Here’s a bit of “translation strategy lore” that doesn’t need to
go into the JEP, but I think might be useful to contemplate.
When we employed Q-descriptors, we translated Foo! (or Foo.val)
uniformly to /QFoo;/ but now we do something different.
Here are assembly sequences that used to employ Q-descriptors but which
will have to change:
// Foo foo = …; return (Foo!)foo;
(one ref on stack)
checkcast[QFoo;] (if TOS is already LFoo;)
⇒
dup
invokestatic Objects::requireNonNull
pop
// (Foo!)obj
(one ref on stack)
checkcast[QFoo;] (otherwise)
⇒
invokestatic Objects::requireNonNull
checkcast[LFoo;]
// obj instanceof Foo!
(one ref on stack)
instanceof[QFoo;]
⇒
instanceof[LFoo;] (note that loading is lazier here)
// new Foo![dim]
(one int on stack)
anewarray[QFoo;]
⇒
ldc[Condy[Foo.class.asNullRestrictedType]]
swap
invokestatic Array::newInstance(Class,int)
checkcast[[LFoo;] (as necessary)
// new Foo![dim0][dim1…]
(#Dim ints on stack)
multianewarray[(‘[’*#Dim)QFoo;,#Dim]
⇒
ldc #Dim (or bipush etc.)
dup; istore $P
newarray[T_INTEGER]
dup2; swap; iinc $P, -1; iload $P; iastore (#Dim times)
invokestatic Array::newInstance(Class,int[])
checkcast[[[…LFoo;] (as necessary)
For arrays, generally speaking, we erase Foo![][] to Foo[][], not
translating to multi-level /[[…QFoo;/
Thus remaining hypothetical uses of /[…QLFoo;/ would get replaced by
/[…LFoo;/.
For example:
multianewarray[(‘[’*#Dim)[…QFoo;,#Dim]
⇒
multianewarray[(‘[’*#Dim)[…LFoo;,#Dim]
