[release/10.0-rc2] Fix DefaultIfEmptyIterator.TryGetElementAt returning default value for out-of-bounds indices #120003
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…ment not found Co-authored-by: eiriktsarpalis <[email protected]>
…tElementAt Co-authored-by: eiriktsarpalis <[email protected]>
jeffhandley
approved these changes
Sep 23, 2025
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Tagging subscribers to this area: @dotnet/area-system-linq |
eiriktsarpalis
approved these changes
Sep 23, 2025
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We discussed this during Tactics. We are not going to approve/merge this into RC2 yet as builds are already getting produced. If the window opens up for more items to be merged in for RC2, this would get approved and we would merge it in. /cc @eiriktsarpalis |
Member
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Closing this RC2 backport. The 10.0 fix will be present in the GA release. |
jeffhandley
added
Servicing-rejected
and removed
Servicing-consider
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Backport of #119838 to release/10.0-rc2
/cc @jeffhandley @eiriktsarpalis
Customer Impact
Customer reported in:
DefaultIfEmptyIterator<TSource>.TryGetElementAtreturns_defaultwhen not found (dotnet/runtime#119834).NET 9 regressed the behavior of the
DefaultIfEmptyLINQ method resulting in incorrect results when chained withElementAtOrDefaultusing an out of bounds index. This fix has been applied to .NET 11, .NET 10 GA, and .NET 9 Servicing (for the October servicing release). Therelease/10.0PR didn't get merged before the RC2 snap, but we should include this fix in RC2 so that 10.0 RC2 and 9.0 servicing are aligned in behavior.Regression
The regression was introduced in Consolidate LINQ's internal IIListProvider/IPartition into base Iterator class (#98969).
Testing
Added unit testing verifying the impacted behavior.
Risk
Low. Applies a straightforward fix to a simple bug.