Add more helpful message to constructor saying it cant be used

Author: mborland

include/boost/decimal/decimal128_t.hpp

@@ -257,6 +257,13 @@ BOOST_DECIMAL_EXPORT class decimal128_t final
     #endif
     constexpr decimal128_t(T1 coeff, T2 exp, bool sign = false) noexcept;
 
+    #ifdef BOOST_DECIMAL_HAS_CONCEPTS
+    template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
+    #else
+    template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
+    #endif
+    constexpr decimal128_t(T1, T2, bool) noexcept { static_assert(false, "Construction from signed integer, exponent, and sign is ambiguous, so it is disallowed. You must use an Unsigned Integer for the coefficient to construct from {coefficient, exponent, sign}"); }
+
     #ifdef BOOST_DECIMAL_HAS_CONCEPTS
     template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
     #else

include/boost/decimal/decimal32_t.hpp

@@ -282,6 +282,13 @@ BOOST_DECIMAL_EXPORT class decimal32_t final // NOLINT(cppcoreguidelines-special
     #endif
     constexpr decimal32_t(T1 coeff, T2 exp, bool sign = false) noexcept;
 
+    #ifdef BOOST_DECIMAL_HAS_CONCEPTS
+    template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
+    #else
+    template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
+    #endif
+    constexpr decimal32_t(T1, T2, bool) noexcept { static_assert(false, "Construction from signed integer, exponent, and sign is ambiguous, so it is disallowed. You must use an Unsigned Integer for the coefficient to construct from {coefficient, exponent, sign}"); }
+
     #ifdef BOOST_DECIMAL_HAS_CONCEPTS
     template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
     #else

include/boost/decimal/decimal64_t.hpp

@@ -319,6 +319,13 @@ BOOST_DECIMAL_EXPORT class decimal64_t final
     #endif
     constexpr decimal64_t(T1 coeff, T2 exp, bool sign = false) noexcept;
 
+    #ifdef BOOST_DECIMAL_HAS_CONCEPTS
+    template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
+    #else
+    template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
+    #endif
+    constexpr decimal64_t(T1, T2, bool) noexcept { static_assert(false, "Construction from signed integer, exponent, and sign is ambiguous, so it is disallowed. You must use an Unsigned Integer for the coefficient to construct from {coefficient, exponent, sign}"); }
+
     #ifdef BOOST_DECIMAL_HAS_CONCEPTS
     template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
     #else

include/boost/decimal/decimal_fast128_t.hpp

@@ -157,6 +157,13 @@ BOOST_DECIMAL_EXPORT class decimal_fast128_t final
     #endif
     constexpr decimal_fast128_t(T1 coeff, T2 exp, bool sign = false) noexcept;
 
+    #ifdef BOOST_DECIMAL_HAS_CONCEPTS
+    template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
+    #else
+    template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
+    #endif
+    constexpr decimal_fast128_t(T1, T2, bool) noexcept { static_assert(false, "Construction from signed integer, exponent, and sign is ambiguous, so it is disallowed. You must use an Unsigned Integer for the coefficient to construct from {coefficient, exponent, sign}"); }
+
     #ifdef BOOST_DECIMAL_HAS_CONCEPTS
     template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
     #else

include/boost/decimal/decimal_fast32_t.hpp

@@ -150,6 +150,9 @@ BOOST_DECIMAL_EXPORT class decimal_fast32_t final
     template <typename T1, typename T2, std::enable_if_t<detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
     constexpr decimal_fast32_t(T1 coeff, T2 exp, bool sign = false) noexcept;
 
+    template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
+    constexpr decimal_fast32_t(T1, T2, bool) noexcept { static_assert(false, "Construction from signed integer, exponent, and sign is ambiguous, so it is disallowed. You must use an Unsigned Integer for the coefficient to construct from {coefficient, exponent, sign}"); }
+
     template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
     constexpr decimal_fast32_t(T1 coeff, T2 exp) noexcept;
 

include/boost/decimal/decimal_fast64_t.hpp

@@ -168,6 +168,13 @@ BOOST_DECIMAL_EXPORT class decimal_fast64_t final
     #endif
     constexpr decimal_fast64_t(T1 coeff, T2 exp, bool sign = false) noexcept;
 
+    #ifdef BOOST_DECIMAL_HAS_CONCEPTS
+    template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
+    #else
+    template <typename T1, typename T2, std::enable_if_t<!detail::is_unsigned_v<T1> && detail::is_integral_v<T2>, bool> = true>
+    #endif
+    constexpr decimal_fast64_t(T1, T2, bool) noexcept { static_assert(false, "Construction from signed integer, exponent, and sign is ambiguous, so it is disallowed. You must use an Unsigned Integer for the coefficient to construct from {coefficient, exponent, sign}"); }
+
     #ifdef BOOST_DECIMAL_HAS_CONCEPTS
     template <BOOST_DECIMAL_SIGNED_INTEGRAL T1, BOOST_DECIMAL_INTEGRAL T2>
     #else