path: root/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/Conversions.java

/*******************************************************************************
 * Copyright (c) 2004, 2010 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    IBM - Initial API and implementation
 *    Markus Schorn (Wind River Systems)
 *    Bryan Wilkinson (QNX)
 *    Andrew Ferguson (Symbian)
 *    Sergey Prigogin (Google)
 *******************************************************************************/
package org.eclipse.cdt.internal.core.dom.parser.cpp.semantics;

import static org.eclipse.cdt.core.dom.ast.IASTExpression.ValueCategory.LVALUE;
import static org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.ExpressionTypes.valueCategoryFromReturnType;
import static org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.SemanticUtil.*;

import java.util.Collections;

import org.eclipse.cdt.core.dom.ast.DOMException;
import org.eclipse.cdt.core.dom.ast.IASTExpression;
import org.eclipse.cdt.core.dom.ast.IASTExpression.ValueCategory;
import org.eclipse.cdt.core.dom.ast.IASTInitializerClause;
import org.eclipse.cdt.core.dom.ast.IASTLiteralExpression;
import org.eclipse.cdt.core.dom.ast.IASTName;
import org.eclipse.cdt.core.dom.ast.IArrayType;
import org.eclipse.cdt.core.dom.ast.IBasicType;
import org.eclipse.cdt.core.dom.ast.IBasicType.Kind;
import org.eclipse.cdt.core.dom.ast.IBinding;
import org.eclipse.cdt.core.dom.ast.IEnumeration;
import org.eclipse.cdt.core.dom.ast.IFunctionType;
import org.eclipse.cdt.core.dom.ast.IPointerType;
import org.eclipse.cdt.core.dom.ast.IProblemBinding;
import org.eclipse.cdt.core.dom.ast.IQualifierType;
import org.eclipse.cdt.core.dom.ast.IType;
import org.eclipse.cdt.core.dom.ast.IValue;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTInitializerList;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPBasicType;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPClassType;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPConstructor;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPEnumeration;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPFunction;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPFunctionType;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPMethod;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPNamespace;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPPointerToMemberType;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPReferenceType;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateArgument;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateInstance;
import org.eclipse.cdt.core.parser.util.CharArrayUtils;
import org.eclipse.cdt.internal.core.dom.parser.ArithmeticConversion;
import org.eclipse.cdt.internal.core.dom.parser.ITypeContainer;
import org.eclipse.cdt.internal.core.dom.parser.Value;
import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTName;
import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPBasicType;
import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPPointerToMemberType;
import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPPointerType;
import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPQualifierType;
import org.eclipse.cdt.internal.core.dom.parser.cpp.ClassTypeHelper;
import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.Cost.DeferredUDC;
import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.Cost.Rank;
import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.Cost.ReferenceBinding;

/**
 * Routines for calculating the cost of conversions.
 */
public class Conversions {
	public enum UDCMode {ALLOWED, FORBIDDEN, DEFER}
	public enum Context {ORDINARY, IMPLICIT_OBJECT, FIRST_PARAM_OF_DIRECT_COPY_CTOR, REQUIRE_DIRECT_BINDING}

	private static final char[] INITIALIZER_LIST_NAME = "initializer_list".toCharArray(); //$NON-NLS-1$
	private static final char[] STD_NAME = "std".toCharArray(); //$NON-NLS-1$

	/**
	 * Computes the cost of an implicit conversion sequence [over.best.ics] 13.3.3.1
	 * The semantics of the initialization is explained in 8.5-16
	 * @param target the target (parameter) type
	 * @param exprType the source (argument) type
	 * @param valueCat value category of the expression
	 * @return the cost of converting from source to target
	 * @throws DOMException
	 */
	public static Cost checkImplicitConversionSequence(IType target, IType exprType,
			ValueCategory valueCat, UDCMode udc, Context ctx) throws DOMException {
		final boolean isImpliedObject= ctx == Context.IMPLICIT_OBJECT;
		if (isImpliedObject) 
			udc= UDCMode.FORBIDDEN;
		
		target= getNestedType(target, TDEF);
		exprType= getNestedType(exprType, TDEF | REF);
		final IType cv1T1= getNestedType(target, TDEF | REF);
		final IType T1= getNestedType(cv1T1, TDEF | REF | ALLCVQ);
		
		if (target instanceof ICPPReferenceType) {
			ReferenceBinding refBindingType= ReferenceBinding.OTHER_REF;
			// [8.5.3-5] initialization of a reference 
			final boolean isLValueRef= !((ICPPReferenceType) target).isRValueReference();
			final IType cv2T2= exprType;
			final IType T2= getNestedType(cv2T2, TDEF | REF | ALLCVQ);

			// mstodo: will change when implementing rvalue references on this pointer
			final boolean isImplicitWithoutRefQualifier = isImpliedObject; 
			if (!isImplicitWithoutRefQualifier) {
				if (isLValueRef) {
					refBindingType= ReferenceBinding.LVALUE_REF;
				} else {
					refBindingType= ReferenceBinding.RVALUE_REF_BINDS_RVALUE;
				}
			}

			if (exprType instanceof InitializerListType) {
				if (isLValueRef && getCVQualifier(cv1T1) != CVQualifier.CONST)
					return Cost.NO_CONVERSION;

				Cost cost= listInitializationSequence(((InitializerListType) exprType), T1, udc, false);
				if (cost.converts()) {
					cost.setReferenceBinding(refBindingType);
				}
				return cost;
			}

			// If the reference is an lvalue reference and ...
			if (isLValueRef) {
				// ... the initializer expression is an lvalue (but is not a bit field)
				// [for overload resolution bit-fields are treated the same, error if selected as best match]
				if (valueCat == LVALUE) {
					// ... and "cv1 T1" is reference-compatible with "cv2 T2" 
					Cost cost= isReferenceCompatible(cv1T1, cv2T2, isImpliedObject);
					if (cost != null) {
						cost.setReferenceBinding(refBindingType);
						return cost;
					} 
				}
				// ... or has a class type (i.e., T2 is a class type), where T1 is not reference-related to T2, and can be
				// implicitly converted to an lvalue of type 'cv3 T3', where 'cv1 T1' is reference-compatible with 
				// 'cv3 T3' (this conversion is selected by enumerating the applicable conversion functions (13.3.1.6)
				// and choosing the best one through overload resolution (13.3)),
				if (T2 instanceof ICPPClassType && udc != UDCMode.FORBIDDEN && isReferenceRelated(T1, T2) < 0) {
					Cost cost= initializationByConversionForDirectReference(cv1T1, cv2T2, (ICPPClassType) T2, true, ctx);
					if (cost != null) {
						cost.setReferenceBinding(refBindingType);
						return cost;
					}
				}
			}
			
