2 files changed, 22 insertions, 1 deletions
diff --git a/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java b/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
index c74130b44..2bf15cb7c 100644
--- a/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
+++ b/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
@@ -49,7 +49,9 @@ public enum ErrorMessageID {
     OverridesNothingButNameExistsID,
     ForwardReferenceExtendsOverDefinitionID,
     ExpectedTokenButFoundID,
-    MixedLeftAndRightAssociativeOpsID;
+    MixedLeftAndRightAssociativeOpsID,
+    CantInstantiateAbstractClassOrTraitID,
+    ;
 
     public int errorNumber() {
         return ordinal() - 2;
diff --git a/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala b/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
index e818e7a42..34190c114 100644
--- a/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
@@ -1127,4 +1127,23 @@ object messages {
           |""".stripMargin
   }
 
+  case class CantInstantiateAbstractClassOrTrait(cls: Symbol, isTrait: Boolean)(implicit ctx: Context)
+  extends Message(CantInstantiateAbstractClassOrTraitID) {
+    val kind = "Usage"
+    private val traitOrAbstract = if (isTrait) hl"a trait" else hl"abstract"
+    val msg = hl"""${cls.name} is ${traitOrAbstract}; it cannot be instantiated"""
+    val explanation =
+      hl"""|Abstract classes and traits need to be extended by a concrete class or object
+           |to make their functionality accessible.
+           |
+           |You may want to create an anonymous class extending ${cls.name} with
+           |  ${s"class ${cls.name} { }"}
+           |  
+           |or add a companion object with
+           |  ${s"object ${cls.name} extends ${cls.name}"}
+           |
+           |You need to implement any abstract members in both cases.
+           |""".stripMargin
+  }
+
 }