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// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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using System.Collections.Generic;

namespace ICSharpCode.Decompiler.TypeSystem
{
	/// <summary>
	/// Type parameter of a generic class/method.
	/// </summary>
	public interface IUnresolvedTypeParameter : INamedElement
	{
		/// <summary>
		/// Get the type of this type parameter's owner.
		/// </summary>
		/// <returns>SymbolKind.TypeDefinition or SymbolKind.Method</returns>
		SymbolKind OwnerType { get; }
		
		/// <summary>
		/// Gets the index of the type parameter in the type parameter list of the owning method/class.
		/// </summary>
		int Index { get; }
		
		/// <summary>
		/// Gets the list of attributes declared on this type parameter.
		/// </summary>
		IList<IUnresolvedAttribute> Attributes { get; }
		
		/// <summary>
		/// Gets the variance of this type parameter.
		/// </summary>
		VarianceModifier Variance { get; }
		
		/// <summary>
		/// Gets the region where the type parameter is defined.
		/// </summary>
		DomRegion Region { get; }
		
		ITypeParameter CreateResolvedTypeParameter(ITypeResolveContext context);
	}
	
	/// <summary>
	/// Type parameter of a generic class/method.
	/// </summary>
	public interface ITypeParameter : IType, ISymbol
	{
		/// <summary>
		/// Get the type of this type parameter's owner.
		/// </summary>
		/// <returns>SymbolKind.TypeDefinition or SymbolKind.Method</returns>
		SymbolKind OwnerType { get; }
		
		/// <summary>
		/// Gets the owning method/class.
		/// This property may return null (for example for the dummy type parameters used by <see cref="ParameterListComparer.NormalizeMethodTypeParameters"/>).
		/// </summary>
		/// <remarks>
		/// For "class Outer&lt;T&gt; { class Inner {} }",
		/// inner.TypeParameters[0].Owner will be the outer class, because the same
		/// ITypeParameter instance is used both on Outer`1 and Outer`1+Inner.
		/// </remarks>
		IEntity Owner { get; }
		
		/// <summary>
		/// Gets the index of the type parameter in the type parameter list of the owning method/class.
		/// </summary>
		int Index { get; }
		
		/// <summary>
		/// Gets the name of the type parameter.
		/// </summary>
		new string Name { get; }
		
		/// <summary>
		/// Gets the list of attributes declared on this type parameter.
		/// </summary>
		IList<IAttribute> Attributes { get; }
		
		/// <summary>
		/// Gets the variance of this type parameter.
		/// </summary>
		VarianceModifier Variance { get; }
		
		/// <summary>
		/// Gets the region where the type parameter is defined.
		/// </summary>
		DomRegion Region { get; }
		
		/// <summary>
		/// Gets the effective base class of this type parameter.
		/// </summary>
		IType EffectiveBaseClass { get; }
		
		/// <summary>
		/// Gets the effective interface set of this type parameter.
		/// </summary>
		ICollection<IType> EffectiveInterfaceSet { get; }
		
		/// <summary>
		/// Gets if the type parameter has the 'new()' constraint.
		/// </summary>
		bool HasDefaultConstructorConstraint { get; }
		
		/// <summary>
		/// Gets if the type parameter has the 'class' constraint.
		/// </summary>
		bool HasReferenceTypeConstraint { get; }
		
		/// <summary>
		/// Gets if the type parameter has the 'struct' constraint.
		/// </summary>
		bool HasValueTypeConstraint { get; }
	}
	
	/// <summary>
	/// Represents the variance of a type parameter.
	/// </summary>
	public enum VarianceModifier : byte
	{
		/// <summary>
		/// The type parameter is not variant.
		/// </summary>
		Invariant,
		/// <summary>
		/// The type parameter is covariant (used in output position).
		/// </summary>
		Covariant,
		/// <summary>
		/// The type parameter is contravariant (used in input position).
		/// </summary>
		Contravariant
	};
}