SI-6539 Annotation for methods unfit for post-typer ASTs

Motivated by the `.value` method in the SBT task-syntax branch,
which should only be called within the context of the argument
to a setting initialization macro.

The facility is akin to a fatal deprecation.

3 files changed, 20 insertions, 0 deletions

diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index e24971a309..4c7694c319 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -944,6 +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 DeprecatedAttr             = requiredClass[scala.deprecated]
     lazy val DeprecatedNameAttr         = requiredClass[scala.deprecatedName]
     lazy val DeprecatedInheritanceAttr  = requiredClass[scala.deprecatedInheritance]
diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index 7cb9a0e105..7a0f5f2caf 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -743,6 +743,9 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     def elisionLevel        = getAnnotation(ElidableMethodClass) flatMap { _.intArg(0) }
     def implicitNotFoundMsg = getAnnotation(ImplicitNotFoundClass) flatMap { _.stringArg(0) }
 
+    def isCompileTimeOnly       = hasAnnotation(CompileTimeOnlyAttr)
+    def compileTimeOnlyMessage  = getAnnotation(CompileTimeOnlyAttr) flatMap (_ stringArg 0)
+
     /** Is this symbol an accessor method for outer? */
     final def isOuterAccessor = {
       hasFlag(STABLE | ARTIFACT) &&
diff --git a/src/reflect/scala/reflect/macros/compileTimeOnly.scala b/src/reflect/scala/reflect/macros/compileTimeOnly.scala
new file mode 100644
index 0000000000..4018e7db71
--- /dev/null
+++ b/src/reflect/scala/reflect/macros/compileTimeOnly.scala
@@ -0,0 +1,16 @@
+package scala.reflect
+package macros
+
+import scala.annotation.meta._
+
+/**
+ * An annotation that designates a member should not be referred to after
+ * type checking (which includes macro expansion); it must only be used in
+ * the arguments of some other macro that will eliminate it from the AST.
+ *
+ * @param  message the error message to print during compilation if a reference remains
+ *                 after type checking
+ * @since  2.10.0
+ */
+@getter @setter @beanGetter @beanSetter
+final class compileTimeOnly(message: String = "") extends scala.annotation.StaticAnnotation