Runtime Work

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/P4/Support.swift

@@ -0,0 +1,55 @@
+public struct Error: Equatable {
+    public private(set) var msg: String
+
+    public init(withMessage msg: String) {
+        self.msg = msg
+    }
+}
+
+public struct Nothing: CustomStringConvertible {
+    public var description: String {
+        return "Nothing"
+    }
+
+    public init() {}
+}
+
+
+public enum Result<T>: Equatable, CustomStringConvertible {
+    case Ok(T)
+    case Error(Error)
+
+    public static func == (lhs: Result, rhs: Result) -> Bool {
+        switch (lhs, rhs) {
+        case (Ok, Ok):
+            return true
+        case (Error(let le), Error(let re)):
+            return le.msg == re.msg
+        default:
+            return false
+        }
+    }
+
+    public func error() -> Error? {
+        if case Result.Error(let e) = self {
+            return e
+        }
+        return nil
+    }
+
+    public var description: String {
+        switch self {
+            case Result.Error(let e):
+                return e.msg
+            case Result.Ok(let o):
+                return "\(o)"
+        }
+    }
+}
+
+@freestanding(expression) public macro RequireOkResult<T>(_: Result<T>) -> Bool =
+    #externalMacro(module: "P4Macros", type: "RequireResult")
+@freestanding(expression) public macro RequireErrorResult<T>(_: Error, _: Result<T>) -> Bool =
+    #externalMacro(module: "P4Macros", type: "RequireErrorResult")
+@freestanding(expression) public macro UseOkResult<T>(_: Result<T>) -> T =
+    #externalMacro(module: "P4Macros", type: "UseOkResult")