package.json

@@ -1,6 +1,6 @@
 {
   "name": "@thilawyn/traitify-ts",
-  "version": "0.1.10",
+  "version": "0.1.11",
   "type": "module",
   "publishConfig": {
     "registry": "https://git.jvalver.de/api/packages/thilawyn/npm/"
@@ -29,7 +29,7 @@
   },
   "dependencies": {
     "lodash-es": "^4.17.21",
-    "type-fest": "^4.10.2"
+    "type-fest": "^4.10.3"
   },
   "devDependencies": {
     "@rollup/plugin-node-resolve": "^15.2.3",

src/Trait.ts

@@ -6,7 +6,7 @@ import { Extend, StaticMembers } from "./util"
 export class Trait<
     SuperExpression extends TraitExpression<
         typeof TraitExpression.NullSuperclass,
-        Trait<any, any, any, any>[]
+        readonly Trait<any, any, any, any>[]
     >,
     Abstract        extends object,
     StaticAbstract  extends object,

src/TraitBuilder.ts

@@ -6,44 +6,18 @@ import { Extend, StaticMembers } from "./util"
 
 declare const implSuperSymbol: unique symbol
 
-type ImplSuper<This> = (
-    This extends TraitBuilder<
-        any,
-        infer Abstract,
-        infer StaticAbstract,
-        infer ImplClass
-    >
-        ? (
-            AbstractClass<
-                Simplify<
-                    Extend<[
-                        Abstract,
-                        InstanceType<ImplClass>,
-                    ]>
-                >
-            > &
-
-            Simplify<
-                Extend<[
-                    StaticAbstract,
-                    StaticMembers<ImplClass>,
-                ]>
-            > &
-            { readonly [implSuperSymbol]: true }
-        )
-        : never
-)
-
 
 export class TraitBuilder<
     SuperExpression extends TraitExpression<
         typeof TraitExpression.NullSuperclass,
-        Trait<any, any, any, any>[]
+        readonly Trait<any, any, any, any>[]
     >,
     Abstract        extends object,
     StaticAbstract  extends object,
     ImplClass       extends AbstractClass<object, []>,
 > {
+    declare ["constructor"]: typeof TraitBuilder
+
     constructor(
         readonly traitSuperExpression:  SuperExpression,
         readonly traitAbstract:         Abstract,
@@ -51,10 +25,11 @@ export class TraitBuilder<
         readonly traitApply:            (Super: AbstractClass<object>) => ImplClass,
     ) {}
 
+
     abstract<A extends Abstract>(
         _: (Super: AbstractClass<Abstract>) => AbstractClass<A, []>
     ) {
-        return new TraitBuilder(
+        return new this.constructor(
             this.traitSuperExpression,
             {} as Simplify<A>,
             this.traitStaticAbstract,
@@ -65,7 +40,7 @@ export class TraitBuilder<
     staticAbstract<A extends StaticAbstract>(
         _: (Super: AbstractClass<StaticAbstract>) => AbstractClass<A, []>
     ) {
-        return new TraitBuilder(
+        return new this.constructor(
             this.traitSuperExpression,
             this.traitAbstract,
             {} as Simplify<A>,
@@ -74,11 +49,11 @@ export class TraitBuilder<
     }
 
     implement<
-        ImplClassWithAbstract extends ImplSuper<typeof this>  // TODO: find a way to set the constraint to concrete classes while keeping the Super arg as an abstract class
+        ImplClassWithAbstract extends TraitBuilder.ImplSuper<typeof this>  // TODO: find a way to set the constraint to concrete classes while keeping the Super arg as an abstract class
     >(
-        apply: (Super: ImplSuper<typeof this>) => ImplClassWithAbstract
+        apply: (Super: TraitBuilder.ImplSuper<typeof this>) => ImplClassWithAbstract
     ) {
-        return new TraitBuilder(
+        return new this.constructor(
             this.traitSuperExpression,
             this.traitAbstract,
             this.traitStaticAbstract,
@@ -103,6 +78,7 @@ export class TraitBuilder<
         )
     }
 
+
     build() {
         return new Trait(
             this.traitSuperExpression,
@@ -113,6 +89,37 @@ export class TraitBuilder<
     }
 }
 
