Final failure for spec:compiler fixed.

I had refactored all recv instrs so that they can use super to
encode but for recvrest the encode order swapped two elements
of the same time which decode would then reverse when reading
from IR persistence.

core/src/main/java/org/jruby/ir/IRBuilder.java

@@ -2895,7 +2895,7 @@ protected void receiveNonBlockArgs(final ArgsNode argsNode, Variable keywords) {
             // You need at least required+opt+1 incoming args for the rest arg to get any args at all
             // If it is going to get something, then it should ignore required+opt args from the beginning
             // because they have been accounted for already.
-            addInstr(new ReceiveRestArgInstr(argumentResult(argName), keywords, signature.required() + opt, argIndex));
+            addInstr(new ReceiveRestArgInstr(argumentResult(argName), keywords, argIndex, signature.required() + opt));
         }
 
         // Post(-opt and rest) required args

core/src/main/java/org/jruby/ir/instructions/ReceiveRestArgInstr.java

@@ -21,7 +21,7 @@ public class ReceiveRestArgInstr extends ReceiveIndexedArgBase implements FixedA
     /** Number of arguments already accounted for */
     public final int required;
 
-    public ReceiveRestArgInstr(Variable result, Variable keywords, int required, int argIndex) {
+    public ReceiveRestArgInstr(Variable result, Variable keywords, int argIndex, int required) {
         super(Operation.RECV_REST_ARG, result, keywords, argIndex);
         this.required = required;
     }
@@ -33,7 +33,7 @@ public String[] toStringNonOperandArgs() {
 
     @Override
     public Instr clone(CloneInfo info) {
-        if (info instanceof SimpleCloneInfo) return new ReceiveRestArgInstr(info.getRenamedVariable(result), info.getRenamedVariable(getKeywords()), required, argIndex);
+        if (info instanceof SimpleCloneInfo) return new ReceiveRestArgInstr(info.getRenamedVariable(result), info.getRenamedVariable(getKeywords()), argIndex, required);
 
         InlineCloneInfo ii = (InlineCloneInfo) info;