject object, RubyNil nil, RubyBoolean.Tr
     MethodHandle buildAliasHandle(DynamicMethod method, IRubyObject self, RubyClass dispatchClass) throws Throwable {
         MethodHandle mh = null;
 
-        if (method instanceof AliasMethod) {
+        if (method instanceof PartialDelegatingMethod) {
+            mh = getHandle(self, dispatchClass, ((PartialDelegatingMethod) method).getDelegate());
+        } else if (method instanceof AliasMethod) {
             AliasMethod alias = (AliasMethod) method;
             DynamicMethod innerMethod = alias.getRealMethod();
             String name = alias.getName();

diff --git a/spec/ruby/core/module/initialize_copy_spec.rb b/spec/ruby/core/module/initialize_copy_spec.rb
@@ -7,4 +7,12 @@ def mod.hello
     end
     mod.dup.methods(false).should == [:hello]
   end
+
+  # jruby/jruby#5245, https://bugs.ruby-lang.org/issues/3461
+  it "should produce a duped module with inspectable class methods" do
+    mod = Module.new
+    def mod.hello
+    end
+    mod.dup.method(:hello).inspect.should =~ /Module.*hello/
+  end
 end
diff --git a/test/mri/excludes/TestModule.rb b/test/mri/excludes/TestModule.rb
@@ -5,7 +5,6 @@
 exclude :test_define_module_under_private_constant, "we don't evaluate colon2-like class opening via colon2 logic, can't tell if private are ok"
 exclude :test_include_module_with_constants_does_not_invalidate_method_cache, "no RubyVM constant in JRuby"
 exclude :test_initialize_copy_empty, "needs investigation"
-exclude :test_inspect_segfault, "a minor inspect difference?"
 exclude :test_invalid_attr, "needs investigation"
 exclude :test_method_redefinition, "needs investigation"
 exclude :test_private_constant_reopen, "needs investigation"