Can you please post the offending code?

Oh, crap, I actually don't think I can. Just close this one and I'll try to provide better info if it turns up again. Sorry.

Sure, thanks!

This error is still the most common one I get and I basically get it on any random lift Mapper model class. I now got it on a really small file with no super-duper secret code so I'll post it:

The error:

java.lang.Error: A in trait Mapper cannot be instantiated from object dfk.ka.model.EmailAttachment
	at scala.tools.nsc.symtab.SymbolTable.abort(SymbolTable.scala:34)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.throwError$1(Types.scala:3489)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.instParam$1(Types.scala:3492)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.toInstance$1(Types.scala:3504)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3520)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3389)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3211)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3207)
	at scala.tools.nsc.symtab.Types$class.map2Conserve(Types.scala:4980)
	at scala.tools.nsc.symtab.SymbolTable.map2Conserve(SymbolTable.scala:13)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOverArgs(Types.scala:3207)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3114)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3522)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3389)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$16.apply(Types.scala:3229)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$16.apply(Types.scala:3226)
	at scala.collection.LinearSeqOptimized$class.exists(LinearSeqOptimized.scala:79)
	at scala.collection.immutable.List.exists(List.scala:45)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3226)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3128)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3522)
	at scala.tools.nsc.symtab.Types$Type.asSeenFrom(Types.scala:546)
	at scala.tools.nsc.symtab.Types$Type.computeMemberType(Types.scala:575)
	at scala.tools.nsc.symtab.Symbols$MethodSymbol.typeAsMemberOf(Symbols.scala:1853)
	at scala.tools.nsc.symtab.Types$Type.memberType(Types.scala:566)
	at scala.tools.nsc.typechecker.Implicits$ImplicitInfo.tpe(Implicits.scala:118)
	at scala.tools.nsc.typechecker.Implicits$ImplicitInfo.isCyclicOrErroneous(Implicits.scala:139)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation.survives(Implicits.scala:683)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6$$anonfun$7.apply(Implicits.scala:715)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6$$anonfun$7.apply(Implicits.scala:715)
	at scala.collection.TraversableLike$$anonfun$filter$1.apply(TraversableLike.scala:213)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.filter(TraversableLike.scala:212)
	at scala.collection.immutable.List.filter(List.scala:45)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6.apply(Implicits.scala:715)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6.apply(Implicits.scala:714)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:200)
	at scala.collection.immutable.List.flatMap(List.scala:45)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation.<init>(Implicits.scala:714)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.searchImplicit(Implicits.scala:830)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.implicitManifestOrOfExpectedType(Implicits.scala:1154)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.bestImplicit(Implicits.scala:1181)
	at scala.tools.nsc.typechecker.Implicits$class.inferImplicit(Implicits.scala:67)
	at scala.tools.nsc.Global$analyzer$.inferImplicit(Global.scala:351)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$applyImplicitArgs$1.apply(Typers.scala:121)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$applyImplicitArgs$1.apply(Typers.scala:116)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.nsc.typechecker.Typers$Typer.applyImplicitArgs(Typers.scala:116)
	at scala.tools.nsc.typechecker.Typers$Typer.adapt(Typers.scala:761)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4280)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4421)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.initialize(Symbols.scala:839)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3897)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typedBlock(Typers.scala:1919)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3951)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.typedFunction(Typers.scala:2042)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3978)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArg(Typers.scala:2191)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArgToPoly$1(Typers.scala:2477)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2485)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2485)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:65)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:63)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.Tuple2$Zipped.map(Tuple2.scala:63)
	at scala.tools.nsc.typechecker.Typers$Typer.doTypedApply(Typers.scala:2485)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3371)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.typedFunction(Typers.scala:2042)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3978)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArg(Typers.scala:2191)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArgToPoly$1(Typers.scala:2477)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2485)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2485)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:65)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:63)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.Tuple2$Zipped.map(Tuple2.scala:63)
	at scala.tools.nsc.typechecker.Typers$Typer.doTypedApply(Typers.scala:2485)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3371)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4421)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.cookJavaRawInfo(Symbols.scala:864)
