Moved literal message into error Message class

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -2384,7 +2384,7 @@ object Parsers {
           if (in.token == CASE)
             syntaxErrorOrIncomplete(OnlyCaseClassOrCaseObjectAllowed())
           else
-            syntaxErrorOrIncomplete("expected class or object definition")
+            syntaxErrorOrIncomplete(ExpectedClassOrObjectDef())
           if (mustStartStat) // do parse all definitions even if they are probably local (i.e. a "}" has been forgotten)
             defOrDcl(in.offset, defAnnotsMods(modifierTokens))
         }

compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java

@@ -87,6 +87,7 @@ public enum ErrorMessageID {
     ValueClassParameterMayNotBeAVarID,
     ValueClassNeedsExactlyOneValParamID,
     OnlyCaseClassOrCaseObjectAllowedID,
+    ExpectedClassOrObjectDefID,
     ;
 
     public int errorNumber() {

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -1573,4 +1573,11 @@ object messages {
     val explanation = ""
   }
 
+  case class ExpectedClassOrObjectDef()(implicit ctx: Context)
+    extends Message(ExpectedClassOrObjectDefID) {
+    val kind = "Syntax"
+    val msg = "expected class or object definition"
+    val explanation = ""
+  }
+
 }

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -792,4 +792,15 @@ class ErrorMessagesTests extends ErrorMessagesTest {
         assertEquals(err, OnlyCaseClassOrCaseObjectAllowed())
       }
 
+  @Test def expectedClassOrObjectDef =
+    checkMessagesAfter("frontend") {
+      """Foo"""
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val err :: Nil = messages
+        assertEquals(err, ExpectedClassOrObjectDef())
+      }
+
 }