Compiler symbol: is synthetic?

Hello,

Suppose I have a Symbol instance generated by the Scala compiler.
http://www.scala-lang.org/archives/downloads/distrib/files/nightly/docs/compiler/scala/tools/nsc/symtab/Symbols$Symbol.html

I want to find out if this Symbol represents a proper class(java or
scala),trait,interface or object. As you can see, Symbol supports many
is[X] predicates, including isJavaDefined, isSynthetic, isClass, etc.
I've tried filtering symbols using these predicates, but I still end up
admitting things like:

Compiler$$anonfun$1
Compiler$$anonfun$2
Compiler$$anonfun$act$1
Compiler$$anonfun$act$1$$anonfun$apply$3
Compiler$$anonfun$expandSource$1
Compiler$$anonfun$expandSource$2
Compiler$$anonfun$expandSource$2$$anonfun$apply$1
Compiler$$anonfun$expandSource$2$$anonfun$apply$2
CompilerShutdownEvent$

I assume these are synthetic classes generated by scalac. Is there some
way to check if a symbol is 'generated' or real? bearing in mind that
these symbols may have been loaded from binary .class files (which I
assume complicates the question by throwing away relevant scala context)

(btw, i've thought of just filtering on their names - but I'm hoping
there's a more robust alternative)

Thanks!