Adds support for IS_OP opcode

Mentioned in:
- #190
- #191
- #195

ASTree.cpp

@@ -1104,6 +1104,17 @@ PycRef<ASTNode> BuildFromCode(PycRef<PycCode> code, PycModule* mod)
                 stack.push(new ASTBinary(left, right, ASTBinary::BIN_IP_MAT_MULTIPLY));
             }
             break;
+        case Pyc::IS_OP_A:
+            {
+                PycRef<ASTNode> right = stack.top();
+                stack.pop();
+                PycRef<ASTNode> left = stack.top();
+                stack.pop();
+                // The operand will be 0 for 'is' and 1 for 'is not'.
+                // Map those back to the appropriate values in ASTCompare::op_str()
+                stack.push(new ASTCompare(left, right, operand ? 9 : 8));
+            }
+            break;
         case Pyc::JUMP_IF_FALSE_A:
         case Pyc::JUMP_IF_TRUE_A:
         case Pyc::JUMP_IF_FALSE_OR_POP_A:

tests/input/is_op.py

@@ -0,0 +1,9 @@
+a = 10
+b = 10
+
+if a is b:
+    pass
+
+if a is not b:
+    pass
+

tests/tokenized/is_op.txt

@@ -0,0 +1,9 @@
+a = 10 <EOL>
+b = 10 <EOL>
+if a is b : <EOL>
+<INDENT>
+pass <EOL>
+<OUTDENT>
+if a is not b : <EOL>
+<INDENT>
+pass <EOL>