Fix scala#7121: Disallow quotes in annotations

Author: nicolasstucki

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

@@ -23,6 +23,7 @@ import dotty.tools.dotc.typer.Inliner
 
 import scala.collection.mutable
 import dotty.tools.dotc.util.SourcePosition
+import dotty.tools.dotc.util.Property
 
 import scala.annotation.constructorOnly
 
@@ -33,20 +34,25 @@ import scala.annotation.constructorOnly
 class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(ictx) {
   import tpd._
 
+  private val InAnnotation = Property.Key[Unit]()
+
   override def transform(tree: Tree)(implicit ctx: Context): Tree =
     if (tree.source != ctx.source && tree.source.exists)
       transform(tree)(ctx.withSource(tree.source))
     else tree match {
       case tree: DefDef if tree.symbol.is(Inline) && level > 0 => EmptyTree
       case tree: DefTree =>
+        lazy val annotCtx = ctx.fresh.setProperty(InAnnotation, ()).withOwner(tree.symbol)
         for (annot <- tree.symbol.annotations)
-          transform(annot.tree)(given ctx.withOwner(tree.symbol))
+          transform(annot.tree)(given annotCtx)
         checkLevel(super.transform(tree))
       case _ => checkLevel(super.transform(tree))
     }
 
   /** Transform quoted trees while maintaining phase correctness */
   override protected def transformQuotation(body: Tree, quote: Tree)(implicit ctx: Context): Tree = {
+    if (ctx.property(InAnnotation).isDefined)
+      ctx.error("Cannot have a quote in an annotation", quote.sourcePos)
     val body1 = transform(body)(quoteContext)
     super.transformQuotation(body1, quote)
   }

tests/neg/i7121.scala

@@ -0,0 +1,13 @@
+import scala.quoted._
+
+class annot1[T](x: Expr[T]) extends scala.annotation.Annotation
+class annot2[T: Type](x: T) extends scala.annotation.Annotation
+
+class Test()(implicit qtx: QuoteContext) {
+  @annot1('{4}) // error
+  def foo(str: String) = ()
+
+  @annot2(4)(given '[Int]) // error
+  def foo2(str: String) = ()
+
+}