			// Otherwise, the reference shall be an lvalue reference to a non-volatile const type (i.e., cv1
			// shall be const), or the reference shall be an rvalue reference and the initializer expression
			// shall be an rvalue or have function type.
			boolean ok;
			if (isLValueRef) {
				ok = getCVQualifier(cv1T1) == CVQualifier.CONST;
			} else {
				ok= valueCat.isRValue() || T2 instanceof IFunctionType;
			}
			if (!ok) {
				return Cost.NO_CONVERSION;
			}

			// If T1 is a function type, then
			if (T1 instanceof IFunctionType) {
				// if T2 is the same type as T1, the reference is bound to the initializer expression lvalue;
				if (T2.isSameType(T1)) {
					Cost cost= new Cost(T1, T2, Rank.IDENTITY);
					cost.setReferenceBinding(refBindingType);
					return cost;
				}
				// if T2 is a class type and the initializer expression can be implicitly converted to an lvalue of
				// type T1 (this conversion is selected by enumerating the applicable conversion functions (13.3.1.6)
				// and choosing the best one through overload resolution (13.3)), the reference is bound to the
				// function lvalue that is the result of the conversion;
				if (T2 instanceof ICPPClassType) {
					Cost cost= initializationByConversionForDirectReference(cv1T1, cv2T2, (ICPPClassType) T2, true, ctx);
					if (cost != null) {
						cost.setReferenceBinding(refBindingType);
						return cost;
					}
				}
				// — otherwise, the program is ill-formed.
				return Cost.NO_CONVERSION;
			}
			
			// Otherwise, if T2 is a class type and 
			if (T2 instanceof ICPPClassType) {
				// ... the initializer expression is an rvalue and 'cv1 T1' is reference-compatible with 'cv2 T2'
				// ..., then the reference is bound to the initializer expression rvalue in the first case
				if (valueCat.isRValue()) {
					Cost cost= isReferenceCompatible(cv1T1, cv2T2, isImpliedObject);
					if (cost != null) {
						// [13.3.3.1.4-1] direct binding has either identity or conversion rank.					
						if (cost.getInheritanceDistance() > 0) {
							cost.setRank(Rank.CONVERSION);
						} 
						cost.setReferenceBinding(refBindingType);
						return cost;
					} 
				}

				// or T1 is not reference-related to T2 and the initializer expression can be implicitly
				// converted to an rvalue of type 'cv3 T3' (this conversion is selected by enumerating the
				// applicable conversion functions (13.3.1.6) and choosing the best one through overload
				// resolution (13.3)), then the reference is bound to the initializer expression rvalue in the
				// first case and to the object that is the result of the conversion in the second case (or,
				// in either case, to the appropriate base class sub-object of the object).
				if (udc != UDCMode.FORBIDDEN && isReferenceRelated(T1, T2) < 0) {
					Cost cost= initializationByConversionForDirectReference(cv1T1, cv2T2, (ICPPClassType) T2, false, ctx);
					if (cost != null) {
						cost.setReferenceBinding(refBindingType);
						return cost;
					}
				}
			}
			
			// If the initializer expression is an rvalue, with T2 an array type, and 'cv1 T1' is
			// reference-compatible with 'cv2 T2' the reference is bound to the object represented by the
			// rvalue (see 3.10).
			if (T2 instanceof IArrayType && valueCat.isRValue()) {
				Cost cost= isReferenceCompatible(cv1T1, cv2T2, isImpliedObject);
				if (cost != null) {
					cost.setReferenceBinding(refBindingType);
					return cost;
				}
			}

			// Otherwise, a temporary of type 'cv1 T1' is created and initialized from the initializer
			// expression using the rules for a non-reference copy initialization (8.5). The reference is then
			// bound to the temporary. If T1 is reference-related to T2, cv1 must be the same cv-qualification
			// as, or greater cv-qualification than, cv2; otherwise, the program is ill-formed.
				
			// 13.3.3.1.7 no temporary object when converting the implicit object parameter
			if (!isImpliedObject && ctx != Context.REQUIRE_DIRECT_BINDING) {
				if (isReferenceRelated(T1, T2) < 0 || compareQualifications(cv1T1, cv2T2) >= 0) {
					Cost cost= nonReferenceConversion(valueCat, cv2T2, T1, udc);
					if (cost.converts()) {
						cost.setReferenceBinding(refBindingType);
					}
					return cost;
				}
			}
			return Cost.NO_CONVERSION;
		} 
		
		// Non-reference binding
		return nonReferenceConversion(valueCat, exprType, T1, udc);
	}

	/**
	 * C++0x: 13.3.1.6 Initialization by conversion function for direct reference binding	 
	 */
	private static Cost initializationByConversionForDirectReference(final IType cv1T1, final IType cv2T2, final ICPPClassType T2, boolean needLValue, Context ctx)
			throws DOMException {
		ICPPMethod[] fcns= SemanticUtil.getConversionOperators(T2);
		Cost operatorCost= null;
		FunctionCost bestUdcCost= null;
		boolean ambiguousConversionOperator= false;
		if (fcns.length > 0 && !(fcns[0] instanceof IProblemBinding)) {
			for (final ICPPMethod op : fcns) {
				// Note: the special case of initializing a temporary to be bound to the first parameter 
				// of a copy constructor called with a single argument in the context of direct-initialization
				// is (more naturally) handled here rather than in copyInitializationOfClass().
				if (op.isExplicit() && ctx != Context.FIRST_PARAM_OF_DIRECT_COPY_CTOR)
					continue;
				final ICPPFunctionType ft = op.getType();
				IType t= getNestedType(ft.getReturnType(), TDEF);
				final boolean isLValueRef= t instanceof ICPPReferenceType && !((ICPPReferenceType) t).isRValueReference();
				if (isLValueRef == needLValue) { // require an lvalue or rvalue
					IType implicitParameterType= CPPSemantics.getImplicitParameterType(op);
					Cost udcCost= isReferenceCompatible(getNestedType(implicitParameterType, TDEF | REF), cv2T2, true); // expression type to implicit object type
					if (udcCost != null) {
						// Make sure top-level cv-qualifiers are compared
						udcCost.setReferenceBinding(ReferenceBinding.LVALUE_REF);
						FunctionCost udcFuncCost= new FunctionCost(op, udcCost);
						int cmp= udcFuncCost.compareTo(null, bestUdcCost);
						if (cmp <= 0) {
							Cost cost= isReferenceCompatible(cv1T1, getNestedType(t, TDEF | REF), false); // converted to target
							if (cost != null) {
								bestUdcCost= udcFuncCost;
								ambiguousConversionOperator= cmp == 0;
								operatorCost= cost;
								operatorCost.setUserDefinedConversion(op);
							}
						}
					}
				}
			}
		}

		if (operatorCost != null && !ambiguousConversionOperator) {
			return operatorCost;
		}
		return null;
	}

