[clang] [clang-tools-extra] [clang] Refactor `clang::Linkage` (PR #71049)

[Vlad Serebrennikov via cfe-commits]

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@@ -1996,7 +1996,7 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
     TypeBits.Dependence = static_cast<unsigned>(Dependence);
     TypeBits.CacheValid = false;
     TypeBits.CachedLocalOrUnnamed = false;
-    TypeBits.CachedLinkage = NoLinkage;
+    TypeBits.CachedLinkage = llvm::to_underlying(Linkage::Invalid);
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Endilll wrote:

CC @AaronBallman This passes Clang tests with all those `llvm_unreachable` around, so I'm rather confident about this. Note that I removed `NFC` tag from the title.

https://github.com/llvm/llvm-project/pull/71049