Fix SI-4541.

Catch type errors when duplicating trees.
In this case, to access a protected member from a specialized
class is an error, so we would have to make the member public
anyway.
Better it is then to report an error and have the user make the
field public explicitly.

Review by @dragos.

2 files changed, 16 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index 4b488a6437..c4c769d7cf 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -1448,20 +1448,29 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
 
         case ddef @ DefDef(_, _, _, vparamss, _, _) if info.isDefinedAt(symbol) =>
           // log("--> method: " + ddef + " in " + ddef.symbol.owner + ", " + info(symbol))
+          def reportTypeError(body: =>Tree) =
+            try body
+            catch {
+              case te: TypeError =>
+                reporter.error(te.pos, te.toString)
+                ddef
+            }
           if (symbol.isConstructor) {
 
             val t = atOwner(symbol)(forwardCtorCall(tree.pos, gen.mkSuperSelect, vparamss, symbol.owner))
 
             if (symbol.isPrimaryConstructor)
               localTyper.typedPos(symbol.pos)(deriveDefDef(tree)(_ => Block(List(t), Literal(Constant()))))
-            else  // duplicate the original constructor
-              duplicateBody(ddef, info(symbol).target)
+            else // duplicate the original constructor
+              reportTypeError(duplicateBody(ddef, info(symbol).target))
           }
           else info(symbol) match {
             case Implementation(target) =>
               assert(body.isDefinedAt(target), "sym: " + symbol.fullName + " target: " + target.fullName)
               // we have an rhs, specialize it
-              val tree1 = duplicateBody(ddef, target)
+              val tree1 = reportTypeError {
+                duplicateBody(ddef, target)
+              }
               debuglog("implementation: " + tree1)
               deriveDefDef(tree1)(transform)
 
@@ -1472,7 +1481,9 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
               }
               else {
                 // we have an rhs, specialize it
-                val tree1 = duplicateBody(ddef, target)
+                val tree1 = reportTypeError {
+                  duplicateBody(ddef, target)
+                }
                 debuglog("implementation: " + tree1)
                 deriveDefDef(tree1)(transform)
               }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala b/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
index b7a6ea677e..6386273c9d 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
@@ -360,7 +360,7 @@ abstract class Duplicators extends Analyzer {
           tree
 
         case _ =>
-          debuglog("Duplicators default case: " + tree.summaryString)
+          // log("Duplicators default case: " + tree.summaryString + " -> " + tree)
           if (tree.hasSymbol && tree.symbol != NoSymbol && (tree.symbol.owner == definitions.AnyClass)) {
             tree.symbol = NoSymbol // maybe we can find a more specific member in a subclass of Any (see AnyVal members, like ==)
           }