Added Strideable stubs to Failable<Strideable, T> type

Sources/Validation/Failable+Helpers/Failable+Strideable.swift

@@ -0,0 +1,56 @@
+extension Failable where T: Strideable {
+    
+    /// See [`Strideable.Stride`](https://developer.apple.com/documentation/swift/strideable/1541220-stride).
+    public typealias Stride = T.Stride
+    
+    /// See [`Strideable.advance(by:)`](https://developer.apple.com/documentation/swift/strideable/1641148-advanced).
+    public func advance(by n: Stride)throws -> Failable<T, Validations> {
+        return try Failable(self.value.advanced(by: n))
+    }
+    
+    /// See [`Strideable.distance(to:)`](https://developer.apple.com/documentation/swift/strideable/1641148-advanced).
+    public func distance(to other: Failable<T, Validations>) -> Stride {
+        return self.value.distance(to: other.value)
+    }
+    
+    /// See [`Strideable.+(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2885404).
+    public static func + (lhs: Failable<T, Validations>, rhs: Stride)throws -> Failable<T, Validations> {
+        return try lhs.advance(by: rhs)
+    }
+    
+    /// See [`Strideable.+(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2886679).
+    public static func + (lhs: Stride, rhs: Failable<T, Validations>)throws -> Failable<T, Validations> {
+        return try rhs.advance(by: lhs)
+    }
+    
+    /// See [`Strideable.+=(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2884440).
+    public static func += (lhs: inout Failable<T, Validations>, rhs: Stride)throws {
+        try lhs <~ lhs.advance(by: rhs).value
+    }
+    
+    /// See [`Strideable.-(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2884623).
+    public static func - (lhs: Failable<T, Validations>, rhs: Stride)throws -> Failable<T, Validations> {
+        return try lhs.advance(by: -rhs)
+    }
+    
+    /// See [`Strideable.-(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2886160).
+    public static func - (lhs: Failable<T, Validations>, rhs: Failable<T, Validations>) -> Stride {
+        return rhs.distance(to: lhs)
+    }
+    
+    /// See [`Strideable.-=(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2885177).
+    public static func -= (lhs: inout Failable<T, Validations>, rhs: Stride)throws {
+        try lhs <~ lhs.advance(by: -rhs).value
+    }
+}
+
+extension Failable where T: Strideable, T.Stride: SignedInteger {
+    
+    /// See [`Stridable....(_:_:)`](https://developer.apple.com/documentation/swift/strideable/2950083).
+    public static func ... (
+        lhs: Failable<T, Validations>,
+        rhs: Failable<T, Validations>
+    )throws -> Failable<ClosedRange<T>, ElementValidation<ClosedRange<T>, Validations>> {
+        return try (lhs.value...rhs.value).failable()
+    }
+}