marks Expr.splice and Expr.value with @compileTimeOnly

Now that @compileTimeOnly is part of the standard library, why don't
we use it within the standard library.

3 files changed, 25 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/api/Exprs.scala b/src/reflect/scala/reflect/api/Exprs.scala
index 009d9dbfdb..5b6ff2325c 100644
--- a/src/reflect/scala/reflect/api/Exprs.scala
+++ b/src/reflect/scala/reflect/api/Exprs.scala
@@ -8,6 +8,7 @@ package reflect
 package api
 
 import scala.reflect.runtime.{universe => ru}
+import scala.annotation.compileTimeOnly
 
 /**
  * <span class="badge badge-red" style="float: right;">EXPERIMENTAL</span>
@@ -91,7 +92,7 @@ trait Exprs { self: Universe =>
      * }}}
      * because expr of type Expr[T] itself does not have a method foo.
      */
-    // @compileTimeOnly("Cannot use splice outside reify")
+    @compileTimeOnly("splice must be enclosed within a reify {} block")
     def splice: T
 
     /**
@@ -108,7 +109,7 @@ trait Exprs { self: Universe =>
      * object Impls { def foo_impl(c: Context)(x: c.Expr[X]): c.Expr[x.value.T] = ... }
      * }}}
      */
-    // @compileTimeOnly("Cannot use value except for signatures of macro implementations")
+    @compileTimeOnly("cannot use value except for signatures of macro implementations")
     val value: T
 
     override def canEqual(x: Any) = x.isInstanceOf[Expr[_]]
diff --git a/test/files/neg/compile-time-only-b.check b/test/files/neg/compile-time-only-b.check
new file mode 100644
index 0000000000..8292a0ddeb
--- /dev/null
+++ b/test/files/neg/compile-time-only-b.check
@@ -0,0 +1,7 @@
+compile-time-only-b.scala:13: error: splice must be enclosed within a reify {} block
+  val ignored3 = reify(fortyTwo).splice
+                                 ^
+compile-time-only-b.scala:14: error: cannot use value except for signatures of macro implementations
+  val ignored4 = reify(fortyTwo).value
+                                 ^
+two errors found
diff --git a/test/files/neg/compile-time-only-b.scala b/test/files/neg/compile-time-only-b.scala
new file mode 100644
index 0000000000..d5568dbe67
--- /dev/null
+++ b/test/files/neg/compile-time-only-b.scala
@@ -0,0 +1,15 @@
+import scala.reflect.runtime.universe._
+
+object Test extends App {
+  // HAHA!!!
+  // no compileTimeOnly errors here, because scalac does constant folding
+  // the type of reify(42) is Expr[42.type]
+  // therefore the type of expr.splice is 42.type, which is then constfolded
+  val expr = reify(42)
+  val ignored1 = expr.splice
+  val ignored2 = expr.value
+
+  val fortyTwo = 42
+  val ignored3 = reify(fortyTwo).splice
+  val ignored4 = reify(fortyTwo).value
+}
\ No newline at end of file