[clang] [WIP] Implement `-dump-deserialized-declaration-ranges` flag. (PR #133910)

[Viktoriia Bakalova via cfe-commits]

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@@ -49,6 +51,135 @@ LLVM_INSTANTIATE_REGISTRY(FrontendPluginRegistry)
 
 namespace {
 
+/// Dumps deserialized declarations.
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VitaNuo wrote:

Yes, sorry, I responded to the comment before pushing the actual change.

https://github.com/llvm/llvm-project/pull/133910