[constexpr] IntType

See https://github.com/harfbuzz/harfbuzz/pull/2875

src/hb-algs.hh

@@ -83,7 +83,8 @@ static inline constexpr uint16_t hb_uint16_swap (uint16_t v)
 static inline constexpr uint32_t hb_uint32_swap (uint32_t v)
 { return (hb_uint16_swap (v) << 16) | hb_uint16_swap (v >> 16); }
 
-template <typename Type, int Bytes = sizeof (Type)> struct BEInt;
+template <typename Type, int Bytes = sizeof (Type)>
+struct BEInt;
 template <typename Type>
 struct BEInt<Type, 1>
 {
@@ -124,11 +125,13 @@ struct BEInt<Type, 2>
 template <typename Type>
 struct BEInt<Type, 3>
 {
+  static_assert (!hb_is_signed (Type), "");
   public:
   BEInt () = default;
   constexpr BEInt (Type V) : v {uint8_t ((V >> 16) & 0xFF),
 				uint8_t ((V >>  8) & 0xFF),
 				uint8_t ((V      ) & 0xFF)} {}
+
   constexpr operator Type () const { return (v[0] << 16)
 					  + (v[1] <<  8)
 					  + (v[2]      ); }

src/hb-open-type.hh

@@ -53,14 +53,18 @@ namespace OT {
  */
 
 /* Integer types in big-endian order and no alignment requirement */
-template <typename Type, unsigned int Size = sizeof (Type)>
+template <typename Type,
+	  unsigned int Size = sizeof (Type),
+	  typename Wide = hb_conditional<hb_is_signed (Type), signed, unsigned>>
 struct IntType
 {
   typedef Type type;
-  typedef hb_conditional<hb_is_signed (Type), signed, unsigned> wide_type;
 
-  IntType& operator = (wide_type i) { v = i; return *this; }
-  operator wide_type () const { return v; }
+  IntType () = default;
+  explicit constexpr IntType (Wide V) : v {V} {}
+  IntType& operator = (Wide i) { v = i; return *this; }
+  operator Wide () const { return v; }
+
   bool operator == (const IntType &o) const { return (Type) v == (Type) o.v; }
   bool operator != (const IntType &o) const { return !(*this == o); }