Split out code to be shared between CheckedNumeric and ClampedNumeric

base/numerics/safe_math_impl.h

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_NUMERICS_SAFE_MATH_IMPL_H_
-#define BASE_NUMERICS_SAFE_MATH_IMPL_H_
-
-#include <stddef.h>
-#include <stdint.h>
-
-#include <climits>
-#include <cmath>
-#include <cstdlib>
-#include <limits>
-#include <type_traits>
-
-#include "base/numerics/safe_conversions.h"
-
-namespace base {
-namespace internal {
-
-// Everything from here up to the floating point operations is portable C++,
-// but it may not be fast. This code could be split based on
-// platform/architecture and replaced with potentially faster implementations.
-
-// This is used for UnsignedAbs, where we need to support floating-point
-// template instantiations even though we don't actually support the operations.
-// However, there is no corresponding implementation of e.g. SafeUnsignedAbs,
-// so the float versions will not compile.
-template <typename Numeric,
-          bool IsInteger = std::is_integral<Numeric>::value,
-          bool IsFloat = std::is_floating_point<Numeric>::value>
-struct UnsignedOrFloatForSize;
-
-template <typename Numeric>
-struct UnsignedOrFloatForSize<Numeric, true, false> {
-  using type = typename std::make_unsigned<Numeric>::type;
-};
-
-template <typename Numeric>
-struct UnsignedOrFloatForSize<Numeric, false, true> {
-  using type = Numeric;
-};
-
-// Probe for builtin math overflow support on Clang and version check on GCC.
-#if defined(__has_builtin)
-#define USE_OVERFLOW_BUILTINS (__has_builtin(__builtin_add_overflow))
-#elif defined(__GNUC__)
-#define USE_OVERFLOW_BUILTINS (__GNUC__ >= 5)
-#else
-#define USE_OVERFLOW_BUILTINS (0)
-#endif
-
-template <typename T>
-bool CheckedAddImpl(T x, T y, T* result) {
-  static_assert(std::is_integral<T>::value, "Type must be integral");
-  // Since the value of x+y is undefined if we have a signed type, we compute
-  // it using the unsigned type of the same size.
-  using UnsignedDst = typename std::make_unsigned<T>::type;
-  using SignedDst = typename std::make_signed<T>::type;
-  UnsignedDst ux = static_cast<UnsignedDst>(x);
-  UnsignedDst uy = static_cast<UnsignedDst>(y);
-  UnsignedDst uresult = static_cast<UnsignedDst>(ux + uy);
-  *result = static_cast<T>(uresult);
-  // Addition is valid if the sign of (x + y) is equal to either that of x or
-  // that of y.
-  return (std::is_signed<T>::value)
-             ? static_cast<SignedDst>((uresult ^ ux) & (uresult ^ uy)) >= 0
-             : uresult >= uy;  // Unsigned is either valid or underflow.
-}
-
-template <typename T, typename U, class Enable = void>
-struct CheckedAddOp {};
-
-template <typename T, typename U>
-struct CheckedAddOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename MaxExponentPromotion<T, U>::type;
-  template <typename V>
-  static bool Do(T x, U y, V* result) {
-#if USE_OVERFLOW_BUILTINS
-    return !__builtin_add_overflow(x, y, result);
-#else
-    using Promotion = typename BigEnoughPromotion<T, U>::type;
-    Promotion presult;
-    // Fail if either operand is out of range for the promoted type.
-    // TODO(jschuh): This could be made to work for a broader range of values.
-    bool is_valid = IsValueInRangeForNumericType<Promotion>(x) &&
-                    IsValueInRangeForNumericType<Promotion>(y);
-
-    if (IsIntegerArithmeticSafe<Promotion, T, U>::value) {
-      presult = static_cast<Promotion>(x) + static_cast<Promotion>(y);
-    } else {
-      is_valid &= CheckedAddImpl(static_cast<Promotion>(x),
-                                 static_cast<Promotion>(y), &presult);
-    }
-    *result = static_cast<V>(presult);
-    return is_valid && IsValueInRangeForNumericType<V>(presult);
-#endif
-  }
-};
-
-template <typename T>
-bool CheckedSubImpl(T x, T y, T* result) {
-  static_assert(std::is_integral<T>::value, "Type must be integral");
-  // Since the value of x+y is undefined if we have a signed type, we compute
-  // it using the unsigned type of the same size.
