The JDK 8 compiler needs to type-check an argument expression against every possible target type. There are cases in which an argument expression, however, does not need this kind of treatment.

Javac is currently using a very simple algorithm to decide as to whether speculative attribution is needed or not. This leads to an abuse of speculative attribution (some performance tests showed that javac is spending around 1.7 secs doing speculative attribution on a total of 8 sec of average execution time).