Disallow local term references in staged types (scala#16362)

Fixes scala#15917
Fixes scala#16355

Author: nicolasstucki

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

@@ -176,8 +176,10 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
   /** If the type refers to a locally defined symbol (either directly, or in a pickled type),
    *  check that its staging level matches the current level.
    *  - Static types and term are allowed at any level.
-   *  - If a type reference is used a higher level, then it is inconsistent. Will attempt to heal before failing.
-   *  - If a term reference is used a different level, then it is inconsistent.
+   *  - If a type reference is used a higher level, then it is inconsistent.
+   *    Will attempt to heal before failing.
+   *  - If a term reference is used a higher level, then it is inconsistent.
+   *    It cannot be healed because the term will not exist in any future stage.
    *
    *  If `T` is a reference to a type at the wrong level, try to heal it by replacing it with
    *  a type tag of type `quoted.Type[T]`.
@@ -206,6 +208,8 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
               tryHeal(prefix.symbol, tp, pos)
             case _ =>
               mapOver(tp)
+        case tp @ TermRef(NoPrefix, _) if !tp.symbol.isStatic && level > levelOf(tp.symbol) =>
+          levelError(tp.symbol, tp, pos)
         case tp: ThisType if level != -1 && level != levelOf(tp.cls) =>
           levelError(tp.cls, tp, pos)
         case tp: AnnotatedType =>

tests/neg-macros/i15917.scala

@@ -0,0 +1,6 @@
+import scala.quoted.*
+
+def m(using Quotes): Expr[Option[_]] =
+  val s = 3
+  type st = s.type
+  '{ Some(${ Expr(s) }: st) } // error

tests/neg-macros/i16355a.scala

@@ -0,0 +1,35 @@
+//> using scala "3.2.1"
+import scala.quoted.Expr
+import scala.quoted.Type
+import scala.quoted.quotes
+import scala.quoted.Quotes
+
+object macros {
+
+  inline transparent def mkNames[A]: List[Any] = ${ mkNamesImpl[A] }
+
+  def mkNamesImpl[A: Type](using Quotes): Expr[List[Any]] = {
+    import quotes.reflect._
+
+    val fieldNames = TypeRepr.of[A].typeSymbol.declaredFields.map(_.name)
+
+    val types = fieldNames
+      .map { f =>
+        val t1 = ConstantType(StringConstant(f))
+        t1.asType match {
+          case '[t1Type] => TypeRepr.of[(t1Type, "aa")]
+        }
+      }
+      .reduceLeft[TypeRepr](OrType(_, _))
+
+    types.asType match {
+      case '[ttt] =>
+        Expr.ofList[ttt](
+          fieldNames.map { v =>
+            Expr[(v.type, "aa")](v -> "aa").asExprOf[ttt] // error
+          }
+        )
+    }
+  }
+
+}

tests/neg-macros/i16355b.scala

@@ -0,0 +1,4 @@
+import scala.quoted._
+def test(v: String)(using Quotes): Any =
+  Type.of : Type[v.type] // error
+  Type.of[v.type] // error