Macro calling the apply of a case class nested in a trait leads to a typer error

[987Nabil]

Compiler version

3.1.0

Minimized code

package test
trait B {
  case class C(i: Int)
}

object A extends B

object X {
  val z = Y.testStuff[A.C]
}

package test
object Y {
  inline def testStuff[T]: T =
    ${testStuffImpl}

  def testStuffImpl[T: Type](using Quotes): Expr[T] = {
    import quotes.reflect.*

    Apply(
      Ref(Symbol.requiredMethod("test.A.C.apply")),
      List(Literal(IntConstant(1)))
    ).asExpr.asInstanceOf[Expr[T]]
  }
}

Output

exception while typing C.this of class class dotty.tools.dotc.ast.Trees$This # -1
exception while typing C.this.apply of class class dotty.tools.dotc.ast.Trees$Select # -1
exception while typing C.this.apply(1) of class class dotty.tools.dotc.ast.Trees$Apply # -1
exception while typing C.this.apply(1):test.A.C of class class dotty.tools.dotc.ast.Trees$Typed # -1
exception while typing C.this.apply(1):test.A.C of class class dotty.tools.dotc.ast.Trees$Inlined # -1
exception while typing def z: test.A.C = C.this.apply(1):test.A.C of class class dotty.tools.dotc.ast.Trees$DefDef # -1
exception while typing @scala.annotation.internal.SourceFile(
  "xxx/src/main/scala/test/B.scala"
) final module class X() extends Object() {
  private def writeReplace(): AnyRef = 
    new scala.runtime.ModuleSerializationProxy(classOf[test.X.type])
  def z: test.A.C = C.this.apply(1):test.A.C
} of class class dotty.tools.dotc.ast.Trees$TypeDef # -1
exception while typing package test {
  @scala.annotation.internal.SourceFile(
    "xxx/src/main/scala/test/B.scala"
  ) trait B() extends Object {
    case class C(i: Int) extends Object(), Product, Serializable {
      override def hashCode(): Int = 
        {
          var acc: Int = -889275714
          acc = scala.runtime.Statics#mix(acc, this.productPrefix.hashCode())
          acc = scala.runtime.Statics#mix(acc, C.this.i)
          scala.runtime.Statics#finalizeHash(acc, 1)
        }
      override def equals(x$0: Any): Boolean = 
        this.eq(x$0.$asInstanceOf[Object]).||(
          matchResult1[Boolean]: 
            {
              case val x1: (x$0 : Object) = x$0
              if 
                x1.$isInstanceOf[B.this.C @unchecked].&&(
                  x1.$asInstanceOf[B.this.C @unchecked].test$B$C$$$outer.eq(
                    B.this
                  )
                )
               then 
                {
                  case val x$0: B.this.C = x1.$asInstanceOf[B.this.C @unchecked]
                  return[matchResult1] this.i.==(x$0.i).&&(x$0.canEqual(this))
                }
               else ()
              return[matchResult1] false
            }
        )
      override def toString(): String = 
        scala.runtime.ScalaRunTime._toString(this)
      override def canEqual(that: Any): Boolean = 
        that.isInstanceOf[B.this.C @unchecked]
      override def productArity: Int = 1
      override def productPrefix: String = "C"
      override def productElement(n: Int): Any = 
        matchResult2[Int]: 
          {
            case val x3: (n : Int) = n
            if 0.==(x3) then return[matchResult2] this._1 else ()
            throw new IndexOutOfBoundsException(n.toString())
          }
      override def productElementName(n: Int): String = 
        matchResult3[String]: 
          {
            case val x4: (n : Int) = n
            if 0.==(x4) then return[matchResult3] "i" else ()
            throw new IndexOutOfBoundsException(n.toString())
          }
      def i: Int
      def copy(i: Int): B.this.C = new B.this.C(i)
      def copy$default$1: Int @uncheckedVariance = C.this.i
      def _1: Int = this.i
      private val $outer: test.B
      final def test$B$C$$$outer: test.B = C.this.$outer
    }
    final lazy module def C: B.this.C = new B.this.C()
    final module class C() extends AnyRef(), scala.deriving.Mirror.Product {
      def apply(i: Int): B.this.C = new B.this.C(i)
      def unapply(x$1: B.this.C): B.this.C = x$1
      override def toString: String = "C"
      type MirroredMonoType = B.this.C
      def fromProduct(x$0: Product): test.B.C.MirroredMonoType = 
        new B.this.C(x$0.productElement(0).$asInstanceOf[Int])
      private val $outer: test.B
      final def test$B$C$$$$outer: test.B = test.B.C.$outer
    }
  }
  final lazy module val A: test.A = new test.A()
  @scala.annotation.internal.SourceFile(
    "xxx/src/main/scala/test/B.scala"
  ) final module class A() extends Object(), test.B {
    private def writeReplace(): AnyRef = 
      new scala.runtime.ModuleSerializationProxy(classOf[test.A.type])
  }
  final lazy module val X: test.X = new test.X()
  @scala.annotation.internal.SourceFile(
    "xxx/src/main/scala/test/B.scala"
  ) final module class X() extends Object() {
    private def writeReplace(): AnyRef = 
      new scala.runtime.ModuleSerializationProxy(classOf[test.X.type])
    def z: test.A.C = C.this.apply(1):test.A.C
  }
} of class class dotty.tools.dotc.ast.Trees$PackageDef # -1
java.lang.AssertionError: assertion failed: asTerm called on not-a-Term val <none> while compiling /xxx/src/main/scala/test/B.scala, xxx/src/main/scala/test/Y.scala
[error] ## Exception when compiling 18 sources to xxx/target/scala-3.1.0/classes
[error] java.lang.AssertionError: assertion failed: asTerm called on not-a-Term val <none>
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
[error] dotty.tools.dotc.core.Symbols$Symbol.asTerm(Symbols.scala:163)
[error] dotty.tools.dotc.transform.ExplicitOuter$.dotty$tools$dotc$transform$ExplicitOuter$$$outerParamAccessor(ExplicitOuter.scala:228)
[error] dotty.tools.dotc.transform.ExplicitOuter$OuterOps$.loop$1(ExplicitOuter.scala:429)
[error] dotty.tools.dotc.transform.ExplicitOuter$OuterOps$.path$extension(ExplicitOuter.scala:438)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedThis(Erasure.scala:805)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2756)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2818)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:696)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2725)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2817)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3003)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:837)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2755)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2818)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2880)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedTyped(Erasure.scala:658)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2760)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2818)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2880)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.typedInlined(Typer.scala:1793)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedInlined(Erasure.scala:899)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2777)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2818)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3003)
[error] dotty.tools.dotc.typer.Typer.$anonfun$39(Typer.scala:2211)
[error] dotty.tools.dotc.typer.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:225)
[error] dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2211)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedDefDef(Erasure.scala:955)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2732)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2817)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2909)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2959)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1053)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2409)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1043)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$2(Typer.scala:2743)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2747)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2817)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2909)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2959)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1053)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2532)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2788)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2818)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3003)
[error] dotty.tools.dotc.transform.Erasure.run(Erasure.scala:132)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:308)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:309)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:261)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:272)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:280)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:289)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:228)
[error] dotty.tools.dotc.Driver.finish(Driver.scala:60)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:40)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:88)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:192)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:247)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:182)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:210)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:177)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:175)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:461)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:416)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:503)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:403)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:169)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:482)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:420)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2365)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2315)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:30)
[error] sbt.internal.io.Retry$.apply(Retry.scala:46)
[error] sbt.internal.io.Retry$.apply(Retry.scala:28)
[error] sbt.internal.io.Retry$.apply(Retry.scala:23)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:30)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2313)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:68)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:282)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:23)
[error] sbt.Execute.work(Execute.scala:291)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:282)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:64)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
[error] java.base/java.lang.Thread.run(Thread.java:834)
[error]      

