Change trytoShow's to not use raw string

Author: dwijnand

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

@@ -280,10 +280,7 @@ object Decorators {
           case ex: CyclicReference => "... (caught cyclic reference) ..."
           case NonFatal(ex)
           if !ctx.mode.is(Mode.PrintShowExceptions) && !ctx.settings.YshowPrintErrors.value =>
-            val msg = ex match
-              case te: TypeError => te.toMessage.message
-              case _ => ex.getMessage
-            s"[cannot display due to $msg, raw string = $x]"
+            s"... (cannot display due to ${ex.className} ${ex.getMessage}) ..."
       case _ => String.valueOf(x).nn
 
     /** Returns the simple class name of `x`. */

compiler/test/dotty/tools/dotc/core/ShowDecoratorTest.scala

@@ -0,0 +1,21 @@
+package dotty.tools
+package dotc
+package core
+
+import Contexts.*, Decorators.*, Denotations.*, SymDenotations.*, Symbols.*, Types.*
+import printing.Formatting.Show
+
+import org.junit.Test
+import org.junit.Assert.*
+
+class ShowDecoratorTest extends DottyTest:
+  import ShowDecoratorTest.*
+
+  @Test def t1 = assertEquals("... (cannot display due to FooException boom) ...", Foo().tryToShow)
+end ShowDecoratorTest
+
+object ShowDecoratorTest:
+  import printing.*, Texts.*
+  class FooException extends Exception("boom")
+  case class Foo() extends Showable:
+    def toText(printer: Printer): Text = throw new FooException