	/**
	 * 8.5-16
	 */
	private static Cost nonReferenceConversion(ValueCategory valueCat, IType source, IType target, UDCMode udc) throws DOMException {
		if (source instanceof InitializerListType) {
			return listInitializationSequence(((InitializerListType) source), target, udc, false);
		}

		IType uqTarget= SemanticUtil.getNestedType(target, TDEF | REF | CVTYPE);
		IType uqSource= SemanticUtil.getNestedType(source, TDEF | REF | CVTYPE);
		if (uqTarget instanceof ICPPClassType) {
			if (uqSource instanceof ICPPClassType) {
				// 13.3.3.1-6 Conceptual derived to base conversion
				int depth= calculateInheritanceDepth(uqSource, uqTarget);
				if (depth >= 0) {
					if (depth == 0) {
						return new Cost(source, target, Rank.IDENTITY);
					}
					Cost cost= new Cost(source, target, Rank.CONVERSION);
					cost.setInheritanceDistance(depth);
					return cost;
				}
			}
			if (udc == UDCMode.FORBIDDEN)
				return Cost.NO_CONVERSION;
			
			return copyInitializationOfClass(valueCat, source, (ICPPClassType) uqTarget, udc == UDCMode.DEFER);
		}
		
		if (uqSource instanceof ICPPClassType) {
			if (udc == UDCMode.FORBIDDEN)
				return Cost.NO_CONVERSION;

			return initializationByConversion(valueCat, source, (ICPPClassType) uqSource, target, udc == UDCMode.DEFER);
		}

		return checkStandardConversionSequence(uqSource, target);
	}

	/**
	 * 13.3.3.1.5 List-initialization sequence [over.ics.list]
	 */
	static Cost listInitializationSequence(InitializerListType arg, IType target, UDCMode udc, boolean isDirect) throws DOMException {
		IType listType= getInitListType(target);
		if (listType != null) {
			IType[] exprTypes= arg.getExpressionTypes();
			ValueCategory[] valueCats= arg.getValueCategories();
			Cost worstCost= new Cost(arg, target, Rank.IDENTITY);
			for (int i = 0; i < exprTypes.length; i++) {
				IType exprType = exprTypes[i];
				Cost cost= checkImplicitConversionSequence(listType, exprType, valueCats[i], UDCMode.ALLOWED, Context.ORDINARY);
				if (!cost.converts())
					return cost;
				if (cost.isNarrowingConversion()) {
					cost.setRank(Rank.NO_MATCH);
					return cost;
				}
				if (cost.compareTo(worstCost) > 0) {
					worstCost= cost;
				}
			}
			return worstCost;
		}
		
		IType noCVTarget= getNestedType(target, CVTYPE | TDEF);
		if (noCVTarget instanceof ICPPClassType) {
			if (udc == UDCMode.FORBIDDEN)
				return Cost.NO_CONVERSION;
			
			ICPPClassType classTarget= (ICPPClassType) noCVTarget;
			if (ClassTypeHelper.isAggregateClass(classTarget)) {
				Cost cost= new Cost(arg, target, Rank.IDENTITY);
				cost.setUserDefinedConversion(null);
				return cost;
			}
			return listInitializationOfClass(arg, classTarget, isDirect, udc == UDCMode.DEFER);
		}
		
		IASTInitializerClause[] args = arg.getInitializerList().getClauses();
		if (args.length == 1) {
			final IASTInitializerClause firstArg = args[0];
			if (firstArg instanceof IASTExpression) {
				IASTExpression expr= (IASTExpression) firstArg;
				Cost cost= checkImplicitConversionSequence(target, expr.getExpressionType(), expr.getValueCategory(), udc, Context.ORDINARY);
				if (cost.isNarrowingConversion()) {
					return Cost.NO_CONVERSION;
				}
				return cost;
			}
		} else if (args.length == 0) {
			return new Cost(arg, target, Rank.IDENTITY);
		}
		
		return Cost.NO_CONVERSION;
	}

	static IType getInitListType(IType target) {
		if (target instanceof ICPPClassType && target instanceof ICPPTemplateInstance) {
			ICPPTemplateInstance inst = (ICPPTemplateInstance) target;
			if (CharArrayUtils.equals(INITIALIZER_LIST_NAME, inst.getNameCharArray())) {
				IBinding owner = inst.getOwner();
				if (owner instanceof ICPPNamespace
						&& CharArrayUtils.equals(STD_NAME, owner.getNameCharArray())
						&& owner.getOwner() == null) {
					ICPPTemplateArgument[] args = inst.getTemplateArguments();
					if (args.length == 1) {
						ICPPTemplateArgument arg = args[0];
						if (arg.isTypeValue()) {
							return arg.getTypeValue();
						}
					}
				}
			}
		}
		return null;
	}

	/**
	 * [3.9.3-4] Implements cv-ness (partial) comparison. There is a (partial)
	 * ordering on cv-qualifiers, so that a type can be said to be more
	 * cv-qualified than another.
	 * @return <ul>
	 * <li>3 if cv1 == const volatile cv2 
	 * <li>2 if cv1 == volatile cv2
	 * <li>1 if cv1 == const cv2
	 * <li>EQ 0 if cv1 == cv2
	 * <li>LT -1 if cv1 is less qualified than cv2 or not comparable
	 * </ul>
	 */
	private static final int compareQualifications(IType t1, IType t2) {
		return getCVQualifier(t1).partialComparison(getCVQualifier(t2));
	}

