Merge pull request #8450 from dotty-staging/fix-#8389

Fix #8389: Hande immutable.Seq

Author: liufengyun

library/src/scala/tasty/reflect/SourceCodePrinter.scala

@@ -1443,7 +1443,9 @@ class SourceCodePrinter[R <: Reflection & Singleton](val tasty: R)(syntaxHighlig
 
     object Sequence {
       def unapply(tpe: Type)(using ctx: Context): Option[Type] = tpe match {
-        case AppliedType(seq, (tp: Type) :: Nil) if seq.typeSymbol == ctx.requiredClass("scala.collection.Seq") => Some(tp)
+        case AppliedType(seq, (tp: Type) :: Nil)
+            if seq.typeSymbol == ctx.requiredClass("scala.collection.Seq") || seq.typeSymbol == ctx.requiredClass("scala.collection.immutable.Seq") =>
+          Some(tp)
         case _ => None
       }
     }

tests/run-custom-args/tasty-inspector/i8364.scala

@@ -0,0 +1,12 @@
+import scala.tasty._
+import scala.tasty.inspector._
+
+@main def Test = {
+  val inspector = new TastyInspector {
+    def processCompilationUnit(reflect: Reflection)(tree: reflect.Tree): Unit = {
+      import reflect.{_, given _}
+      println(tree.show)
+    }
+  }
+  inspector.inspect("", List("scala.tasty.Reflection"))
+}

tests/run-custom-args/tasty-inspector/i8389.scala

@@ -0,0 +1,32 @@
+import scala.tasty._
+import scala.tasty.inspector._
+
+@main def Test = {
+  // in dotty-example-project
+  val inspector = new TastyInspector {
+    def processCompilationUnit(reflect: Reflection)(tree: reflect.Tree): Unit = {
+      import reflect.{_, given _}
+      println(tree.show)
+    }
+  }
+  inspector.inspect("", List("TraitParams"))
+}
+
+object TraitParams {
+
+  trait Base(val msg: String)
+  class A extends Base("Hello")
+  class B extends Base("Dotty!")
+
+  // Union types only exist in Dotty, so there's no chance that this will accidentally be compiled with Scala 2
+  private def printMessages(msgs: (A | B)*) = println(msgs.map(_.msg).mkString(" "))
+
+  def test: Unit = {
+
+    printMessages(new A, new B)
+
+    // Sanity check the classpath: this won't run if the dotty jar is not present.
+    val x: Int => Int = z => z
+    x(1)
+  }
+}