AssignmentInIfConditionCheck.cpp

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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 "AssignmentInIfConditionCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::bugprone {
 
void AssignmentInIfConditionCheck::registerMatchers(MatchFinder *Finder) {
  Finder->addMatcher(translationUnitDecl(), this);
}
 
void AssignmentInIfConditionCheck::check(
    const ast_matchers::MatchFinder::MatchResult &Result) {
  class Visitor : public RecursiveASTVisitor<Visitor> {
    AssignmentInIfConditionCheck &Check;
 
  public:
    explicit Visitor(AssignmentInIfConditionCheck &Check) : Check(Check) {}
    bool VisitIfStmt(IfStmt *If) {
      class ConditionVisitor : public RecursiveASTVisitor<ConditionVisitor> {
        AssignmentInIfConditionCheck &Check;
 
      public:
        explicit ConditionVisitor(AssignmentInIfConditionCheck &Check)
            : Check(Check) {}
 
        // Dont traverse into any lambda expressions.
        bool TraverseLambdaExpr(LambdaExpr *, DataRecursionQueue * = nullptr) {
          return true;
        }
 
        // Dont traverse into any requires expressions.
        bool TraverseRequiresExpr(RequiresExpr *,
                                  DataRecursionQueue * = nullptr) {
          return true;
        }
 
        // Only traverse the result expression of a statement expression,
        // looking through labels and attributes on the last statement.
        bool TraverseStmtExpr(StmtExpr *SE,
                              DataRecursionQueue *Queue = nullptr) {
          if (auto *Last =
                  dyn_cast_if_present<ValueStmt>(SE->getSubStmt()->body_back()))
            return TraverseStmt(Last->getExprStmt(), Queue);
          return true;
        }
 
        bool VisitBinaryOperator(BinaryOperator *BO) {
          if (BO->isAssignmentOp())
            Check.report(BO);
          return true;
        }
 
        bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr *OCE) {
          if (OCE->isAssignmentOp())
            Check.report(OCE);
          return true;
        }
      };
 
      ConditionVisitor(Check).TraverseStmt(If->getCond());
      return true;
    }
  };
  Visitor(*this).TraverseAST(*Result.Context);
}
 
void AssignmentInIfConditionCheck::report(const Expr *AssignmentExpr) {
  const SourceLocation OpLoc =
      isa<BinaryOperator>(AssignmentExpr)
          ? cast<BinaryOperator>(AssignmentExpr)->getOperatorLoc()
          : cast<CXXOperatorCallExpr>(AssignmentExpr)->getOperatorLoc();
 
  diag(OpLoc, "an assignment within an 'if' condition is bug-prone")
      << AssignmentExpr->getSourceRange();
  diag(OpLoc,
       "if it should be an assignment, move it out of the 'if' condition",
       DiagnosticIDs::Note);
  diag(OpLoc, "if it is meant to be an equality check, change '=' to '=='",
       DiagnosticIDs::Note);
}
 
} // namespace clang::tidy::bugprone