Fix for crasher in explicitouter.

Closes SI-4970, review by moors.

2 files changed, 47 insertions, 40 deletions

diff --git a/src/compiler/scala/reflect/internal/TreeGen.scala b/src/compiler/scala/reflect/internal/TreeGen.scala
index ce7fba6686..fae3975ed5 100644
--- a/src/compiler/scala/reflect/internal/TreeGen.scala
+++ b/src/compiler/scala/reflect/internal/TreeGen.scala
@@ -64,44 +64,47 @@ abstract class TreeGen {
    *  termSym as the Ident's symbol.  In that case, termSym must
    *  not be NoSymbol.
    */
-  def mkAttributedQualifier(tpe: Type, termSym: Symbol): Tree = tpe match {
-    case NoPrefix =>
-      EmptyTree
-    case ThisType(clazz) =>
-      if (clazz.isEffectiveRoot) EmptyTree
-      else mkAttributedThis(clazz)
-    case SingleType(pre, sym) =>
-      mkApplyIfNeeded(mkAttributedStableRef(pre, sym))
-    case TypeRef(pre, sym, args) =>
-      if (sym.isRoot) {
-        mkAttributedThis(sym)
-      } else if (sym.isModuleClass) {
-        mkApplyIfNeeded(mkAttributedRef(pre, sym.sourceModule))
-      } else if (sym.isModule || sym.isClass) {
-        assert(phase.erasedTypes, tpe)
-        mkAttributedThis(sym)
-      } else if (sym.isType) {
-        assert(termSym != NoSymbol, tpe)
-        mkAttributedIdent(termSym) setType tpe
-      } else {
-        mkAttributedRef(pre, sym)
-      }
+  def mkAttributedQualifier(tpe: Type, termSym: Symbol): Tree = {
+    def failMessage = "mkAttributedQualifier(" + tpe + ", " + termSym + ")"
+    tpe match {
+      case NoPrefix =>
+        EmptyTree
+      case ThisType(clazz) =>
+        if (clazz.isEffectiveRoot) EmptyTree
+        else mkAttributedThis(clazz)
+      case SingleType(pre, sym) =>
+        mkApplyIfNeeded(mkAttributedStableRef(pre, sym))
+      case TypeRef(pre, sym, args) =>
+        if (sym.isRoot) {
+          mkAttributedThis(sym)
+        } else if (sym.isModuleClass) {
+          mkApplyIfNeeded(mkAttributedRef(pre, sym.sourceModule))
+        } else if (sym.isModule || sym.isClass) {
+          assert(phase.erasedTypes, failMessage)
+          mkAttributedThis(sym)
+        } else if (sym.isType) {
+          assert(termSym != NoSymbol, failMessage)
+          mkAttributedIdent(termSym) setType tpe
+        } else {
+          mkAttributedRef(pre, sym)
+        }
 
-    case ConstantType(value) =>
-      Literal(value) setType tpe
+      case ConstantType(value) =>
+        Literal(value) setType tpe
 
-    case AnnotatedType(_, atp, _) =>
-      mkAttributedQualifier(atp)
+      case AnnotatedType(_, atp, _) =>
+        mkAttributedQualifier(atp)
 
-    case RefinedType(parents, _) =>
-      // I am unclear whether this is reachable, but
-      // the following implementation looks logical -Lex
-      val firstStable = parents.find(_.isStable)
-      assert(!firstStable.isEmpty, tpe)
-      mkAttributedQualifier(firstStable.get)
+      case RefinedType(parents, _) =>
+        // I am unclear whether this is reachable, but
+        // the following implementation looks logical -Lex
+        val firstStable = parents.find(_.isStable)
+        assert(!firstStable.isEmpty, failMessage + " parents = " + parents)
+        mkAttributedQualifier(firstStable.get)
 
-    case _ =>
-      abort("bad qualifier: " + tpe)
+      case _ =>
+        abort("bad qualifier received: " + failMessage)
+    }
   }
   /** If this is a reference to a method with an empty
    *  parameter list, wrap it in an apply.
diff --git a/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala b/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala
index 1bc283841b..192c4e9b59 100644
--- a/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala
+++ b/src/compiler/scala/tools/nsc/transform/ExplicitOuter.scala
@@ -346,12 +346,16 @@ abstract class ExplicitOuter extends InfoTransform
      *  @pre mixinClass is an inner class
      */
     def mixinOuterAccessorDef(mixinClass: Symbol): Tree = {
-      val outerAcc = outerAccessor(mixinClass) overridingSymbol currentClass
-      assert(outerAcc != NoSymbol)
-      val path =
-        if (mixinClass.owner.isTerm) THIS(mixinClass.owner.enclClass)
-        else gen.mkAttributedQualifier(currentClass.thisType baseType mixinClass prefix)
-
+      val outerAcc    = outerAccessor(mixinClass) overridingSymbol currentClass
+      def mixinPrefix = currentClass.thisType baseType mixinClass prefix;
+      assert(outerAcc != NoSymbol, "No outer accessor for inner mixin " + mixinClass + " in " + currentClass)
+      // I added the mixinPrefix.typeArgs.nonEmpty condition to address the
+      // crash in SI-4970.  I feel quite sure this can be improved.
+      val path = (
+        if (mixinClass.owner.isTerm) gen.mkAttributedThis(mixinClass.owner.enclClass)
+        else if (mixinPrefix.typeArgs.nonEmpty) gen.mkAttributedThis(mixinPrefix.typeSymbol)
+        else gen.mkAttributedQualifier(mixinPrefix)
+      )
       localTyper typed {
         (DEF(outerAcc) withPos currentClass.pos) === {
           // Need to cast for nested outer refs in presence of self-types. See ticket #3274.