RFR: JDK-8234899: Compiler reports AssertionError for conditional operator ? : and pattern matching for instanceof

[Jan Lahoda]

Hi,

Consider code like:
boolean result = t ? true : (!(o1 instanceof String a3));

When javac starts to generate "(!(o1 instanceof String a3))", there is 
the "false" jump pending. The "!" operator is generating its operand in 
the genCond mode. But, the handling for LetExpr (into which the pattern 
matching is translated) will not explicitly resolve the pending jump 
(i.e. terminate the jump right before the code for ("o1 instanceof 
String a3"). But as the desugared code for "o1 instanceof String a3" 
will create a new variable, the pending jump is resolved at the point 
the variable is generated - but that is already too late. And hence an 
AssertionError, or other trouble may happen.

The proposal is to resolve (terminate) the pending jumps before 
generating a LetExpr in condition mode (as is done in non-condition mode).

A similar problem may happen for switch expressions, so the proposal is 
to resolve the jumps for switch expressions as well.

Proposed webrev:
http://cr.openjdk.java.net/~jlahoda/8234899/webrev.00/
JBS:
https://bugs.openjdk.java.net/browse/JDK-8234899

How does this look?

Thanks,
     Jan