Evolving the wrapper classes

[Dan Smith]

> On Jun 17, 2020, at 4:13 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
> 
>> - Where necessary (depending on the operations being performed), the compiler generates conversions between 'I' and 'java/lang/Integer$val'. 'I' is preferred wherever possible.
> 
> We have to use QInteger$val whenever we use int as a type parameter, the rest of the time, we can use I.  

Right. Specifically, if we support inline types as type arguments before we get to specialization, we'll use erasure, which looks like:

new java/util/ArrayList;
// dup, init
astore 1

aload 1
iconst_0
invokestatic Qjava/lang/Integer$val;.<new>(I)Qjava/lang/Integer$val; // <-- conversion
invokevirtual java/util/ArrayList.add:(Ljava/lang/Object;)Z
pop

aload1
iconst_0
invokevirtual java/util/ArrayList.get(I)Ljava/lang/Object;
checkcast Qjava/lang/Integer$val;
invokevirtual Qjava/lang/Integer$val;.intValue()I  // <-- conversion

And then there's also instance method invocations:

iconst_0
invokestatic Qjava/lang/Integer$val;.<new>(I)Qjava/lang/Integer$val; // <-- conversion
invokevirtual Qjava/lang/Integer$val;.floatValue()F

(Note that none of these conversions are "boxing" or "unboxing". They're strictly compilation artifacts. It may be useful to come up with a new word for them.)