+export namespace TraitBuilder {
+    export type ImplSuper<This> = (
+        This extends TraitBuilder<
+            any,
+            infer Abstract,
+            infer StaticAbstract,
+            infer ImplClass
+        >
+            ? (
+                AbstractClass<
+                    Simplify<
+                        Extend<[
+                            Abstract,
+                            InstanceType<ImplClass>,
+                        ]>
+                    >
+                > &
+
+                Simplify<
+                    Extend<[
+                        StaticAbstract,
+                        StaticMembers<ImplClass>,
+                    ]>
+                > &
+                { readonly [implSuperSymbol]: true }
+            )
+            : never
+    )
+}
+
+
 export const trait = new TraitBuilder(
     new TraitExpression(TraitExpression.NullSuperclass, []),
     {} as object,

src/TraitExpression.ts

@@ -6,7 +6,7 @@ import { Extend, StaticMembers } from "./util"
 
 export class TraitExpression<
     Superclass   extends AbstractClass<object>,
-    const Traits extends Trait<any, any, any, any>[],
+    const Traits extends readonly Trait<any, any, any, any>[],
 > {
     constructor(
         readonly superclass:  Superclass,
@@ -95,7 +95,7 @@ export namespace TraitExpression {
 
 
 export type Implements<
-    Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
+    Exp extends TraitExpression<any, readonly Trait<any, any, any, any>[]>
 > = (
     Simplify<
         Extend<
@@ -107,7 +107,7 @@ export type Implements<
 )
 
 export type StaticImplements<
-    Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
+    Exp extends TraitExpression<any, readonly Trait<any, any, any, any>[]>
 > = (
     Simplify<
         Extend<
@@ -120,7 +120,7 @@ export type StaticImplements<
 
 
 export type TraitExpressionClass<
-    Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
+    Exp extends TraitExpression<any, readonly Trait<any, any, any, any>[]>
 > = (
     AbstractClass<
         TraitExpressionInstance<Exp>,
@@ -130,7 +130,7 @@ export type TraitExpressionClass<
 )
 
 export type TraitExpressionConcreteClass<
-    Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
+    Exp extends TraitExpression<any, readonly Trait<any, any, any, any>[]>
 > = (
     Class<
         TraitExpressionInstance<Exp>,
@@ -140,7 +140,7 @@ export type TraitExpressionConcreteClass<
 )
 
 export type TraitExpressionInstance<
-    Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
+    Exp extends TraitExpression<any, readonly Trait<any, any, any, any>[]>
 > = (
     InstanceType<TraitExpression.Superclass<Exp>> &  // Keep the instance of the superclass outside of any kind of type manipulation
                                                      // as it can accidentely remove abstract properties
@@ -152,7 +152,7 @@ export type TraitExpressionInstance<
 )
 
 export type TraitExpressionStaticMembers<
-    Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
+    Exp extends TraitExpression<any, readonly Trait<any, any, any, any>[]>
 > = (
     Simplify<
         Extend<[

src/TraitExpressionBuilder.ts

@@ -5,85 +5,70 @@ import { TraitExpression } from "./TraitExpression"
 import { Extendable, StaticMembers } from "./util"
 
