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

[Yanzuo Liu via cfe-commits]

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Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/200166 at github.com>


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@@ -0,0 +1,171 @@
+//===----------------------------------------------------------------------===//
+//
+// 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/Tooling/FixIt.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::performance {
+
+static bool hasOperatorStar(const CXXRecordDecl *RD) {
+  const DeclarationName OpStar =
+      RD->getASTContext().DeclarationNames.getCXXOperatorName(OO_Star);
+  return !RD->lookup(OpStar).empty();
+}
+
+static StringRef findValueMethod(const CXXRecordDecl *RD) {
+  ASTContext &Ctx = RD->getASTContext();
+  for (StringRef Name : {"value", "Value"}) {
+    const DeclarationName DN = &Ctx.Idents.get(Name);
+    if (!RD->lookup(DN).empty())
+      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 ASTContext &Ctx) {
+  if (Call->getBeginLoc().isMacroID())
+    return std::nullopt;
+  if (!ObjExpr->isLValue())
+    return std::nullopt;
+  if (!hasOperatorStar(OptionalClass))
+    return std::nullopt;
+
+  StringRef ObjText = tooling::fixit::getText(*ObjExpr, Ctx);
+  StringRef ArgText = tooling::fixit::getText(*FallbackArg, Ctx);
+
+  if (ObjText.empty() || ArgText.empty())
+    return std::nullopt;
+
+  const std::string Replacement =
+      ("(" + ObjText + " ? *" + ObjText + " : " + ArgText + ")").str();
----------------
zwuis wrote:

`ObjExpr` may have side effects. Should we handle this case?

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