[clang-tools-extra] [clang-tidy]suggest use `std::span` as replacement of c array in C++20 for modernize-avoid-c-arrays (PR #108555)

[Julian Schmidt via cfe-commits]

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@@ -72,11 +74,29 @@ void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
 
 void AvoidCArraysCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *ArrayType = Result.Nodes.getNodeAs<TypeLoc>("typeloc");
-
+  const bool IsInParam =
+      Result.Nodes.getNodeAs<ParmVarDecl>("param_decl") != nullptr;
+  const bool IsVLA = ArrayType->getTypePtr()->isVariableArrayType();
+  enum class RecommendType { Array, Vector, Span };
+  llvm::SmallVector<const char *> RecommendTypes{};
+  if (IsVLA) {
+    RecommendTypes.push_back("std::vector<>");
+  } else if (ArrayType->getTypePtr()->isIncompleteArrayType() && IsInParam) {
+    // in function parameter, we also don't know the size of
+    // IncompleteArrayType.
+    if (Result.Context->getLangOpts().CPlusPlus20)
+      RecommendTypes.push_back("std::span<>");
+    else {
+      RecommendTypes.push_back("std::array<>");
+      RecommendTypes.push_back("std::vector<>");
+    }
+  } else {
+    RecommendTypes.push_back("std::array<>");
+  }
+  llvm::errs() << llvm::join(RecommendTypes, " or ") << "\n";
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5chmidti wrote:

There is a leftover `llvm::errs` from debugging here.

https://github.com/llvm/llvm-project/pull/108555