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

[Aaron Ballman via cfe-commits]

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@@ -1921,7 +1920,20 @@ bool NamedDecl::declarationReplaces(NamedDecl *OldD, bool IsKnownNewer) const {
 }
 
 bool NamedDecl::hasLinkage() const {
-  return getFormalLinkage() != NoLinkage;
+  switch (getFormalLinkage()) {
+  case Linkage::Invalid:
+    llvm_unreachable("Linkage hasn't been computed!");
+  case Linkage::None:
+    return false;
+  case Linkage::Internal:
+    return true;
+  case Linkage::UniqueExternal:
+  case Linkage::VisibleNone:
+    llvm_unreachable("Non-formal linkage is not allowed here!");
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AaronBallman wrote:

Ah I see the logic now, this is actually an NFC change. I think it's fine to leave in as-is in this patch.

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