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.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index c1dc91dbfc..726c8d3b24 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1376,6 +1376,11 @@ 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}")
+    }
+
     private def lessAccessible(otherSym: Symbol, memberSym: Symbol): Boolean = (
          (otherSym != NoSymbol)
       && !otherSym.isProtected
@@ -1562,6 +1567,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
       checkDeprecated(sym, tree.pos)
       if (settings.Xmigration28.value)
         checkMigration(sym, tree.pos)
+      checkCompileTimeOnly(sym, tree.pos)
 
       if (sym eq NoSymbol) {
         unit.warning(tree.pos, "Select node has NoSymbol! " + tree + " / " + tree.tpe)