Fix #5715: Make sure the val has a RHS

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

@@ -1018,9 +1018,9 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
    */
   class MapToUnderlying extends TreeMap {
     override def transform(tree: Tree)(implicit ctx: Context): Tree = tree match {
-      case tree: Ident if tree.symbol.exists && !tree.symbol.owner.isClass && skipLocal(tree.symbol) =>
+      case tree: Ident if tree.symbol.exists && !tree.symbol.owner.isClass && !tree.symbol.isAnonymousFunction && skipLocal(tree.symbol) =>
         tree.symbol.defTree match {
-          case defTree: ValOrDefDef => transform(defTree.rhs)
+          case defTree: ValOrDefDef if !defTree.rhs.isEmpty => transform(defTree.rhs)
           case _ => tree
         }
       case Inlined(_, _, arg) => transform(arg)

tests/run-with-compiler/i5715/Macro_1.scala

@@ -0,0 +1,20 @@
+import scala.quoted._
+import scala.tasty._
+
+object scalatest {
+
+  inline def assert(condition: => Boolean): Unit = ${ assertImpl('condition, '{""}) }
+
+  def assertImpl(cond: Expr[Boolean], clue: Expr[Any])(implicit refl: Reflection): Expr[Unit] = {
+    import refl._
+
+    cond.unseal.underlyingArgument match {
+      case app @ Term.Apply(sel @ Term.Select(lhs, op), rhs :: Nil) =>
+        val Term.IsSelect(select) = sel
+        val cond = Term.Apply(Term.Select.copy(select)(lhs, "exists"), rhs :: Nil).seal[Boolean]
+        '{ scala.Predef.assert($cond) }
+      case _ =>
+        '{ scala.Predef.assert($cond) }
+    }
+  }
+}

tests/run-with-compiler/i5715/Test_2.scala

@@ -0,0 +1,8 @@
+object Test {
+  import scalatest._
+
+  def main(args: Array[String]): Unit = {
+    val l = List(3, 4)
+    assert(l.exists(_ == 3))
+  }
+}