Hello.

I took a look at first two pages with tickets and couldn't found anything with "tooltip".

The phenomenon does not look really new to me: the same thing was happening in past 1.5 years every time when i wanted to give the scala one more chance... Now i (once again...) reinstalled everything completely from scratch:
- jre, jdk 1.6u20
- eclipse galileo 3.5.2 XYZsomething (see details)
- downloaded & installed everything from this update site: [http://download.scala-ide.org/update-current-35] with the eclipse update system
- new workspace
- opened scala view, created new scala project, created HelloWorld-Object in the default package
- clicked the green button... Error Prompt:

eclipse.buildId=M20100211-1343
java.version=1.6.0_20
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=de_DE
Command-line arguments: -os win32 -ws win32 -arch x86


Error
Tue Aug 24 21:23:45 CEST 2010
An internal error occurred during: "Compute launch button tooltip".

java.lang.AssertionError: assertion failed
at scala.Predef$.assert(Predef.scala:77)
at scala.tools.nsc.symtab.SymbolTable.phase_$eq(SymbolTable.scala:69)
at scala.tools.nsc.symtab.Symbols$Symbol.unsafeTypeParams(Symbols.scala:914)
at scala.tools.nsc.symtab.Types$TypeRef.typeParamsDirect(Types.scala:1686)
at scala.tools.nsc.symtab.Types$TypeRef.normalize(Types.scala:1762)
at scala.tools.nsc.symtab.Definitions$definitions$.isFunctionType(Definitions.scala:341)
at scala.tools.nsc.symtab.Types$TypeRef.safeToString(Types.scala:1828)
at scala.reflect.generic.Types$AbsType.toString(Types.scala:27)
at java.lang.String.valueOf(Unknown Source)
at scala.collection.mutable.StringBuilder.append(StringBuilder.scala:178)
at scala.collection.TraversableOnce$$anonfun$addString$1.apply(TraversableOnce.scala:504)
at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
at scala.collection.immutable.List.foreach(List.scala:45)
at scala.collection.TraversableOnce$class.addString(TraversableOnce.scala:502)
at scala.collection.immutable.List.addString(List.scala:45)
at scala.collection.TraversableOnce$class.mkString(TraversableOnce.scala:467)
at scala.collection.immutable.List.mkString(List.scala:45)
at scala.tools.nsc.symtab.Types$TypeRef.safeToString(Types.scala:1845)
at scala.reflect.generic.Types$AbsType.toString(Types.scala:27)
at scala.tools.nsc.ast.TreePrinters$TreePrinter.printRaw(TreePrinters.scala:348)
at scala.tools.nsc.ast.TreePrinters$TreePrinter.print(TreePrinters.scala:392)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$DefOwner$class.addDef(ScalaStructureBuilder.scala:551)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$Builder.addDef(ScalaStructureBuilder.scala:727)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.traverse(ScalaStructureBuilder.scala:798)
at scala.tools.nsc.ast.Trees$Traverser$$anonfun$traverseStats$1.apply(Trees.scala:889)
at scala.tools.nsc.ast.Trees$Traverser$$anonfun$traverseStats$1.apply(Trees.scala:887)
at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
at scala.collection.immutable.List.foreach(List.scala:45)
at scala.tools.nsc.ast.Trees$Traverser.traverseStats(Trees.scala:887)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.traverse(ScalaStructureBuilder.scala:817)
at scala.reflect.generic.Trees$Traverser$$anonfun$traverse$3.apply$mcV$sp(Trees.scala:473)
at scala.reflect.generic.Trees$Traverser.atOwner(Trees.scala:581)
at scala.reflect.generic.Trees$Traverser.traverse(Trees.scala:472)
at scala.tools.nsc.ast.Trees$Traverser.traverse(Trees.scala:881)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.scala$tools$eclipse$javaelements$ScalaStructureBuilder$StructureBuilderTraverser$$super$traverse(ScalaStructureBuilder.scala:763)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$$anonfun$traverse$3.apply$mcV$sp(ScalaStructureBuilder.scala:775)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.atBuilder(ScalaStructureBuilder.scala:836)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.traverse(ScalaStructureBuilder.scala:775)
at scala.reflect.generic.Trees$Traverser$$anonfun$traverseTrees$1.apply(Trees.scala:566)
at scala.reflect.generic.Trees$Traverser$$anonfun$traverseTrees$1.apply(Trees.scala:566)
at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
at scala.collection.immutable.List.foreach(List.scala:45)
at scala.reflect.generic.Trees$Traverser.traverseTrees(Trees.scala:566)
at scala.reflect.generic.Trees$Traverser$$anonfun$traverse$1.apply$mcV$sp(Trees.scala:465)
