Fix #8843: Normalize type when constant folding

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -510,7 +510,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
    */
   def constToLiteral(tree: Tree)(implicit ctx: Context): Tree = {
     val tree1 = ConstFold(tree)
-    tree1.tpe.widenTermRefExpr.dealias match {
+    tree1.tpe.widenTermRefExpr.dealias.normalized match {
       case ConstantType(value) =>
         if (isIdempotentExpr(tree1)) Literal(value).withSpan(tree.span)
         else tree1 match {

tests/pos/i8843.scala

@@ -0,0 +1,11 @@
+class C:
+  type X <: Tuple
+
+inline def f(c: C): Unit = {
+  inline val size = compiletime.constValue[Tuple.Size[c.X]]
+  val n = size
+  val m: Int = n
+  ???
+}
+
+def test: Unit = f(??? : C { type X = Tuple1[Any] })