[clang-tools-extra] Enforce SL.con.3: Add check to replace operator[] with at() (PR #90043)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,81 @@
+//===--- AvoidBoundsErrorsCheck.cpp - clang-tidy --------------------------===//
+//
+// 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 "AvoidBoundsErrorsCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+#include <iostream>
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::cppcoreguidelines {
+
+bool isApplicable(const QualType &Type) {
+  const auto TypeStr = Type.getAsString();
+  bool Result = false;
+  // Only check for containers in the std namespace
+  if (TypeStr.find("std::vector") != std::string::npos) {
+    Result = true;
+  }
+  if (TypeStr.find("std::array") != std::string::npos) {
+    Result = true;
+  }
+  if (TypeStr.find("std::deque") != std::string::npos) {
+    Result = true;
+  }
+  if (TypeStr.find("std::map") != std::string::npos) {
+    Result = true;
+  }
+  if (TypeStr.find("std::unordered_map") != std::string::npos) {
+    Result = true;
+  }
+  if (TypeStr.find("std::flat_map") != std::string::npos) {
+    Result = true;
+  }
+  // TODO Add std::span with C++26
+  return Result;
+}
+
+void AvoidBoundsErrorsCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      callExpr(callee(cxxMethodDecl(hasName("operator[]")).bind("f")))
+          .bind("x"),
+      this);
+}
+
+void AvoidBoundsErrorsCheck::check(const MatchFinder::MatchResult &Result) {
+  const ASTContext &Context = *Result.Context;
+  const SourceManager &Source = Context.getSourceManager();
+  const auto *MatchedExpr = Result.Nodes.getNodeAs<CallExpr>("x");
+  const auto *MatchedFunction = Result.Nodes.getNodeAs<CXXMethodDecl>("f");
+  const auto Type = MatchedFunction->getThisType();
+  if (!isApplicable(Type)) {
+    return;
+  }
+
+  // Get original code.
+  const SourceLocation b(MatchedExpr->getBeginLoc());
+  const SourceLocation e(MatchedExpr->getEndLoc());
+  const std::string OriginalCode =
+      Lexer::getSourceText(CharSourceRange::getTokenRange(b, e), Source,
+                           getLangOpts())
+          .str();
+  const auto Range = SourceRange(b, e);
+
+  // Build replacement.
+  std::string NewCode = OriginalCode;
+  const auto BeginOpen = NewCode.find("[");
+  NewCode.replace(BeginOpen, 1, ".at(");
+  const auto BeginClose = NewCode.find("]");
+  NewCode.replace(BeginClose, 1, ")");
+
+  diag(MatchedExpr->getBeginLoc(), "Do not use operator[], use at() instead.")
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PiotrZSL wrote:

keep diagnostic an lower case, not need for point at the end

https://github.com/llvm/llvm-project/pull/90043