Aladdin - Scala Bugtracking
[#1106] project: compiler priority: low category: bug
submitter assigned to status date submitted
Nikolay Adriaan fixed 2007-05-14 16:58:38.0
subject [contrib #469] Passing singleton type as type constructor parameter crashes compiler
code 
class Par[S]
val p = new Par[String]
class Foo[T[x]<:Par[x]](t: T[String])

new Foo[p.type](p) // crashes compiler

The following works, however:

class Foo[T[x]<:Par[x]]
new Foo[p.type]

and

def f[T[x]<:Par[x]](t: T[String]) {}
f[p.type](p)

give errors: type arguments [Test.this.p.type] do not conform to method f's type parameter bounds [T&lt;: [x]>: Nothing &lt;: Test.this.Par[x]]

(The syntax of the parameter bounds in the compiler message is weird. I don't understand the &lt;: between the T and [x]. Does the Nothing refer to the [x]? ...)
what happened 
class scala.tools.nsc.symtab.Types$$anon$1
-1356532724
Exception in thread "main" java.lang.Error
        at scala.tools.nsc.symtab.Types$class.appliedType(Types.scala:1689)
        at scala.tools.nsc.symtab.SymbolTable.appliedType(SymbolTable.scala:10)
        at scala.tools.nsc.symtab.Types$AsSeenFromMap.instParam$0(Types.scala:1947)
        at scala.tools.nsc.symtab.Types$AsSeenFromMap.toInstance$0(Types.scala:1959)
        at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:1965)
        at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:1900)
        at scala.List$.loop$0(List.scala:243)
        at scala.List$.mapConserve(List.scala:260)
        at scala.tools.nsc.symtab.Types$TypeMap.mapOver(Types.scala:1819)
        at scala.tools.nsc.symtab.Types$AsSeenFromMap.apply(Types.scala:1967)
        at scala.tools.nsc.symtab.Types$Type.asSeenFrom(Types.scala:314)
        at scala.tools.nsc.symtab.Types$Type.memberType(Types.scala:343)
        at scala.tools.nsc.typechecker.Infer$Inferencer.checkAccessible(Infer.scala:370)
        at scala.tools.nsc.typechecker.Typers$Typer.typedSelect$0(Typers.scala:2193)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:2589)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2650)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$96.apply(Typers.scala:2013)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$96.apply(Typers.scala:2013)
        at scala.tools.nsc.typechecker.Typers$Typer.silent(Typers.scala:517)
        at scala.tools.nsc.typechecker.Typers$Typer.typedApply$0(Typers.scala:2013)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:2567)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2650)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2694)
        at scala.tools.nsc.typechecker.Typers$Typer.computeType(Typers.scala:2734)
        at scala.tools.nsc.typechecker.Namers$Namer.typeSig(Namers.scala:683)
        at scala.tools.nsc.typechecker.Namers$Namer$$anon$0.complete(Namers.scala:356)
        at scala.tools.nsc.symtab.Symbols$Symbol.info(Symbols.scala:413)
        at scala.tools.nsc.symtab.Symbols$Symbol.initialize(Symbols.scala:521)
        at scala.tools.nsc.typechecker.Typers$Typer.addGetterSetter(Typers.scala:989)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$30.apply(Typers.scala:1056)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$30.apply(Typers.scala:1056)
        at scala.List.flatMap(List.scala:966)
        at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1056)
        at scala.tools.nsc.typechecker.Typers$Typer.typedModuleDef(Typers.scala:969)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:2418)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2650)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2683)
        at scala.tools.nsc.typechecker.Typers$Typer.typedStat$0(Typers.scala:1398)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$58.apply(Typers.scala:1428)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$58.apply(Typers.scala:1428)
        at scala.List$.loop$0(List.scala:243)
        at scala.List$.mapConserve(List.scala:260)
        at scala.List$.loop$0(List.scala:247)
        at scala.List$.mapConserve(List.scala:260)
        at scala.List$.loop$0(List.scala:247)
        at scala.List$.mapConserve(List.scala:260)
        at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:1428)
        at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1058)
        at scala.tools.nsc.typechecker.Typers$Typer.typedModuleDef(Typers.scala:969)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:2418)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2650)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2683)
        at scala.tools.nsc.typechecker.Typers$Typer.typedStat$0(Typers.scala:1398)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$58.apply(Typers.scala:1428)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$58.apply(Typers.scala:1428)
        at scala.List$.loop$0(List.scala:243)
        at scala.List$.mapConserve(List.scala:260)
        at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:1428)
        at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1058)
        at scala.tools.nsc.typechecker.Typers$Typer.typedModuleDef(Typers.scala:969)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:2418)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2650)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2683)
        at scala.tools.nsc.typechecker.Typers$Typer.typedStat$0(Typers.scala:1398)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$58.apply(Typers.scala:1428)
        at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$58.apply(Typers.scala:1428)
        at scala.List$.loop$0(List.scala:243)
        at scala.List$.mapConserve(List.scala:260)
        at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:1428)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:2411)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2650)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:2683)
        at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$1.apply(Analyzer.scala:38)
        at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:241)
        at scala.tools.nsc.Global$GlobalPhase$$anonfun$2.apply(Global.scala:230)
        at scala.tools.nsc.Global$GlobalPhase$$anonfun$2.apply(Global.scala:230)
        at scala.Iterator$class.foreach(Iterator.scala:369)
        at scala.collection.mutable.ListBuffer$$anon$0.foreach(ListBuffer.scala:245)
        at scala.tools.nsc.Global$GlobalPhase.run(Global.scala:230)
        at scala.tools.nsc.Global$Run.compileSources(Global.scala:498)
        at scala.tools.nsc.Interpreter$Request.compile(Interpreter.scala:669)
        at scala.tools.nsc.Interpreter.interpret(Interpreter.scala:433)
        at scala.tools.nsc.InterpreterLoop.interpretStartingWith(InterpreterLoop.scala:236)
        at scala.tools.nsc.InterpreterLoop.command(InterpreterLoop.scala:223)
        at scala.tools.nsc.InterpreterLoop.repl(InterpreterLoop.scala:136)
        at scala.tools.nsc.InterpreterLoop.main(InterpreterLoop.scala:271)
        at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:92)
        at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
what expected Compiler error message
[back to overview]
Changes of this bug report
Nikolay  edited on  2007-05-14 16:59:05.0
Adriaan  edited on  2007-05-16 01:28:56.0
I agree that the internal representation of higher-kinded types isn't optimal -- suggestions welcome

here, T's info is a polytype that contains a typebounds: [x] (>: Nothing <: Par[x]) the polytype denotes that the type takes one type argument

should be fixed in r11056

Adriaan  edited on  2007-05-16 01:29:08.0