	/**
	 * [8.5.3] "cv1 T1" is reference-related to "cv2 T2" if T1 is the same type as T2,
	 * or T1 is a base class of T2.
	 * Note this is not a symmetric relation.
	 * @return inheritance distance, or -1, if <code>cv1t1</code> is not reference-related to <code>cv2t2</code>
	 */
	private static final int isReferenceRelated(IType cv1Target, IType cv2Source) {
		IType t= SemanticUtil.getNestedType(cv1Target, TDEF | REF);
		IType s= SemanticUtil.getNestedType(cv2Source, TDEF | REF);
		
		// The way cv-qualification is currently modeled means
		// we must cope with IPointerType objects separately.
		if (t instanceof IPointerType) {
			if (s instanceof IPointerType) {
				t= SemanticUtil.getNestedType(((IPointerType) t).getType(), TDEF | REF);
				s= SemanticUtil.getNestedType(((IPointerType) s).getType(), TDEF | REF);
			} else {
				return -1;
			}
		} else if (t instanceof IArrayType) {
			if (s instanceof IArrayType) {
				final IArrayType at = (IArrayType) t;
				final IArrayType st = (IArrayType) s;
				final IValue av= at.getSize();
				final IValue sv= st.getSize();
				if (av == sv || (av != null && av.equals(sv))) {
					t= SemanticUtil.getNestedType(at.getType(), TDEF | REF | ALLCVQ);
					s= SemanticUtil.getNestedType(st.getType(), TDEF | REF | ALLCVQ);
				} else {
					return -1;
				}
			} else {
				return -1;
			}
		} else {
			if (t instanceof IQualifierType)
				t= SemanticUtil.getNestedType(((IQualifierType) t).getType(), TDEF | REF);
			if (s instanceof IQualifierType)
				s= SemanticUtil.getNestedType(((IQualifierType) s).getType(), TDEF | REF);

			if (t instanceof ICPPClassType && s instanceof ICPPClassType) {
				return SemanticUtil.calculateInheritanceDepth(s, t);
			}
		}
		if (t == s || (t != null && s != null && t.isSameType(s))) {
			return 0;
		}
		return -1;
	}

	/**
	 * [8.5.3] "cv1 T1" is reference-compatible with "cv2 T2" if T1 is reference-related
	 * to T2 and cv1 is the same cv-qualification as, or greater cv-qualification than, cv2.
	 * Note this is not a symmetric relation.
	 * @return The cost for converting or <code>null</code> if <code>cv1t1</code> is not
	 * reference-compatible with <code>cv2t2</code>
	 */
	private static final Cost isReferenceCompatible(IType cv1Target, IType cv2Source, boolean isImpliedObject) {
		int inheritanceDist= isReferenceRelated(cv1Target, cv2Source);
		if (inheritanceDist < 0)
			return null;
		final int cmp= compareQualifications(cv1Target, cv2Source);
		if (cmp < 0)
			return null;
		
		Cost cost= new Cost(cv2Source, cv1Target, Rank.IDENTITY);
		cost.setQualificationAdjustment(cmp);
		if (inheritanceDist > 0) {
			cost.setInheritanceDistance(inheritanceDist);
			cost.setRank(Rank.CONVERSION);
		}

		if (isImpliedObject) {
			cost.setImpliedObject();
		}
		return cost;
	}
	
	/**
	 * [4] Standard Conversions
	 * Computes the cost of using the standard conversion sequence from source to target.
	 */
	private static final Cost checkStandardConversionSequence(IType source, IType target) {
		final Cost cost= new Cost(source, target, Rank.IDENTITY);
		if (lvalue_to_rvalue(cost))
			return cost;

		if (promotion(cost))
			return cost;
		
		if (conversion(cost)) 
			return cost;

		if (qualificationConversion(cost))
			return cost;

		// If we can't convert the qualifications, then we can't do anything
		cost.setRank(Rank.NO_MATCH);
		return cost;
	}

	// 13.3.1.7 Initialization by list-initialization
	static Cost listInitializationOfClass(InitializerListType arg, ICPPClassType t, boolean isDirect, boolean deferUDC) throws DOMException {
		if (deferUDC) {
			Cost c= new Cost(arg, t, Rank.USER_DEFINED_CONVERSION);
			c.setDeferredUDC(isDirect ? DeferredUDC.DIRECT_LIST_INIT_OF_CLASS : DeferredUDC.LIST_INIT_OF_CLASS);
			return c;
		}

		// If T has an initializer-list constructor
		ICPPConstructor usedCtor= null;
		Cost bestCost= null;
		boolean hasInitListConstructor= false;
		final ICPPConstructor[] constructors = t.getConstructors();
		ICPPConstructor[] ctors= constructors;
		for (ICPPConstructor ctor : ctors) {
			final int minArgCount = ctor.getRequiredArgumentCount();
			if (minArgCount == 0) {
				if (arg.getExpressionTypes().length == 0) {
					Cost c= new Cost(arg, t, Rank.IDENTITY);
					c.setUserDefinedConversion(ctor);
					return c;
				}
			} else if (minArgCount <= 1) {
				IType[] parTypes= ctor.getType().getParameterTypes();
				if (parTypes.length > 0) {
					final IType target = parTypes[0];
					if (getInitListType(target) != null) {
						hasInitListConstructor= true;
						Cost cost= listInitializationSequence(arg, target, UDCMode.FORBIDDEN, isDirect);
						if (cost.converts()) {
							int cmp= cost.compareTo(bestCost);
							if (bestCost == null || cmp < 0) {
								usedCtor= ctor;
								cost.setUserDefinedConversion(ctor);
								bestCost= cost;
							} else if (cmp == 0) {
								bestCost.setAmbiguousUDC(true);
							}
						}
					}
				}
			}
		}
		if (hasInitListConstructor) {
			if (bestCost == null)
				return Cost.NO_CONVERSION;
			
			if (!bestCost.isAmbiguousUDC() && !isDirect) {
				if (usedCtor != null && usedCtor.isExplicit()) {
					bestCost.setRank(Rank.NO_MATCH);
				}
			}
			return bestCost;
		}

		// No initializer-list constructor
		final ICPPASTInitializerList initializerList = arg.getInitializerList();

		LookupData data= new LookupData();
		IASTName name = new CPPASTName(t.getNameCharArray());
		name.setParent(initializerList);
	    name.setPropertyInParent(CPPSemantics.STRING_LOOKUP_PROPERTY);
    	final IASTInitializerClause[] expandedArgs = initializerList.getClauses();
		data.setFunctionArguments(false, expandedArgs);
		data.fNoNarrowing= true;

