Add Enumerable.TryGetNonEnumeratedCount (Implements #27183) #48239
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Tagging subscribers to this area: @eiriktsarpalis Issue DetailsFix #27183.
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Note regarding the This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change. |
eiriktsarpalis
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eiriktsarpalis
changed the title
| @@ -190,7 +190,7 @@ public void Reserve(int count) | |||
| public bool ReserveOrAdd(IEnumerable<T> items) | |||
| { | |||
| int itemCount; | |||
| if (EnumerableHelpers.TryGetCount(items, out itemCount)) | |||
| if (System.Linq.Enumerable.TryGetNonEnumeratedCount(items, out itemCount)) | |||
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I wanted to avoid bringing all the enumerable methods into scope since this is a System.Collections namespace.
| /// The method is typically a constant-time operation, but ultimately this depends on the complexity | ||
| /// characteristics of the underlying collection implementation. | ||
| /// </remarks> | ||
| public static bool TryGetNonEnumeratedCount<TSource>(this IEnumerable<TSource> source, out int count) |
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This doesn't need to be generic? if it does, I think a non-generic overload would also make sense.
(roslyn is considering using this method as part of list pattern lowering, we probably don't want to skip it for IEnumerable see https://github.com/dotnet/csharplang/blob/master/meetings/2021/LDM-2021-02-03.md).
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We could do that, however it becomes more difficult to check for generic interfaces, which would require some form of reflection.
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which would require some form of reflection.
That's definitely a no-go because the point of using this is performance. Perhaps those generic interfaces need a non-generic base with Count prop. IMO TryGetNonEnumeratedCount shouldn't care about TSource.
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Linker test build failures seem unrelated to the change. |
ghost
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Fix #27183.