[release/10.0] Fix issue with array interface devirtualization #120371
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The instantiated methods should use the parameter type of the interface, not the element type of the array. Fixes #120270.
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@davidwrighton PTAL |
JulieLeeMSFT
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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@davidwrighton, please review the code to backport. CC @dotnet/jit-contrib. |
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Oct 10, 2025
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Backport of #120313 to release/10.0
/cc @AndyAyersMS
Customer Impact
Reported in #120270
Regression
When we enabled devirtualization of array interface methods, the interface got instantiated with the array element type, not the interface parameter type. This devirtualization is new in .NET 10.
This can cause runtime failures as these two can diverge, eg
enum[]can be cast toIEnumerable<int>.Testing
Fixed the repro case and several similar test cases (added). This corrects behavior for the value class case and disables the optimization for some ref class cases.
Risk
Low. We are now creating the proper type (for value classes) or disabling the optimization (for ref classes cast to shared interface types).