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Dynalink is an invokedynamic-based high-level linking and metaobject protocol library. It enables creation of languages on the JVM that can easily interoperate with plain Java objects and each other.
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/*
   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")
   and the BSD License (the "BSD License"), with licensee being free to
   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache
   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the
   following notice applies to you:

       You may obtain a copy of the Apache License at

           http://www.apache.org/licenses/LICENSE-2.0

       Unless required by applicable law or agreed to in writing, software
       distributed under the License is distributed on an "AS IS" BASIS,
       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
       implied. See the License for the specific language governing
       permissions and limitations under the License.

   If you choose to use this file in compliance with the BSD License, the
   following notice applies to you:

       Redistribution and use in source and binary forms, with or without
       modification, are permitted provided that the following conditions are
       met:
       * Redistributions of source code must retain the above copyright
         notice, this list of conditions and the following disclaimer.
       * Redistributions in binary form must reproduce the above copyright
         notice, this list of conditions and the following disclaimer in the
         documentation and/or other materials provided with the distribution.
       * Neither the name of the copyright holder nor the names of
         contributors may be used to endorse or promote products derived from
         this software without specific prior written permission.

       THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
       IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
       TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
       PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
       BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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*/

package org.dynalang.dynalink.linker;


/**
 * Optional interface to be implemented by {@link GuardingTypeConverterFactory} implementers. Language-specific
 * conversions can cause increased overloaded method resolution ambiguity, as many methods can become applicable because
 * of additional conversions. The static way of selecting the "most specific" method will fail more often, because there
 * will be multiple maximally specific method with unrelated signatures. In these cases, language runtimes can be asked
 * to resolve the ambiguity by expressing preferences for one conversion over the other.
 * @author Attila Szegedi
 */
public interface ConversionComparator {
    /**
     * Enumeration of possible outcomes of comparing one conversion to another.
     */
    enum Comparison {
        INDETERMINATE,
        TYPE_1_BETTER,
        TYPE_2_BETTER,
    }

    /**
     * Determines which of the two target types is the preferred conversion target from a source type.
     * @param sourceType the source type.
     * @param targetType1 one potential target type
     * @param targetType2 another potential target type.
     * @return one of Comparison constants that establish which - if any - of the target types is preferred for the
     * conversion.
     */
    public Comparison compareConversion(Class sourceType, Class targetType1, Class targetType2);
}