Extra help for -Vcyclic

scala · Apr 9, 2024 · b8901c0 · b8901c0
1 parent aa0faec
commit b8901c0
Show file tree

Hide file tree

Showing 2 changed files with 5 additions and 3 deletions.
diff --git a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
@@ -852,9 +852,11 @@ trait TypeDiagnostics extends splain.SplainDiagnostics {
         else if (organics.length == 1) organics(0)
         else organics.find(_.pos.focus == pos.focus).getOrElse(organics(0))
       }
+      def help = if (!badsym.isSynthetic || settings.cyclic.value) "" else
+        s"; $badsym is synthetic; use -Vcyclic to find which definition needs an explicit type"
       condOpt(tree) {
-        case ValDef(_, _, TypeTree(), _)       => s"recursive $badsym needs type"
-        case DefDef(_, _, _, _, TypeTree(), _) => s"${cyclicAdjective(badsym)} $badsym needs result type"
+        case ValDef(_, _, TypeTree(), _)       => s"recursive $badsym needs type$help"
+        case DefDef(_, _, _, _, TypeTree(), _) => s"${cyclicAdjective(badsym)} $badsym needs result type$help"
         case Import(_, _)                      =>
           sm"""encountered unrecoverable cycle resolving import.
               |Note: this is often due in part to a class depending on a definition nested within its companion.

diff --git a/test/files/neg/t7808b.check b/test/files/neg/t7808b.check
@@ -1,4 +1,4 @@
-t7808b.scala:5: error: recursive value x$1 needs type
+t7808b.scala:5: error: recursive value x$1 needs type; value x$1 is synthetic; use -Vcyclic to find which definition needs an explicit type
     val (ls, rs) = z match {
          ^
 1 error