src/TraitExpressionBuilder.ts

@@ -5,75 +5,60 @@ 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>[],
 > {
+    declare ["constructor"]: typeof TraitExpressionBuilder
+
     constructor(
         readonly expressionSuperclass:  Superclass,
         readonly expressionTraits:      Traits,
     ) {}
 
+
+    static spreadSupertraits<
+        const T extends Trait<
+            TraitExpression<
+                typeof TraitExpression.NullSuperclass,
+                Trait<any, any, any, any>[]
+            >,
+            any,
+            any,
+            any
+        >[]
+    >(
+        traits: T
+    ) {
+        return traits.flatMap(trait => [
+            ...trait.superExpression.traits,
+            trait,
+        ]) as TraitExpressionBuilder.SpreadSupertraits<T>
+    }
+
+    static uniqTraits<
+        const T extends Trait<
+            TraitExpression<
+                typeof TraitExpression.NullSuperclass,
+                Trait<any, any, any, any>[]
+            >,
+            any,
+            any,
+            any
+        >[]
+    >(
+        traits: T
+    ) {
+        return uniq(traits) as TraitExpressionBuilder.UniqTraits<T>
+    }
+
+
     extends<
         Super extends AbstractClass<object>
     >(
         superclass: Super
     ) {
-        return new TraitExpressionBuilder(
+        return new this.constructor(
             superclass,
             this.expressionTraits,
         )
@@ -92,16 +77,13 @@ export class TraitExpressionBuilder<
     >(
         ...traits: T
     ) {
-        return new TraitExpressionBuilder(
+        return new this.constructor(
             this.expressionSuperclass,
 
-            uniq([
+            this.constructor.uniqTraits([
                 ...this.expressionTraits,
-                ...traits.flatMap(trait => [
+                ...this.constructor.spreadSupertraits(traits),
-                    ...trait.superExpression.traits,
-                    trait,
             ]),
-            ]) as TraitsUniq<[...Traits, ...SpreadSupertraits<T>]>,
         )
     }
 
@@ -118,24 +100,22 @@ export class TraitExpressionBuilder<
     >(
         ...traits: T
     ) {
-        return new TraitExpressionBuilder(
+        return new this.constructor(
             this.expressionSuperclass,
 
-            uniq([
+            this.constructor.uniqTraits([
-                ...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 +134,59 @@ 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 UniqTraits<Traits> = (
+        Traits extends [
+            ...infer Rest,
+            infer El extends Trait<any, any, any, any>,
+        ]
+            ? IsTraitInTupleFromRight<Rest, El> extends true
+                ? UniqTraits<Rest>
+                : [...UniqTraits<Rest>, El]
+            : []
+    )
+    type IsTraitInTupleFromRight<Traits, T> = (
+        Traits extends [...infer Rest, infer El]
+            ? IsEqual<El, T> extends true
+                ? true
+                : IsTraitInTupleFromRight<Rest, T>
+            : false
+    )
+
+    export 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 const expression = new TraitExpressionBuilder(TraitExpression.NullSuperclass, [])

src/tests.ts

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