Unexpected: rename ast to expected and make the field required

.changeset/gentle-readers-call.md

@@ -8,3 +8,4 @@ Refactor `ParseResult` module:
 - rename `UnionMember` to `Member`
 - ast `ast` field to `Member`
 - replace `Index` with `Tuple`
+- `Unexpected`: rename `ast` to `expected` and make the field required

docs/modules/ParseResult.ts.md

@@ -159,7 +159,7 @@ Added in v1.0.0
 **Signature**
 
 ```ts
-export declare const unexpected: (ast: Option.Option<AST.AST>) => Unexpected
+export declare const unexpected: (expected: AST.AST) => Unexpected
 ```
 
 Added in v1.0.0
@@ -327,7 +327,7 @@ Error that occurs when an unexpected key or index is present.
 ```ts
 export interface Unexpected {
   readonly _tag: "Unexpected"
-  readonly ast: Option.Option<AST.AST>
+  readonly expected: AST.AST
 }
 ```
 

src/ArrayFormatter.ts

@@ -1,7 +1,6 @@
 /**
  * @since 1.0.0
  */
-import * as Option from "effect/Option"
 import * as ReadonlyArray from "effect/ReadonlyArray"
 import type { ParseIssue } from "./ParseResult.js"
 import { formatExpected, getMessage } from "./TreeFormatter.js"
@@ -31,8 +30,7 @@ const format = (self: ParseIssue, path: ReadonlyArray<PropertyKey> = []): Array<
       return [{
         _tag,
         path,
-        message: "Unexpected" +
-          (Option.isSome(self.ast) ? `, expected ${formatExpected(self.ast.value)}` : "")
+        message: `Unexpected, expected ${formatExpected(self.expected)}`
       }]
     case "Union":
       return ReadonlyArray.flatMap(self.errors, (e) => {

src/ParseResult.ts

@@ -203,16 +203,16 @@ export const missing: Missing = { _tag: "Missing" }
  */
 export interface Unexpected {
   readonly _tag: "Unexpected"
-  readonly ast: Option.Option<AST.AST>
+  readonly expected: AST.AST
 }
 
 /**
  * @category constructors
  * @since 1.0.0
  */
 export const unexpected = (
-  ast: Option.Option<AST.AST>
-): Unexpected => ({ _tag: "Unexpected", ast })
+  expected: AST.AST
+): Unexpected => ({ _tag: "Unexpected", expected })
 
 /**
  * Error that occurs when a union has an error.

src/Parser.ts

@@ -357,6 +357,7 @@ const go = (ast: AST.AST, isDecoding: boolean): Parser<any, any> => {
       if (Option.isSome(ast.rest)) {
         requiredLen += ast.rest.value.length - 1
       }
+      const expectedAST = AST.createUnion(ast.elements.map((_, i) => AST.createLiteral(i)))
       return (input: unknown, options) => {
         if (!Array.isArray(input)) {
           return ParseResult.fail(ParseResult.type(ast, input))
@@ -383,7 +384,7 @@ const go = (ast: AST.AST, isDecoding: boolean): Parser<any, any> => {
         // ---------------------------------------------
         if (Option.isNone(ast.rest)) {
           for (let i = ast.elements.length; i <= len - 1; i++) {
-            const e = ParseResult.index(i, [ParseResult.unexpected(Option.none())])
+            const e = ParseResult.index(i, [ParseResult.unexpected(expectedAST)])
             if (allErrors) {
               es.push([stepKey++, e])
               continue
@@ -614,7 +615,7 @@ const go = (ast: AST.AST, isDecoding: boolean): Parser<any, any> => {
           for (const key of Internal.ownKeys(input)) {
             const eu = ParseResult.eitherOrUndefined(expected(key, options))
             if (eu && Either.isLeft(eu)) {
-              const e = ParseResult.key(key, [ParseResult.unexpected(Option.some(expectedAST))])
+              const e = ParseResult.key(key, [ParseResult.unexpected(expectedAST)])
               if (allErrors) {
                 es.push([stepKey++, e])
                 continue

src/TreeFormatter.ts

@@ -164,7 +164,7 @@ const go = (e: ParseIssue): Tree<string> => {
       return make("is forbidden")
     case "Unexpected":
       return make(
-        "is unexpected" + (Option.isSome(e.ast) ? `, expected ${formatExpected(e.ast.value)}` : "")
+        `is unexpected, expected ${formatExpected(e.expected)}`
       )
     case "Key": {
       const es = e.errors.map(go)