		// 13.3.3.1.4
		ICPPConstructor[] filteredConstructors = constructors;
		if (expandedArgs.length == 1) {
			filteredConstructors= new ICPPConstructor[constructors.length];
			int j=0;
			for (ICPPConstructor ctor : constructors) {
				if (ctor.getRequiredArgumentCount() < 2) {
					IType[] ptypes= ctor.getType().getParameterTypes();
					if (ptypes.length > 0) {
						IType ptype= getNestedType(ptypes[0], TDEF | REF | CVTYPE);
						if (!t.isSameType(ptype)) {
							filteredConstructors[j++]= ctor;
						}
					}
				}
			}
		}
		final IBinding result= CPPSemantics.resolveFunction(data, filteredConstructors, true);
		final Cost c;
		if (result instanceof ICPPMethod) {
			c= new Cost(arg, t, Rank.IDENTITY);
			c.setUserDefinedConversion((ICPPMethod) result);
		} else if (result instanceof IProblemBinding
				&& ((IProblemBinding) result).getID() == IProblemBinding.SEMANTIC_AMBIGUOUS_LOOKUP) {
			c = new Cost(arg, t, Rank.USER_DEFINED_CONVERSION);
			c.setAmbiguousUDC(true);
		} else {
			c= Cost.NO_CONVERSION;
		}
		return c;
	}

	/**
	 * 13.3.1.4 Copy-initialization of class by user-defined conversion [over.match.copy]
	 */
	static final Cost copyInitializationOfClass(ValueCategory valueCat, IType source, ICPPClassType t, boolean deferUDC) throws DOMException {
		if (deferUDC) {
			Cost c= new Cost(source, t, Rank.USER_DEFINED_CONVERSION);
			c.setDeferredUDC(DeferredUDC.COPY_INIT_OF_CLASS);
			return c;
		}

		FunctionCost cost1= null;
		Cost cost2= null;
		ICPPFunction[] ctors= t.getConstructors();
		ctors = CPPTemplates.instantiateForFunctionCall(null, ctors,
				Collections.singletonList(source), Collections.singletonList(valueCat), false);

		for (ICPPFunction f : ctors) {
			if (!(f instanceof ICPPConstructor) || f instanceof IProblemBinding)
				continue;
			
			ICPPConstructor ctor= (ICPPConstructor) f;
			// Note: the special case of initializing a temporary to be bound to the first parameter 
			// of a copy constructor called with a single argument in the context of direct-initialization
			// is (more naturally) handled in initializationByConversionForDirectReference.
			if (!ctor.isExplicit()) {
				final ICPPFunctionType ft = ctor.getType();
				final IType[] ptypes = ft.getParameterTypes();
				FunctionCost c1;
				if (ptypes.length == 0) {
					if (ctor.takesVarArgs()) {
						c1= new FunctionCost(ctor, new Cost(source, null, Rank.ELLIPSIS_CONVERSION));
					} else {
						continue;
					}
				} else {
					IType ptype= SemanticUtil.getNestedType(ptypes[0], TDEF);
					// We don't need to check the implicit conversion sequence if the type is void
					if (SemanticUtil.isVoidType(ptype)) 
						continue;
					if (ctor.getRequiredArgumentCount() > 1) 
						continue;
					
					c1= new FunctionCost(ctor, checkImplicitConversionSequence(ptype, source, valueCat, UDCMode.FORBIDDEN, Context.ORDINARY));
				}
				int cmp= c1.compareTo(null, cost1);
				if (cmp <= 0) {
					cost1= c1;
					cost2= new Cost(t, t, Rank.IDENTITY);
					cost2.setUserDefinedConversion(ctor);
					if (cmp == 0) {
						cost2.setAmbiguousUDC(true);
					}
				}
			}
		}
		
		final IType uqSource= getNestedType(source, TDEF | REF | CVTYPE);
		if (uqSource instanceof ICPPClassType) {
			ICPPMethod[] ops = SemanticUtil.getConversionOperators((ICPPClassType) uqSource); 
			CPPTemplates.instantiateConversionTemplates(ops, t);
			for (final ICPPMethod op : ops) {
				if (op != null && !(op instanceof IProblemBinding)) {
					if (op.isExplicit())
						continue;
					final IType returnType = op.getType().getReturnType();
					final IType uqReturnType= getNestedType(returnType, REF | TDEF | CVTYPE);
					final int dist = SemanticUtil.calculateInheritanceDepth(uqReturnType, t);
					if (dist >= 0) {
						IType implicitType= CPPSemantics.getImplicitParameterType(op);
						final Cost udcCost = isReferenceCompatible(getNestedType(implicitType, TDEF | REF), source, true);
						if (udcCost != null) {
							// Make sure top-level cv-qualifiers are compared
							udcCost.setReferenceBinding(ReferenceBinding.LVALUE_REF);
							FunctionCost c1= new FunctionCost(op, udcCost);
							int cmp= c1.compareTo(null, cost1);
							if (cmp <= 0) {
								cost1= c1;
								cost2= new Cost(t, t, Rank.IDENTITY);
								if (dist > 0) {
									cost2.setInheritanceDistance(dist);
									cost2.setRank(Rank.CONVERSION);
								}
								cost2.setUserDefinedConversion(op);
								if (cmp == 0) {
									cost2.setAmbiguousUDC(true);
								}
							}
						}
					}
				}
			}
		}
		if (cost1 == null || !cost1.getCost(0).converts())
			return Cost.NO_CONVERSION;
		
		return cost2;
	}

	/**
	 * 13.3.1.5 Initialization by conversion function [over.match.conv]
	 */
	static Cost initializationByConversion(ValueCategory valueCat, IType source, ICPPClassType uqSource, IType target, boolean deferUDC) throws DOMException {
		if (deferUDC) {
			Cost c= new Cost(source, target, Rank.USER_DEFINED_CONVERSION);
			c.setDeferredUDC(DeferredUDC.INIT_BY_CONVERSION);
			return c;
		}
		ICPPMethod[] ops = SemanticUtil.getConversionOperators(uqSource); 
		CPPTemplates.instantiateConversionTemplates(ops, target);
		FunctionCost cost1= null;
		Cost cost2= null;
		for (final ICPPMethod op : ops) {
			if (op != null && !(op instanceof IProblemBinding)) {
				final boolean isExplicitConversion= op.isExplicit();
				if (isExplicitConversion /** && !direct **/)
					continue;
				