 
-type SpreadSupertraits<Traits> = (
-    Traits extends [
-        infer El extends Trait<any, any, any, any>,
-        ...infer Rest,
-    ]
-        ? [
-            ...Trait.Supertraits<El>,
-            El,
-            ...SpreadSupertraits<Rest>,
-        ]
-        : []
-)
-
-type TraitsUniq<Traits> = (
-    Traits extends [
-        ...infer Rest,
-        infer El extends Trait<any, any, any, any>,
-    ]
-        ? IsTraitInTupleFromRight<Rest, El> extends true
-            ? TraitsUniq<Rest>
-            : [...TraitsUniq<Rest>, El]
-        : []
-)
-type IsTraitInTupleFromRight<Traits, T> = (
-    Traits extends [...infer Rest, infer El]
-        ? IsEqual<El, T> extends true
-            ? true
-            : IsTraitInTupleFromRight<Rest, T>
-        : false
-)
-
-
-type BuildTraitExpression<
-    Superclass extends AbstractClass<object>,
-    Traits     extends Trait<any, any, any, any>[],
-> = (
-    Extendable<TraitTuple.MapAbstract<Traits>> extends false
-        ? "Type conflict between the traits abstract definitions."
-        : Extendable<TraitTuple.MapStaticAbstract<Traits>> extends false
-            ? "Type conflict between the traits static abstract definitions."
-            : Extendable<[
-                InstanceType<Superclass>,
-                ...TraitTuple.MapImplInstance<Traits>,
-            ]> extends false
-                ? "Type conflict between the traits implementation instance and/or the superclass instance."
-                : Extendable<[
-                    StaticMembers<Superclass>,
-                    ...TraitTuple.MapImplStaticMembers<Traits>,
-                ]> extends false
-                    ? "Type conflict between the traits implementation static members and/or the superclass static members."
-                    : TraitExpression<Superclass, Traits>
-)
-
-
 export class TraitExpressionBuilder<
     Superclass   extends AbstractClass<object>,
-    const Traits extends Trait<any, any, any, any>[],
+    const Traits extends readonly Trait<any, any, any, any>[],
 > {
+    declare ["constructor"]: typeof TraitExpressionBuilder
+
     constructor(
         readonly expressionSuperclass:  Superclass,
         readonly expressionTraits:      Traits,
     ) {}
 
+
+    static spreadSupertraits<
+        const T extends readonly Trait<
+            TraitExpression<
+                typeof TraitExpression.NullSuperclass,
+                readonly Trait<any, any, any, any>[]
+            >,
+            any,
+            any,
+            any
+        >[]
+    >(
+        traits: T
+    ) {
+        return traits.flatMap(trait => [
+            ...trait.superExpression.traits,
+            trait,
+        ]) as TraitExpressionBuilder.SpreadSupertraits<T>
+    }
+
+    static traitsUniq<
+        const T extends readonly Trait<
+            TraitExpression<
+                typeof TraitExpression.NullSuperclass,
+                readonly Trait<any, any, any, any>[]
+            >,
+            any,
+            any,
+            any
+        >[]
+    >(
+        traits: T
+    ) {
+        return uniq(traits) as TraitExpressionBuilder.TraitsUniq<T>
+    }
+
+
     extends<
         Super extends AbstractClass<object>
     >(
         superclass: Super
     ) {
-        return new TraitExpressionBuilder(
+        return new this.constructor(
             superclass,
             this.expressionTraits,
         )
     }
 
     expresses<
-        const T extends Trait<
+        const T extends readonly Trait<
             TraitExpression<
                 typeof TraitExpression.NullSuperclass,
-                Trait<any, any, any, any>[]
+                readonly Trait<any, any, any, any>[]
             >,
             any,
             any,
@@ -91,25 +76,25 @@ export class TraitExpressionBuilder<
         >[]
     >(
         ...traits: T
-    ) {
+    ): TraitExpressionBuilder<
-        return new TraitExpressionBuilder(
+        Superclass,
+        TraitExpressionBuilder.ExpressesReturnTypeTraits<Traits, T>
+    > {
+        return new this.constructor(
             this.expressionSuperclass,
 
-            uniq([
+            this.constructor.traitsUniq([
                 ...this.expressionTraits,
-                ...traits.flatMap(trait => [
+                ...this.constructor.spreadSupertraits(traits),
-                    ...trait.superExpression.traits,
+            ]),
-                    trait,
-                ]),
-            ]) as TraitsUniq<[...Traits, ...SpreadSupertraits<T>]>,
         )
     }
 
     expressesFirst<
-        const T extends Trait<
+        const T extends readonly Trait<
             TraitExpression<
                 typeof TraitExpression.NullSuperclass,
-                Trait<any, any, any, any>[]
+                readonly Trait<any, any, any, any>[]
             >,
             any,
             any,
@@ -117,25 +102,26 @@ export class TraitExpressionBuilder<
         >[]
     >(
         ...traits: T
-    ) {
+    ): TraitExpressionBuilder<
-        return new TraitExpressionBuilder(
+        Superclass,
+        TraitExpressionBuilder.ExpressesFirstReturnTypeTraits<Traits, T>
+    > {
+        return new this.constructor(
             this.expressionSuperclass,
 
