RFR 8202372: Diagnostic with incorrect line info generated when compiling lambda expression

[Maurizio Cimadamore]

Hi,
I put together a webrev based on the fix that B. Blaser put together few 
days ago. I've enhanced the test as I realized that the erroneous 
condition could present in multiple situations (the patch seems to fix 
all of them).

The underlying issue is that when we create a fake block for the lambda 
expression (which is needed for speculatively check its contents), we 
forget setting its position - meaning that all diags reported against 
the rewritten block will now appear off sync.

One solution would be to tweak the code to never use speculative trees 
to report diagnostic - but that would be very invasive; a cheaper fix 
(the one attempted here) is to add the required positional info to the 
rewritten tree so that it matches the original position.

http://cr.openjdk.java.net/~mcimadamore/8202372/

Cheers
Maurizio