RFR(12): JDK-8207229: Trees.getScope crashes for broken lambda; JDK-8207230: Trees.getScope runs Analyzers

[Jan Lahoda]

Hi,

The proposed patch attempts to fix two problems with Trees.getScope:
-a NPE when a lambda is categorized as an implicit lambda, but has a 
parameter with type (in erroneous source); when 
Attr.fallbackDescriptorType constructs the fallback descriptor, it uses 
the (unattributed) type of the parameter, which then leads to the NPE. 
The proposal is to check if the type of the parameter is present, and 
use syms.errType if not present.
-Analyzers appear to run while the Scope is being computed by 
Trees.getScope. This does not seem necessary (as the attribution 
typically runs on a copy of the AST, not on the real AST).

Bugs:
https://bugs.openjdk.java.net/browse/JDK-8207229
https://bugs.openjdk.java.net/browse/JDK-8207230

Webrev:
http://cr.openjdk.java.net/~jlahoda/8207229/webrev.00/

Does this look reasonable?

Thanks,
     Jan