Added cycle detection to getParts.

3 files changed, 20 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 6d36c77b28..655e5dfe09 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -724,11 +724,15 @@ trait Implicits {
      */
     private def companionImplicits(tp: Type): Infoss = {
       val partMap = new LinkedHashMap[Symbol, Type]
+      val seen = mutable.HashSet[Type]()  // cycle detection
 
       /** Enter all parts of `tp` into `parts` set.
        *  This method is performance critical: about 2-4% of all type checking is spent here
        */
       def getParts(tp: Type) {
+        if (seen(tp))
+          return
+        seen += tp
         tp match {
           case TypeRef(pre, sym, args) =>
             if (sym.isClass) {
diff --git a/test/files/neg/bug4221.check b/test/files/neg/bug4221.check
new file mode 100644
index 0000000000..471332e3c1
--- /dev/null
+++ b/test/files/neg/bug4221.check
@@ -0,0 +1,6 @@
+bug4221.scala:8: error: type mismatch;
+ found   : Unit
+ required: Wrapper[S]
+  def wrap[S <: Cl#Sub[S]](v: S): Wrapper[S] = {
+                                               ^
+one error found
diff --git a/test/files/neg/bug4221.scala b/test/files/neg/bug4221.scala
new file mode 100644
index 0000000000..0a8b8add18
--- /dev/null
+++ b/test/files/neg/bug4221.scala
@@ -0,0 +1,10 @@
+class Cl {
+        class Sub[TheSub <: Sub[TheSub]]
+}
+
+case class Wrapper[T](v: T)
+
+object O {
+  def wrap[S <: Cl#Sub[S]](v: S): Wrapper[S] = {
+  }
+}