src/jdk.compiler/share/classes/com/sun/tools/javac/util/RichDiagnosticFormatter.java

@@ -232,10 +232,12 @@
         }
         return -1;
     }
 
     private boolean unique(TypeVar typevar) {
+        typevar = (TypeVar)typevar.underlyingTypeOrType();
+
         int found = 0;
         for (Type t : whereClauses.get(WhereClauseKind.TYPEVAR).keySet()) {
             if (t.toString().equals(typevar.toString())) {
                 found++;
             }