-  using UnsignedDst = typename std::make_unsigned<T>::type;
-  using SignedDst = typename std::make_signed<T>::type;
-  UnsignedDst ux = static_cast<UnsignedDst>(x);
-  UnsignedDst uy = static_cast<UnsignedDst>(y);
-  UnsignedDst uresult = static_cast<UnsignedDst>(ux - uy);
-  *result = static_cast<T>(uresult);
-  // Subtraction is valid if either x and y have same sign, or (x-y) and x have
-  // the same sign.
-  return (std::is_signed<T>::value)
-             ? static_cast<SignedDst>((uresult ^ ux) & (ux ^ uy)) >= 0
-             : x >= y;
-}
-
-template <typename T, typename U, class Enable = void>
-struct CheckedSubOp {};
-
-template <typename T, typename U>
-struct CheckedSubOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename MaxExponentPromotion<T, U>::type;
-  template <typename V>
-  static bool Do(T x, U y, V* result) {
-#if USE_OVERFLOW_BUILTINS
-    return !__builtin_sub_overflow(x, y, result);
-#else
-    using Promotion = typename BigEnoughPromotion<T, U>::type;
-    Promotion presult;
-    // Fail if either operand is out of range for the promoted type.
-    // TODO(jschuh): This could be made to work for a broader range of values.
-    bool is_valid = IsValueInRangeForNumericType<Promotion>(x) &&
-                    IsValueInRangeForNumericType<Promotion>(y);
-
-    if (IsIntegerArithmeticSafe<Promotion, T, U>::value) {
-      presult = static_cast<Promotion>(x) - static_cast<Promotion>(y);
-    } else {
-      is_valid &= CheckedSubImpl(static_cast<Promotion>(x),
-                                 static_cast<Promotion>(y), &presult);
-    }
-    *result = static_cast<V>(presult);
-    return is_valid && IsValueInRangeForNumericType<V>(presult);
-#endif
-  }
-};
-
-template <typename T>
-bool CheckedMulImpl(T x, T y, T* result) {
-  static_assert(std::is_integral<T>::value, "Type must be integral");
-  // Since the value of x*y is potentially undefined if we have a signed type,
-  // we compute it using the unsigned type of the same size.
-  using UnsignedDst = typename std::make_unsigned<T>::type;
-  using SignedDst = typename std::make_signed<T>::type;
-  const UnsignedDst ux = SafeUnsignedAbs(x);
-  const UnsignedDst uy = SafeUnsignedAbs(y);
-  UnsignedDst uresult = static_cast<UnsignedDst>(ux * uy);
-  const bool is_negative =
-      std::is_signed<T>::value && static_cast<SignedDst>(x ^ y) < 0;
-  *result = is_negative ? 0 - uresult : uresult;
-  // We have a fast out for unsigned identity or zero on the second operand.
-  // After that it's an unsigned overflow check on the absolute value, with
-  // a +1 bound for a negative result.
-  return uy <= UnsignedDst(!std::is_signed<T>::value || is_negative) ||
-         ux <= (std::numeric_limits<T>::max() + UnsignedDst(is_negative)) / uy;
-}
-
-template <typename T, typename U, class Enable = void>
-struct CheckedMulOp {};
-
-template <typename T, typename U>
-struct CheckedMulOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename MaxExponentPromotion<T, U>::type;
-  template <typename V>
-  static bool Do(T x, U y, V* result) {
-#if USE_OVERFLOW_BUILTINS
-#if defined(__clang__)
-    // TODO(jschuh): Get the Clang runtime library issues sorted out so we can
-    // support full-width, mixed-sign multiply builtins.
-    // https://crbug.com/613003
-    static const bool kUseMaxInt =
-        // Narrower type than uintptr_t is always safe.
-        std::numeric_limits<__typeof__(x * y)>::digits <
-            std::numeric_limits<intptr_t>::digits ||
-        // Safe for intptr_t and uintptr_t if the sign matches.
