src/abstract.ts

@@ -3,6 +3,10 @@ import { Opaque } from "type-fest"
 
 export type AbstractTag = "@thilawyn/traitify-ts/Abstract"
 
-export function abstract<Abstract extends object = {}>() {
-    return {} as Opaque<Abstract, AbstractTag>
+export function abstract<
+    Abstract extends {} = {}
+>(): (
+    Opaque<Abstract, AbstractTag>
+) {
+    return undefined as any
 }

src/tests.ts

@@ -1,41 +1,44 @@
-import { Implements, TraitAbstractMembers, expression, trait } from "."
+import { Implements, TraitAbstractMembers, abstract, expression, trait } from "."
 
 
-const PrintsHelloOnNew = trait()(Super =>
-    class PrintsHelloOnNew extends Super {
+const PrintsHelloOnNew = trait(
+    abstract(),
+    Super => class PrintsHelloOnNew extends Super {
         constructor(...args: any[]) {
             super(...args)
             console.log("Hello!")
         }
-    }
+    },
 )
 
-const Identifiable = <ID>() => (
-    trait<{ readonly id: ID }>()(Super =>
-        class Identifiable extends Super {
-            equals(el: Identifiable) {
-                return this.id === el.id
-            }
+const Identifiable = <ID>() => trait(
+    abstract<{ readonly id: ID }>(),
+    Super => class Identifiable extends Super {
+        equals(el: Identifiable) {
+            return this.id === el.id
         }
-    )
+    },
 )
 
-const StatefulSubscription = trait<{
-    readonly status: (
-        { _tag: "awaitingPayment" } |
-        { _tag: "active", activeSince: Date, expiresAt?: Date } |
-        { _tag: "expired", expiredSince: Date }
-    )
-}>()(Super =>
-    class StatefulSubscription extends Super {}
+const StatefulSubscription = trait(
+    abstract<{
+        readonly status: (
+            { _tag: "awaitingPayment" } |
+            { _tag: "active", activeSince: Date, expiresAt?: Date } |
+            { _tag: "expired", expiredSince: Date }
+        )
+    }>(),
+
+    Super => class StatefulSubscription extends Super {},
 )
 
 interface ActiveStatefulSubscriptionAbstractMembers extends TraitAbstractMembers<typeof StatefulSubscription> {
     readonly status: { _tag: "active", activeSince: Date, expiresAt?: Date }
 }
 
-const ActiveStatefulSubscription = trait<ActiveStatefulSubscriptionAbstractMembers>()(Super =>
-    class ActiveStatefulSubscription extends Super {}
+const ActiveStatefulSubscription = trait(
+    abstract<ActiveStatefulSubscriptionAbstractMembers>(),
+    Super => class ActiveStatefulSubscription extends Super {},
 )
 
 

src/trait.ts

@@ -1,6 +1,7 @@
 import { Fn } from "hotscript"
 import { AbstractClass, Class, Opaque } from "type-fest"
 import { StaticMembers } from "./util"
+import { AbstractTag } from "."
 
 
 type AddAbstractToImpl<
@@ -105,14 +106,16 @@ export type TraitApplier<
 )
 
 export function trait<
-    Abstract extends object = {}
->(): (
-    <ImplWithAbstract extends Class<Abstract, []>>(
-        apply: TraitApplier<Abstract, ImplWithAbstract>
-    ) => Trait<
-        Abstract,
-        RemoveAbstractFromImpl<ImplWithAbstract, Abstract>
-    >
-) {
-    return apply => ({ apply }) as any
+    Abstract         extends {},
+    ImplWithAbstract extends Class<Abstract, []>,
+>(
+    abstract: Opaque<Abstract, AbstractTag>,
+    apply: (Super: Opaque<AbstractClass<Abstract>, TraitApplierSuperTag>) => (
+        Opaque<ImplWithAbstract, TraitApplierSuperTag>
+    ),
+): Trait<
+    Abstract,
+    RemoveAbstractFromImpl<ImplWithAbstract, Abstract>
+> {
+    return { apply } as any
 }