[clang-tools-extra] [clangd] Add inlay hints for default function arguments and implicit lambda captures (PR #95712)

[Younan Zhang via cfe-commits]

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@@ -372,6 +382,34 @@ maybeDropCxxExplicitObjectParameters(ArrayRef<const ParmVarDecl *> Params) {
   return Params;
 }
 
+llvm::StringRef getLambdaCaptureName(const LambdaCapture &Capture) {
+  if (Capture.capturesVariable())
+    return Capture.getCapturedVar()->getName();
+  if (Capture.capturesThis())
+    return llvm::StringRef{"this"};
+  return llvm::StringRef{"unknown"};
+}
+
+template <typename R, typename P>
+std::string joinAndTruncate(R &&Range, size_t MaxLength,
+                            P &&GetAsStringFunction) {
+  std::string Out;
+  bool IsFirst = true;
+  for (auto &&Element : Range) {
+    if (!IsFirst)
+      Out.append(", ");
+    else
+      IsFirst = false;
----------------
zyn0217 wrote:

nit: 1. We don't usually append to a string; instead, we use `llvm::raw_string_ostream`. 2. This whole thing can be simplified by [`llvm::ListSeparator`](https://github.com/llvm/llvm-project/blob/ef18986b2033a44e69b7c3553a356e9037ac1413/llvm/include/llvm/ADT/StringExtras.h#L507-L529)

https://github.com/llvm/llvm-project/pull/95712