-        (IntegerBitsPlusSign<__typeof__(x * y)>::value ==
-             IntegerBitsPlusSign<intptr_t>::value &&
-         std::is_signed<T>::value == std::is_signed<U>::value);
-#else
-    static const bool kUseMaxInt = true;
-#endif
-    if (kUseMaxInt)
-      return !__builtin_mul_overflow(x, y, result);
-#endif
-    using Promotion = typename FastIntegerArithmeticPromotion<T, U>::type;
-    Promotion presult;
-    // Fail if either operand is out of range for the promoted type.
-    // TODO(jschuh): This could be made to work for a broader range of values.
-    bool is_valid = IsValueInRangeForNumericType<Promotion>(x) &&
-                    IsValueInRangeForNumericType<Promotion>(y);
-
-    if (IsIntegerArithmeticSafe<Promotion, T, U>::value) {
-      presult = static_cast<Promotion>(x) * static_cast<Promotion>(y);
-    } else {
-      is_valid &= CheckedMulImpl(static_cast<Promotion>(x),
-                                 static_cast<Promotion>(y), &presult);
-    }
-    *result = static_cast<V>(presult);
-    return is_valid && IsValueInRangeForNumericType<V>(presult);
-  }
-};
-
-// Avoid poluting the namespace once we're done with the macro.
-#undef USE_OVERFLOW_BUILTINS
-
-// Division just requires a check for a zero denominator or an invalid negation
-// on signed min/-1.
-template <typename T>
-bool CheckedDivImpl(T x, T y, T* result) {
-  static_assert(std::is_integral<T>::value, "Type must be integral");
-  if (y && (!std::is_signed<T>::value ||
-            x != std::numeric_limits<T>::lowest() || y != static_cast<T>(-1))) {
-    *result = x / y;
-    return true;
-  }
-  return false;
-}
-
-template <typename T, typename U, class Enable = void>
-struct CheckedDivOp {};
-
-template <typename T, typename U>
-struct CheckedDivOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename MaxExponentPromotion<T, U>::type;
-  template <typename V>
-  static bool Do(T x, U y, V* result) {
-    using Promotion = typename BigEnoughPromotion<T, U>::type;
-    Promotion presult;
-    // Fail if either operand is out of range for the promoted type.
-    // TODO(jschuh): This could be made to work for a broader range of values.
-    bool is_valid = IsValueInRangeForNumericType<Promotion>(x) &&
-                    IsValueInRangeForNumericType<Promotion>(y);
-    is_valid &= CheckedDivImpl(static_cast<Promotion>(x),
-                               static_cast<Promotion>(y), &presult);
-    *result = static_cast<V>(presult);
-    return is_valid && IsValueInRangeForNumericType<V>(presult);
-  }
-};
-
-template <typename T>
-bool CheckedModImpl(T x, T y, T* result) {
-  static_assert(std::is_integral<T>::value, "Type must be integral");
-  if (y > 0) {
-    *result = static_cast<T>(x % y);
-    return true;
-  }
-  return false;
-}
-
-template <typename T, typename U, class Enable = void>
-struct CheckedModOp {};
-
-template <typename T, typename U>
-struct CheckedModOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename MaxExponentPromotion<T, U>::type;
-  template <typename V>
-  static bool Do(T x, U y, V* result) {
-    using Promotion = typename BigEnoughPromotion<T, U>::type;
-    Promotion presult;
-    bool is_valid = CheckedModImpl(static_cast<Promotion>(x),
-                                   static_cast<Promotion>(y), &presult);
-    *result = static_cast<V>(presult);
-    return is_valid && IsValueInRangeForNumericType<V>(presult);
-  }
-};
-
-template <typename T, typename U, class Enable = void>
-struct CheckedLshOp {};
-
-// Left shift. Shifts less than 0 or greater than or equal to the number
-// of bits in the promoted type are undefined. Shifts of negative values
-// are undefined. Otherwise it is defined when the result fits.
-template <typename T, typename U>
-struct CheckedLshOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = T;
-  template <typename V>
-  static bool Do(T x, U shift, V* result) {
-    using ShiftType = typename std::make_unsigned<T>::type;
-    static const ShiftType kBitWidth = IntegerBitsPlusSign<T>::value;
-    const ShiftType real_shift = static_cast<ShiftType>(shift);
-    // Signed shift is not legal on negative values.
