[clang-tools-extra] [clang-tidy] Add readability-constant-operand-order check (PR #167158)

[Yanzuo Liu via cfe-commits]

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@@ -0,0 +1,197 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "ConstantOperandOrderCheck.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/OperationKinds.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+/// Out-of-line ctor so vtable is emitted.
+ConstantOperandOrderCheck::ConstantOperandOrderCheck(StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {
+  // Read options (StringRef -> std::string).
+  PreferredSide = Options.get(PreferredSideOption, "Right").str();
+
+  // Parse BinaryOperators option (comma-separated).
+  std::string OpsCSV =
+      Options.get(BinaryOperatorsOption, "==,!=,<,<=,>,>=").str();
+
+  llvm::SmallVector<llvm::StringRef, 8> Tokens;
+  llvm::StringRef(OpsCSV).split(Tokens, ',');
+  Operators.clear();
+  for (auto Tok : Tokens) {
+    llvm::StringRef Trim = Tok.trim();
+    if (!Trim.empty())
+      Operators.emplace_back(Trim.str());
+  }
+}
+
+ConstantOperandOrderCheck::~ConstantOperandOrderCheck() = default;
+
+void ConstantOperandOrderCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, PreferredSideOption, PreferredSide);
+  Options.store(Opts, BinaryOperatorsOption,
+                llvm::join(Operators.begin(), Operators.end(), ","));
+}
+
+// ------------------------ helpers ------------------------
+
+namespace {
+
+static const Expr *strip(const Expr *E) {
+  return E ? E->IgnoreParenImpCasts() : nullptr;
+}
+
+static bool isSimpleConstantExpr(const Expr *E) {
+  E = strip(E);
+  if (!E)
+    return false;
+
+  if (isa<IntegerLiteral>(E) || isa<FloatingLiteral>(E) ||
+      isa<StringLiteral>(E) || isa<CharacterLiteral>(E) ||
+      isa<CXXBoolLiteralExpr>(E) || isa<CXXNullPtrLiteralExpr>(E) ||
+      isa<GNUNullExpr>(E))
+    return true;
+
+  if (const auto *DRE = dyn_cast<DeclRefExpr>(E)) {
+    if (isa<EnumConstantDecl>(DRE->getDecl()))
+      return true;
+    if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl()))
+      return VD->isConstexpr() || VD->getType().isConstQualified();
+  }
+
+  return false;
+}
+
+static bool hasSideEffectsExpr(const Expr *E, ASTContext &Ctx) {
+  E = strip(E);
+  return E && E->HasSideEffects(Ctx);
+}
+
+static std::string invertOperatorText(llvm::StringRef Op) {
+  if (Op == "<")
+    return ">";
+  if (Op == ">")
+    return "<";
+  if (Op == "<=")
+    return ">=";
+  if (Op == ">=")
+    return "<=";
+  // symmetric: ==, !=
+  return Op.str();
+}
+
+} // namespace
+
+// ------------------------ matchers ------------------------
+
+void ConstantOperandOrderCheck::registerMatchers(MatchFinder *Finder) {
+  if (Operators.empty())
+    return;
+
+  for (const auto &Op : Operators) {
+    Finder->addMatcher(binaryOperator(hasOperatorName(Op),
+                                      hasLHS(expr().bind("lhs")),
+                                      hasRHS(expr().bind("rhs")))
+                           .bind("binop"),
+                       this);
+  }
+}
+
+// ------------------------ check / fixit ------------------------
+
+void ConstantOperandOrderCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Bin = Result.Nodes.getNodeAs<BinaryOperator>("binop");
+  const auto *L = Result.Nodes.getNodeAs<Expr>("lhs");
+  const auto *R = Result.Nodes.getNodeAs<Expr>("rhs");
+  if (!Bin || !L || !R)
+    return;
+
+  const ASTContext &Ctx = *Result.Context;
+  SourceManager &SM = *Result.SourceManager;
+
+  const Expr *LCore = strip(L);
+  const Expr *RCore = strip(R);
+  const bool LIsConst = isSimpleConstantExpr(LCore);
+  const bool RIsConst = isSimpleConstantExpr(RCore);
+
+  // Only when exactly one side is constant.
+  if (LIsConst == RIsConst)
+    return;
----------------
zwuis wrote:

Please add tests for this case.

https://github.com/llvm/llvm-project/pull/167158