Fix scala#7048: Check for splice stability

Author: nicolasstucki

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

@@ -18,6 +18,7 @@ import dotty.tools.dotc.util.SourcePosition
 import dotty.tools.dotc.util.Spans._
 import dotty.tools.dotc.transform.SymUtils._
 import dotty.tools.dotc.transform.TreeMapWithStages._
+import dotty.tools.dotc.typer.Checking
 import dotty.tools.dotc.typer.Implicits.SearchFailureType
 import dotty.tools.dotc.typer.Inliner
 
@@ -31,7 +32,7 @@ import scala.annotation.constructorOnly
  *
  *  Type healing consists in transforming a phase inconsistent type `T` into a splice of `implicitly[Type[T]]`.
  */
-class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(ictx) {
+class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(ictx) with Checking {
   import tpd._
 
   private val InAnnotation = Property.Key[Unit]()
@@ -212,7 +213,8 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
     val reqType = defn.QuotedTypeClass.typeRef.appliedTo(tp)
     val tag = ctx.typer.inferImplicitArg(reqType, pos.span)
     tag.tpe match
-      case _: TermRef =>
+      case tp: TermRef =>
+        checkStable(tp, pos)
         Some(tag.select(tpnme.splice))
       case _: SearchFailureType =>
         levelError(sym, tp, pos,

tests/neg/i7048e.scala

@@ -0,0 +1,39 @@
+import scala.quoted.{given, _}
+
+abstract class Test {
+  type T
+
+  val T: Type[T]
+  val getT: Type[T] = T // need this to avoid getting `null`
+  given Type[T] = getT
+
+  def foo with QuoteContext: Expr[Any] = {
+
+    val r = '{Option.empty[T]} // error
+
+    {
+      val t: Test = this
+      import t.{given}
+      println(summon[Type[t.T]].show)
+      val r = '{Option.empty[t.T]} // access to value t from wrong staging level
+      val r2 = '{Option.empty[${t.T}]} // works
+    }
+
+    {
+      val r1 = '{Option.empty[${T}]} // works
+      val r2 = '{Option.empty[List[${T}]]} // works
+      val r3 = '{sumstmon[Type[${T}]]} // access to Test.this from wrong staging level
+      val r4 = '{summon[${T} <:< Any]} // error
+    }
+
+    {
+      val s = '{Option.empty[${T}]}
+      val r = '{identity($s)} // works
+      val r2 = '{identity(${s: Expr[Option[T]]})} // error
+    }
+
+    r
+  }
+}
+
+@main def main = ()