Please review JDK-8072426 at <http://cr.openjdk.java.net/~attila/8072426/webrev.00> for <https://bugs.openjdk.java.net/browse/JDK-8072426>
This is what basically became an epic yak shaving exercise after we determined that POJOs aren't subjected to ToPrimitive (earlier known as java.math.RoundingMode.UP != "UP" problem). While we originally advocated for throwing TypeError for POJOs [[DefaultValue]] that would've prevented their implicit toString() in string concatenation too. Instead, I opted to fix this once and forever but it turned out that the biggest issue with it is the fact that JSObject was also not handled correctly for ToPrimitive; fixing that turned out to be the most challenging part, introducing a new JSObject.getDefaultValue() method and deprecating JSObject.toNumber() (which isn't used anymore at all). As an unexpected boon, JSObjectLinker no longer needs to do any conversions, so its GuardingTypeConverterFactory functionality has been entirely removed. NashornPrimitiveLinker will now automatically take care of converting JSObject instances to various primitive types, as per specification behavior. Finally, the ScriptRuntime changes to the equals() and equalDifferentType() are purely refactoring of some common type testing subexpressions and conversions, as well as short-circuiting of some comparisons. They aren't strictly necessary for this issue, but just for clear understanding of what's happening it seemed like a good idea to make them more concise (ScriptRuntime.EQ and .NE, of which the two affected methods are sub-parts are also not invoked terribly often, and I'll soon make them be invoked even less frequently.) Thanks, Attila.