	at scala.tools.nsc.typechecker.Infer$Inferencer.checkAccessible(Infer.scala:285)
	at scala.tools.nsc.typechecker.Typers$Typer.makeAccessible(Typers.scala:524)
	at scala.tools.nsc.typechecker.Typers$Typer.typedIdent$1(Typers.scala:3819)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4176)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typedBlock(Typers.scala:1919)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3951)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4421)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.cookJavaRawInfo(Symbols.scala:864)
	at scala.tools.nsc.typechecker.Infer$Inferencer.checkAccessible(Infer.scala:285)
	at scala.tools.nsc.typechecker.Typers$Typer.makeAccessible(Typers.scala:524)
	at scala.tools.nsc.typechecker.Typers$Typer.typedIdent$1(Typers.scala:3819)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4176)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4421)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.cookJavaRawInfo(Symbols.scala:864)
	at scala.tools.nsc.typechecker.Infer$Inferencer.checkAccessible(Infer.scala:285)
	at scala.tools.nsc.typechecker.Typers$Typer.makeAccessible(Typers.scala:524)
	at scala.tools.nsc.typechecker.Typers$Typer.typedSelect$1(Typers.scala:3613)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4165)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typedBlock(Typers.scala:1919)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3951)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.typedFunction(Typers.scala:2042)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3978)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArg(Typers.scala:2191)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArgToPoly$1(Typers.scala:2477)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2485)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2485)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:65)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:63)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.Tuple2$Zipped.map(Tuple2.scala:63)
	at scala.tools.nsc.typechecker.Typers$Typer.doTypedApply(Typers.scala:2485)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3371)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.transformedOrTyped(Typers.scala:4428)
	at scala.tools.nsc.typechecker.Typers$Typer.typedDefDef(Typers.scala:1760)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3919)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1512)
	at scala.tools.nsc.typechecker.Typers$Typer.typedClassDef(Typers.scala:1278)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3910)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3906)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4331)
	at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$3.apply(Analyzer.scala:94)
	at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:329)
	at scala.tools.nsc.interactive.Global$TyperRun$$anonfun$applyPhase$1.apply(Global.scala:1031)
	at scala.tools.nsc.interactive.Global$TyperRun$$anonfun$applyPhase$1.apply(Global.scala:1031)
	at scala.tools.nsc.symtab.SymbolTable.atPhase(SymbolTable.scala:95)
	at scala.tools.nsc.interactive.Global$TyperRun.applyPhase(Global.scala:1031)
	at scala.tools.nsc.interactive.Global$TyperRun.typeCheck(Global.scala:1024)
	at scala.tools.nsc.interactive.Global.scala$tools$nsc$interactive$Global$$typeCheck(Global.scala:554)
	at scala.tools.nsc.interactive.Global.scala$tools$nsc$interactive$Global$$typedTree(Global.scala:711)
	at scala.tools.nsc.interactive.Global$$anonfun$getTypedTree$1.apply(Global.scala:723)
	at scala.tools.nsc.interactive.Global$$anonfun$getTypedTree$1.apply(Global.scala:723)
	at scala.tools.nsc.interactive.Global$$anonfun$respond$1.apply(Global.scala:585)
	at scala.tools.nsc.interactive.Global$$anonfun$respond$1.apply(Global.scala:585)
	at scala.tools.nsc.interactive.Global.respondGradually(Global.scala:592)
	at scala.tools.nsc.interactive.Global.respond(Global.scala:585)
	at scala.tools.nsc.interactive.Global.getTypedTree(Global.scala:723)
	at scala.tools.nsc.interactive.CompilerControl$AskTypeItem.apply$mcV$sp(CompilerControl.scala:297)
	at scala.tools.nsc.interactive.CompilerControl$class.postWorkItem(CompilerControl.scala:107)
	at scala.tools.nsc.interactive.CompilerControl$class.askType(CompilerControl.scala:140)
	at scala.tools.nsc.interactive.Global.askType(Global.scala:27)
	at scala.tools.eclipse.ScalaPresentationCompiler.body(ScalaPresentationCompiler.scala:88)
	at scala.tools.eclipse.markoccurrences.ScalaOccurrencesFinder$$anonfun$findOccurrences$1$$anonfun$apply$1$$anon$1.index(ScalaOccurrencesFinder.scala:20)
	at scala.tools.refactoring.implementations.MarkOccurrences.occurrencesForSymbol$1(MarkOccurrences.scala:23)
	at scala.tools.refactoring.implementations.MarkOccurrences$$anonfun$2.apply(MarkOccurrences.scala:62)
	at scala.tools.refactoring.implementations.MarkOccurrences$$anonfun$2.apply(MarkOccurrences.scala:30)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:200)
	at scala.collection.immutable.List.flatMap(List.scala:45)
	at scala.tools.refactoring.implementations.MarkOccurrences.occurrencesOf(MarkOccurrences.scala:30)
	at scala.tools.eclipse.markoccurrences.ScalaOccurrencesFinder$$anonfun$findOccurrences$1$$anonfun$apply$1.apply(ScalaOccurrencesFinder.scala:26)
	at scala.tools.eclipse.markoccurrences.ScalaOccurrencesFinder$$anonfun$findOccurrences$1$$anonfun$apply$1.apply(ScalaOccurrencesFinder.scala:17)
	at scala.tools.nsc.util.InterruptReq.liftedTree1$1(InterruptReq.scala:20)
	at scala.tools.nsc.util.InterruptReq.execute(InterruptReq.scala:19)
	at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:329)
	at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:334)
	at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:334)
	at scala.tools.nsc.interactive.PresentationCompilerThread.run(PresentationCompilerThread.scala:22)