Expectation

The apply of the case class can be called and an object can be created.

PS: When using a proxy method to the apply, it works just fine.

[nicolasstucki]

The example code has a bug hidden by the unchecked/unsound cast to Expr[T]. Using the asExprOf checked cast

-    ).asExpr.asInstanceOf[Expr[T]]
+    ).asExprOf[T]

we get

9 |  val z = Y.testStuff[A.C]
  |          ^^^^^^^^^^^^^^^^
  |Exception occurred while executing macro expansion.
  |java.lang.Exception: Expr cast exception: test.A.C.apply(1)
  |of type: test.A.C
  |did not conform to type: scala.Nothing
  |
  |     at scala.quoted.runtime.impl.QuotesImpl.asExprOf(QuotesImpl.scala:71)
  |     at scala.quoted.runtime.impl.QuotesImpl$reflect$TreeMethods$.asExprOf(QuotesImpl.scala:113)
  |     at scala.quoted.runtime.impl.QuotesImpl$reflect$TreeMethods$.asExprOf(QuotesImpl.scala:112)
  |     at test.Y$.testStuffImpl(Bar.scala:23)
  |
  | This location contains code that was inlined from Foo.scala:9

From this, we know that testStuffImpl is called as testStuffImpl[Nothing]. Therefore the code requires the following change to work (and should also use asExprOf)

  inline def testStuff[T]: T =
-   ${ testStuffImpl }
+   ${ testStuffImpl[T] }