Fix #9206: Add missing type symbol in Scala2 constructors

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

@@ -380,8 +380,7 @@ object SymDenotations {
       myParamss = pss
 
     final def setParamss(tparams: List[Symbol], vparamss: List[List[Symbol]])(using Context): Unit =
-      rawParamss = (if tparams.isEmpty then vparamss else tparams :: vparamss)
-        .filterConserve(!_.isEmpty)
+      rawParamss = (tparams :: vparamss).filterConserve(!_.isEmpty)
 
     final def setParamssFromDefs(tparams: List[TypeDef[?]], vparamss: List[List[ValDef[?]]])(using Context): Unit =
       setParamss(tparams.map(_.symbol), vparamss.map(_.map(_.symbol)))

compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

@@ -573,7 +573,11 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
 
         // println("reading type for " + denot) // !!! DEBUG
         val tp = at(inforef, () => readType()(ctx))
-        if denot.is(Method) then denot.rawParamss = paramssOfType(tp)
+        if denot.is(Method) then
+          var params = paramssOfType(tp)
+          if denot.isConstructor && denot.owner.typeParams.nonEmpty then
+            params = denot.owner.typeParams :: params
+          denot.rawParamss = params
 
         denot match {
           case denot: ClassDenotation if !isRefinementClass(denot.symbol) =>

tests/run-macros/i9206/Macros_1.scala

@@ -0,0 +1,11 @@
+
+import scala.quoted.{Expr, QuoteContext}
+
+object Inspect {
+  inline def inspect[T <: AnyKind]: String = ${ inspectTpe[T] }
+
+  def inspectTpe[T <: AnyKind](using tpe: quoted.Type[T], qctx0: QuoteContext): Expr[String] = {
+    val tree = summon[quoted.Type[T]].unseal.tpe.typeSymbol.tree
+    Expr(tree.show)
+  }
+}

tests/run-macros/i9206/Test_2.scala

@@ -0,0 +1,10 @@
+import Inspect._
+
+object Test extends App {
+  inspect[scala.collection.immutable.List[Int]]
+  inspect[java.lang.String]
+  inspect[String]
+  inspect[List[Unit]]
+  inspect[Some[Unit]]
+  inspect[Tuple1[Unit]]
+}