Fixed over-optimistic anyrefSpecCache (closes SI-5500).

The basic problem here was that generic type params were getting
confused between the various specialized subclasses. For instance,
calling typeParamsSubAnyRef(A, C2$mcLI$sp) might return the wrong
specialized type param, e.g. C2$mcLZ$sp.A$sp (note the Z instead
of the I).

The fix is to cache with both the sym (A) and also the clazz
(C2$mcLI$sp). This may resolve a whole host of other obscure
AnyRef specialization problems.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index 8b1d5b3295..d96dff26db 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -87,9 +87,10 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
   /** Map class symbols to the type environments where they were created. */
   private val typeEnv = mutable.HashMap[Symbol, TypeEnv]() withDefaultValue emptyEnv
 
-  // holds mappings from regular type parameter symbols to symbols of
-  // specialized type parameters which are subtypes of AnyRef
-  private val anyrefSpecCache = perRunCaches.newMap[Symbol, Symbol]()
+  // holds mappings from regular type parameter symbols and their class to
+  // symbols of specialized type parameters which are subtypes of AnyRef
+  // e.g. (sym, clazz) => specializedSym
+  private val anyrefSpecCache = perRunCaches.newMap[(Symbol, Symbol), Symbol]()
 
   // holds mappings from members to the type variables in the class
   // that they were already specialized for, so that they don't get
@@ -435,7 +436,7 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
    *  `sym` in the original class. It will create it if needed or use the one from the cache.
    */
   private def typeParamSubAnyRef(sym: Symbol, clazz: Symbol) = (
-    anyrefSpecCache.getOrElseUpdate(sym,
+    anyrefSpecCache.getOrElseUpdate((sym, clazz),
       clazz.newTypeParameter(sym.name append nme.SPECIALIZED_SUFFIX_NAME toTypeName, sym.pos)
         setInfo TypeBounds(sym.info.bounds.lo, AnyRefClass.tpe)
     ).tpe
@@ -447,8 +448,10 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
     // remove class type parameters and those of normalized members.
     clazz :: decls foreach {
       _.tpe match {
-        case PolyType(tparams, _) => anyrefSpecCache --= tparams
-        case _                    => ()
+        case PolyType(tparams, _) => tparams.foreach {
+          s => anyrefSpecCache.remove((s, clazz))
+        }
+        case _ => ()
       }
     }
   )