Fix #8871: Detect explicit splices of quoted.Type[?]

Author: nicolasstucki

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

@@ -177,6 +177,10 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
             case prefix: ThisType if !tp.symbol.isStatic && level > levelOf(prefix.cls) =>
               tryHeal(tp.symbol, tp, pos)
             case prefix: TermRef if tp.symbol.isSplice =>
+              prefix.symbol.info.argInfos match
+                case (tb: TypeBounds) :: _ =>
+                  ctx.error(em"Cannot splice $tp with wildcard type", pos)
+                case _ =>
               // Heal explice type splice in the code
               if level > 0 then getQuoteTypeTags.getTagRef(prefix) else tp
             case prefix: TermRef if !prefix.symbol.isStatic && level > levelOf(prefix.symbol) =>

tests/pos/i6997.scala renamed to tests/neg/i6997.scala

@@ -2,7 +2,7 @@
 import scala.quoted._
 class Foo {
   def mcrImpl(body: Expr[Any])(using t: Type[_ <: Any])(using ctx: QuoteContext): Expr[Any] = '{
-    val tmp = ???.asInstanceOf[$t]
+    val tmp = ???.asInstanceOf[$t] // error // error
     tmp
   }
 }

tests/neg/i8871.scala

@@ -0,0 +1,8 @@
+import scala.quoted._
+object Macro {
+  def impl[A : Type](using qctx: QuoteContext): Unit = {
+    import qctx.tasty._
+    val tpe = typeOf[A].seal.asInstanceOf[quoted.Type[_ <: AnyRef]]
+    '{ (a: ${tpe}) => ???} // error
+  }
+}

tests/neg/i8871b.scala

@@ -0,0 +1,9 @@
+import scala.quoted._
+object Macro {
+  def impl[A : Type](using qctx: QuoteContext): Unit = {
+    import qctx.tasty._
+    val tpe/*: quoted.Type[? <: AnyKind]*/ = typeOf[A].seal
+    '{ f[$tpe] } // error
+  }
+  def f[T <: AnyKind]: Unit = ()
+}