The offending code:

package dfk.ka.model
import net.liftweb._
import mapper._
import common._

trait Attachment extends CreatedUpdated {
  self: BaseMapper =>
  object data extends MappedBinary(this.asInstanceOf[MapperType])
  object mime extends MappedString(this.asInstanceOf[MapperType], 100)
  object name extends MappedString(this.asInstanceOf[MapperType], 100)
}

class EmailAttachment extends LongKeyedMapper[EmailAttachment] with Attachment with IdPK {
  def getSingleton = EmailAttachment

  object owner extends MappedLongForeignKey(this, EmailTemplate)
}


object EmailAttachment extends EmailAttachment with LongKeyedMetaMapper[EmailAttachment] {

}

It is self contained and only depends on Lift so maybe that could be helpful? I don't feel I'm in any position to reopen stuff here, but you'll get email notifications, right?

Thanks,
Viktor

There are other paths leading to the same kind of error:

java.lang.Error: A in trait Mapper cannot be instantiated from object dfk.ka.model.ParticipantCard
	at scala.tools.nsc.symtab.SymbolTable.abort(SymbolTable.scala:34)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.throwError$1(Types.scala:3489)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.instParam$1(Types.scala:3492)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.toInstance$1(Types.scala:3504)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3520)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3389)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3211)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3207)
	at scala.tools.nsc.symtab.Types$class.map2Conserve(Types.scala:4980)
	at scala.tools.nsc.symtab.SymbolTable.map2Conserve(SymbolTable.scala:13)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOverArgs(Types.scala:3207)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3114)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3522)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3389)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$16.apply(Types.scala:3229)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$16.apply(Types.scala:3226)
	at scala.collection.LinearSeqOptimized$class.exists(LinearSeqOptimized.scala:79)
	at scala.collection.immutable.List.exists(List.scala:45)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3226)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3128)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3522)
	at scala.tools.nsc.symtab.Types$Type.asSeenFrom(Types.scala:546)
	at scala.tools.nsc.symtab.Types$Type.computeMemberType(Types.scala:575)
	at scala.tools.nsc.symtab.Symbols$MethodSymbol.typeAsMemberOf(Symbols.scala:1853)
	at scala.tools.nsc.symtab.Types$Type.memberType(Types.scala:566)
	at scala.tools.nsc.typechecker.Implicits$ImplicitInfo.tpe(Implicits.scala:118)
	at scala.tools.nsc.typechecker.Implicits$ImplicitInfo.isCyclicOrErroneous(Implicits.scala:139)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation.survives(Implicits.scala:683)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6$$anonfun$7.apply(Implicits.scala:715)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6$$anonfun$7.apply(Implicits.scala:715)
	at scala.collection.TraversableLike$$anonfun$filter$1.apply(TraversableLike.scala:213)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.filter(TraversableLike.scala:212)
	at scala.collection.immutable.List.filter(List.scala:45)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6.apply(Implicits.scala:715)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6.apply(Implicits.scala:714)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:200)
	at scala.collection.immutable.List.flatMap(List.scala:45)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation.<init>(Implicits.scala:714)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.searchImplicit(Implicits.scala:830)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.implicitManifestOrOfExpectedType(Implicits.scala:1154)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.bestImplicit(Implicits.scala:1181)
	at scala.tools.nsc.typechecker.Implicits$class.inferImplicit(Implicits.scala:67)
	at scala.tools.nsc.Global$analyzer$.inferImplicit(Global.scala:351)