-    if (!IsValueNegative(x) && real_shift < kBitWidth) {
-      // Just use a multiplication because it's easy.
-      // TODO(jschuh): This could probably be made more efficient.
-      if (!std::is_signed<T>::value || real_shift != kBitWidth - 1)
-        return CheckedMulOp<T, T>::Do(x, static_cast<T>(1) << shift, result);
-      return !x;  // Special case zero for a full width signed shift.
-    }
-    return false;
-  }
-};
-
-template <typename T, typename U, class Enable = void>
-struct CheckedRshOp {};
-
-// Right shift. Shifts less than 0 or greater than or equal to the number
-// of bits in the promoted type are undefined. Otherwise, it is always defined,
-// but a right shift of a negative value is implementation-dependent.
-template <typename T, typename U>
-struct CheckedRshOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = T;
-  template <typename V = result_type>
-  static bool Do(T x, U shift, V* result) {
-    // Use the type conversion push negative values out of range.
-    using ShiftType = typename std::make_unsigned<T>::type;
-    if (static_cast<ShiftType>(shift) < IntegerBitsPlusSign<T>::value) {
-      T tmp = x >> shift;
-      *result = static_cast<V>(tmp);
-      return IsValueInRangeForNumericType<V>(tmp);
-    }
-    return false;
-  }
-};
-
-template <typename T, typename U, class Enable = void>
-struct CheckedAndOp {};
-
-// For simplicity we support only unsigned integer results.
-template <typename T, typename U>
-struct CheckedAndOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename std::make_unsigned<
-      typename MaxExponentPromotion<T, U>::type>::type;
-  template <typename V = result_type>
-  static bool Do(T x, U y, V* result) {
-    result_type tmp = static_cast<result_type>(x) & static_cast<result_type>(y);
-    *result = static_cast<V>(tmp);
-    return IsValueInRangeForNumericType<V>(tmp);
-  }
-};
-
-template <typename T, typename U, class Enable = void>
-struct CheckedOrOp {};
-
-// For simplicity we support only unsigned integers.
-template <typename T, typename U>
-struct CheckedOrOp<T,
-                   U,
-                   typename std::enable_if<std::is_integral<T>::value &&
-                                           std::is_integral<U>::value>::type> {
-  using result_type = typename std::make_unsigned<
-      typename MaxExponentPromotion<T, U>::type>::type;
-  template <typename V = result_type>
-  static bool Do(T x, U y, V* result) {
-    result_type tmp = static_cast<result_type>(x) | static_cast<result_type>(y);
-    *result = static_cast<V>(tmp);
-    return IsValueInRangeForNumericType<V>(tmp);
-  }
-};
-
-template <typename T, typename U, class Enable = void>
-struct CheckedXorOp {};
-
-// For simplicity we support only unsigned integers.
-template <typename T, typename U>
-struct CheckedXorOp<T,
-                    U,
-                    typename std::enable_if<std::is_integral<T>::value &&
-                                            std::is_integral<U>::value>::type> {
-  using result_type = typename std::make_unsigned<
-      typename MaxExponentPromotion<T, U>::type>::type;
-  template <typename V = result_type>
-  static bool Do(T x, U y, V* result) {
-    result_type tmp = static_cast<result_type>(x) ^ static_cast<result_type>(y);
-    *result = static_cast<V>(tmp);
-    return IsValueInRangeForNumericType<V>(tmp);
-  }
-};
-
-// Max doesn't really need to be implemented this way because it can't fail,
-// but it makes the code much cleaner to use the MathOp wrappers.
-template <typename T, typename U, class Enable = void>
-struct CheckedMaxOp {};
-
-template <typename T, typename U>
-struct CheckedMaxOp<
-    T,
-    U,
-    typename std::enable_if<std::is_arithmetic<T>::value &&
-                            std::is_arithmetic<U>::value>::type> {
-  using result_type = typename MaxExponentPromotion<T, U>::type;
-  template <typename V = result_type>
-  static bool Do(T x, U y, V* result) {
-    *result = IsGreater<T, U>::Test(x, y) ? static_cast<result_type>(x)
-                                          : static_cast<result_type>(y);
-    return true;
-  }
-};
-
-// Min doesn't really need to be implemented this way because it can't fail,
-// but it makes the code much cleaner to use the MathOp wrappers.
