diff -r 88fa65d2ac87 -r ead62a035849 langtools/src/share/classes/com/sun/tools/javac/code/Types.java
--- a/langtools/src/share/classes/com/sun/tools/javac/code/Types.java	Mon Jun 09 10:17:16 2014 +0200
+++ b/langtools/src/share/classes/com/sun/tools/javac/code/Types.java	Mon Jun 09 12:54:02 2014 +0100
@@ -1212,17 +1212,38 @@
         TypeRelation isSameTypeLoose = new LooseSameTypeVisitor();
 
         private class LooseSameTypeVisitor extends SameTypeVisitor {
+
+            /** cache of the type-variable pairs being (recursively) tested. */
+            private Set<TypePair> cache = new HashSet<>();
+
             @Override
             boolean sameTypeVars(TypeVar tv1, TypeVar tv2) {
-                return tv1.tsym == tv2.tsym && visit(tv1.getUpperBound(), tv2.getUpperBound());
+                return tv1.tsym == tv2.tsym && checkSameBounds(tv1, tv2);
             }
             @Override
             protected boolean containsTypes(List<Type> ts1, List<Type> ts2) {
                 return containsTypeEquivalent(ts1, ts2);
             }
-        }
-
-    /**
+
+            /**
+             * Since type-variable bounds can be recursive, we need to protect against
+             * infinite loops - where the same bounds are checked over and over recursively.
+             */
+            private boolean checkSameBounds(TypeVar tv1, TypeVar tv2) {
+                TypePair p = new TypePair(tv1, tv2, true);
+                if (cache.add(p)) {
+                    try {
+                        return visit(tv1.getUpperBound(), tv2.getUpperBound());
+                    } finally {
+                        cache.remove(p);
+                    }
+                } else {
+                    return false;
+                }
+            }
+        };
+
+        /**
          * Strict type-equality relation - type variables are considered
          * equals if they share the same object identity.
          */
@@ -3396,9 +3417,16 @@
         class TypePair {
             final Type t1;
             final Type t2;
+            boolean strict;
+
             TypePair(Type t1, Type t2) {
+                this(t1, t2, false);
+            }
+
+            TypePair(Type t1, Type t2, boolean strict) {
                 this.t1 = t1;
                 this.t2 = t2;
+                this.strict = strict;
             }
             @Override
             public int hashCode() {
@@ -3409,8 +3437,8 @@
                 if (!(obj instanceof TypePair))
                     return false;
                 TypePair typePair = (TypePair)obj;
-                return isSameType(t1, typePair.t1)
-                    && isSameType(t2, typePair.t2);
+                return isSameType(t1, typePair.t1, strict)
+                    && isSameType(t2, typePair.t2, strict);
             }
         }
         Set<TypePair> mergeCache = new HashSet<>();