[clang-tools-extra] [clang-reorder-fields] Support designated initializers (PR #142150)

[Clement Courbet via cfe-commits]

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@@ -289,35 +321,213 @@ static void reorderFieldsInConstructor(
                      Replacements);
 }
 
+/// Replacement for broken InitListExpr::isExplicit function.
+/// TODO: Remove when InitListExpr::isExplicit is fixed.
+static bool isImplicitILE(const InitListExpr *ILE, const ASTContext &Context) {
+  // The ILE is implicit if either:
+  // - The left brace loc of the ILE matches the start of first init expression
+  //   (for non designated decls)
+  // - The right brace loc of the ILE matches the end of first init expression
+  //   (for designated decls)
+  // The first init expression should be taken from the syntactic form, but
+  // since the ILE could be implicit, there might not be a syntactic form.
+  // For that reason we have to check against all init expressions.
+  for (const Expr *Init : ILE->inits()) {
+    if (ILE->getLBraceLoc() == Init->getBeginLoc() ||
+        ILE->getRBraceLoc() == Init->getEndLoc())
+      return true;
+  }
+  return false;
+}
+
+/// Compares compatible designators according to the new struct order.
+/// Returns a negative value if Lhs < Rhs, positive value if Lhs > Rhs and 0 if
+/// they are equal.
+static int cmpDesignators(const DesignatorIter &Lhs, const DesignatorIter &Rhs,
+                          const ReorderedStruct &Struct) {
+  if (Lhs.getTag() == DesignatorIter::STRUCT) {
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legrosbuffle wrote:

a `switch` might make this a bit more readable

https://github.com/llvm/llvm-project/pull/142150