test/ArrayFormatter.test.ts

@@ -81,7 +81,7 @@ describe("ArrayFormatter", () => {
     expectIssues(schema, ["a", 1], [{
       _tag: "Unexpected",
       path: [1],
-      message: "Unexpected"
+      message: "Unexpected, expected 0"
     }])
   })
 

test/Schema/allErrors.test.ts

@@ -40,9 +40,9 @@ describe("Schema > allErrors option", () => {
           ["a", "b"],
           `Tuple or array: <anonymous tuple or array schema>
 ├─ [0]
-│  └─ is unexpected
+│  └─ is unexpected, expected never
 └─ [1]
-   └─ is unexpected`,
+   └─ is unexpected, expected never`,
           Util.allErrors
         )
       })
@@ -174,9 +174,9 @@ describe("Schema > allErrors option", () => {
           [1, 1] as any,
           `Tuple or array: <anonymous tuple or array schema>
 ├─ [0]
-│  └─ is unexpected
+│  └─ is unexpected, expected never
 └─ [1]
-   └─ is unexpected`,
+   └─ is unexpected, expected never`,
           Util.allErrors
         )
       })

test/Schema/onExcess.test.ts

@@ -10,14 +10,14 @@ describe("Schema > onExcess", () => {
       [1, "b"],
       `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
     )
     await Util.expectEncodeFailure(
       schema,
       [1, "b"] as any,
       `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
     )
   })
 
@@ -70,11 +70,11 @@ describe("Schema > onExcess", () => {
 ├─ Union member: <anonymous tuple or array schema>
 │  └─ Tuple or array: <anonymous tuple or array schema>
 │     └─ [2]
-│        └─ is unexpected
+│        └─ is unexpected, expected 0 or 1
 └─ Union member: <anonymous tuple or array schema>
    └─ Tuple or array: <anonymous tuple or array schema>
       └─ [1]
-         └─ is unexpected`
+         └─ is unexpected, expected 0`
       )
       await Util.expectParseFailure(
         schema,
@@ -83,11 +83,11 @@ describe("Schema > onExcess", () => {
 ├─ Union member: <anonymous tuple or array schema>
 │  └─ Tuple or array: <anonymous tuple or array schema>
 │     └─ [2]
-│        └─ is unexpected
+│        └─ is unexpected, expected 0 or 1
 └─ Union member: <anonymous tuple or array schema>
    └─ Tuple or array: <anonymous tuple or array schema>
       └─ [1]
-         └─ is unexpected`,
+         └─ is unexpected, expected 0`,
         Util.onExcessPropertyError
       )
       await Util.expectEncodeSuccess(

test/Schema/tuple.test.ts

@@ -53,14 +53,14 @@ describe("Schema > tuple", () => {
         [undefined],
         `Tuple or array: <anonymous tuple or array schema>
 └─ [0]
-   └─ is unexpected`
+   └─ is unexpected, expected never`
       )
       await Util.expectParseFailure(
         schema,
         [1],
         `Tuple or array: <anonymous tuple or array schema>
 └─ [0]
-   └─ is unexpected`
+   └─ is unexpected, expected never`
       )
     })
 
@@ -99,7 +99,7 @@ describe("Schema > tuple", () => {
         [1, "b"],
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -136,7 +136,7 @@ describe("Schema > tuple", () => {
         [1, "b"],
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -162,7 +162,7 @@ describe("Schema > tuple", () => {
         [1, "b"],
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -193,7 +193,7 @@ describe("Schema > tuple", () => {
         [1, "b"],
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -365,7 +365,7 @@ describe("Schema > tuple", () => {
         [1, "b"] as any,
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -378,7 +378,7 @@ describe("Schema > tuple", () => {
         [1, "b"] as any,
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -398,7 +398,7 @@ describe("Schema > tuple", () => {
         [1, "b"] as any,
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })
 
@@ -412,7 +412,7 @@ describe("Schema > tuple", () => {
         [1, "b"] as any,
         `Tuple or array: <anonymous tuple or array schema>
 └─ [1]
-   └─ is unexpected`
+   └─ is unexpected, expected 0`
       )
     })