RFR: JDK-8222169: java.lang.AssertionError switch expression in ternary operator - ?

[Jan Lahoda]

Hi,

There is a regression in how let expressions are handled in Gen, related 
to recent changes for switch expressions. Consider code like:

int t(boolean b, Integer i) {
     return b ? 0 : i++;
}

This gets desugared into:
int t(boolean b, Integer i) {
         return b ? 0 : (let /*synthetic*/ final Integer $1357563986 = i 
in (let i = Integer.valueOf((int)(i.intValue() + 1)); in 
$1357563986)).intValue();
     }

When Gen.visitLetExpr is generating the let expression, it records the 
stack size, so that for further statements, it can assert the statements 
start at an appropriate stack depth (at "statement start"). But, the 
issue here is that when the stack size is recorded, the state of the 
bytecode is before the target of the jump for "b == false", which jumps 
to the "else" section. I.e. the state of the bytecode is before the ':', 
not after. And so '0' is on the stack. But, the code for the let 
expression is after the target of the jump, and so the real stack at the 
beginning of the code for the let expression is empty.

The proposed solution is to simply resolve the jumps before recording 
the size of the stack - that should ensure the correct stack size is 
recorded. We already do that for Gen.visitSwitchExpression, but missed 
it for visitLetExpr.

Webrev: http://cr.openjdk.java.net/~jlahoda/8222169/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8222169

The patch also includes test based on Vicente's:
http://cr.openjdk.java.net/~vromero/8222795/webrev.00/

How does this look?

Thanks,
     Jan