/// <summary>
/// Creates a list pattern.
/// </summary>
/// <param name="collectionType">The type of the collection.</param>
/// <param name="variable">The variable to assign to.</param>
/// <param name="patterns">The list of <see cref="CSharpPattern"/> patterns to apply to the elements of the collection, optionally containing a slice pattern.</param>
/// <returns>A <see cref="ListCSharpPattern" /> representing a list pattern.</returns>
public static ListCSharpPattern List(Type collectionType, ParameterExpression variable, IEnumerable <CSharpPattern> patterns)
{
collectionType ??= variable?.Type;
var inputType = collectionType;
if (inputType != null && inputType.IsValueType && !inputType.IsNullableType())
{
// NB: The pattern implies a null check so we "widen" the target type to nullable.
inputType = typeof(Nullable <>).MakeGenericType(inputType);
}
var info = ObjectPatternInfo(PatternInfo(inputType, collectionType), variable);
ValidateType(collectionType);
Expression lengthAccess, indexerAccess;
var input = Expression.Parameter(collectionType, "o");
var index = Expression.Parameter(typeof(Index), "i");
if (Helpers.IsVector(collectionType))
{
indexerAccess = CSharpExpression.ArrayAccess(input, index);
lengthAccess = Expression.ArrayLength(input);
}
else
{
var expr = CSharpExpression.IndexerAccess(input, index);
indexerAccess = expr;
lengthAccess = Expression.MakeMemberAccess(input, expr.LengthOrCount);
}
return(List(info, Expression.Lambda(lengthAccess, input), Expression.Lambda(indexerAccess, input, index), patterns));
}
/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
/// </summary>
/// <param name="array">The <see cref="Array" /> property of the result.</param>
/// <param name="indexes">The <see cref="Indexes" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public ArrayAccessCSharpExpression Update(Expression array, IEnumerable <Expression> indexes)
{
if (array == Array && SameElements(ref indexes, Indexes))
{
return(this);
}
return(CSharpExpression.ArrayAccess(array, indexes));
}
/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
/// </summary>
/// <param name="array">The <see cref="Array" /> property of the result.</param>
/// <param name="indexes">The <see cref="Indexes" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public ArrayAccessCSharpExpression Update(Expression array, IEnumerable <Expression> indexes)
{
if (array == Array && indexes == Indexes)
{
return(this);
}
return(CSharpExpression.ArrayAccess(array, indexes));
}
