[clang-tools-extra] [clang-tidy] Add performance-expensive-value-or check (PR #200166)

[Endre Fülöp via cfe-commits]

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+//===----------------------------------------------------------------------===//
+//
+// 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 "ExpensiveValueOrCheck.h"
+#include "../utils/Matchers.h"
+#include "../utils/OptionsUtils.h"
+#include "../utils/TypeTraits.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::performance {
+
+static bool hasOperatorStar(const CXXRecordDecl *RD) {
+  return llvm::any_of(RD->methods(), [](const CXXMethodDecl *M) {
+    return M->getOverloadedOperator() == OO_Star;
+  });
+}
+
+static StringRef findValueMethod(const CXXRecordDecl *RD) {
+  for (const auto *M : RD->methods()) {
+    if (!M->getDeclName().isIdentifier())
+      continue;
+    StringRef Name = M->getName();
+    if (Name == "value" || Name == "Value")
+      return Name;
+  }
+  return {};
+}
+
+static std::string buildSuggestion(const CXXRecordDecl *OptionalClass) {
+  const bool HasDeref = hasOperatorStar(OptionalClass);
+  StringRef ValueName = findValueMethod(OptionalClass);
+
+  if (HasDeref && !ValueName.empty())
+    return (llvm::Twine("consider using 'operator*' or '") + ValueName +
+            "()' with a separate fallback")
+        .str();
+  if (HasDeref)
+    return "consider using 'operator*' with a separate fallback";
+  if (!ValueName.empty())
+    return (llvm::Twine("consider using '") + ValueName +
+            "()' with a separate fallback")
+        .str();
+  return "consider avoiding the copy";
+}
+
+static std::optional<FixItHint>
+buildFixIt(const CXXMemberCallExpr *Call, const Expr *ObjExpr,
+           const Expr *FallbackArg, const CXXRecordDecl *OptionalClass,
+           const SourceManager &SM, const LangOptions &LO) {
+  if (Call->getBeginLoc().isMacroID())
+    return std::nullopt;
+  if (!ObjExpr->isLValue())
+    return std::nullopt;
+  if (!hasOperatorStar(OptionalClass))
+    return std::nullopt;
+
+  StringRef ObjText = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(ObjExpr->getSourceRange()), SM, LO);
+  StringRef ArgText = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(FallbackArg->getSourceRange()), SM, LO);
+
+  if (ObjText.empty() || ArgText.empty())
+    return std::nullopt;
+
+  const std::string Replacement =
+      ("(" + ObjText + " ? *" + ObjText + " : " + ArgText + ")").str();
+  return FixItHint::CreateReplacement(Call->getSourceRange(), Replacement);
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gamesh411 wrote:

Thanks for suggesting this! Adopted `tooling::fixit::getText`. Added the `clangTooling` link dependency to the performance module CMake. There is precedent for other modules already using it.

https://github.com/llvm/llvm-project/pull/200166