[release/9.0] Consider existence of EETypes and metadata for typeof checks#107598
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agocke merged 5 commits intorelease/9.0from Sep 11, 2024
Merged
[release/9.0] Consider existence of EETypes and metadata for typeof checks#107598agocke merged 5 commits intorelease/9.0from
agocke merged 5 commits intorelease/9.0from
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Backport of #107347 to release/9.0
/cc @MichalStrehovsky
Customer Impact
Under some circumstances, the compiler could assume code under
if (someType == typeof(Foo))is unreachable and optimize it into an infinite loop. This can happen when typeFoowas only visible in metadata and not actually used at runtime.Regression
Regressed when the optimization was introduced in #103883
Testing
Added targeted test for this situation. This situation is a corner case and difficult to hit.
Risk
Risk is low. This is restricting the number of cases when the optimization kicks in. When running our size validation tooling on half a dozen apps, this change produced no diffs. The new restriction doesn't kick in often.
IMPORTANT: If this backport is for a servicing release, please verify that:
The PR target branch is
release/X.0-staging, notrelease/X.0.If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.