	at scala.tools.nsc.typechecker.Typers$Typer.wrapImplicit$1(Typers.scala:168)
	at scala.tools.nsc.typechecker.Typers$Typer.inferView(Typers.scala:172)
	at scala.tools.nsc.typechecker.Typers$Typer.adaptToMember(Typers.scala:992)
	at scala.tools.nsc.typechecker.Typers$Typer.adaptToMemberWithArgs(Typers.scala:1031)
	at scala.tools.nsc.typechecker.Typers$Typer.typedSelect$1(Typers.scala:3561)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4165)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3353)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArg(Typers.scala:2191)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedArgs$3.apply(Typers.scala:2204)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedArgs$3.apply(Typers.scala:2203)
	at scala.Tuple3$Zipped$$anonfun$map$1.apply(Tuple3.scala:66)
	at scala.Tuple3$Zipped$$anonfun$map$1.apply(Tuple3.scala:64)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.Tuple3$Zipped.map(Tuple3.scala:64)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArgs(Typers.scala:2203)
	at scala.tools.nsc.typechecker.Typers$Typer.doTypedApply(Typers.scala:2421)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$tryTypedApply$1$1.apply(Typers.scala:3295)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$tryTypedApply$1$1.apply(Typers.scala:3295)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.tryTypedApply$1(Typers.scala:3295)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3369)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4104)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4271)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4344)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4421)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.paramss(Symbols.scala:920)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$DefOwner$class.addDef(ScalaStructureBuilder.scala:645)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$Builder.addDef(ScalaStructureBuilder.scala:839)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$DefOwner$class.addDef(ScalaStructureBuilder.scala:635)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$Builder.addDef(ScalaStructureBuilder.scala:839)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:904)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:912)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:912)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.traverse(ScalaStructureBuilder.scala:871)
	at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$2$$anonfun$apply$4$$anonfun$apply$1.apply$mcV$sp(ScalaCompilationUnit.scala:77)
	at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$2$$anonfun$apply$4$$anonfun$apply$1.apply(ScalaCompilationUnit.scala:76)
	at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$2$$anonfun$apply$4$$anonfun$apply$1.apply(ScalaCompilationUnit.scala:76)
	at scala.tools.nsc.util.InterruptReq.liftedTree1$1(InterruptReq.scala:20)
	at scala.tools.nsc.util.InterruptReq.execute(InterruptReq.scala:19)
	at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:329)
	at scala.tools.nsc.interactive.PresentationCompilerThread.run(PresentationCompilerThread.scala:22)

Was the example code at all helpful? I just noticed that it wasn't all that self-contained:

object owner extends MappedLongForeignKey(this, EmailTemplate)

But I think this line can simply be discarded and the error will most likely occur anyway.

This error is by far the most annoying problem I have with the IDE. It occurs extremely frequently for me and it's often different classes, but it's always lift mapper classes of the pattern:

class Foo extends LongKeyedMapper[Foo] {
  def getSingleton = Foo
...
}

object Foo extends Foo with LongKeyedMetaMapper[Foo] {
...
}

It doesn't occur immediately when opening a file with offending code, but often when I have many files open, and I think it often isn't the offending file that is the one in focus, but rather maybe a dependency of the file I'm currently editing. But I'm not too sure, it's really hard to catch it just as it happens…

Thanks,
Viktor

Hey Viktor, thanks a lot for reporting this (again:)). Currently, we are quite busy working the final 2.0.0 release, as soon as it is out, we will have a look (likely beginning of next year).

