clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.h

//===--- SimplifyBooleanExpr.h clang-tidy -----------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SIMPLIFY_BOOLEAN_EXPR_H
#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SIMPLIFY_BOOLEAN_EXPR_H

#include "../ClangTidy.h"

namespace clang {
namespace tidy {
namespace readability {

/// \brief Looks for boolean expressions involving boolean constants and
// simplifies them to use the appropriate boolean expression directly.
///
/// Examples:
/// `if (b == true)`                           becomes `if (b)`
/// `if (b == false)`                          becomes `if (!b)`
/// `if (b && true)`                           becomes `if (b)`
/// `if (b && false)`                          becomes `if (false)`
/// `if (b || true)`                           becomes `if (true)`
/// `if (b || false)`                          becomes `if (b)`
/// `e ? true : false`                         becomes `e`
/// `e ? false : true`                         becomes `!e`
/// `if (true) t(); else f();`                 becomes `t();`
/// `if (false) t(); else f();`                becomes `f();`
/// `if (e) return true; else return false;`   becomes `return e;`
/// `if (e) return false; else return true;`   becomes `return !e;`
/// `if (e) b = true; else b = false;`         becomes `b = e;`
/// `if (e) b = false; else b = true;`         becomes `b = !e;`
/// `if (e) return true; return false;`        becomes `return e;`
/// `if (e) return false; return true;`        becomes `return !e;`
///
/// The resulting expression `e` is modified as follows:
/// 1. Unnecessary parentheses around the expression are removed.
/// 2. Negated applications of `!` are eliminated.
/// 3. Negated applications of comparison operators are changed to use the
///    opposite condition.
/// 4. Implicit conversions of pointer to `bool` are replaced with explicit
///    comparisons to `nullptr`.
/// 5. Implicit casts to `bool` are replaced with explicit casts to `bool`.
/// 6. Object expressions with `explicit operator bool` conversion operators
///    are replaced with explicit casts to `bool`.
///
/// Examples:
/// 1. The ternary assignment `bool b = (i < 0) ? true : false;` has redundant
/// parentheses and becomes `bool b = i < 0;`.
///
/// 2. The conditional return `if (!b) return false; return true;` has an
/// implied double negation and becomes `return b;`.
///
/// 3. The conditional return `if (i < 0) return false; return true;` becomes
/// `return i >= 0;`.
/// The conditional return `if (i != 0) return false; return true;` becomes
/// `return i == 0;`.
///
/// 4. The conditional return `if (p) return true; return false;` has an
/// implicit conversion of a pointer to `bool` and becomes
/// `return p != nullptr;`.
/// The ternary assignment `bool b = (i & 1) ? true : false;` has an implicit
/// conversion of `i & 1` to `bool` and becomes
/// `bool b = static_cast<bool>(i & 1);`.
///
/// 5. The conditional return `if (i & 1) return true; else return false;` has
/// an implicit conversion of an integer quantity `i & 1` to `bool` and becomes
/// `return static_cast<bool>(i & 1);`
///
/// 6. Given `struct X { explicit operator bool(); };`, and an instance `x` of
/// `struct X`, the conditional return `if (x) return true; return false;`
/// becomes `return static_cast<bool>(x);`
///
/// When a conditional boolean return or assignment appears at the end of a
/// chain of `if`, `else if` statements, the conditional statement is left
/// unchanged unless the option `ChainedConditionalReturn` or
/// `ChainedConditionalAssignment`, respectively, is specified as non-zero.
/// The default value for both options is zero.
///
class SimplifyBooleanExprCheck : public ClangTidyCheck {
public:
  SimplifyBooleanExprCheck(StringRef Name, ClangTidyContext *Context);

  void storeOptions(ClangTidyOptions::OptionMap &Options) override;
  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;

private:
  void matchBoolBinOpExpr(ast_matchers::MatchFinder *Finder, bool Value,
                          StringRef OperatorName, StringRef BooleanId);

  void matchExprBinOpBool(ast_matchers::MatchFinder *Finder, bool Value,
                          StringRef OperatorName, StringRef BooleanId);

  void matchBoolCompOpExpr(ast_matchers::MatchFinder *Finder, bool Value,
                           StringRef OperatorName, StringRef BooleanId);

  void matchExprCompOpBool(ast_matchers::MatchFinder *Finder, bool Value,
                           StringRef OperatorName, StringRef BooleanId);

  void matchBoolCondition(ast_matchers::MatchFinder *Finder, bool Value,
                          StringRef BooleanId);

  void matchTernaryResult(ast_matchers::MatchFinder *Finder, bool Value,
                          StringRef TernaryId);

  void matchIfReturnsBool(ast_matchers::MatchFinder *Finder, bool Value,
                          StringRef Id);

  void matchIfAssignsBool(ast_matchers::MatchFinder *Finder, bool Value,
                          StringRef Id);

  void matchCompoundIfReturnsBool(ast_matchers::MatchFinder *Finder, bool Value,
                                  StringRef Id);

  void
  replaceWithExpression(const ast_matchers::MatchFinder::MatchResult &Result,
                        const CXXBoolLiteralExpr *BoolLiteral, bool UseLHS,
                        bool Negated = false);

  void
  replaceWithThenStatement(const ast_matchers::MatchFinder::MatchResult &Result,
                           const CXXBoolLiteralExpr *BoolLiteral);

  void
  replaceWithElseStatement(const ast_matchers::MatchFinder::MatchResult &Result,
                           const CXXBoolLiteralExpr *FalseConditionRemoved);

  void
  replaceWithCondition(const ast_matchers::MatchFinder::MatchResult &Result,
                       const ConditionalOperator *Ternary,
                       bool Negated = false);

  void replaceWithReturnCondition(
      const ast_matchers::MatchFinder::MatchResult &Result, const IfStmt *If,
      bool Negated = false);

  void
  replaceWithAssignment(const ast_matchers::MatchFinder::MatchResult &Result,
                        const IfStmt *If, bool Negated = false);

  void replaceCompoundReturnWithCondition(
      const ast_matchers::MatchFinder::MatchResult &Result,
      const CompoundStmt *Compound, bool Negated = false);

  const bool ChainedConditionalReturn;
  const bool ChainedConditionalAssignment;
};

} // namespace readability
} // namespace tidy
} // namespace clang

#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SIMPLIFY_BOOLEAN_EXPR_H