				final IType returnType = op.getType().getReturnType();
				IType uqReturnType= getNestedType(returnType, TDEF | ALLCVQ);
				Cost c2= checkImplicitConversionSequence(target, uqReturnType, valueCategoryFromReturnType(uqReturnType), UDCMode.FORBIDDEN, Context.ORDINARY);
				if (c2.converts()) {
					if (isExplicitConversion && c2.getRank() != Rank.IDENTITY)
						continue;
					IType implicitType= CPPSemantics.getImplicitParameterType(op);
					final Cost udcCost = isReferenceCompatible(getNestedType(implicitType, TDEF | REF), source, true);
					if (udcCost != null) {
						// Make sure top-level cv-qualifiers are compared
						udcCost.setReferenceBinding(ReferenceBinding.LVALUE_REF);
						FunctionCost c1= new FunctionCost(op, udcCost);
						int cmp= c1.compareTo(null, cost1);
						if (cmp <= 0) {
							cost1= c1;
							cost2= c2;
							cost2.setUserDefinedConversion(op);
							if (cmp == 0) {
								cost2.setAmbiguousUDC(true);
							}
						}
					}
				}
			}
		}
		if (cost1 == null || !cost1.getCost(0).converts())
			return Cost.NO_CONVERSION;
		
		return cost2;
	}

	/**
	 * Attempts the conversions below and returns whether this completely converts the source to
	 * the target type.
	 * [4.1] Lvalue-to-rvalue conversion
	 * [4.2] array-to-ptr
	 * [4.3] function-to-ptr
	 */
	private static final boolean lvalue_to_rvalue(final Cost cost) {
		IType target = getNestedType(cost.target, REF | TDEF | ALLCVQ);
		IType source= getNestedType(cost.source, REF | TDEF);
		
		// 4.2 array to pointer conversion
		if (source instanceof IArrayType) {
			if (target instanceof IPointerType) {
				// 4.2-2 a string literal can be converted to pointer to char
				source = unqualifyStringLiteral(source, (IPointerType) target, cost);
			}
			if (!(source instanceof IPointerType)) {
				source = new CPPPointerType(getNestedType(((IArrayType) source).getType(), TDEF));
			}
		} else if (source instanceof IFunctionType) {
			// 4.3 function to pointer conversion
			source = new CPPPointerType(source);
		} else {
			if (source instanceof IPointerType) {
				// A string literal may have been converted to a pointer when 
				// computing the type of a conditional expression.
				if (target instanceof IPointerType) {
					// 4.2-2 a string literal can be converted to pointer to char
					source = unqualifyStringLiteral(source, (IPointerType) target, cost);
				}
			} 
			source = getNestedType(source, TDEF | REF | ALLCVQ);
		}

		if (source == null || target == null) {
			cost.setRank(Rank.NO_MATCH);
			return true;
		} 
		cost.source= source;
		cost.target= target;
		return source.isSameType(target);
	}

	private static IType unqualifyStringLiteral(IType source, final IPointerType target, final Cost cost) {
		if (target instanceof ICPPPointerToMemberType)
			return source;
		
		final IType targetPtrTgt= getNestedType((target).getType(), TDEF);
		if (targetPtrTgt instanceof IQualifierType && ((IQualifierType) targetPtrTgt).isConst()) 
			return source;

		IType srcTarget= ((ITypeContainer) source).getType();
		if (!(srcTarget instanceof IQualifierType)) 
			return source;
		
		final IQualifierType srcQTarget= (IQualifierType) srcTarget;
		if (srcQTarget.isConst() && !srcQTarget.isVolatile()) {
			srcTarget= srcQTarget.getType();
			if (srcTarget instanceof CPPBasicType) {
				IASTExpression val = ((CPPBasicType) srcTarget).getCreatedFromExpression();
				if (val instanceof IASTLiteralExpression) {
					IASTLiteralExpression lit= (IASTLiteralExpression) val;
					if (lit.getKind() == IASTLiteralExpression.lk_string_literal) {
						source= new CPPPointerType(srcTarget, false, false, false);
						CVQualifier cvqTarget = getCVQualifier(targetPtrTgt).add(CVQualifier.CONST);
						cost.setQualificationAdjustment(cvqTarget.partialComparison(CVQualifier.NONE) << 3);
					}
				}
			}
		}
		return source;
	}
	
	/**
	 * [4.4] Qualifications 
	 * @param cost
	 */
	private static final boolean qualificationConversion(Cost cost) {
		IType s = cost.source;
		IType t = cost.target;
		boolean constInEveryCV2k = true;
		boolean firstPointer= true;
		int adjustments= 0;
		int shift=0;
		while (true) {
			s= getNestedType(s, TDEF | REF);
			t= getNestedType(t, TDEF | REF);
			if (s instanceof IPointerType && t instanceof IPointerType) {
				final int cmp= compareQualifications(t, s);  // is t more qualified than s?
				if (cmp < 0 || (cmp > 0 && !constInEveryCV2k)) {
					return false;
				} 
				final IPointerType tPtr = (IPointerType) t;
				final IPointerType sPtr = (IPointerType) s;
				if (haveMemberPtrConflict(sPtr, tPtr))
					return false;
						
				constInEveryCV2k &= (firstPointer || tPtr.isConst());
				s= sPtr.getType();
				t= tPtr.getType();
				firstPointer= false;
				adjustments |= (cmp << shift);
				shift+= 3;
			} else {
				break;
			}
		}

		int cmp= compareQualifications(t, s);  // is t more qualified than s?
		if (cmp < 0 || (cmp > 0 && !constInEveryCV2k)) {
			return false;
		} 

		adjustments |= (cmp << shift);
		s= getNestedType(s, ALLCVQ | TDEF | REF);
		t= getNestedType(t, ALLCVQ | TDEF | REF);
		
		if (adjustments > 0) {
			cost.setQualificationAdjustment(adjustments);
		}
		return s != null && t != null && s.isSameType(t);
	}

