src/TraitExpression.ts

@@ -7,19 +7,21 @@ import { ExtendFn, ExtendableFn, SimplifyFn, StaticMembersFn } from "./util"
 export class TraitExpressionNullSuperclass {}
 
 export class TraitExpression<
-    Super  extends AbstractClass<{}>,
-    Traits extends Trait<any, any, any>[],
+    Super     extends AbstractClass<{}>,
+    OwnTraits extends Trait<any, any, any>[],
+    AllTraits extends Trait<any, any, any>[],
 > {
     constructor(
         readonly superclass:  Super,
-        readonly traits:      Traits,
+        readonly ownTraits:   OwnTraits,
+        readonly allTraits:   AllTraits,
     ) {}
 
     get extends(): (
         AbstractClass<
             Pipe<[
                 InstanceType<Super>,
-                ...Call<Tuples.Map<TraitOwnImplInstanceFn>, Traits>,
+                ...Call<Tuples.Map<TraitOwnImplInstanceFn>, OwnTraits>,
             ], [
                 ExtendFn,
                 SimplifyFn,
@@ -30,14 +32,14 @@ export class TraitExpression<
 
         Pipe<[
             Super,
-            ...Call<Tuples.Map<TraitOwnImplClassFn>, Traits>,
+            ...Call<Tuples.Map<TraitOwnImplClassFn>, OwnTraits>,
         ], [
             Tuples.Map<StaticMembersFn>,
             ExtendFn,
             SimplifyFn,
         ]>
     ) {
-        return this.traits.reduce(
+        return this.ownTraits.reduce(
             (previous, trait) => trait.apply(previous),
             this.superclass as Opaque<Super, TraitApplierSuperTag>,
         ) as any
@@ -60,7 +62,11 @@ export class TraitExpression<
     }
 }
 
-export const emptyTraitExpression = new TraitExpression(TraitExpressionNullSuperclass, [] as const)
+export const emptyTraitExpression = new TraitExpression(
+    TraitExpressionNullSuperclass,
+    [] as const,
+    [] as const,
+)
 
 interface PrependTraitSupertraitsFn extends Fn {
     return: this["arg0"] extends Trait<any, any, any>
@@ -95,93 +101,3 @@ export type Implements<Exp extends TraitExpression<any, any>> = (
         ]>
         : never
 )
-
-
-class TraitExpressionBuilder<
-    Super  extends AbstractClass<{}>,
-    Traits extends Trait<any, any, any>[],
-> {
-    constructor(public expression: TraitExpression<Super, Traits>) {}
-
-    extends<
-        NewSuper extends AbstractClass<any>
-    >(superclass: NewSuper) {
-        return new TraitExpressionBuilder(
-            new TraitExpression(
-                superclass,
-                this.expression.traits,
-            )
-        )
-    }
-
-    expresses<
-        AppendTraits extends Trait<any, any, any>[]
-    >(...traits: AppendTraits) {
-        return new TraitExpressionBuilder(
-            new TraitExpression(
-                this.expression.superclass,
-                [...this.expression.traits, ...traits] as const,
-            )
-        )
-    }
-
-    get() {
-        return this.expression as GetTraitExpression<Super, Traits>
-    }
-
-    then<V>(fn: (expression: ReturnType<typeof this.get>) => V): V {
-        return fn(this.get())
-    }
-}
-
-
-type AbstractMembersExtendable<
-    Super  extends AbstractClass<{}>,
-    Traits extends Trait<any, any, any>[],
-> = (
-    Call<ExtendableFn, [
-        InstanceType<Super>,
-        ...Call<Tuples.Map<TraitOwnAbstractFn>, Traits>,
-    ]>
-)
-
-type ImplInstanceExtendable<
-    Super  extends AbstractClass<{}>,
-    Traits extends Trait<any, any, any>[],
-> = (
-    Call<ExtendableFn, [
-        InstanceType<Super>,
-        ...Call<Tuples.Map<TraitOwnImplInstanceFn>, Traits>,
-    ]>
-)
-
-type ImplStaticMembersExtendable<
-    Super  extends AbstractClass<{}>,
-    Traits extends Trait<any, any, any>[],
-> = (
-    Pipe<[
-        Super,
-        ...Call<Tuples.Map<TraitOwnImplClassFn>, Traits>,
-    ], [
-        Tuples.Map<StaticMembersFn>,
-        ExtendableFn,
-    ]>
-)
-
-type GetTraitExpression<
-    Super  extends AbstractClass<{}>,
-    Traits extends Trait<any, any, any>[],
-> = (
-    Call<Tuples.IsEmpty, Traits> extends true
-        ? "Cannot express an empty list of traits."
-        : AbstractMembersExtendable<Super, Traits> extends false
-            ? "Type conflict between the traits abstract members and/or the superclass instance."
-            : ImplInstanceExtendable<Super, Traits> extends false
-                ? "Type conflict between the traits implementation instances and/or the superclass instance."
-                : ImplStaticMembersExtendable<Super, Traits> extends false
-                    ? "Type conflict between the traits implementation static members and/or the superclass static members."
-                    : TraitExpression<Super, Traits>
-)
-
-
-export const expression = new TraitExpressionBuilder(emptyTraitExpression)