Great, thanks! I'm eagerly awaiting that! I think I have reported this issue many times in different forms and maybe you guys will get annoyed at me if I bump it more :)

BUT! I just feel the need to clarify that this error happens all the time for me and that the compiler crashes and I loose all functionality from the presentation compiler. Maybe this is obvious by the stack trace for you guys, but anyway. The error can turn up like this:

Compiler crash while building structure for /Users/viktor/dev/projects/dfkka/src/main/scala/dfk/ka/snippet/ActivityApplicationWizard.scala

java.lang.Error: A in trait Mapper cannot be instantiated from object dfk.ka.model.Activity
	at scala.tools.nsc.symtab.SymbolTable.abort(SymbolTable.scala:34)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.throwError$1(Types.scala:3489)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.instParam$1(Types.scala:3492)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.toInstance$1(Types.scala:3504)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3520)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3389)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3211)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3207)
	at scala.tools.nsc.symtab.Types$class.map2Conserve(Types.scala:4980)
	at scala.tools.nsc.symtab.SymbolTable.map2Conserve(SymbolTable.scala:13)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOverArgs(Types.scala:3207)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3114)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3522)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3389)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$16.apply(Types.scala:3229)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$16.apply(Types.scala:3226)
	at scala.collection.LinearSeqOptimized$class.exists(LinearSeqOptimized.scala:79)
	at scala.collection.immutable.List.exists(List.scala:45)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3226)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3128)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3522)
	at scala.tools.nsc.symtab.Types$Type.asSeenFrom(Types.scala:546)
	at scala.tools.nsc.symtab.Types$Type.computeMemberType(Types.scala:575)
	at scala.tools.nsc.symtab.Symbols$MethodSymbol.typeAsMemberOf(Symbols.scala:1853)
	at scala.tools.nsc.symtab.Types$Type.memberType(Types.scala:566)
	at scala.tools.nsc.typechecker.Implicits$ImplicitInfo.tpe(Implicits.scala:118)
	at scala.tools.nsc.typechecker.Implicits$ImplicitInfo.isCyclicOrErroneous(Implicits.scala:139)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation.survives(Implicits.scala:683)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6$$anonfun$7.apply(Implicits.scala:715)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6$$anonfun$7.apply(Implicits.scala:715)
	at scala.collection.TraversableLike$$anonfun$filter$1.apply(TraversableLike.scala:213)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.filter(TraversableLike.scala:212)
	at scala.collection.immutable.List.filter(List.scala:45)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6.apply(Implicits.scala:715)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation$$anonfun$6.apply(Implicits.scala:714)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:200)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:200)
	at scala.collection.immutable.List.flatMap(List.scala:45)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch$ImplicitComputation.<init>(Implicits.scala:714)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.searchImplicit(Implicits.scala:830)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.implicitManifestOrOfExpectedType(Implicits.scala:1154)
	at scala.tools.nsc.typechecker.Implicits$ImplicitSearch.bestImplicit(Implicits.scala:1181)
	at scala.tools.nsc.typechecker.Implicits$class.inferImplicit(Implicits.scala:67)
	at scala.tools.nsc.Global$analyzer$.inferImplicit(Global.scala:351)
	at scala.tools.nsc.typechecker.Typers$Typer.wrapImplicit$1(Typers.scala:168)
	at scala.tools.nsc.typechecker.Typers$Typer.inferView(Typers.scala:172)
	at scala.tools.nsc.typechecker.Typers$Typer.adaptToMember(Typers.scala:992)
	at scala.tools.nsc.typechecker.Typers$Typer.adaptToMemberWithArgs(Typers.scala:1031)
	at scala.tools.nsc.typechecker.Typers$Typer.typedSelect$1(Typers.scala:3563)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4167)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3355)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3355)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3355)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4106)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typedQualifier(Typers.scala:4352)
	at scala.tools.nsc.typechecker.Typers$Typer.typedQualifier(Typers.scala:4358)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4146)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3355)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedApply$1$1.apply(Typers.scala:3355)
	at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:624)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3355)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4106)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4346)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4423)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.cookJavaRawInfo(Symbols.scala:864)
	at scala.tools.nsc.typechecker.Infer$Inferencer.checkAccessible(Infer.scala:285)
	at scala.tools.nsc.typechecker.Typers$Typer.makeAccessible(Typers.scala:524)
	at scala.tools.nsc.typechecker.Typers$Typer.typedIdent$1(Typers.scala:3821)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4178)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4036)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4346)
	at scala.tools.nsc.typechecker.Typers$Typer.typedCase(Typers.scala:1957)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedCases$1.apply(Typers.scala:1975)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$typedCases$1.apply(Typers.scala:1974)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedCases(Typers.scala:1974)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4005)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4346)
	at scala.tools.nsc.typechecker.Typers$Typer.typedFunction(Typers.scala:2042)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3980)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4002)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4346)
	at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:4423)
	at scala.tools.nsc.typechecker.Namers$Namer.methodSig(Namers.scala:956)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1196)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:727)
	at scala.tools.nsc.symtab.Symbols$Symbol.initialize(Symbols.scala:839)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3899)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1512)
	at scala.tools.nsc.typechecker.Typers$Typer.typedClassDef(Typers.scala:1278)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3912)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3908)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:2100)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$24.apply(Typers.scala:2184)
	at scala.collection.immutable.List.loop$1(List.scala:117)
	at scala.collection.immutable.List.mapConserve(List.scala:133)
	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:2184)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3908)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4333)
	at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$3.apply(Analyzer.scala:94)
	at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:329)
	at scala.tools.nsc.interactive.Global$TyperRun$$anonfun$applyPhase$1.apply(Global.scala:1044)
	at scala.tools.nsc.interactive.Global$TyperRun$$anonfun$applyPhase$1.apply(Global.scala:1044)
	at scala.tools.nsc.symtab.SymbolTable.atPhase(SymbolTable.scala:95)
	at scala.tools.nsc.interactive.Global$TyperRun.applyPhase(Global.scala:1044)
	at scala.tools.nsc.interactive.Global$TyperRun.typeCheck(Global.scala:1037)
	at scala.tools.nsc.interactive.Global.scala$tools$nsc$interactive$Global$$typeCheck(Global.scala:555)
	at scala.tools.nsc.interactive.Global$$anonfun$backgroundCompile$5$$anonfun$apply$7.apply(Global.scala:472)
	at scala.tools.nsc.interactive.Global$$anonfun$backgroundCompile$5.apply(Global.scala:468)
	at scala.tools.nsc.interactive.Global$$anonfun$backgroundCompile$5.apply(Global.scala:468)
	at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:704)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:703)
	at scala.tools.nsc.interactive.Global.backgroundCompile(Global.scala:468)
	at scala.tools.nsc.interactive.PresentationCompilerThread.run(PresentationCompilerThread.scala:25)

