4741726: allow Object += String

Summary: remove code in line with restriction removed from JLS
Reviewed-by: mcimadamore
Contributed-by: michaelbailey0@gmail.com

src/share/classes/com/sun/tools/javac/comp/Attr.java

@@ -1609,17 +1609,10 @@ public class Attr extends JCTree.Visitor {
                               tree.getTag() - JCTree.ASGOffset,
                               owntype,
                               operand);
-            if (types.isSameType(operator.type.getReturnType(), syms.stringType)) {
-                // String assignment; make sure the lhs is a string
-                chk.checkType(tree.lhs.pos(),
-                              owntype,
-                              syms.stringType);
-            } else {
-                chk.checkDivZero(tree.rhs.pos(), operator, operand);
-                chk.checkCastable(tree.rhs.pos(),
-                                  operator.type.getReturnType(),
-                                  owntype);
-            }
+            chk.checkDivZero(tree.rhs.pos(), operator, operand);
+            chk.checkCastable(tree.rhs.pos(),
+                              operator.type.getReturnType(),
+                              owntype);
         }
         result = check(tree, owntype, VAL, pkind, pt);
     }

test/tools/javac/expression/ObjectAppend.java → test/tools/javac/StringConversion2.java

 /*
- * Copyright 2002 Sun Microsystems, Inc.  All Rights Reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -23,14 +23,17 @@
 
 /*
  * @test
- * @bug 4642850
- * @summary compiler allows Object += String
- * @author gafter
- *
- * @compile/fail ObjectAppend.java
+ * @bug 4741726
+ * @summary allow Object += String
  */
 
-class ObjectAppend {{
-    Object o = null;
-    o += "string";
-}}
+public class StringConversion2
+{
+    public static void main(String[] args) {
+        Object o = "Hello ";
+        String s = "World!";
+        o += s;
+        if (!o.equals("Hello World!"))
+            throw new Error("test failed");
+    }
+}