[clang] [FrontEnd] Use SetVector (NFC) (PR #107743)

[Kazu Hirata via cfe-commits]

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@@ -5157,14 +5163,12 @@ void RewriteModernObjC::CollectBlockDeclRefInfo(BlockExpr *Exp) {
     // Unique all "by copy" declarations.
     for (unsigned i = 0; i < BlockDeclRefs.size(); i++)
       if (!BlockDeclRefs[i]->getDecl()->hasAttr<BlocksAttr>()) {
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kazutakahirata wrote:

Fixed in the latest iteration.  Thanks!

https://github.com/llvm/llvm-project/pull/107743