SI-6976 Fix value class separate compilation crasher.

We can't guarantee that the owner of the value class
is initialized, and if it isn't, the search for the
companion module will turn up bubkis.

This is a localized fix, but I'd be suprised if there
weren't other places that suffered from the same problem.

Wouldn't it be nicer to have something like:

    // doesn't force info
    sym.raw.info
    sym.raw.companionModule

    // forces info
    sym.info
    sym.companionModule

1 files changed, 8 insertions, 4 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
index 6f3d7932a5..5318524870 100644
--- a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
+++ b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
@@ -64,14 +64,18 @@ abstract class ExtensionMethods extends Transform with TypingTransformers {
     }
   }
 
-  /** Return the extension method that corresponds to given instance method `meth`.
-   */
+  private def companionModuleForce(sym: Symbol) = {
+    sym.andAlso(_.owner.initialize) // See SI-6976. `companionModule` only calls `rawInfo`. (Why?)
+    sym.companionModule
+  }
+
+  /** Return the extension method that corresponds to given instance method `meth`. */
   def extensionMethod(imeth: Symbol): Symbol = atPhase(currentRun.refchecksPhase) {
-    val companionInfo = imeth.owner.companionModule.info
+    val companionInfo = companionModuleForce(imeth.owner).info
     val candidates = extensionNames(imeth) map (companionInfo.decl(_)) filter (_.exists)
     val matching = candidates filter (alt => normalize(alt.tpe, imeth.owner) matches imeth.tpe)
     assert(matching.nonEmpty,
-      s"no extension method found for $imeth:${imeth.tpe} among ${candidates map (c => c.name+":"+c.tpe)} / ${extensionNames(imeth)}")
+      s"no extension method found for $imeth:${imeth.tpe} among ${candidates.map(c => c.name+":"+c.tpe).toList} / ${extensionNames(imeth).toList}")
     matching.head
   }