KT-877 - wrong codegen for unary plus

compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/UnaryPlus.java

@@ -21,7 +21,12 @@ public class UnaryPlus implements IntrinsicMethod {
         if(nullable) {
             expectedType = JetTypeMapper.unboxType(expectedType);
         }
-        receiver.put(expectedType, v);
+        if(receiver != null && receiver != StackValue.none())
+            receiver.put(expectedType, v);
+        else {
+            assert arguments != null;
+            codegen.gen(arguments.get(0), expectedType);
+        }
         return StackValue.onStack(expectedType);
     }
 }

compiler/testData/codegen/regressions/kt877.jet

@@ -0,0 +1,9 @@
+fun box() : String {
+  var a : Int = -1
+  if((+a) != -1) return "fail 1"
+  a = 1
+  if((+a) != 1) return "fail 2"
+  if((+-1) != -1) return "fail 3"
+  if((-+a) != -1) return "fail 4"
+  return "OK"
+}

compiler/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java

@@ -351,4 +351,8 @@ public class PrimitiveTypesTest extends CodegenTestCase {
     public void testKt757 () {
         blackBoxFile("regressions/kt757.jet");
     }
+
+    public void testKt877 () {
+        blackBoxFile("regressions/kt877.jet");
+    }
 }