[clang] [clang-tools-extra] [clangd] CodeCompletion surface param names if possible (PR #206716)

[via cfe-commits]

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@@ -3320,6 +3320,11 @@ static void AddFunctionParameterChunks(
 
   for (unsigned P = Start, N = Function->getNumParams(); P != N; ++P) {
     const ParmVarDecl *Param = Function->getParamDecl(P);
+    // Select the first parameter name for consistent results with Index.
+    for (auto *Redecl : Function->redecls()) {
+      if (auto *RParam = Redecl->getParamDecl(P); RParam->getIdentifier())
+        Param = RParam;
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timon-ul wrote:

I just noticed that I missed the `break` by accident, but it passes, so `redecl()` is going through them from last to first, which is kinda annoying since I would prefer the other way around. Will think of a nicer way of doing this.

https://github.com/llvm/llvm-project/pull/206716