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 {

/// Looks for boolean expressions involving boolean constants and simplifies
/// them to use the appropriate boolean expression directly.
///
/// Examples:
///
/// ===========================================  ================
/// Initial expression                           Result
/// -------------------------------------------  ----------------
/// `if (b == true)`                             `if (b)`
/// `if (b == false)`                            `if (!b)`
/// `if (b && true)`                             `if (b)`
/// `if (b && false)`                            `if (false)`
/// `if (b || true)`                             `if (true)`
/// `if (b || false)`                            `if (b)`
/// `e ? true : false`                           `e`
/// `e ? false : true`                           `!e`
/// `if (true) t(); else f();`                   `t();`
/// `if (false) t(); else f();`                  `f();`
/// `if (e) return true; else return false;`     `return e;`
/// `if (e) return false; else return true;`     `return !e;`
/// `if (e) b = true; else b = false;`           `b = e;`
/// `if (e) b = false; else b = true;`           `b = !e;`
/// `if (e) return true; return false;`          `return e;`
/// `if (e) return false; return true;`          `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);

  void issueDiag(const ast_matchers::MatchFinder::MatchResult &Result,
                 SourceLocation Loc, StringRef Description,
                 SourceRange ReplacementRange, StringRef Replacement);

  const bool ChainedConditionalReturn;
  const bool ChainedConditionalAssignment;
};

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

#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_SIMPLIFY_BOOLEAN_EXPR_H