AvaloniaUI/Avalonia · error · ArgumentException

Destination too short.

Error message

Destination too short.

What it means

Centralized ThrowHelper.ThrowArgumentException_DestinationTooShort throws ArgumentException "Destination too short." It is invoked from PooledStack<T>.CopyTo(Span<T>) when `span.Length < _size`, i.e. the destination span cannot hold the whole stack. It is the PooledStack analogue of PooledList's span-too-short check, hoisted into ThrowHelper to reduce IL/code size.

Source

Thrown at src/Avalonia.Base/Collections/Pooled/ThrowHelper.cs:70

            throw new ArrayTypeMismatchException();
        }

        [DoesNotReturn]
        internal static void ThrowIndexOutOfRangeException()
        {
            throw new IndexOutOfRangeException();
        }

        [DoesNotReturn]
        internal static void ThrowArgumentOutOfRangeException()
        {
            throw new ArgumentOutOfRangeException();
        }

        [DoesNotReturn]
        internal static void ThrowArgumentException_DestinationTooShort()
        {
            throw new ArgumentException("Destination too short.");
        }

        [DoesNotReturn]
        internal static void ThrowArgumentException_OverlapAlignmentMismatch()
        {
            throw new ArgumentException("Overlap alignment mismatch.");
        }

        [DoesNotReturn]
        internal static void ThrowArgumentOutOfRange_IndexException()
        {
            throw GetArgumentOutOfRangeException(ExceptionArgument.index,
                                                    ExceptionResource.ArgumentOutOfRange_Index);
        }

        [DoesNotReturn]
        internal static void ThrowIndexArgumentOutOfRange_NeedNonNegNumException()
        {

View on GitHub (pinned to 11c5427268)

Solutions

1. Allocate the span to Count: `Span<T> buf = new T[stack.Count]; stack.CopyTo(buf);`.
2. Read elements directly via stack.ToArray() if a materialized array is acceptable.
3. Validate `span.Length >= stack.Count` before copying.

Example fix

// before
Span<T> buf = new T[8];
stack.CopyTo(buf); // throws if stack.Count > 8

// after
Span<T> buf = new T[stack.Count];
stack.CopyTo(buf);

if (span.Length < stack.Count)
    span = new T[stack.Count];
stack.CopyTo(span);

When it happens

Trigger: Calling `stack.CopyTo(span)` with a span shorter than stack.Count; copying into a stackalloc or rented buffer sized to the wrong value.

Common situations: Under-sizing a destination buffer (using Capacity or an unrelated count); slicing a span too short; renting from a pool by an estimated size.

Related errors

• Destination span is shorter than the list to be copied.
• array
• Stack was empty.
• Collection was modified during enumeration.
• Enumeration was not started. | Enumeration has ended.

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/0b066f15b6a5b2a8. Report an issue: GitHub.