So it crashes when building the structure for file A with some problems on file B.

The most common error messages with the same stacktrace are:

• Error during askOption.
• Exception thrown while creating override indicators for Foo.scala
• Compiler crash while building structure for /Users/viktor/dev/projects/.../Bar.scala

Thanks,
Viktor

hedefalk, do you still see this problem?
I cannot reproduce it with Scala IDE 2.0.0-2.9 and Lift 2.4M4.

Here's a more complete Scala file:

package dfk.ka.model
import net.liftweb._
import mapper._
import common._

trait Attachment extends CreatedUpdated {
  self: BaseMapper =>
  object data extends MappedBinary(this.asInstanceOf[MapperType])
  object mime extends MappedString(this.asInstanceOf[MapperType], 100)
  object name extends MappedString(this.asInstanceOf[MapperType], 100)
}

class EmailAttachment extends LongKeyedMapper[EmailAttachment] with Attachment with IdPK {
  def getSingleton = EmailAttachment

  object owner extends MappedLongForeignKey(this, EmailTemplate)
}

object EmailTemplate extends EmailTemplate with LongKeyedMetaMapper[EmailTemplate]

class EmailTemplate extends LongKeyedMapper[EmailTemplate] with Attachment with IdPK {
  def getSingleton = EmailTemplate
}

object EmailAttachment extends EmailAttachment with LongKeyedMetaMapper[EmailAttachment] {

}

Oh, yes I do. Everyday :)

Here's an updated stack trace using:

Eclipse SDK 3.7.1.M20120111-0800 org.eclipse.sdk.ide null
Scala IDE for Eclipse 2.1.0.nightly-2_09-201201300526-ec7d91c org.scala-ide.sdt.feature.feature.group scala-ide.org

and Lift 2.4:

