source: trunk/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory-5.5.0/TypeSystem/NullableType.cs @ 15682

// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// 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
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;

namespace ICSharpCode.NRefactory.TypeSystem
{
  /// <summary>
  /// Static helper methods for working with nullable types.
  /// </summary>
  public static class NullableType
  {
    /// <summary>
    /// Gets whether the specified type is a nullable type.
    /// </summary>
    public static bool IsNullable(IType type)
    {
      if (type == null)
        throw new ArgumentNullException("type");
      ParameterizedType pt = type as ParameterizedType;
      return pt != null && pt.TypeParameterCount == 1 && pt.GetDefinition().KnownTypeCode == KnownTypeCode.NullableOfT;
    }
    
    public static bool IsNonNullableValueType(IType type)
    {
      return type.IsReferenceType == false && !IsNullable(type);
    }
    
    /// <summary>
    /// Returns the element type, if <paramref name="type"/> is a nullable type.
    /// Otherwise, returns the type itself.
    /// </summary>
    public static IType GetUnderlyingType(IType type)
    {
      if (type == null)
        throw new ArgumentNullException("type");
      ParameterizedType pt = type as ParameterizedType;
      if (pt != null && pt.TypeParameterCount == 1 && pt.FullName == "System.Nullable")
        return pt.GetTypeArgument(0);
      else
        return type;
    }
    
    /// <summary>
    /// Creates a nullable type.
    /// </summary>
    public static IType Create(ICompilation compilation, IType elementType)
    {
      if (compilation == null)
        throw new ArgumentNullException("compilation");
      if (elementType == null)
        throw new ArgumentNullException("elementType");
      
      IType nullableType = compilation.FindType(KnownTypeCode.NullableOfT);
      ITypeDefinition nullableTypeDef = nullableType.GetDefinition();
      if (nullableTypeDef != null)
        return new ParameterizedType(nullableTypeDef, new [] { elementType });
      else
        return nullableType;
    }
    
    /// <summary>
    /// Creates a nullable type reference.
    /// </summary>
    public static ParameterizedTypeReference Create(ITypeReference elementType)
    {
      if (elementType == null)
        throw new ArgumentNullException("elementType");
      return new ParameterizedTypeReference(KnownTypeReference.NullableOfT, new [] { elementType });
    }
  }
}