[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.")
+      << FixItHint::CreateReplacement(Range, NewCode);
----------------
PiotrZSL wrote:

you could verify at this level that exceptions are enabled (check LangOptions).
Because fix may not be perfect, you may consider attaching fix to note instead of warning.
And raise also a note that would point where operator[] is defined, and where method at is.

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