ir: moving to labeled chunks, no more IRLabel nodes

codeCore/src/prog8/code/Either.kt

@@ -0,0 +1,24 @@
+package prog8.code
+
+/**
+ * By convention, the right side of an `Either` is used to hold successful values.
+ */
+sealed class Either<out L, out R> {
+
+    data class Left<out L>(val value: L) : Either<L, Nothing>()
+
+    data class Right<out R>(val value: R) : Either<Nothing, R>()
+
+    fun isRight() = this is Right<R>
+
+    fun isLeft() = this is Left<L>
+
+    inline fun <C> fold(ifLeft: (L) -> C, ifRight: (R) -> C): C = when (this) {
+        is Right -> ifRight(value)
+        is Left -> ifLeft(value)
+    }
+
+}
+
+fun <L> left(a: L) = Either.Left(a)
+fun <R> right(b: R) = Either.Right(b)