[clang] Add Clang attribute to ensure that fields are initialized explicitly (PR #102040)

[Erich Keane via cfe-commits]

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@@ -4561,6 +4569,15 @@ static void TryConstructorInitialization(Sema &S,
 
   CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
   if (Result != OR_Deleted) {
+    if (!IsListInit && Kind.getKind() == InitializationKind::IK_Default &&
+        DestRecordDecl != nullptr && DestRecordDecl->isAggregate() &&
+        DestRecordDecl->hasUninitializedExplicitInitFields()) {
+      S.Diag(Kind.getLocation(), diag::warn_field_requires_explicit_init)
+          << ("in " +
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erichkeane wrote:

Check out the `select{whatever | something else}0` form of diagnostics.

https://github.com/llvm/llvm-project/pull/102040