up

src/dependency/Supported.ts

@@ -1,3 +1,5 @@
+import { isNonNullObject } from "../utils/isNonNullObject.js"
+
 export type Supported<T> = {
   "@type": "Supported"
   content: T
@@ -11,3 +13,7 @@ export function Supported<T>(content: T, supports: Set<string>): Supported<T> {
     supports,
   }
 }
+
+export function isSupported(x: any): x is Supported<any> {
+  return isNonNullObject(x) && x["@type"] === "Supported"
+}

src/merge/merge.ts

@@ -1,4 +1,5 @@
 import { isNothing } from "../cell/index.js"
+import { isSupported, supportedMerge } from "../dependency/index.js"
 import { defineGeneric, defineHandler } from "../generic/index.js"
 import {
   intervalContainsNumber,
@@ -65,3 +66,5 @@ defineHandler(merge, [isInterval, isNumber], (content, increment) =>
 defineHandler(merge, [isNumber, isInterval], (content, increment) =>
   intervalContainsNumber(increment, content) ? content : theContradiction,
 )
+
+defineHandler(merge, [isSupported, isSupported], supportedMerge)

src/utils/Set.ts

@@ -20,7 +20,7 @@ export function setIsSupersetOf<T>(x: Set<T>, y: Set<T>): boolean {
   return setIsSubsetOf(y, x)
 }
 
-export function setIsDisjointFrom(x: Set<T>, y: Set<T>): boolean {
+export function setIsDisjointFrom<T>(x: Set<T>, y: Set<T>): boolean {
   for (const e of x) {
     if (y.has(e)) {
       return false