RFR: JDK-8187950: javax.lang.model APIs throws CompletionFailure or a subtype of CompletionFailure.

[Jan Lahoda]

Hi,

Currently, when a calling some API methods, the client (e.g. 
TaskListener, an annotation Processor or a JavacTask client) may get a 
CompletionFailure, if the given Symbol was not completed yet. This is 
not only problematic for the clients, but if the client catches and 
ignores the exception, the javac may be unable to report an appropriate 
error.

The proposed patch here:
-separates "user " and "javac" modes, in which CompletionFailure 
handling differs a bit
-in javac mode, CompletionFailures should be handled as they are currently
-in user (code) mode, when a CompletionFailure is thrown (and would go 
outside of an API method), the API method will suppress the exception, 
and the Symbol's state (completer, kind, type) will be restored to 
original when the mode is switched back to javac mode. If the Symbol is 
then completed again inside javac, the CompletionFailure is thrown again 
and the appropriate errors are reported.

Bug: https://bugs.openjdk.java.net/browse/JDK-8187950
Webrev: http://cr.openjdk.java.net/~jlahoda/8187950/webrev.00/

How does this look?

Thanks,
     Jan