src/TraitExpressionBuilder.ts

@@ -0,0 +1,134 @@
+import { Call, Fn, Pipe, Tuples } from "hotscript"
+import { AbstractClass } from "type-fest"
+import { Trait, TraitExpression, TraitOwnAbstractFn, TraitOwnImplClassFn, TraitOwnImplInstanceFn, TraitSupertraitsFn, emptyTraitExpression } from "."
+import { ExtendableFn, StaticMembersFn } from "./util"
+
+
+class TraitExpressionBuilder<
+    Super     extends AbstractClass<{}>,
+    OwnTraits extends Trait<any, any, any>[],
+    AllTraits extends Trait<any, any, any>[],
+> {
+    constructor(public expression: TraitExpression<Super, OwnTraits, AllTraits>) {}
+
+    extends<
+        NewSuper extends AbstractClass<any>
+    >(superclass: NewSuper) {
+        return new TraitExpressionBuilder(
+            new TraitExpression(
+                superclass,
+                this.expression.ownTraits,
+                this.expression.allTraits,
+            )
+        )
+    }
+
+    expresses<
+        Traits extends Trait<any, any, any>[]
+    >(
+        ...traits: Traits
+    ) {
+        return new TraitExpressionBuilder(
+            new TraitExpression(
+                this.expression.superclass,
+                [...this.expression.ownTraits, ...traits] as const,
+                [
+                    ...this.expression.allTraits,
+                    ...this.spreadSupertraits(traits) as SpreadTraitsHierarchy<Traits>,
+                ] as const,
+            )
+        )
+    }
+
+    private spreadSupertraits<
+        Traits extends Trait<
+            TraitExpression<any, any, Trait<any, any, any>[]>,
+            any,
+            any
+        >[]
+    >(
+        traits: Traits
+    ) {
+        return traits.flatMap(trait => [
+            ...trait.superExpression.allTraits,
+            trait,
+        ])
+    }
+
+    get() {
+        return this.expression as GetTraitExpression<Super, OwnTraits, AllTraits>
+    }
+
+    then<V>(fn: (expression: ReturnType<typeof this.get>) => V): V {
+        return fn(this.get())
+    }
+}
+
+
+type SpreadTraitsHierarchy<Traits extends Trait<any, any, any>[]> = (
+    Call<
+        Tuples.FlatMap<PrependTraitSupertraitsFn>,
+        Traits
+    >
+)
+interface PrependTraitSupertraitsFn extends Fn {
+    return: this["arg0"] extends Trait<any, any, any>
+        ? [
+            ...Call<TraitSupertraitsFn, this["arg0"]>,
+            this["arg0"],
+        ]
+        : never
+}
+
+
+type AbstractMembersExtendable<
+    Super  extends AbstractClass<{}>,
+    Traits extends Trait<any, any, any>[],
+> = (
+    Call<ExtendableFn, [
+        InstanceType<Super>,
+        ...Call<Tuples.Map<TraitOwnAbstractFn>, Traits>,
+    ]>
+)
+
+type ImplInstanceExtendable<
+    Super  extends AbstractClass<{}>,
+    Traits extends Trait<any, any, any>[],
+> = (
+    Call<ExtendableFn, [
+        InstanceType<Super>,
+        ...Call<Tuples.Map<TraitOwnImplInstanceFn>, Traits>,
+    ]>
+)
+
+type ImplStaticMembersExtendable<
+    Super  extends AbstractClass<{}>,
+    Traits extends Trait<any, any, any>[],
+> = (
+    Pipe<[
+        Super,
+        ...Call<Tuples.Map<TraitOwnImplClassFn>, Traits>,
+    ], [
+        Tuples.Map<StaticMembersFn>,
+        ExtendableFn,
+    ]>
+)
+
+type GetTraitExpression<
+    Super     extends AbstractClass<{}>,
+    OwnTraits extends Trait<any, any, any>[],
+    AllTraits extends Trait<any, any, any>[],
+> = (
+    Call<Tuples.IsEmpty, OwnTraits> extends true
+        ? "Cannot express an empty list of traits."
+        : AbstractMembersExtendable<Super, OwnTraits> extends false
+            ? "Type conflict between the traits abstract members and/or the superclass instance."
+            : ImplInstanceExtendable<Super, OwnTraits> extends false
+                ? "Type conflict between the traits implementation instances and/or the superclass instance."
+                : ImplStaticMembersExtendable<Super, OwnTraits> extends false
+                    ? "Type conflict between the traits implementation static members and/or the superclass static members."
+                    : TraitExpression<Super, OwnTraits, AllTraits>
+)
+
+
+export const expression = new TraitExpressionBuilder(emptyTraitExpression)

src/index.ts

@@ -1,3 +1,4 @@
 export * from "./TraitExpression"
+export * from "./TraitExpressionBuilder"
 export * from "./abstract"
 export * from "./trait"

src/trait.ts

@@ -28,7 +28,7 @@ type RemoveAbstractFromImplClass<
 
 
 export class Trait<
-    Super     extends TraitExpression<typeof TraitExpressionNullSuperclass, any>,
+    Super     extends TraitExpression<typeof TraitExpressionNullSuperclass, Trait<any, any, any>[], Trait<any, any, any>[]>,
     Abstract  extends {},
     ImplClass extends Class<{}, []>,
 > {