src/effect/EffectSchemaTraitExpression.ts

@@ -13,6 +13,9 @@ export class EffectSchemaTraitExpression<
     Static                  extends object,
 
     const Traits            extends readonly Trait<any, any, any, any>[],
+
+    const Mutability        extends "Immutable" | "Mutable",
+    const EncodedMutability extends "Immutable" | "Mutable",
 >
 implements TraitExpressionLike<
     S.Class<unknown, Fields, I, R, C, Inherited, Proto>,
@@ -22,12 +25,14 @@ implements TraitExpressionLike<
         readonly superclass:         S.Class<unknown, Fields, I, R, C, Inherited, Proto>,
         readonly superclassStatic:   Static,
         readonly traits:             Traits,
+        readonly mutability:         Mutability,
+        readonly encodedMutability:  EncodedMutability,
     ) {}
 
 
     extends<Self>(): (
         AbstractConstructor<
-            S.Struct.Type<Fields> &
+            ApplyMutability<S.Struct.Type<Fields>, Mutability> &
             Omit<Inherited, keyof Fields> &
             Proto,
 
@@ -38,7 +43,8 @@ implements TraitExpressionLike<
             S.Class<
                 Self,
                 Fields,
-                I, R, C,
+                ApplyMutability<I, EncodedMutability>,
+                R, C,
                 Simplify<
                     Extend<[
                         Inherited,
@@ -69,3 +75,10 @@ implements TraitExpressionLike<
         return (_target: StaticImplements<typeof this>) => {}
     }
 }
+
+
+type ApplyMutability<T, Mutability extends "Immutable" | "Mutable"> = (
+    Mutability extends "Immutable"
+        ? { +readonly [P in keyof T]: T[P] }
+        : { -readonly [P in keyof T]: T[P] }
+)

src/effect/EffectSchemaTraitExpressionBuilder.ts

@@ -1,5 +1,4 @@
 import { Schema as S } from "@effect/schema"
-import * as Types from "effect/Types"
 import { Simplify } from "type-fest"
 import { Trait, TraitTuple } from "../Trait"
 import { TraitExpression } from "../TraitExpression"
@@ -22,6 +21,8 @@ export class EffectSchemaInitialTraitExpressionBuilder {
             S.Class<unknown>(identifier)(fields, annotations),
             {},
             [],
+            "Immutable",
+            "Immutable",
         )
     }
 
@@ -37,6 +38,8 @@ export class EffectSchemaInitialTraitExpressionBuilder {
             S.TaggedClass<unknown>()(tag, fields, annotations),
             {},
             [],
+            "Immutable",
+            "Immutable",
         )
     }
 
@@ -65,6 +68,8 @@ export class EffectSchemaInitialTraitExpressionBuilder {
             >,
 
             [],
+            "Immutable",
+            "Immutable",
         )
     }
 }
@@ -78,43 +83,56 @@ export class EffectSchemaTraitExpressionBuilder<
     Static                  extends object,
 
     const Traits            extends readonly Trait<any, any, any, any>[],
+
+    const Mutability        extends "Immutable" | "Mutable",
+    const EncodedMutability extends "Immutable" | "Mutable",
 > {
     constructor(
         readonly expressionSuperclass:         S.Class<unknown, Fields, I, R, C, Inherited, Proto>,
         readonly expressionSuperclassStatic:   Static,
         readonly expressionTraits:             Traits,
+        readonly expressionMutability:         Mutability,
+        readonly expressionEncodedMutability:  EncodedMutability,
     ) {}
 
 
-    // mutable() {
+    mutable() {
-    //     return new EffectSchemaTraitExpressionBuilder(
+        return new EffectSchemaTraitExpressionBuilder(
-    //         this.expressionSuperclass as S.Class<unknown, Fields, Types.Mutable<A>, I, R, C, Inherited, Proto>,
+            this.expressionSuperclass,
-    //         this.expressionSuperclassStatic,
+            this.expressionSuperclassStatic,
-    //         this.expressionTraits,
+            this.expressionTraits,
-    //     )
+            "Mutable",
-    // }
+            this.expressionEncodedMutability,
+        )
+    }
 
-    // immutable() {
+    immutable() {
-    //     return new EffectSchemaTraitExpressionBuilder(
+        return new EffectSchemaTraitExpressionBuilder(
-    //         this.expressionSuperclass as S.Class<unknown, Fields, Readonly<A>, I, R, C, Inherited, Proto>,
+            this.expressionSuperclass,
-    //         this.expressionSuperclassStatic,
+            this.expressionSuperclassStatic,
-    //         this.expressionTraits,
+            this.expressionTraits,
-    //     )
+            "Immutable",
-    // }
+            this.expressionEncodedMutability,
+        )
+    }
 
     mutableEncoded() {
         return new EffectSchemaTraitExpressionBuilder(
-            this.expressionSuperclass as S.Class<unknown, Fields, Types.Mutable<I>, R, C, Inherited, Proto>,
+            this.expressionSuperclass,
             this.expressionSuperclassStatic,
             this.expressionTraits,
+            this.expressionMutability,
+            "Mutable",
         )
     }
 
     immutableEncoded() {
         return new EffectSchemaTraitExpressionBuilder(
-            this.expressionSuperclass as S.Class<unknown, Fields, Readonly<I>, R, C, Inherited, Proto>,
+            this.expressionSuperclass,
             this.expressionSuperclassStatic,
             this.expressionTraits,
+            this.expressionMutability,
+            "Immutable",
         )
     }
 
@@ -140,6 +158,9 @@ export class EffectSchemaTraitExpressionBuilder<
                 ...this.expressionTraits,
                 ...spreadSupertraits(traits),
             ]) as TraitExpressionBuilder.ExpressesReturnTypeTraits<Traits, T>,
+
+            this.expressionMutability,
+            this.expressionEncodedMutability,
         )
     }
 
@@ -166,13 +187,17 @@ export class EffectSchemaTraitExpressionBuilder<
                             Proto,
                             Static,
 
-                            Traits
+                            Traits,
+                            Mutability,
+                            EncodedMutability
                         >
     ) {
         return new EffectSchemaTraitExpression(
             this.expressionSuperclass,
             this.expressionSuperclassStatic,
             this.expressionTraits,
+            this.expressionMutability,
+            this.expressionEncodedMutability,
         ) as any
     }
 }

src/effect/tests.ts

@@ -8,21 +8,6 @@ type RequiredKeys<T> = {
     [K in keyof T]-?: {} extends Pick<T, K> ? never : K
   }[keyof T]
 
-type Extr<T> =
-    T extends EffectSchemaTraitExpression<
-    infer Fields,
-    infer I,
-    infer R,
-    infer C,
-    infer Inherited,
-    infer Proto,
-    infer Static,
-
-    infer Traits
-    >
-        ? Static
-        : never
-
 type InspectSchemaClass<T> = T extends S.Class<infer Self, infer Fields, infer I, infer R, infer C, infer Inherited, infer Proto>
     ? Inherited
     : never
@@ -33,7 +18,7 @@ const userExp = effectSchemaExpression
         id:    S.BigIntFromSelf,
         role:  S.Union(S.Literal("User"), S.Literal("Admin")),
     })
-    // .mutable()
+    .mutable()
     .mutableEncoded()
     .build()
 
@@ -46,7 +31,7 @@ export class User extends userExp.extends<User>() implements Implements<typeof u
 User.Encoded
 
 const user = new User({ id: 0n, role: "User" })
-// user.id = 0n
+user.id = 0n
 
 
 const adminExp = effectSchemaExpression