Migrated from http://lampsvn.epfl.ch/trac/scala/ticket/134
Reporter rafaeldff
Going through the following steps often, but not always, causes the error:
1 - Create a new scala project
2 - Create a package (I named it pkg) and then a new Scala class file (I named it URIs.scala)
3 - Post the following code into it:

package pkg

import java.net.URI

class Parameter(val name:String, val value:String)

object URIBuilder {
   class AbsoluteHierarchicalURIBuilder {
      var scheme = "http"
      var queryParams: List[Parameter] = Nil
      /* null defaults are expected by java.net.URI constructor */
      var authority:String = null
      var path:String = null
      
      private def queryString: String = 
         queryParams.map(p => p.name + "=" + p.value).mkString("","&","")
      /** Control abstraction for methods returning this **/
      private def s(f: => Unit): AbsoluteHierarchicalURIBuilder = {f; this}
         
      def withScheme(it:String) = s{scheme = it}
      def withAuthority(it:String) = s{authority = it}
      def withPath(it:String) = s{path = it}
      def withQuery(params: List[Parameter]) = s{this.queryParams = queryParams ::: params}
      def build: URI = new URI(scheme, authority, path, queryString, null)
   }
   
   def make = new AbsoluteHierarchicalURIBuilder();
   
}

4 - Create a new Scala object file (I named it CausingProblems) and paste the following code:

package pkg

object CausingProblems {
   val uri = URIBuilder.make withAuthority "some" withPath "PATH" withQuery Nil build;
}

5 - Create a new line below "_object CausingProblems {_" and type in

case class Foo

Usually Eclipse hangs in step 5 and the error log shows this message:

eclipse.buildId=I20061102-1715
java.version=1.6.0_02
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=pt_BR
Command-line arguments:  -os win32 -ws win32 -arch x86 -data D:\dev\eclipseScala\workspace
This is a continuation of log file D:\dev\eclipseScala\workspace\.metadata\.bak_6.log
Created Time: 2007-09-26 03:41:21.562

Error
Wed Sep 26 03:41:29 BRT 2007
probable infinite typer cycle on c4939r::CausingProblems

java.lang.Error
at lampion.eclipse.Plugin$class.logError(Plugin.scala:230)
at scala.tools.eclipse.Driver.logError(Driver.scala:7)
at lampion.core.Plugin$ProjectImpl$class.logError(Plugin.scala:15)
at scala.tools.eclipse.Driver$Project.logError(Driver.scala:10)
at lampion.compiler.Typers0$$anonfun$9.apply(Typers0.scala:246)
at lampion.compiler.Typers0$$anonfun$9.apply(Typers0.scala:244)
at scala.collection.jcl.MutableIterator$class.retain(MutableIterator.scala:60)
at scala.collection.jcl.MutableIterator$Wrapper.retain(MutableIterator.scala:14)
at scala.collection.jcl.MutableIterable$class.retain(MutableIterable.scala:45)
at scala.collection.jcl.Set$class.retain(Set.scala:27)
at scala.collection.jcl.LinkedHashSet.retain(LinkedHashSet.scala:18)
at lampion.compiler.Typers0$class.flushTyper(Typers0.scala:244)
at lampion.compiler.Typers0$class.afterParsing(Typers0.scala:333)
at scala.tools.eclipse.Driver$Project.afterParsing(Driver.scala:10)
at lampion.presentation.Presentations$ProjectImpl$class.protected$afterParsing(Presentations.scala:335)
at scala.tools.eclipse.Driver$Project.protected$afterParsing(Driver.scala:10)
at lampion.presentation.Presentations$ProjectImpl$Job.run(Presentations.scala:335)

I'm using Eclipse 3.3.0 with the "Lampion Scala Plugin 2.6.1.B3".