Add a const field to the ToInt trait to allow its use in const …

…contexts (#179)

src/int.rs

@@ -1187,27 +1187,31 @@ impl ToInt<i8> for Z0 {
     fn to_int() -> i8 {
         Self::I8
     }
+    const INT: i8 = Self::I8;
 }
 
 impl ToInt<i16> for Z0 {
     #[inline]
     fn to_int() -> i16 {
         Self::I16
     }
+    const INT: i16 = Self::I16;
 }
 
 impl ToInt<i32> for Z0 {
     #[inline]
     fn to_int() -> i32 {
         Self::I32
     }
+    const INT: i32 = Self::I32;
 }
 
 impl ToInt<i64> for Z0 {
     #[inline]
     fn to_int() -> i64 {
         Self::I64
     }
+    const INT: i64 = Self::I64;
 }
 
 // negative numbers
@@ -1220,6 +1224,7 @@ where
     fn to_int() -> i8 {
         Self::I8
     }
+    const INT: i8 = Self::I8;
 }
 
 impl<U> ToInt<i16> for NInt<U>
@@ -1230,6 +1235,7 @@ where
     fn to_int() -> i16 {
         Self::I16
     }
+    const INT: i16 = Self::I16;
 }
 
 impl<U> ToInt<i32> for NInt<U>
@@ -1240,6 +1246,7 @@ where
     fn to_int() -> i32 {
         Self::I32
     }
+    const INT: i32 = Self::I32;
 }
 
 impl<U> ToInt<i64> for NInt<U>
@@ -1250,6 +1257,7 @@ where
     fn to_int() -> i64 {
         Self::I64
     }
+    const INT: i64 = Self::I64;
 }
 
 // positive numbers
@@ -1262,6 +1270,7 @@ where
     fn to_int() -> i8 {
         Self::I8
     }
+    const INT: i8 = Self::I8;
 }
 
 impl<U> ToInt<i16> for PInt<U>
@@ -1272,6 +1281,7 @@ where
     fn to_int() -> i16 {
         Self::I16
     }
+    const INT: i16 = Self::I16;
 }
 
 impl<U> ToInt<i32> for PInt<U>
@@ -1282,6 +1292,7 @@ where
     fn to_int() -> i32 {
         Self::I32
     }
+    const INT: i32 = Self::I32;
 }
 
 impl<U> ToInt<i64> for PInt<U>
@@ -1292,6 +1303,7 @@ where
     fn to_int() -> i64 {
         Self::I64
     }
+    const INT: i64 = Self::I64;
 }
 
 #[cfg(test)]
@@ -1316,6 +1328,15 @@ mod tests {
         assert_eq!(-2_i8, N2::to_int());
         assert_eq!(-3_i8, N3::to_int());
         assert_eq!(-4_i8, N4::to_int());
+        assert_eq!(0_i8, Z0::INT);
+        assert_eq!(1_i8, P1::INT);
+        assert_eq!(2_i8, P2::INT);
+        assert_eq!(3_i8, P3::INT);
+        assert_eq!(4_i8, P4::INT);
+        assert_eq!(-1_i8, N1::INT);
+        assert_eq!(-2_i8, N2::INT);
+        assert_eq!(-3_i8, N3::INT);
+        assert_eq!(-4_i8, N4::INT);
 
         // i16
         assert_eq!(0_i16, Z0::to_int());
@@ -1327,6 +1348,15 @@ mod tests {
         assert_eq!(-2_i16, N2::to_int());
         assert_eq!(-3_i16, N3::to_int());
         assert_eq!(-4_i16, N4::to_int());
+        assert_eq!(0_i16, Z0::INT);
+        assert_eq!(1_i16, P1::INT);
+        assert_eq!(2_i16, P2::INT);
+        assert_eq!(3_i16, P3::INT);
+        assert_eq!(4_i16, P4::INT);
+        assert_eq!(-1_i16, N1::INT);
+        assert_eq!(-2_i16, N2::INT);
+        assert_eq!(-3_i16, N3::INT);
+        assert_eq!(-4_i16, N4::INT);
 
         // i32
         assert_eq!(0_i32, Z0::to_int());
@@ -1338,6 +1368,15 @@ mod tests {
         assert_eq!(-2_i32, N2::to_int());
         assert_eq!(-3_i32, N3::to_int());
         assert_eq!(-4_i32, N4::to_int());
+        assert_eq!(0_i32, Z0::INT);
+        assert_eq!(1_i32, P1::INT);
+        assert_eq!(2_i32, P2::INT);
+        assert_eq!(3_i32, P3::INT);
+        assert_eq!(4_i32, P4::INT);
+        assert_eq!(-1_i32, N1::INT);
+        assert_eq!(-2_i32, N2::INT);
+        assert_eq!(-3_i32, N3::INT);
+        assert_eq!(-4_i32, N4::INT);
 
         // i64
         assert_eq!(0_i64, Z0::to_int());
@@ -1349,5 +1388,14 @@ mod tests {
         assert_eq!(-2_i64, N2::to_int());
         assert_eq!(-3_i64, N3::to_int());
         assert_eq!(-4_i64, N4::to_int());
+        assert_eq!(0_i64, Z0::INT);
+        assert_eq!(1_i64, P1::INT);
+        assert_eq!(2_i64, P2::INT);
+        assert_eq!(3_i64, P3::INT);
+        assert_eq!(4_i64, P4::INT);
+        assert_eq!(-1_i64, N1::INT);
+        assert_eq!(-2_i64, N2::INT);
+        assert_eq!(-3_i64, N3::INT);
+        assert_eq!(-4_i64, N4::INT);
     }
 }

src/type_operators.rs

@@ -587,4 +587,6 @@ pub trait Gcd<Rhs> {
 pub trait ToInt<T> {
     /// Method returning the concrete value for the type.
     fn to_int() -> T;
+    /// The concrete value for the type. Can be used in `const` contexts.
+    const INT: T;
 }