Added Neg operator for i*. (#3624)

corelib/src/integer.cairo

@@ -1929,6 +1929,13 @@ impl I8SubEq of SubEq<i8> {
     }
 }
 
+impl I8Neg of Neg<i8> {
+    #[inline(always)]
+    fn neg(a: i8) -> i8 {
+        0 - a
+    }
+}
+
 extern fn i8_wide_mul(lhs: i8, rhs: i8) -> i16 implicits() nopanic;
 impl I8Mul of Mul<i8> {
     fn mul(lhs: i8, rhs: i8) -> i8 {
@@ -2021,6 +2028,13 @@ impl I16SubEq of SubEq<i16> {
     }
 }
 
+impl I16Neg of Neg<i16> {
+    #[inline(always)]
+    fn neg(a: i16) -> i16 {
+        0 - a
+    }
+}
+
 extern fn i16_wide_mul(lhs: i16, rhs: i16) -> i32 implicits() nopanic;
 impl I16Mul of Mul<i16> {
     fn mul(lhs: i16, rhs: i16) -> i16 {
@@ -2113,6 +2127,13 @@ impl I32SubEq of SubEq<i32> {
     }
 }
 
+impl I32Neg of Neg<i32> {
+    #[inline(always)]
+    fn neg(a: i32) -> i32 {
+        0 - a
+    }
+}
+
 extern fn i32_wide_mul(lhs: i32, rhs: i32) -> i64 implicits() nopanic;
 impl I32Mul of Mul<i32> {
     fn mul(lhs: i32, rhs: i32) -> i32 {
@@ -2205,6 +2226,13 @@ impl I64SubEq of SubEq<i64> {
     }
 }
 
+impl I64Neg of Neg<i64> {
+    #[inline(always)]
+    fn neg(a: i64) -> i64 {
+        0 - a
+    }
+}
+
 extern fn i64_wide_mul(lhs: i64, rhs: i64) -> i128 implicits() nopanic;
 impl I64Mul of Mul<i64> {
     fn mul(lhs: i64, rhs: i64) -> i64 {
@@ -2297,6 +2325,12 @@ impl I128SubEq of SubEq<i128> {
     }
 }
 
+impl I128Neg of Neg<i128> {
+    #[inline(always)]
+    fn neg(a: i128) -> i128 {
+        0 - a
+    }
+}
 
 /// If `lhs` >= `rhs` returns `Ok(lhs - rhs)` else returns `Err(2**128 + lhs - rhs)`.
 extern fn i128_diff(lhs: i128, rhs: i128) -> Result<u128, u128> implicits(RangeCheck) nopanic;