java.lang.Error: KeyType in trait KeyedMapper cannot be instantiated from dfk.ka.model.ParticipantCard
	at scala.tools.nsc.symtab.SymbolTable.abort(SymbolTable.scala:34)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.throwError$1(Types.scala:3494)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.instParam$1(Types.scala:3497)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.toInstance$1(Types.scala:3509)
	at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:3525)
	at scala.tools.nsc.symtab.Types$Type.asSeenFrom(Types.scala:546)
	at scala.tools.nsc.symtab.Types$TypeRef.transform(Types.scala:1729)
	at scala.tools.nsc.symtab.Types$TypeRef.betaReduce(Types.scala:1864)
	at scala.tools.nsc.symtab.Types$TypeRef.normalize0(Types.scala:1885)
	at scala.tools.nsc.symtab.Types$TypeRef.normalize(Types.scala:1898)
	at scala.tools.nsc.symtab.Types$TypeRef.normalize0(Types.scala:1885)
	at scala.tools.nsc.symtab.Types$TypeRef.normalize(Types.scala:1898)
	at scala.tools.nsc.symtab.Types$deAlias$.apply(Types.scala:2965)
	at scala.tools.nsc.symtab.Types$deAlias$.apply(Types.scala:2962)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3216)
	at scala.tools.nsc.symtab.Types$TypeMap$$anonfun$mapOverArgs$1.apply(Types.scala:3212)
	at scala.tools.nsc.symtab.Types$class.map2Conserve(Types.scala:4985)
	at scala.tools.nsc.symtab.SymbolTable.map2Conserve(SymbolTable.scala:13)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOverArgs(Types.scala:3212)
	at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:3119)
	at scala.tools.nsc.symtab.Types$deAlias$.apply(Types.scala:2963)
	at scala.tools.nsc.symtab.Types$class.existentialAbstraction(Types.scala:2889)
	at scala.tools.nsc.symtab.SymbolTable.existentialAbstraction(SymbolTable.scala:13)
	at scala.tools.nsc.symtab.Types$ExistentialType.instantiateTypeParams(Types.scala:2223)
	at scala.tools.nsc.typechecker.Typers$Typer.typedArgToPoly$1(Typers.scala:2474)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2487)
	at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$32.apply(Typers.scala:2487)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:65)
	at scala.Tuple2$Zipped$$anonfun$map$1.apply(Tuple2.scala:63)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.Tuple2$Zipped.map(Tuple2.scala:63)
	at scala.tools.nsc.typechecker.Typers$Typer.doTypedApply(Typers.scala:2487)
	at scala.tools.nsc.typechecker.Typers$Typer.typedApply$1(Typers.scala:3373)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:4106)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typedBlock(Typers.scala:1920)
	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3953)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4273)
	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4333)
	at scala.tools.nsc.typechecker.Typers$Typer.typePrimaryConstrBody(Typers.scala:1064)
	at scala.tools.nsc.typechecker.Typers$Typer.parentTypes(Typers.scala:1137)
	at scala.tools.nsc.typechecker.Namers$Namer.templateSig(Namers.scala:733)
	at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:1191)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:551)
	at scala.tools.nsc.typechecker.Namers$Namer$$anonfun$typeCompleter$1.apply(Namers.scala:549)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1385)
	at scala.tools.nsc.typechecker.Namers$$anon$1.complete(Namers.scala:1381)
	at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:730)
	at scala.tools.nsc.symtab.Symbols$Symbol.initialize(Symbols.scala:842)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$ModuleOwner$class.addModule(ScalaStructureBuilder.scala:471)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$Builder.addModule(ScalaStructureBuilder.scala:844)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:905)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:925)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:925)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:925)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:925)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:925)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:925)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:925)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser$$anonfun$traverse$1.apply(ScalaStructureBuilder.scala:925)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$TreeTraverser.traverse(ScalaStructureBuilder.scala:925)
	at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.traverse(ScalaStructureBuilder.scala:876)
	at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$2$$anonfun$apply$4$$anonfun$apply$1.apply$mcV$sp(ScalaCompilationUnit.scala:77)
	at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$2$$anonfun$apply$4$$anonfun$apply$1.apply(ScalaCompilationUnit.scala:76)
	at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$2$$anonfun$apply$4$$anonfun$apply$1.apply(ScalaCompilationUnit.scala:76)
	at scala.tools.nsc.util.InterruptReq.liftedTree1$1(InterruptReq.scala:20)
	at scala.tools.nsc.util.InterruptReq.execute(InterruptReq.scala:19)
	at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:330)
	at scala.tools.nsc.interactive.PresentationCompilerThread.run(PresentationCompilerThread.scala:22)

I think this may be a duplicate of #1001220. In a nutshell, if a project is missing a dependency, sbt cannot build and the compiler goes nuts and spits out the sort of exception you reported.