Migration message and version cleanup

The @migration annotation can now be used like @deprecation.
Old syntax is still supported, but deprecated.

Improve wording and consistency of migration messages, migration
warnings also print the version in which the change occurred now.

Partially fixes SI-4990.

2 files changed, 6 insertions, 4 deletions

diff --git a/src/compiler/scala/reflect/internal/Symbols.scala b/src/compiler/scala/reflect/internal/Symbols.scala
index a59ea2c1bf..75fd733e7e 100644
--- a/src/compiler/scala/reflect/internal/Symbols.scala
+++ b/src/compiler/scala/reflect/internal/Symbols.scala
@@ -494,8 +494,8 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     // string.  So this needs attention.  For now the fact that migration is
     // private[scala] ought to provide enough protection.
     def hasMigrationAnnotation = hasAnnotation(MigrationAnnotationClass)
-    def migrationMessage    = getAnnotation(MigrationAnnotationClass) flatMap { _.stringArg(2) }
-    def migrationVersion    = getAnnotation(MigrationAnnotationClass) map { version => version.intArg(0).get + "." + version.intArg(1).get }
+    def migrationMessage    = getAnnotation(MigrationAnnotationClass) flatMap { _.stringArg(0) }
+    def migrationVersion    = getAnnotation(MigrationAnnotationClass) flatMap { _.stringArg(1) }
     def elisionLevel        = getAnnotation(ElidableMethodClass) flatMap { _.intArg(0) }
     def implicitNotFoundMsg = getAnnotation(ImplicitNotFoundClass) flatMap { _.stringArg(0) }
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 645d3ecfa0..98f1c96cad 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1273,8 +1273,10 @@ abstract class RefChecks extends InfoTransform with reflect.internal.transform.R
      *  indicating it has changed semantics between versions.
      */
     private def checkMigration(sym: Symbol, pos: Position) = {
-      for (msg <- sym.migrationMessage)
-        unit.warning(pos, sym.fullLocationString + " has changed semantics:\n" + msg)
+      if (sym.hasMigrationAnnotation)
+        unit.warning(pos, "%s has changed semantics in version %s:\n%s".format(
+          sym.fullLocationString, sym.migrationVersion.get, sym.migrationMessage.get)
+        )
     }
 
     private def lessAccessible(otherSym: Symbol, memberSym: Symbol): Boolean = (