[clang-tools-extra] [clang-tidy] Add modernize-use-span-param check (PR #182027)

[Victor Chernyakin via cfe-commits]

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@@ -0,0 +1,190 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UseSpanParamCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+// Methods on std::vector that only read data (compatible with std::span).
+static bool isReadOnlyVectorMethod(StringRef Name) {
+  return Name == "operator[]" || Name == "at" || Name == "data" ||
+         Name == "size" || Name == "empty" || Name == "begin" ||
+         Name == "end" || Name == "cbegin" || Name == "cend" ||
+         Name == "rbegin" || Name == "rend" || Name == "crbegin" ||
+         Name == "crend" || Name == "front" || Name == "back";
+}
+
+// Check if all uses of the parameter in the function body are read-only.
+static bool allUsesAreReadOnly(const ParmVarDecl *Param,
+                               const FunctionDecl *Func, ASTContext &Context) {
+  const Stmt *Body = Func->getBody();
+  if (!Body)
+    return false;
+
+  const auto Refs = match(
+      findAll(declRefExpr(to(equalsNode(Param))).bind("ref")), *Body, Context);
+
+  for (const auto &Ref : Refs) {
+    const auto *DRE = Ref.getNodeAs<DeclRefExpr>("ref");
+    if (!DRE)
+      return false;
+
+    // Walk up through implicit casts to find the "real" parent.
+    const Expr *Current = DRE;
+    while (true) {
+      const auto Parents = Context.getParents(*Current);
+      if (Parents.empty())
+        return false;
+      const auto &Parent = Parents[0];
+      if (const auto *ICE = Parent.get<ImplicitCastExpr>()) {
+        Current = ICE;
+        continue;
+      }
----------------
localspook wrote:

Should we also skip past `ParenExpr`s?

https://github.com/llvm/llvm-project/pull/182027