Refine @compileTimeOnly

 - Don't default the message, and show it exclusively.
 - Fix cut-and-pasto in the @since tag
 - Be tolerant if the annotaion class is missing, as seems to
   have been the case compiling the continuations plugin.
 - s/\t/  / in the test file to show the errors are positioned
   correctly.
 - Use defensive getOrElse

3 files changed, 10 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 726c8d3b24..ee7805cb3d 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1377,8 +1377,13 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
     }
 
     private def checkCompileTimeOnly(sym: Symbol, pos: Position) = {
-      if (sym.isCompileTimeOnly)
-        unit.error(pos, s"reference to ${sym.fullLocationString} should not survive typechecking: ${sym.compileTimeOnlyMessage.get}")
+      if (sym.isCompileTimeOnly) {
+        def defaultMsg =
+          s"""|Reference to ${sym.fullLocationString} should not have survived past type checking,
+              |it should have been processed and eliminated during expansion of an enclosing macro.""".stripMargin
+        // The getOrElse part should never happen, it's just here as a backstop.
+        unit.error(pos, sym.compileTimeOnlyMessage getOrElse defaultMsg)
+      }
     }
 
     private def lessAccessible(otherSym: Symbol, memberSym: Symbol): Boolean = (
diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index 4c7694c319..2a7b55cb5a 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -944,7 +944,7 @@ trait Definitions extends api.StandardDefinitions {
     lazy val BeanPropertyAttr           = requiredClass[scala.beans.BeanProperty]
     lazy val BooleanBeanPropertyAttr    = requiredClass[scala.beans.BooleanBeanProperty]
     lazy val CloneableAttr              = requiredClass[scala.annotation.cloneable]
-    lazy val CompileTimeOnlyAttr        = requiredClass[scala.reflect.macros.compileTimeOnly]
+    lazy val CompileTimeOnlyAttr        = getClassIfDefined("scala.reflect.macros.compileTimeOnly")
     lazy val DeprecatedAttr             = requiredClass[scala.deprecated]
     lazy val DeprecatedNameAttr         = requiredClass[scala.deprecatedName]
     lazy val DeprecatedInheritanceAttr  = requiredClass[scala.deprecatedInheritance]
diff --git a/src/reflect/scala/reflect/macros/compileTimeOnly.scala b/src/reflect/scala/reflect/macros/compileTimeOnly.scala
index 4018e7db71..5a3a352a53 100644
--- a/src/reflect/scala/reflect/macros/compileTimeOnly.scala
+++ b/src/reflect/scala/reflect/macros/compileTimeOnly.scala
@@ -10,7 +10,7 @@ import scala.annotation.meta._
  *
  * @param  message the error message to print during compilation if a reference remains
  *                 after type checking
- * @since  2.10.0
+ * @since  2.10.1
  */
 @getter @setter @beanGetter @beanSetter
-final class compileTimeOnly(message: String = "") extends scala.annotation.StaticAnnotation
+final class compileTimeOnly(message: String) extends scala.annotation.StaticAnnotation