-template <typename T, typename U, class Enable = void>
-struct CheckedMinOp {};
-
-template <typename T, typename U>
-struct CheckedMinOp<
-    T,
-    U,
-    typename std::enable_if<std::is_arithmetic<T>::value &&
-                            std::is_arithmetic<U>::value>::type> {
-  using result_type = typename LowestValuePromotion<T, U>::type;
-  template <typename V = result_type>
-  static bool Do(T x, U y, V* result) {
-    *result = IsLess<T, U>::Test(x, y) ? static_cast<result_type>(x)
-                                       : static_cast<result_type>(y);
-    return true;
-  }
-};
-
-// This is just boilerplate that wraps the standard floating point arithmetic.
-// A macro isn't the nicest solution, but it beats rewriting these repeatedly.
-#define BASE_FLOAT_ARITHMETIC_OPS(NAME, OP)                                    \
-  template <typename T, typename U>                                            \
-  struct Checked##NAME##Op<                                                    \
-      T, U, typename std::enable_if<std::is_floating_point<T>::value ||        \
-                                    std::is_floating_point<U>::value>::type> { \
-    using result_type = typename MaxExponentPromotion<T, U>::type;             \
-    template <typename V>                                                      \
-    static bool Do(T x, U y, V* result) {                                      \
-      using Promotion = typename MaxExponentPromotion<T, U>::type;             \
-      Promotion presult = x OP y;                                              \
-      *result = static_cast<V>(presult);                                       \
-      return IsValueInRangeForNumericType<V>(presult);                         \
-    }                                                                          \
-  };
-
-BASE_FLOAT_ARITHMETIC_OPS(Add, +)
-BASE_FLOAT_ARITHMETIC_OPS(Sub, -)
-BASE_FLOAT_ARITHMETIC_OPS(Mul, *)
-BASE_FLOAT_ARITHMETIC_OPS(Div, /)
-
-#undef BASE_FLOAT_ARITHMETIC_OPS
-
-// Wrap the unary operations to allow SFINAE when instantiating integrals versus
-// floating points. These don't perform any overflow checking. Rather, they
-// exhibit well-defined overflow semantics and rely on the caller to detect
-// if an overflow occured.
-
-template <typename T,
-          typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
-constexpr T NegateWrapper(T value) {
-  using UnsignedT = typename std::make_unsigned<T>::type;
-  // This will compile to a NEG on Intel, and is normal negation on ARM.
-  return static_cast<T>(UnsignedT(0) - static_cast<UnsignedT>(value));
-}
-
-template <
-    typename T,
-    typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr>
-constexpr T NegateWrapper(T value) {
-  return -value;
-}
-
-template <typename T,
-          typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
-constexpr typename std::make_unsigned<T>::type InvertWrapper(T value) {
-  return ~value;
-}
-
-template <typename T,
-          typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
-constexpr T AbsWrapper(T value) {
-  return static_cast<T>(SafeUnsignedAbs(value));
-}
-
-template <
-    typename T,
-    typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr>
-constexpr T AbsWrapper(T value) {
-  return value < 0 ? -value : value;
-}
-
-// Floats carry around their validity state with them, but integers do not. So,
-// we wrap the underlying value in a specialization in order to hide that detail
-// and expose an interface via accessors.
-enum NumericRepresentation {
-  NUMERIC_INTEGER,
-  NUMERIC_FLOATING,
-  NUMERIC_UNKNOWN
-};
-
-template <typename NumericType>
-struct GetNumericRepresentation {
-  static const NumericRepresentation value =
-      std::is_integral<NumericType>::value
-          ? NUMERIC_INTEGER
-          : (std::is_floating_point<NumericType>::value ? NUMERIC_FLOATING
-                                                        : NUMERIC_UNKNOWN);
-};
-
-template <typename T, NumericRepresentation type =
-                          GetNumericRepresentation<T>::value>
-class CheckedNumericState {};
-
-// Integrals require quite a bit of additional housekeeping to manage state.
