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Copyright (C) 2002-2004 Jan Arne Petersen 
Copyright (C) 2004-2005 Thomas E Enebo 
Copyright (C) 2014 Timur Duehr 
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in which case the provisions of the GPL or the LGPL are applicable instead
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 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * License Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.eclipse.org/legal/epl-v20.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2002-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2004-2005 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2014 Timur Duehr <tduehr@gmail.com>
 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
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package org.jruby.internal.runtime.methods;

import org.jruby.RubyModule;
import org.jruby.runtime.Block;
import org.jruby.runtime.CallType;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.Visibility;
import org.jruby.runtime.builtin.IRubyObject;

This class represents a singleton type of method used as a marker for
breaking method lookup loops. Like UndefinedMethod, only one instance is ever created, it
can't be invoked, and shouldn't be returned as though it were a real method.
/**
 * This class represents a singleton type of method used as a marker for
 * breaking method lookup loops. Like UndefinedMethod, only one instance is ever created, it
 * can't be invoked, and shouldn't be returned as though it were a real method.
 */
public class NullMethod extends DynamicMethod {
    public static final NullMethod INSTANCE = new NullMethod();

    
Constructor for the one NullMethod instance.
/**
     * Constructor for the one NullMethod instance.
     */
    private NullMethod() {
        super("null");
    }

    
The one implementation of call, which throws an exception because
NullMethod can't be invoked.
See Also:
call/**
     * The one implementation of call, which throws an exception because
     * NullMethod can't be invoked.
     *
     * @see DynamicMethod.call
     */
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String name, IRubyObject[] args, Block block) {
        throw new UnsupportedOperationException("BUG: invoking NullMethod.call; report at http://bugs.jruby.org");
    }

    
A dummy implementation of dup that just returns the singleton instance.
Returns:
The singleton instance/**
     * A dummy implementation of dup that just returns the singleton instance.
     *
     * @return The singleton instance
     */
    public DynamicMethod dup() {
        return INSTANCE;
    }

    
Retrieve the singleton instance.
Returns:
The singleton instance/**
     * Retrieve the singleton instance.
     *
     * @return The singleton instance
     */
    public static NullMethod getInstance() {
        return INSTANCE;
    }

    
Dummy override of setImplementationClass that does nothing.
Params:
implClass – Ignored/**
     * Dummy override of setImplementationClass that does nothing.
     *
     * @param implClass Ignored
     */
    @Override
    public void setImplementationClass(RubyModule implClass) {
        throw new UnsupportedOperationException("BUG: NullMethod is immutable: setImplmentationClass called; report at http://bugs.jruby.org");
        // NullMethod should be immutable
    }

    
Dummy implementation of setVisibility that does nothing.
Params:
visibility – Ignored/**
     * Dummy implementation of setVisibility that does nothing.
     *
     * @param visibility Ignored
     */
    @Override
    public void setVisibility(Visibility visibility) {
        throw new UnsupportedOperationException("BUG: NullMethod is immutable: setVisibility called; report at http://bugs.jruby.org");
        // NullMethod should be immutable
    }

    
Dummy implementation of setCallConfig that does nothing.
Params:
callConfig – Ignored/**
     * Dummy implementation of setCallConfig that does nothing.
     *
     * @param callConfig Ignored
     */
    @Override
    @Deprecated
    public void setCallConfig(CallConfiguration callConfig) {
        throw new UnsupportedOperationException("BUG: NullMethod is immutable: setCallConfig called; report at http://bugs.jruby.org");
        // NullMethod should be immutable
    }

    
NullMethod is always visible because it's only used as a marker to
break method lookup loops.
Params:
caller – The calling object
callType – The type of call
Returns:
true always/**
     * NullMethod is always visible because it's only used as a marker to
     * break method lookup loops.
     *
     * @param caller The calling object
     * @param callType The type of call
     * @return true always
     */
    @Override
    public boolean isCallableFrom(IRubyObject caller, CallType callType) {
        return true;
    }
}