*** empty log message ***

3 files changed, 18 insertions, 4 deletions

diff --git a/sources/scalac/symtab/Modifiers.java b/sources/scalac/symtab/Modifiers.java
index 173eda4e61..ab222e723f 100644
--- a/sources/scalac/symtab/Modifiers.java
+++ b/sources/scalac/symtab/Modifiers.java
@@ -48,6 +48,9 @@ public interface Modifiers {
     int INCONSTRUCTOR = 0x01000000;   // transient flag for Analyzer
     int PARAMACCESSOR = 0x02000000;   // for methods: is an access method for a val parameter
                                       // for parameters: is a val parameter
+    int CLOSURELOCK   = PARAMACCESSOR;
+                                      // secondary meaning: a lock to test that closures of type
+                                      // symbols are non-cyclic.
 
     int ACCESSOR      = 0x04000000;   // function is an access function for a
                                       // value or variable
diff --git a/sources/scalac/symtab/Symbol.java b/sources/scalac/symtab/Symbol.java
index d2bbd8f8b7..3390eb7a26 100644
--- a/sources/scalac/symtab/Symbol.java
+++ b/sources/scalac/symtab/Symbol.java
@@ -1970,7 +1970,12 @@ abstract class TypeSymbol extends Symbol {
      */
     public final Type[] closure() {
         if (kind == ALIAS) return info().symbol().closure();
-        return (Type[])closures.getValue(this);
+        if ((flags & CLOSURELOCK) != 0 && Global.instance.currentPhase.id <= Global.instance.PHASE.REFCHECK.id())
+            throw new Type.Error("illegal cyclic reference involving " + this);
+        flags |= CLOSURELOCK;
+        Type[] result = (Type[])closures.getValue(this);
+        flags &= ~CLOSURELOCK;
+        return result;
     }
 
     public void reset(Type completer) {
diff --git a/sources/scalac/symtab/Type.java b/sources/scalac/symtab/Type.java
index 3c260d93b7..2b2044a872 100644
--- a/sources/scalac/symtab/Type.java
+++ b/sources/scalac/symtab/Type.java
@@ -215,8 +215,14 @@ public class Type implements Modifiers, Kinds, TypeTags, EntryTags {
             throw new Type.Malformed(pre, sym.nameString());
         if (sym.isTypeAlias()) {
             Symbol[] params = sym.typeParams();
-            if (args.length == params.length)
-                return pre.memberInfo(sym).subst(params, args);
+            if (args.length == params.length) {
+                if (sym.isLocked()) throw new Type.Error(
+                    "illegal cyclic reference involving " + sym);
+                sym.flags |= LOCKED;
+                Type result = pre.memberInfo(sym).subst(params, args);
+                sym.flags &= ~LOCKED;
+                return result;
+            }
             assert args.length == 0 || args.length == params.length:
                 Debug.show(pre, sym, args, params);
         }
@@ -2690,7 +2696,7 @@ public class Type implements Modifiers, Kinds, TypeTags, EntryTags {
     /** Return the least upper bound of non-empty array of types `tps'.
      */
     public static Type lub0(Type[] tps) {
-        //System.out.println("lub" + ArrayApply.toString(tps));//DEBUG
+        //for (int i = 0; i < recCount; i++) System.out.print("  "); System.out.println("lub" + ArrayApply.toString(tps));//debug
 
         if (tps.length == 0) return Global.instance.definitions.ALL_TYPE();