Use target self as frame self for instance_eval. Fixes #2301.

This is a bit of a scary change, so pushing to a test branch for
now.

Author: headius

core/src/main/java/org/jruby/RubyBasicObject.java

@@ -1688,7 +1688,7 @@ public IRubyObject instance_exec19(ThreadContext context, IRubyObject[] args, Bl
      * with this implementation.
      */
     protected IRubyObject yieldUnder(final ThreadContext context, RubyModule under, IRubyObject[] args, Block block, EvalType evalType) {
-        context.preExecuteUnder(under, block);
+        context.preExecuteUnder(this, under, block);
 
         IRubyObject savedBindingSelf = block.getBinding().getSelf();
         IRubyObject savedFrameSelf = block.getBinding().getFrame().getSelf();
@@ -1730,7 +1730,7 @@ private Block setupBlock(Block block, EvalType evalType) {
      * with this implementation.
      */
     protected IRubyObject yieldUnder(final ThreadContext context, RubyModule under, Block block, EvalType evalType) {
-        context.preExecuteUnder(under, block);
+        context.preExecuteUnder(this, under, block);
 
         IRubyObject savedBindingSelf = block.getBinding().getSelf();
         IRubyObject savedFrameSelf = block.getBinding().getFrame().getSelf();
@@ -1873,7 +1873,7 @@ protected RubyModule getInstanceEvalClass() {
     public IRubyObject evalUnder(final ThreadContext context, RubyModule under, RubyString src, String file, int line, EvalType evalType) {
         Visibility savedVisibility = context.getCurrentVisibility();
         context.setCurrentVisibility(PUBLIC);
-        context.preExecuteUnder(under, Block.NULL_BLOCK);
+        context.preExecuteUnder(this, under, Block.NULL_BLOCK);
         try {
             return Interpreter.evalSimple(context, this, src, file, line, evalType);
         } finally {

core/src/main/java/org/jruby/RubyModule.java

@@ -1669,7 +1669,7 @@ private DynamicMethod createProcMethod(String name, Visibility visibility, RubyP
 
     @Deprecated
     public IRubyObject executeUnder(ThreadContext context, org.jruby.runtime.callback.Callback method, IRubyObject[] args, Block block) {
-        context.preExecuteUnder(this, block);
+        context.preExecuteUnder(this, this, block);
         try {
             return method.execute(this, args, block);
         } finally {

core/src/main/java/org/jruby/runtime/ThreadContext.java

@@ -881,14 +881,14 @@ public void postNodeEval() {
     }
 
     // XXX: Again, screwy evaling under previous frame's scope
-    public void preExecuteUnder(RubyModule executeUnderClass, Block block) {
+    public void preExecuteUnder(IRubyObject executeUnderObj, RubyModule executeUnderClass, Block block) {
         Frame frame = getCurrentFrame();
 
         DynamicScope scope = getCurrentScope();
         StaticScope sScope = runtime.getStaticScopeFactory().newBlockScope(scope.getStaticScope());
         sScope.setModule(executeUnderClass);
         pushScope(DynamicScope.newDynamicScope(sScope, scope));
-        pushCallFrame(frame.getKlazz(), frame.getName(), frame.getSelf(), block);
+        pushCallFrame(frame.getKlazz(), frame.getName(), executeUnderObj, block);
         getCurrentFrame().setVisibility(getPreviousFrame().getVisibility());
     }