at scala.reflect.generic.Trees$Traverser.atOwner(Trees.scala:581)
at scala.reflect.generic.Trees$Traverser.traverse(Trees.scala:464)
at scala.tools.nsc.ast.Trees$Traverser.traverse(Trees.scala:881)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.scala$tools$eclipse$javaelements$ScalaStructureBuilder$StructureBuilderTraverser$$super$traverse(ScalaStructureBuilder.scala:763)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser$$anonfun$traverse$1.apply$mcV$sp(ScalaStructureBuilder.scala:763)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.atBuilder(ScalaStructureBuilder.scala:836)
at scala.tools.eclipse.javaelements.ScalaStructureBuilder$StructureBuilderTraverser.traverse(ScalaStructureBuilder.scala:763)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$1.apply(ScalaCompilationUnit.scala:100)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$buildStructure$1.apply(ScalaCompilationUnit.scala:91)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply$mcV$sp(Cached.scala:22)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$class.locked(Cached.scala:83)
at scala.tools.eclipse.util.Cached$class.apply(Cached.scala:20)
at scala.tools.eclipse.ScalaPresentationCompiler$CachedCompilerResult.apply(ScalaPresentationCompiler.scala:67)
at scala.tools.eclipse.ScalaPresentationCompiler.withCompilerResult(ScalaPresentationCompiler.scala:90)
at scala.tools.eclipse.ScalaProject$$anonfun$withCompilerResult$1.apply(ScalaProject.scala:368)
at scala.tools.eclipse.ScalaProject$$anonfun$withCompilerResult$1.apply(ScalaProject.scala:367)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply$mcV$sp(Cached.scala:22)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$class.locked(Cached.scala:83)
at scala.tools.eclipse.util.Cached$class.apply(Cached.scala:20)
at scala.tools.eclipse.ScalaProject$$anon$1.apply(ScalaProject.scala:39)
at scala.tools.eclipse.ScalaProject.withPresentationCompiler(ScalaProject.scala:363)
at scala.tools.eclipse.ScalaProject.withCompilerResult(ScalaProject.scala:367)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$withCompilerResult$1.apply(ScalaCompilationUnit.scala:49)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$class.withDocument(ScalaCompilationUnit.scala:44)
at scala.tools.eclipse.javaelements.ScalaClassFile.withDocument(ScalaClassFile.scala:30)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$class.withCompilerResult(ScalaCompilationUnit.scala:49)
at scala.tools.eclipse.javaelements.ScalaClassFile.withCompilerResult(ScalaClassFile.scala:30)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$class.buildStructure(ScalaCompilationUnit.scala:91)
at scala.tools.eclipse.javaelements.ScalaClassFile.buildStructure(ScalaClassFile.scala:30)
at org.eclipse.jdt.internal.core.Openable.generateInfos(Openable.java:258)
at scala.tools.eclipse.javaelements.ScalaClassFile.generateInfos0(ScalaClassFile.scala:105)
at scala.tools.eclipse.javaelements.CompilationUnitAdapter.generateInfos(CompilationUnitAdapter.scala:59)
at org.eclipse.jdt.internal.core.JavaElement.openWhenClosed(JavaElement.java:515)
at org.eclipse.jdt.internal.core.JavaElement.getElementInfo(JavaElement.java:252)
at org.eclipse.jdt.internal.core.JavaElement.getElementInfo(JavaElement.java:238)
at scala.tools.eclipse.contribution.weaving.jdt.cfprovider.ClassFileProviderAspect.ajc$around$scala_tools_eclipse_contribution_weaving_jdt_cfprovider_ClassFileProviderAspect$12$998f7f7a(ClassFileProviderAspect.aj:307)
at org.eclipse.jdt.internal.compiler.parser.SourceTypeConverter.convert(SourceTypeConverter.java:107)
at org.eclipse.jdt.internal.compiler.parser.SourceTypeConverter.buildCompilationUnit(SourceTypeConverter.java:93)
at org.eclipse.jdt.internal.core.hierarchy.HierarchyResolver.accept(HierarchyResolver.java:147)
at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForType(LookupEnvironment.java:139)
at org.eclipse.jdt.internal.compiler.lookup.PackageBinding.getTypeOrPackage(PackageBinding.java:183)
at org.eclipse.jdt.internal.compiler.lookup.Scope.getPackage(Scope.java:2284)
at org.eclipse.jdt.internal.compiler.ast.QualifiedTypeReference.getTypeBinding(QualifiedTypeReference.java:69)
at org.eclipse.jdt.internal.compiler.ast.TypeReference.internalResolveType(TypeReference.java:130)
at org.eclipse.jdt.internal.compiler.ast.TypeReference.resolveType(TypeReference.java:197)
at org.eclipse.jdt.internal.compiler.lookup.SourceTypeBinding.resolveTypesFor(SourceTypeBinding.java:1370)
at org.eclipse.jdt.internal.compiler.lookup.SourceTypeBinding.methods(SourceTypeBinding.java:1090)
