[clang-tools-extra] [clang-tidy] Fix `cppcoreguidelines-pro-type-member-init` check (PR #169832)

[Baranov Victor via cfe-commits]

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@@ -582,6 +583,33 @@ void ProTypeMemberInitCheck::checkMissingBaseClassInitializer(
 
 void ProTypeMemberInitCheck::checkUninitializedTrivialType(
     const ASTContext &Context, const VarDecl *Var) {
+  // Verify that the record actually needs initialization
+  const CXXRecordDecl *Record = Var->getType()->getAsCXXRecordDecl();
+  if (!Record)
+    return;
+
+  SmallPtrSet<const FieldDecl *, 16> FieldsToInit;
+  bool AnyMemberHasInitPerUnion = false;
+  forEachFieldWithFilter(
+      *Record, Record->fields(), AnyMemberHasInitPerUnion,
+      [&](const FieldDecl *F) {
+        if (IgnoreArrays && F->getType()->isArrayType())
+          return;
+        if (F->hasInClassInitializer() && F->getParent()->isUnion()) {
+          AnyMemberHasInitPerUnion = true;
+          removeFieldInitialized(F, FieldsToInit);
+        }
+        if (!F->hasInClassInitializer() &&
+            utils::type_traits::isTriviallyDefaultConstructible(F->getType(),
+                                                                Context) &&
+            !isEmpty(Context, F->getType()) && !F->isUnnamedBitField() &&
+            !AnyMemberHasInitPerUnion)
+          FieldsToInit.insert(F);
+      });
+
+  if (FieldsToInit.empty())
+    return;
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vbvictor wrote:

Was this part purely copypasted from `checkMissingMemberInitializer`?
If so, can we refactor it into a helper function to avoid duplication

https://github.com/llvm/llvm-project/pull/169832