diff options
| -rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/Implicits.scala | 23 | ||||
| -rw-r--r-- | test/files/neg/unit2anyref.check | 6 |
2 files changed, 21 insertions, 8 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala index 840ec1113d..adafcb2617 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala @@ -302,10 +302,25 @@ self: Analyzer => if (isView) { val found = pt.typeArgs(0) val req = pt.typeArgs(1) - typeErrorMsg(found, req)+ - "\nNote that implicit conversions are not applicable because they are ambiguous:\n "+ - coreMsg+"are possible conversion functions from "+ found+" to "+req - } else { + + /** A nice spot to explain some common situations a little + * less confusingly. + */ + def explanation = { + if ((found =:= AnyClass.tpe) && (AnyRefClass.tpe <:< req)) + "Note: Any is not implicitly converted to AnyRef. You can safely\n" + + "pattern match x: AnyRef or cast x.asInstanceOf[AnyRef] to do so." + else if ((found <:< AnyValClass.tpe) && (AnyRefClass.tpe <:< req)) + "Note: primitive types are not implicitly converted to AnyRef.\n" + + "You can safely force boxing by casting x.asInstanceOf[AnyRef]." + else + "Note that implicit conversions are not applicable because they are ambiguous:\n "+ + coreMsg+"are possible conversion functions from "+ found+" to "+req + } + + typeErrorMsg(found, req) + "\n" + explanation + } + else { "ambiguous implicit values:\n "+coreMsg + "match expected type "+pt }) } diff --git a/test/files/neg/unit2anyref.check b/test/files/neg/unit2anyref.check index 7af4564ffb..2616fd35f9 100644 --- a/test/files/neg/unit2anyref.check +++ b/test/files/neg/unit2anyref.check @@ -1,10 +1,8 @@ unit2anyref.scala:2: error: type mismatch; found : Unit required: AnyRef -Note that implicit conversions are not applicable because they are ambiguous: - both method any2stringadd in object Predef of type (x: Any)scala.runtime.StringAdd - and method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A] - are possible conversion functions from Unit to AnyRef +Note: primitive types are not implicitly converted to AnyRef. +You can safely force boxing by casting x.asInstanceOf[AnyRef]. val x: AnyRef = () // this should not succeed. ^ one error found |