-template <typename T>
-class CheckedNumericState<T, NUMERIC_INTEGER> {
- private:
-  // is_valid_ precedes value_ because member intializers in the constructors
-  // are evaluated in field order, and is_valid_ must be read when initializing
-  // value_.
-  bool is_valid_;
-  T value_;
-
-  // Ensures that a type conversion does not trigger undefined behavior.
-  template <typename Src>
-  static constexpr T WellDefinedConversionOrZero(const Src value,
-                                                 const bool is_valid) {
-    using SrcType = typename internal::UnderlyingType<Src>::type;
-    return (std::is_integral<SrcType>::value || is_valid)
-               ? static_cast<T>(value)
-               : static_cast<T>(0);
-  }
-
- public:
-  template <typename Src, NumericRepresentation type>
-  friend class CheckedNumericState;
-
-  constexpr CheckedNumericState() : is_valid_(true), value_(0) {}
-
-  template <typename Src>
-  constexpr CheckedNumericState(Src value, bool is_valid)
-      : is_valid_(is_valid && IsValueInRangeForNumericType<T>(value)),
-        value_(WellDefinedConversionOrZero(value, is_valid_)) {
-    static_assert(std::is_arithmetic<Src>::value, "Argument must be numeric.");
-  }
-
-  // Copy constructor.
-  template <typename Src>
-  constexpr CheckedNumericState(const CheckedNumericState<Src>& rhs)
-      : is_valid_(rhs.IsValid()),
-        value_(WellDefinedConversionOrZero(rhs.value(), is_valid_)) {}
-
-  template <typename Src>
-  constexpr explicit CheckedNumericState(Src value)
-      : is_valid_(IsValueInRangeForNumericType<T>(value)),
-        value_(WellDefinedConversionOrZero(value, is_valid_)) {}
-
-  constexpr bool is_valid() const { return is_valid_; }
-  constexpr T value() const { return value_; }
-};
-
-// Floating points maintain their own validity, but need translation wrappers.
-template <typename T>
-class CheckedNumericState<T, NUMERIC_FLOATING> {
- private:
-  T value_;
-
-  // Ensures that a type conversion does not trigger undefined behavior.
-  template <typename Src>
-  static constexpr T WellDefinedConversionOrNaN(const Src value,
-                                                const bool is_valid) {
-    using SrcType = typename internal::UnderlyingType<Src>::type;
-    return (StaticDstRangeRelationToSrcRange<T, SrcType>::value ==
-                NUMERIC_RANGE_CONTAINED ||
-            is_valid)
-               ? static_cast<T>(value)
-               : std::numeric_limits<T>::quiet_NaN();
-  }
-
- public:
-  template <typename Src, NumericRepresentation type>
-  friend class CheckedNumericState;
-
-  constexpr CheckedNumericState() : value_(0.0) {}
-
-  template <typename Src>
-  constexpr CheckedNumericState(Src value, bool is_valid)
-      : value_(WellDefinedConversionOrNaN(value, is_valid)) {}
-
-  template <typename Src>
-  constexpr explicit CheckedNumericState(Src value)
-      : value_(WellDefinedConversionOrNaN(
-            value,
-            IsValueInRangeForNumericType<T>(value))) {}
-
-  // Copy constructor.
-  template <typename Src>
-  constexpr CheckedNumericState(const CheckedNumericState<Src>& rhs)
-      : value_(WellDefinedConversionOrNaN(
-            rhs.value(),
-            rhs.is_valid() && IsValueInRangeForNumericType<T>(rhs.value()))) {}
-
-  constexpr bool is_valid() const {
-    // Written this way because std::isfinite is not reliably constexpr.
-    // TODO(jschuh): Fix this if the libraries ever get fixed.
-    return value_ <= std::numeric_limits<T>::max() &&
-           value_ >= std::numeric_limits<T>::lowest();
-  }
-  constexpr T value() const { return value_; }
-};
-
-template <template <typename, typename, typename> class M,
-          typename L,
-          typename R>
-struct MathWrapper {
-  using math = M<typename UnderlyingType<L>::type,
-                 typename UnderlyingType<R>::type,
-                 void>;
-  using type = typename math::result_type;
-};
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_NUMERICS_SAFE_MATH_IMPL_H_