at org.eclipse.jdt.internal.compiler.lookup.SourceTypeBinding.faultInTypesForFieldsAndMethods(SourceTypeBinding.java:593)
at org.eclipse.jdt.internal.compiler.lookup.CompilationUnitScope.faultInTypes(CompilationUnitScope.java:447)
at org.eclipse.jdt.internal.core.hierarchy.HierarchyResolver.resolve(HierarchyResolver.java:781)
at org.eclipse.jdt.internal.core.hierarchy.HierarchyResolver.resolve_aroundBody4(HierarchyResolver.java:587)
at org.eclipse.jdt.internal.core.hierarchy.HierarchyResolver$AjcClosure5.run(HierarchyResolver.java:1)
at scala.tools.eclipse.contribution.weaving.jdt.cfprovider.ClassFileProviderAspect.ajc$around$scala_tools_eclipse_contribution_weaving_jdt_cfprovider_ClassFileProviderAspect$8$2bb6fd97proceed(ClassFileProviderAspect.aj:1)
at scala.tools.eclipse.contribution.weaving.jdt.cfprovider.ClassFileProviderAspect.ajc$around$scala_tools_eclipse_contribution_weaving_jdt_cfprovider_ClassFileProviderAspect$8$2bb6fd97(ClassFileProviderAspect.aj:222)
at org.eclipse.jdt.internal.core.hierarchy.HierarchyResolver.resolve(HierarchyResolver.java:554)
at org.eclipse.jdt.internal.core.hierarchy.HierarchyBuilder.buildSupertypes(HierarchyBuilder.java:115)
at org.eclipse.jdt.internal.core.hierarchy.IndexBasedHierarchyBuilder.build(IndexBasedHierarchyBuilder.java:135)
at org.eclipse.jdt.internal.core.hierarchy.TypeHierarchy.compute(TypeHierarchy.java:300)
at org.eclipse.jdt.internal.core.hierarchy.TypeHierarchy.refresh(TypeHierarchy.java:1255)
at org.eclipse.jdt.internal.core.CreateTypeHierarchyOperation.executeOperation(CreateTypeHierarchyOperation.java:90)
at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:728)
at org.eclipse.jdt.internal.core.JavaModelOperation.runOperation(JavaModelOperation.java:788)
at org.eclipse.jdt.internal.core.SourceType.newSupertypeHierarchy(SourceType.java:726)
at org.eclipse.jdt.internal.core.SourceType.newSupertypeHierarchy(SourceType.java:678)
at org.eclipse.jdt.internal.launching.JavaLaunchableTester.hasSuperclass(JavaLaunchableTester.java:470)
at org.eclipse.jdt.internal.launching.JavaLaunchableTester.test(JavaLaunchableTester.java:613)
at org.eclipse.core.internal.expressions.Property.test(Property.java:58)
at org.eclipse.core.internal.expressions.TestExpression.evaluate(TestExpression.java:99)
at org.eclipse.core.internal.expressions.CompositeExpression.evaluateOr(CompositeExpression.java:68)
at org.eclipse.core.internal.expressions.OrExpression.evaluate(OrExpression.java:21)
at org.eclipse.core.internal.expressions.CompositeExpression.evaluateAnd(CompositeExpression.java:53)
at org.eclipse.core.internal.expressions.AndExpression.evaluate(AndExpression.java:29)
at org.eclipse.core.internal.expressions.CompositeExpression.evaluateAnd(CompositeExpression.java:53)
at org.eclipse.core.internal.expressions.IterateExpression.evaluate(IterateExpression.java:150)
at org.eclipse.core.internal.expressions.CompositeExpression.evaluateAnd(CompositeExpression.java:53)
at org.eclipse.core.internal.expressions.WithExpression.evaluate(WithExpression.java:72)
at org.eclipse.core.internal.expressions.CompositeExpression.evaluateAnd(CompositeExpression.java:53)
at org.eclipse.core.internal.expressions.EnablementExpression.evaluate(EnablementExpression.java:53)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchShortcutExtension.evalEnablementExpression(LaunchShortcutExtension.java:287)
at org.eclipse.debug.internal.ui.contextlaunching.LaunchingResourceManager.getShortcutsForSelection(LaunchingResourceManager.java:439)
at org.eclipse.debug.internal.ui.contextlaunching.LaunchingResourceManager.pruneShortcuts(LaunchingResourceManager.java:374)
at org.eclipse.debug.internal.ui.contextlaunching.LaunchingResourceManager.getLabel(LaunchingResourceManager.java:299)
at org.eclipse.debug.internal.ui.contextlaunching.LaunchingResourceManager.computeLabels(LaunchingResourceManager.java:228)
at org.eclipse.debug.internal.ui.contextlaunching.LaunchingResourceManager$2.run(LaunchingResourceManager.java:138)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

I suppose all this error prompts are very daunting for people who are new to all this... And it's quite depressing even for scala-fans like me.
I hope that this is somehow connected to the good old "Editor does not contain main type"-Error which also occures frequently (at least at my computer, although i did'nt know what should be so special about it)

thanking you in anticipation

greetengs