Fix Module#{to_s,inspect} to not return an extra #<Class: for singleton classes

Author: eregon

CHANGELOG.md

@@ -25,6 +25,7 @@ Bug fixes:
 * Process#exec: set close-on-exec to false for fd redirection (#1805, @XrXr, @rafaelfranca).
 * Building C extensions should now work with frozen string literals (#1786).
 * Keep the Truffle working directory in sync with the native working directory.
+* Fixed `Module#to_s` and `Module#inspect` to not return an extra `#<Class:` for singleton classes.
 
 Compatibility:
 

spec/tags/core/module/to_s_tags.txt

@@ -1854,19 +1854,19 @@ protected DynamicObject toS(DynamicObject module) {
             final ModuleFields fields = Layouts.MODULE.getFields(module);
             if (RubyGuards.isSingletonClass(module)) {
                 final DynamicObject attached = Layouts.CLASS.getAttached(module);
-                final String name;
-                if (Layouts.CLASS.isClass(attached) || Layouts.MODULE.isModule(attached)) {
+                final String attachedName;
+                if (Layouts.MODULE.isModule(attached)) {
+                    attachedName = Layouts.MODULE.getFields(attached).getName();
+                } else {
                     if (callRbInspect == null) {
                         CompilerDirectives.transferToInterpreterAndInvalidate();
                         callRbInspect = insert(CallDispatchHeadNode.createPrivate());
                     }
                     final Object inspectResult = callRbInspect
                             .call(coreLibrary().getTruffleTypeModule(), "rb_inspect", attached);
-                    name = StringOperations.getString((DynamicObject) inspectResult);
-                } else {
-                    name = fields.getName();
+                    attachedName = StringOperations.getString((DynamicObject) inspectResult);
                 }
-                moduleName = "#<Class:" + name + ">";
+                moduleName = "#<Class:" + attachedName + ">";
             } else if (fields.isRefinement()) {
                 final String refinedClass = Layouts.MODULE.getFields(fields.getRefinedClass()).getName();
                 final String refinementNamespace = Layouts.MODULE.getFields(fields.getRefinementNamespace()).getName();