Support COPY opcde

ASTree.cpp

@@ -2540,6 +2540,12 @@ PycRef<ASTNode> BuildFromCode(PycRef<PycCode> code, PycModule* mod)
                 curblock->append(new ASTStore(values, new ASTSubscr(dest, slice)));
             }
             break;
+        case Pyc::COPY_A:
+            {
+                PycRef<ASTNode> value = stack.top(operand);
+                stack.push(value);
+            }
+            break;
         default:
             fprintf(stderr, "Unsupported opcode: %s (%d)\n", Pyc::OpcodeName(opcode), opcode);
             cleanBuild = false;

FastStack.h

@@ -32,11 +32,21 @@ public:
             m_stack[m_ptr--] = nullptr;
     }
 
-    PycRef<ASTNode> top() const
+    PycRef<ASTNode> top(int i = 1) const
     {
-        if (m_ptr > -1)
+        if (i > 0) {
-            return m_stack[m_ptr];
+            int idx = m_ptr + 1 - i;
-        else
+            if ((m_ptr > -1) && (idx >= 0))
+                return m_stack[idx];
+            else {
+                #ifdef BLOCK_DEBUG
+                    fprintf(stderr, "insufficient values on stack\n");
+                #endif
+                return nullptr;
+            }
+        }
+        else {
+            fprintf(stderr, "incorrect operand %i\n", i);
             return nullptr;
     }