No-op ConcurrentStack.PushRange(T[]) if empty

[martincostello]

Resolves #62121.

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Issue Details

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Resolves #62121.

Author:	martincostello
Assignees:	-
Labels:	area-System.Collections, community-contribution
Milestone:	-

[stephentoub]

Thanks.

This would address the case of PushRange(empty), but not of PushRange(empty, 0, 0), which should be functionally identical.

I suggest the right fix is simply to change this condition:

runtime/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentStack.cs

Line 413 in a4cab7d

if (startIndex >= length || startIndex < 0)

from

if (startIndex >= length || startIndex < 0)

to

if (startIndex > length || startIndex < 0)

or even:

if ((uint)startIndex > length)

i.e. it should be fine to have the start index be at the end of the array, as long as the count is 0, which the subsequent check validates.

[martincostello]

Thanks both - I did think about that, but then asking to start from index 0 (which doesn't exist) seemed to be an equally valid mistake to me at first sight on an empty array when the range is specified, so went with this initially to gauge thoughts.

I'll update the PR as suggested 👍

[stephentoub]

asking to start from index 0 (which doesn't exist) seemed to be an equally valid mistake to me

This is how things generally work in .NET, e.g. you can insert at the end of a collection with the index == length, you can take a 0-length substring at the end of a string, etc.