Control flow exceptions

There's a growing number of exceptions in the compiler and standard
libraries which are used solely for control flow. Unfortunately there
isn't currently any straightforward way to distinguish them from
exceptions which actually indicate problems. This is causing me a few
minor headaches with reporting in the IDE, and more generally it's a
bit of a pain.

So I propose the addition of a scala.util.control.ControlException
trait and have all the relevant exceptions mix it in ... this would
allow code which cares to filter out control exceptions simply.

The exceptions affected would be,

 scala.tools.nsc.ast.parser.MarkupParsers
   ConfusedAboutBracesException
   MissingEndTagException
   MarkupParsers.TruncatedXML

 scala.tools.nsc.interactive.CompilerControl
   CancelActionReq
   FreshRunReq
   ShutdownReq

 scala.tools.nsc.interactive.Global
   TyperResult

 scala.tools.nsc.typechecker.Infer
   DeferredNoInstance
   NoInstance

 scala.actors
   KillActorException,
   QuitException
   SuspendActorException

 scala.runtime
   NonLocalReturnException

 scala.util.control
   BreakException

Are there any that I've missed or which shouldn't be included on this list?

Thoughts?

Cheers,


Miles

--
Miles Sabin
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skype:  milessabin
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