[release/6.0] [mini] Don't add unbox tramopline on generic DIM calls #58585
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Don't unbox a valuetype `this` if the generic method is a DIM Fixes #58394
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Tagging subscribers to this area: Issue DetailsBackport of #58521 to release/6.0 /cc @lambdageek Customer ImpactTestingRisk
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marek-safar
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Sep 3, 2021
lambdageek
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Sep 3, 2021
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Backport of #58521 to release/6.0
/cc @lambdageek
Customer Impact
Code using generic default interface methods instantiated to valuetypes will crash. The cause is an incorrect unboxing of the
thisargument of the managed method. The callee would work correctly but when someone usedthis, there would be incorrect data or a crash.Fixes #58394
Testing
CI. Added a new regression test.
Risk
Moderate. I added some additional assertions in the trampoline for calls like this on branches that I thought couldn't happen. It's possible there's some managed code that could hit those assertions. (On the other hand if I preemptively fixed the "couldn't happen" cases incorrectly, or if they're incorrect to begin with, those crashes would be difficult to diagnose since they would be in later unrelated managed methods).