support hk types

Author: bishabosha

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -925,6 +925,7 @@ object TypeOps:
     case tpe: AppliedType      => appliedTypePrefix(tpe.tycon)
     case tpe: AnnotatedType    => appliedTypePrefix(tpe.parent) // TODO: test
     case tpe: AndOrType        => Some(NoPrefix) // TODO: test
+    case tpe: HKTypeLambda     => appliedTypePrefix(tpe.resType)
     case _ =>
       // ignore HKTypeLambda/TypeBounds
       // what do do about

compiler/src/dotty/tools/dotc/transform/SymUtils.scala

@@ -168,7 +168,15 @@ object SymUtils:
         else children.map(problem).find(!_.isEmpty).getOrElse("")
       }
 
-    def isGenericSum(declScope: Symbol)(using Context): Boolean = whyNotGenericSum(declScope).isEmpty
+    def isGenericSum_(declScope: Symbol)(using Context): Either[String, Unit] =
+      val res = whyNotGenericSum(declScope)
+      if res.nonEmpty then
+        Left(res)
+      else
+        Right(())
+
+    def isGenericSum(declScope: Symbol)(using Context): Boolean =
+      isGenericSum_(declScope).isRight
 
     /** If this is a constructor, its owner: otherwise this. */
     final def skipConstructor(using Context): Symbol =

compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala

@@ -600,15 +600,16 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
         ordinalBody(_, _, pre, mirroredType))
     }
 
-    val pre = impl.removeAttachment(SubstPrefix).getOrElse(NoPrefix)
-    val mirroredType = impl.removeAttachment(OriginalMirroredType)
+    lazy val pre = impl.removeAttachment(SubstPrefix).getOrElse(NoPrefix)
+    lazy val mirroredType = impl.removeAttachment(OriginalMirroredType)
 
     if (clazz.is(Module)) {
       if (clazz.is(Case)) makeSingletonMirror()
-      else if (linked.isGenericProduct) makeProductMirror(linked, pre, mirroredType)
-      else if (linked.isGenericSum(clazz)) makeSumMirror(linked, pre, mirroredType)
-      else if (linked.is(Sealed))
-        derive.println(i"$linked is not a sum because ${linked.whyNotGenericSum(clazz)}")
+      else if linked.exists then
+        if (linked.isGenericProduct) makeProductMirror(linked, pre, mirroredType)
+        else if (linked.isGenericSum(clazz)) makeSumMirror(linked, pre, mirroredType)
+        else if (linked.is(Sealed))
+          derive.println(i"$linked is not a sum because ${linked.whyNotGenericSum(clazz)}")
     }
     else if (impl.removeAttachment(ExtendsSingletonMirror).isDefined)
       makeSingletonMirror()

compiler/src/dotty/tools/dotc/typer/Synthesizer.scala

@@ -288,7 +288,8 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
     val useCompanion = cls.useCompanionAsSumMirror
     val declScope = if useCompanion then cls.linkedClass else ctx.owner
 
-    if cls.isGenericSum(declScope) then
+    cls.isGenericSum_(declScope) match
+    case Right(_) =>
 
       val elemLabels = cls.children.map(c => ConstantType(Constant(c.name.toString)))
 
@@ -359,7 +360,9 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
           if useCompanion then companionPath(mirroredType, span)
           else anonymousMirror(monoType, mirroredType, ExtendsSumMirror, Some(pre), span)
         mirrorRef.cast(mirrorType)
-    else EmptyTree
+    case Left(whyNot) =>
+      report.error(i"$cls is not a valid sum type because $whyNot", ctx.source.atSpan(span))
+      EmptyTree
   end sumMirror
 
   def makeMirror

sbt-test/scala2-compat/i13332/build.sbt

@@ -9,5 +9,6 @@ lazy val lib = project.in(file("lib"))
 lazy val app = project.in(file("app"))
   .dependsOn(lib)
   .settings(
-    scalaVersion := scala3Version
+    scalaVersion := scala3Version,
+    scalacOptions += "-Ystop-after:inlining", // temporary until cause of large error is found
   )

sbt-test/scala2-compat/i13332/test

@@ -1 +1,2 @@
-> app/compile
+# temporarily expect failure, actually this will pass, but we stop compilation early to avoid a large error
+-> app/compile