-            uniq([
+            this.constructor.traitsUniq([
-                ...traits.flatMap(trait => [
+                ...this.constructor.spreadSupertraits(traits),
-                    ...trait.superExpression.traits,
-                    trait,
-                ]),
                 ...this.expressionTraits,
-            ]) as TraitsUniq<[...SpreadSupertraits<T>, ...Traits]>,
+            ]),
         )
     }
 
+
     build() {
         return new TraitExpression(
             this.expressionSuperclass,
             this.expressionTraits,
-        ) as BuildTraitExpression<Superclass, Traits>
+        ) as TraitExpressionBuilder.BuildTraitExpression<Superclass, Traits>
     }
 
     then<V>(fn: (expression: ReturnType<typeof this.build>) => V): V {
@@ -154,4 +140,79 @@ export class TraitExpressionBuilder<
     }
 }
 
+export namespace TraitExpressionBuilder {
+    export type SpreadSupertraits<Traits> = (
+        Traits extends [
+            infer El extends Trait<any, any, any, any>,
+            ...infer Rest,
+        ]
+            ? [
+                ...Trait.Supertraits<El>,
+                El,
+                ...SpreadSupertraits<Rest>,
+            ]
+            : []
+    )
+
+    export type TraitsUniq<Traits> = (
+        Traits extends [
+            ...infer Rest,
+            infer El extends Trait<any, any, any, any>,
+        ]
+            ? IsTraitInTupleFromRight<Rest, El> extends true
+                ? TraitsUniq<Rest>
+                : [...TraitsUniq<Rest>, El]
+            : []
+    )
+    type IsTraitInTupleFromRight<Traits, T> = (
+        Traits extends [...infer Rest, infer El]
+            ? IsEqual<El, T> extends true
+                ? true
+                : IsTraitInTupleFromRight<Rest, T>
+            : false
+    )
+
+    export type ExpressesReturnTypeTraits<
+        Traits extends readonly Trait<any, any, any, any>[],
+        T      extends readonly Trait<any, any, any, any>[],
+    > = (
+        TraitExpressionBuilder.TraitsUniq<[
+            ...Traits,
+            ...TraitExpressionBuilder.SpreadSupertraits<T>,
+        ]>
+    )
+
+    export type ExpressesFirstReturnTypeTraits<
+        Traits extends readonly Trait<any, any, any, any>[],
+        T      extends readonly Trait<any, any, any, any>[],
+    > = (
+        TraitExpressionBuilder.TraitsUniq<[
+            ...TraitExpressionBuilder.SpreadSupertraits<T>,
+            ...Traits,
+        ]>
+    )
+
+    export type BuildTraitExpression<
+        Superclass extends AbstractClass<object>,
+        Traits     extends readonly Trait<any, any, any, any>[],
+    > = (
+        Extendable<TraitTuple.MapAbstract<Traits>> extends false
+            ? "Type conflict between the traits abstract definitions."
+            : Extendable<TraitTuple.MapStaticAbstract<Traits>> extends false
+                ? "Type conflict between the traits static abstract definitions."
+                : Extendable<[
+                    InstanceType<Superclass>,
+                    ...TraitTuple.MapImplInstance<Traits>,
+                ]> extends false
+                    ? "Type conflict between the traits implementation instance and/or the superclass instance."
+                    : Extendable<[
+                        StaticMembers<Superclass>,
+                        ...TraitTuple.MapImplStaticMembers<Traits>,
+                    ]> extends false
+                        ? "Type conflict between the traits implementation static members and/or the superclass static members."
+                        : TraitExpression<Superclass, Traits>
+    )
+}
+
+
 export const expression = new TraitExpressionBuilder(TraitExpression.NullSuperclass, [])

src/tests.ts

@@ -64,6 +64,7 @@ const exp = expression
         PrintsHelloOnNew,
         Identifiable<bigint>(),
         // Identifiable<number>(),
+        // StatefulSubscription,
         ActiveStatefulSubscription,
     )
     .build()