Fix defaultParams macro for generic class

build.sbt

@@ -2,7 +2,7 @@ Global / idePackagePrefix := Some("dummy")
 
 def DottyProject(name: String): Project =
   Project.apply(name, file(name)).settings(
-    scalaVersion := "3.1.0",
+    scalaVersion := "3.1.3",
     Compile / scalaSource := baseDirectory.value / "src",
   )
 

build.sc

@@ -1,7 +1,7 @@
 import mill._, scalalib._
 
 trait DottyModule extends ScalaModule {
-  def scalaVersion = "3.1.0"
+  def scalaVersion = "3.1.3"
   def scalacOptions = Seq("-Xcheck-macros")
 }
 

defaultParamsInference/src/Test.scala

@@ -1,12 +1,12 @@
 package dummy
 
-case class Person(name: String, address: String = "Zuricch", foo: Int, age: Int = 26)
+case class Person[T](name: String, address: String = "Zuricch", foo: Int, age: Int = 26, bar: List[T] = Nil)
 
 object Person:
   val x = 10
 
 @main def test(): Unit =
   val p1 = Person("John", foo = 10)
   println(p1)
-  println(defaultParams[Person])
-  assert(defaultParams[Person] == Map("address" -> "Zuricch", "age" -> 26))
+  println(defaultParams[Person[Double]])
+  assert(defaultParams[Person[Double]] == Map("address" -> "Zuricch", "age" -> 26, "bar" -> Nil))

defaultParamsInference/src/macro.scala

@@ -1,12 +1,16 @@
 package dummy
 
+import scala.annotation.experimental
 import scala.quoted.*
 
 inline def defaultParams[T]: Map[String, Any] = ${ defaultParmasImpl[T] }
 
+@experimental // because .typeArgs is @experimental
 def defaultParmasImpl[T](using quotes: Quotes, tpe: Type[T]): Expr[Map[String, Any]] =
   import quotes.reflect.*
-  val sym = TypeTree.of[T].symbol
+  val typ = TypeRepr.of[T]
+  val sym = typ.typeSymbol
+  val typeArgs = typ.typeArgs
   val comp = sym.companionClass
   val mod = Ref(sym.companionModule)
   val names =
@@ -16,10 +20,10 @@ def defaultParmasImpl[T](using quotes: Quotes, tpe: Type[T]): Expr[Map[String, A
     Expr.ofList(names.map(Expr(_)))
 
   val body = comp.tree.asInstanceOf[ClassDef].body
-  val idents: List[Ref] =
+  val idents: List[Term] =
     for case deff @ DefDef(name, _, _, _) <- body
     if name.startsWith("$lessinit$greater$default")
-    yield mod.select(deff.symbol)
+    yield mod.select(deff.symbol).appliedToTypes(typeArgs)
   val identsExpr: Expr[List[Any]] =
     Expr.ofList(idents.map(_.asExpr))