	private static boolean haveMemberPtrConflict(IPointerType s, IPointerType t) {
		final boolean sIsPtrToMember = s instanceof ICPPPointerToMemberType;
		final boolean tIsPtrToMember = t instanceof ICPPPointerToMemberType;
		if (sIsPtrToMember != tIsPtrToMember) {
			return true;
		} 
		if (sIsPtrToMember) {
			final IType sMemberOf = ((ICPPPointerToMemberType) s).getMemberOfClass();
			final IType tMemberOf = ((ICPPPointerToMemberType) t).getMemberOfClass();
			if (sMemberOf == null || tMemberOf == null || !sMemberOf.isSameType(tMemberOf)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Attempts promotions and returns whether the promotion converted the type.
	 * 
	 * [4.5] [4.6] Promotion
	 * 
	 * 4.5-1 char, signed char, unsigned char, short int or unsigned short int
	 * can be converted to int if int can represent all the values of the source
	 * type, otherwise they can be converted to unsigned int.
	 * 4.5-2 wchar_t or an enumeration can be converted to the first of the
	 * following that can hold it: int, unsigned int, long unsigned long.
	 * 4.5-4 bool can be promoted to int 
	 * 4.6 float can be promoted to double
	 */
	private static final boolean promotion(Cost cost) {
		IType src = cost.source;
		IType trg = cost.target;

		boolean canPromote= false;
		if (trg instanceof IBasicType) {
			IBasicType basicTgt = (IBasicType) trg;
			final Kind tKind = basicTgt.getKind();
			
			if (src instanceof ICPPEnumeration) {
				final ICPPEnumeration enumType = (ICPPEnumeration) src;
				if (enumType.isScoped()) {
					return false;
				}
				IType fixedType= enumType.getFixedType();
				if (fixedType == null) {
					if (tKind == Kind.eInt || tKind == Kind.eUnspecified) {
						if (trg instanceof ICPPBasicType) {
							int qualifiers = ArithmeticConversion.getEnumIntTypeModifiers((IEnumeration) src);
							int targetModifiers = ((ICPPBasicType) trg).getModifiers();
							if (qualifiers == (targetModifiers & (IBasicType.IS_LONG | IBasicType.IS_LONG_LONG | IBasicType.IS_SHORT | IBasicType.IS_UNSIGNED))) {
								canPromote = true;
							}
						} else {
							canPromote = true;
						}
					}
				} else {
					if (fixedType.isSameType(trg))
						canPromote= true;
					// Allow to further promote the fixed type
					src= fixedType;
				}
			}
			if (src instanceof IBasicType) {
				final IBasicType basicSrc = (IBasicType) src;
				Kind sKind = basicSrc.getKind();
				if (tKind == Kind.eInt) {
					if (!basicTgt.isLong() && !basicTgt.isLongLong() && !basicTgt.isShort()) {
						switch (sKind) {
						case eInt: // short, and unsigned short
							if (basicSrc.isShort() && !basicTgt.isUnsigned()) {
								canPromote= true;
							}
							break;
						case eChar:
						case eBoolean:
						case eWChar:
						case eChar16:
						case eUnspecified: // treat unspecified as int
							if (!basicTgt.isUnsigned()) {
								canPromote= true;
							}
							break;

						case eChar32:
							if (basicTgt.isUnsigned()) {
								canPromote= true;
							}
							break;
						default:
							break;
						}
					}
				} else if (tKind == Kind.eDouble && sKind == Kind.eFloat) {
					canPromote= true;
				}
			} 
		}
		if (canPromote) {
			cost.setRank(Rank.PROMOTION);
			return true;
		}
		return false;
	}

	/**
	 * Attempts conversions and returns whether the conversion succeeded.
	 * [4.7]  Integral conversions
	 * [4.8]  Floating point conversions
	 * [4.9]  Floating-integral conversions
	 * [4.10] Pointer conversions
	 * [4.11] Pointer to member conversions
	 */
	private static final boolean conversion(Cost cost){
		final IType s = cost.source;
		final IType t = cost.target;

		if (t instanceof IBasicType) {
			// 4.7 integral conversion
			// 4.8 floating point conversion
			// 4.9 floating-integral conversion
			if (s instanceof IBasicType) {
				if (((IBasicType) s).getKind() == Kind.eVoid) 
					return false;
				
				cost.setRank(Rank.CONVERSION);
				cost.setCouldNarrow();
				return true;
			} 
			if (s instanceof ICPPEnumeration && !((ICPPEnumeration) s).isScoped()) {
				// 4.7 An rvalue of an enumeration type can be converted to an rvalue of an integer type.
				cost.setRank(Rank.CONVERSION);
				cost.setCouldNarrow();
				return true;
			} 
			// 4.12 pointer or pointer to member type can be converted to an rvalue of type bool
			final Kind tgtKind = ((IBasicType) t).getKind();
			if (tgtKind == Kind.eBoolean && s instanceof IPointerType) {
				cost.setRank(Rank.CONVERSION_PTR_BOOL);
				return true;
			} 
		}
		
		if (t instanceof IPointerType) {
			IPointerType tgtPtr= (IPointerType) t;
			// 4.10-1 an integral constant expression of integer type that evaluates to 0 can
			// be converted to a pointer type
			// 4.11-1 same for pointer to member
			if (s instanceof IBasicType) {
				if (isNullPointerConstant(s)) {
					cost.setRank(Rank.CONVERSION);
					return true;
				}
				return false;
			}
			if (s instanceof IPointerType) {
				IPointerType srcPtr= (IPointerType) s;
				// 4.10-2 an rvalue of type "pointer to cv T", where T is an object type can be
				// converted to an rvalue of type "pointer to cv void"
				IType tgtPtrTgt= getNestedType(tgtPtr.getType(), TDEF | CVTYPE | REF);
				if (SemanticUtil.isVoidType(tgtPtrTgt)) {
					cost.setRank(Rank.CONVERSION);
					cost.setInheritanceDistance(Short.MAX_VALUE); 
					CVQualifier cv= getCVQualifier(srcPtr.getType());
					cost.source= new CPPPointerType(addQualifiers(CPPSemantics.VOID_TYPE, cv.isConst(), cv.isVolatile(), cv.isRestrict()));
					return false; 
				}
				
