/// <summary>
/// Creates an expression representing an indexer access operation.
/// </summary>
/// <param name="object">The object to access.</param>
/// <param name="argument">The argument that will be used to index or slice the object.</param>
/// <param name="lengthOrCount">The property used to retrieve the element count of the object getting accessed.</param>
/// <param name="indexOrSlice">The member used to index or slice the object.</param>
/// <returns>A new <see cref="IndexerAccessCSharpExpression"/> instance representing the array access operation.</returns>
public static IndexerAccessCSharpExpression IndexerAccess(Expression @object, Expression argument, PropertyInfo lengthOrCount, MemberInfo indexOrSlice)
{
RequiresCanRead(@object, nameof(@object));
//
// The argument can be of type Index or Range. We'll check indexOrSlice accordingly below.
//
RequiresCanRead(argument, nameof(argument));
if (argument.Type != typeof(Index) && argument.Type != typeof(Range))
{
throw Error.InvalidIndexerAccessArgumentType(argument.Type);
}
//
// A type is Countable if it has a property named Length or Count with an accessible getter and a return type of int.
//
lengthOrCount ??= FindCountProperty("Length") ?? FindCountProperty("Count");
PropertyInfo FindCountProperty(string name) => @object.Type.GetProperty(name, BindingFlags.Public | BindingFlags.Instance, binder: null, typeof(int), Type.EmptyTypes, modifiers: null);
ContractUtils.RequiresNotNull(lengthOrCount, nameof(lengthOrCount));
var lengthOrCountGetMethod = lengthOrCount.GetGetMethod(nonPublic: true); // NB: System.Linq.Expressions allows non-public properties.
if (lengthOrCountGetMethod == null)
{
throw LinqError.PropertyDoesNotHaveAccessor(lengthOrCount);
}
if (lengthOrCountGetMethod.IsStatic)
{
throw Error.AccessorCannotBeStatic(lengthOrCountGetMethod);
}
if (lengthOrCountGetMethod.GetParametersCached().Length != 0)
{
throw LinqError.IncorrectNumberOfMethodCallArguments(lengthOrCountGetMethod);
}
if (!TypeUtils.IsValidInstanceType(lengthOrCount, @object.Type))
{
throw LinqError.PropertyNotDefinedForType(lengthOrCount, @object.Type);
}
if (lengthOrCount.PropertyType != typeof(int))
{
throw Error.InvalidLengthOrCountPropertyType(lengthOrCount);
}
ValidateMethodInfo(lengthOrCountGetMethod);
if (argument.Type == typeof(Index))
{
//
// The type has an accessible instance indexer which takes a single int as the argument.
//
indexOrSlice ??= FindIndexer();
PropertyInfo FindIndexer()
{
var indexers = (from p in @object.Type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
let i = p.GetIndexParameters()
where i.Length == 1 && i[0].ParameterType == typeof(int)
select p)
.ToArray();
return(indexers.Length == 1 ? indexers[0] : null);
}
ContractUtils.RequiresNotNull(indexOrSlice, nameof(indexOrSlice));
var index = indexOrSlice as PropertyInfo ?? GetProperty(indexOrSlice as MethodInfo ?? throw Error.InvalidIndexMember(indexOrSlice));
indexOrSlice = index; // NB: Store the property rather than a method.
var indexAccessor = index.GetGetMethod(nonPublic: true); // NB: System.Linq.Expressions allows non-public properties.
if (indexAccessor == null)
{
indexAccessor = index.GetSetMethod(nonPublic: true) ?? throw LinqError.PropertyDoesNotHaveAccessor(indexOrSlice);
if (indexAccessor.GetParametersCached().Length != 2)
{
throw LinqError.IncorrectNumberOfMethodCallArguments(indexAccessor);
}
}
else if (indexAccessor.GetParametersCached().Length != 1)
{
throw LinqError.IncorrectNumberOfMethodCallArguments(indexAccessor);
}
if (indexAccessor.IsStatic)
{
throw Error.AccessorCannotBeStatic(indexAccessor);
}
if (!TypeUtils.IsValidInstanceType(indexAccessor, @object.Type))
{
throw LinqError.PropertyNotDefinedForType(indexAccessor, @object.Type);
}
if (indexAccessor.GetParametersCached()[0].ParameterType != typeof(int))
{
throw Error.InvalidIndexerParameterType(indexOrSlice);
}
ValidateMethodInfo(indexAccessor);
}
else
{
//
// The type has an accessible member named Slice which has two parameters of type int.
//
Debug.Assert(argument.Type == typeof(Range));
indexOrSlice ??= FindSliceMethod();
MethodInfo FindSliceMethod() => @object.Type.GetMethod(@object.Type == typeof(string) ? "Substring" : "Slice", BindingFlags.Public | BindingFlags.Instance, binder: null, new[] { typeof(int), typeof(int) }, modifiers: null);
ContractUtils.RequiresNotNull(indexOrSlice, nameof(indexOrSlice));
var slice = indexOrSlice as MethodInfo ?? throw Error.InvalidSliceMember(indexOrSlice);
ValidateMethodInfo(slice);
if (slice.IsStatic)
{
throw Error.SliceMethodMustNotBeStatic(slice);
}
ValidateCallInstanceType(@object.Type, slice);
var sliceParams = slice.GetParametersCached();
if (sliceParams.Length != 2 || sliceParams[0].ParameterType != typeof(int) || sliceParams[1].ParameterType != typeof(int))
{
throw Error.InvalidSliceParameters(slice);
}
}
return(new IndexerAccessCSharpExpression(@object, argument, lengthOrCount, indexOrSlice));
}