Merge pull request #5832 from dotty-staging/fix-missing-message

Fix missing error message

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/TypeErrors.scala

@@ -17,7 +17,8 @@ import config.Printers.cyclicErrors
 
 class TypeError(msg: String) extends Exception(msg) {
   def this() = this("")
-  def toMessage(implicit ctx: Context): Message = getMessage
+  def toMessage(implicit ctx: Context): Message = super.getMessage
+  override def getMessage: String = throw new Exception("Use toMessage instead for TypeError")
 }
 
 class MalformedType(pre: Type, denot: Denotation, absMembers: Set[Name]) extends TypeError {

compiler/src/dotty/tools/dotc/printing/Formatting.scala

@@ -31,7 +31,8 @@ object Formatting {
           case NonFatal(ex)
           if !ctx.mode.is(Mode.PrintShowExceptions) &&
              !ctx.settings.YshowPrintErrors.value =>
-            s"[cannot display due to $ex, raw string = ${arg.toString}]"
+            val msg = ex match { case te: TypeError => te.toMessage case _ => ex.getMessage }
+            s"[cannot display due to $msg, raw string = ${arg.toString}]"
         }
       case _ => arg.toString
     }

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

@@ -982,7 +982,7 @@ class RefChecks extends MiniPhase { thisPhase =>
     tree
   } catch {
     case ex: TypeError =>
-      ctx.error(ex.getMessage, tree.sourcePos)
+      ctx.error(ex.toMessage, tree.sourcePos)
       tree
   }