Looks like fundamental problems triggered during a big rebuild within Eclipse

I do not have a reproducible test case for this (giant Scala clean/rebuild within Eclipse, this came from the Presentation Compiler) but this seems like a fundamental error, meaning someone should eyeball the line numbers mentioned in the exceptions:

java.lang.ArrayIndexOutOfBoundsException: 116514
at scala.tools.nsc.util.HashSet.findEntryOrUpdate(HashSet.scala:31)
at scala.tools.nsc.symtab.Types$class.scala$tools$nsc$symtab$Types$$unique(Types.scala:2677)
at scala.tools.nsc.symtab.Types$class.singleType(Types.scala:2399)

java.lang.AssertionError: assertion failed: List(object Option, object Option)
at scala.tools.nsc.symtab.Symbols$Symbol.suchThat(Symbols.scala:1037)
at scala.tools.nsc.symtab.Symbols$Symbol.linkedModuleOfClass0(Symbols.scala:1223)
at scala.tools.nsc.symtab.Symbols$Symbol.linkedModuleOfClass(Symbols.scala:1231)
at scala.tools.nsc.typechecker.Namers$Namer.templateSig(Namers.scala:729)

This is specifically from

Scala Eclipse Plugin 2.8.0.r21030-b20100302035619 ch.epfl.lamp.sdt.feature.group