/// <summary>
/// Substitute references to type parameters from 'typeDef'
/// with type arguments from 'typeArgs' in type 'type'.
/// </summary>
internal static Type Substitute(this Type type, Type typeDef, Type[] typeArgs)
{
Debug.Assert(typeDef.IsGenericTypeDefinition);
Debug.Assert(typeDef.GetGenericArguments().Length == typeArgs.Length);
if (type.IsGenericType)
{
var builder = ArrayBuilder <Type> .GetInstance();
foreach (var t in type.GetGenericArguments())
{
builder.Add(t.Substitute(typeDef, typeArgs));
}
var typeDefinition = type.GetGenericTypeDefinition();
return(typeDefinition.MakeGenericType(builder.ToArrayAndFree()));
}
else if (type.IsArray)
{
var elementType = type.GetElementType();
elementType = elementType.Substitute(typeDef, typeArgs);
var n = type.GetArrayRank();
return((n == 1) ? elementType.MakeArrayType() : elementType.MakeArrayType(n));
}
else if (type.IsPointer)
{
var elementType = type.GetElementType();
elementType = elementType.Substitute(typeDef, typeArgs);
return(elementType.MakePointerType());
}
else if (type.IsGenericParameter)
{
if (type.DeclaringType.Equals(typeDef))
{
var ordinal = type.GenericParameterPosition;
return(typeArgs[ordinal]);
}
}
return(type);
}