				final boolean tIsPtrToMember = t instanceof ICPPPointerToMemberType;
				final boolean sIsPtrToMember = s instanceof ICPPPointerToMemberType;
				if (!tIsPtrToMember && !sIsPtrToMember) {
					// 4.10-3 An rvalue of type "pointer to cv D", where D is a class type can be converted
					// to an rvalue of type "pointer to cv B", where B is a base class of D.
					IType srcPtrTgt= getNestedType(srcPtr.getType(), TDEF | CVTYPE | REF);
					if (tgtPtrTgt instanceof ICPPClassType && srcPtrTgt instanceof ICPPClassType) {
						int depth= SemanticUtil.calculateInheritanceDepth(srcPtrTgt, tgtPtrTgt);
						if (depth == -1) {
							cost.setRank(Rank.NO_MATCH);
							return true;
						}
						if (depth > 0) {
							cost.setRank(Rank.CONVERSION);
							cost.setInheritanceDistance(depth);
							CVQualifier cv= getCVQualifier(srcPtr.getType());
							cost.source= new CPPPointerType(addQualifiers(tgtPtrTgt, cv.isConst(), cv.isVolatile(), cv.isRestrict()));
						}
						return false;
					}
				} else if (tIsPtrToMember && sIsPtrToMember) {
					// 4.11-2 An rvalue of type "pointer to member of B of type cv T", where B is a class type, 
					// can be converted to an rvalue of type "pointer to member of D of type cv T" where D is a
					// derived class of B
					ICPPPointerToMemberType spm = (ICPPPointerToMemberType) s;
					ICPPPointerToMemberType tpm = (ICPPPointerToMemberType) t;
					IType st = spm.getType();
					IType tt = tpm.getType();
					if (st != null && tt != null && st.isSameType(tt)) {
						int depth = SemanticUtil.calculateInheritanceDepth(tpm.getMemberOfClass(), 
								spm.getMemberOfClass());
						if (depth == -1) {
							cost.setRank(Rank.NO_MATCH);
							return true;
						}
						if (depth > 0) {
							cost.setRank(Rank.CONVERSION);
							cost.setInheritanceDistance(depth);
							cost.source = new CPPPointerToMemberType(spm.getType(),
									tpm.getMemberOfClass(), spm.isConst(), spm.isVolatile(), spm.isRestrict());
						}
						return false;
					}
				}
			}
		}
		return false;
	}

	private static boolean isNullPointerConstant(IType s) {
		if (s instanceof CPPBasicType) {
			IASTExpression exp = ((CPPBasicType) s).getCreatedFromExpression();
			if (exp != null) {
				Long val= Value.create(exp, Value.MAX_RECURSION_DEPTH).numericalValue();
				if (val != null && val == 0) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * 4.1, 4.2, 4.3
	 */
	public static IType lvalue_to_rvalue(IType type) {
		type= SemanticUtil.getNestedType(type, TDEF | REF);
		if (type instanceof IArrayType) {
			return new CPPPointerType(((IArrayType) type).getType());
		}
		if (type instanceof IFunctionType) {
			return new CPPPointerType(type);
		}
		IType uqType= SemanticUtil.getNestedType(type, TDEF | REF | ALLCVQ);
		if (uqType instanceof ICPPClassType) {
			return type;
		}
		return uqType;
	}

	/**
	 * Composite pointer type computed as described in 5.9-2 except that if the conversion to the
	 * pointer is not possible, we return null.
	 */
	public static IType compositePointerType(IType t1, IType t2) {
		final boolean isPtr1 = t1 instanceof IPointerType;
		if (isPtr1 || isNullPtr(t1)) {
			if (isNullPointerConstant(t2)) {
				return t1;
			}
		}
		final boolean isPtr2 = t2 instanceof IPointerType;
		if (isPtr2 || isNullPtr(t2)) {
			if (isNullPointerConstant(t1)) {
				return t2;
			}
		}
		if (!isPtr1 || !isPtr2)
			return null;
		
		final IPointerType p1= (IPointerType) t1;
		final IPointerType p2= (IPointerType) t2;
		if (haveMemberPtrConflict(p1, p2))
			return null;
		
		final IType target1 = p1.getType();
		if (isVoidType(target1)) {
			return addQualifiers(p1, p2.isConst(), p2.isVolatile(), p2.isRestrict());
		}
		final IType target2 = p2.getType();
		if (isVoidType(target2)) {
			return addQualifiers(p2, p1.isConst(), p1.isVolatile(), p1.isRestrict());
		}
		
		IType t= mergePointers(target1, target2, true);
		if (t == null)
			return null;
		if (t == target1)
			return p1;
		if (t == target2)
			return p2;
		return copyPointer(p1, t, false, false);
	}

	private static IType mergePointers(IType t1, IType t2, boolean allcq) {
		t1= getNestedType(t1, TDEF | REF);
		t2= getNestedType(t2, TDEF | REF);
		if (t1 instanceof IPointerType && t2 instanceof IPointerType) {
			final IPointerType p1 = (IPointerType) t1;
			final IPointerType p2 = (IPointerType) t2;
			final CVQualifier cv1= getCVQualifier(t1);
			final CVQualifier cv2= getCVQualifier(t2);
			if (haveMemberPtrConflict(p1, p2))
				return null;
			if (!allcq && cv1 != cv2) 
				return null;

			final IType p1target = p1.getType();
			IType merged= mergePointers(p1target, p2.getType(), allcq && (cv1.isConst() || cv2.isConst()));
			if (merged == null)
				return null;
			if (p1target == merged && cv1.isAtLeastAsQualifiedAs(cv2))
				return p1;
			if (p2.getType() == merged && cv2.isAtLeastAsQualifiedAs(cv1))
				return p2;
			
			return copyPointer(p1, merged, cv1.isConst() || cv2.isConst(), cv1.isVolatile() || cv2.isVolatile());
		}
		
		final IType uq1= getNestedType(t1, TDEF|REF|CVTYPE);
		final IType uq2= getNestedType(t2, TDEF|REF|CVTYPE);
		if (uq1 == null || ! uq1.isSameType(uq2))
			return null;

		if (uq1 == t1 && uq2 == t2)
			return t1;

		CVQualifier cv1= getCVQualifier(t1);
		CVQualifier cv2= getCVQualifier(t2);
		if (cv1 == cv2) 
			return t1;
		
		if (!allcq)
			return null;

		if (cv1.isAtLeastAsQualifiedAs(cv2))
			return t1;
		if (cv2.isAtLeastAsQualifiedAs(cv1)) 
			return t2;

		// One type is const the other is volatile.
		return new CPPQualifierType(uq1, true, true);
	}

	public static IType copyPointer(final IPointerType p1, IType target, final boolean isConst,
			final boolean isVolatile) {
		if (p1 instanceof ICPPPointerToMemberType) {
			ICPPPointerToMemberType ptm= (ICPPPointerToMemberType) p1;
			return new CPPPointerToMemberType(target, ptm.getMemberOfClass(), isConst, isVolatile, false);
		}
		return new CPPPointerType(target, isConst, isVolatile, false);
	}

	private static boolean isNullPtr(IType t1) {
		// mstodo null-ptr type
		return false;
	}
}