SI-7418 Avoid concurrent use of compiler in REPL startup

Enable the tab completer *after* we're finished binding
$intp and unleashing power mode on the asynchronous
REPL startup thread.

Tested manually:
 - run qbin/scala
 - Paste "".toUp
 - Hit <TAB> like a maniac

Before this patch, the crash was reproducible almost every time.
Afterwards, not the once.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/repl/scala/tools/nsc/interpreter/ILoop.scala b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
index 9f841f2c44..8ec8b2ed5f 100644
--- a/src/repl/scala/tools/nsc/interpreter/ILoop.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ILoop.scala
@@ -642,10 +642,6 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
   }
 
   private def loopPostInit() {
-    in match {
-      case x: JLineReader => x.consoleReader.postInit
-      case _              =>
-    }
     // Bind intp somewhere out of the regular namespace where
     // we can get at it in generated code.
     intp.quietBind(NamedParam[IMain]("$intp", intp)(tagOfIMain, classTag[IMain]))
@@ -661,6 +657,11 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
       unleashAndSetPhase()
       asyncMessage(power.banner)
     }
+    // SI-7418 Now, and only now, can we enable TAB completion.
+    in match {
+      case x: JLineReader => x.consoleReader.postInit
+      case _              =>
+    }
   }
   def process(settings: Settings): Boolean = savingContextLoader {
     this.settings = settings