[cxx-interop] Do not warn for implicit default constructors #84764
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The diagnostic that Swift was emitting (`This zero-initializes the backing memory of the struct ...`) was flaky, because it was only emitted when the default constructor of a C++ struct was instantiated by Swift. If it was instantiated by Clang, the diagnostic wasn't emitted. There is not a lot of value in it. Let's make the behavior consistent by removing the diagnostic. rdar://161999293
egorzhdan requested review from fahadnayyar, susmonteiro, hnrklssn, beccadax and ian-twilightcoder as code owners 
| @swift-ci please test |
Xazax-hun approved these changes Oct 8, 2025
Xazax-hun requested changes Oct 8, 2025
| Is it flaky in the sense that the same test run on the same machine is non deterministic, or flaky in the sense that its behavior differs depending on subtle platform differences, eg SDK version? |
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The diagnostic that Swift was emitting (
This zero-initializes the backing memory of the struct ...) was flaky, because it was only emitted when the default constructor of a C++ struct was instantiated by Swift. If it was instantiated by Clang, the diagnostic wasn't emitted. There is not a lot of value in it. Let's make the behavior consistent by removing the diagnostic.rdar://161999293