diff --git a/CHANGELOG.md b/CHANGELOG.md
index c814152f..0df3fc63 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 - 指定時間待機する関数`Core:sleep`を追加
 - `exists 変数名` の構文で変数が存在するか判定できるように
 - オブジェクトを添字で参照できるように（`object['index']`のように）
+- 「エラー型（`error`）」を導入
+- `Json:parse`がパース失敗時にエラー型の値を返すように
 
 # 0.15.0
 - Mathを強化
diff --git a/docs/get-started.md b/docs/get-started.md
index bd70436c..e20816d4 100644
--- a/docs/get-started.md
+++ b/docs/get-started.md
@@ -51,6 +51,7 @@ this is a comment
 	<tr><td>オブジェクト</td><td><code>obj</code></td><td><code>{ foo: "bar"; a: 42; }</code></td></tr>
 	<tr><td>null</td><td><code>null</code></td><td><code>null</code></td></tr>
 	<tr><td>関数</td><td><code>fn</code></td><td><code>@(x) { x }</code></td></tr>
+	<tr><td>エラー</td><td><code>error</code></td><td><code>(TODO)</code></td></tr>
 </table>
 
 ## 変数
@@ -256,4 +257,15 @@ AiScriptファイルにメタデータを埋め込める機能です。
 	version: 42
 	keywords: ["foo" "bar" "baz"]
 }
-```
\ No newline at end of file
+```
+
+## エラー型
+一部の標準関数は実行失敗時にエラー型の値を返します。
+これによりエラー処理を行うことができます。
+```
+@validate(str){
+	let v=Json:parse(str)
+	if (Core:type(v)=='error') print(v.name)
+	else print('successful')
+}
+```
diff --git a/docs/std.md b/docs/std.md
index 7d4bfe15..ed87a68e 100644
--- a/docs/std.md
+++ b/docs/std.md
@@ -33,10 +33,10 @@ AiScriptのバージョンです。
 JSONを生成します。  
 
 ### @Json:parse(_json_: str): value
-JSONをパースします。  
+JSONをパースします。 引数がJSONとしてパース可能性でない場合、エラー型の値（`name`=`'not_json'`）を返します。 
 
 ### @Json:parsable(_str_: str): bool
-文字列がJSONとしてパース可能であるかの判定を行います。 
+文字列がJSONとしてパース可能であるかの判定を行います。歴史的理由により存在しています 
 
 ## :: Date
 
@@ -236,6 +236,14 @@ _codepoint_ は 0 以上、10FFFF<sub>16</sub> 以下である必要がありま
 ### @Obj:copy(_v_: obj): obj
 オブジェクトのコピーを生成します。  
 
+## :: Error
+
+### @(_v_: error).name(): str
+エラーの識別子となる文字列を返します。
+
+### @(_v_: error).info(): value
+エラーに付加情報がある場合、それを返します。
+
 ## :: Async
 
 ### @Async:interval(_interval_: num, _callback_: fn, _immediate_?: bool): fn
diff --git a/etc/aiscript.api.md b/etc/aiscript.api.md
index 5cc949b2..f5c4ff08 100644
--- a/etc/aiscript.api.md
+++ b/etc/aiscript.api.md
@@ -1,1036 +1,1048 @@
-## API Report File for "@syuilo/aiscript"
-
-> Do not edit this file. It is a report generated by [API Extractor](https://api-extractor.com/).
-
-```ts
-
-// Warning: (ae-forgotten-export) The symbol "NodeBase" needs to be exported by the entry point index.d.ts
-//
-// @public (undocumented)
-type AddAssign = NodeBase & {
-    type: 'addAssign';
-    dest: Expression;
-    expr: Expression;
-};
-
-// Warning: (ae-forgotten-export) The symbol "NodeBase_2" needs to be exported by the entry point index.d.ts
-//
-// @public (undocumented)
-type AddAssign_2 = NodeBase_2 & {
-    type: 'addAssign';
-    dest: Expression_2;
-    expr: Expression_2;
-};
-
-// @public (undocumented)
-abstract class AiScriptError extends Error {
-    constructor(message: string, info?: any);
-    // (undocumented)
-    info?: any;
-}
-
-// @public (undocumented)
-type And = NodeBase & {
-    type: 'and';
-    left: Expression;
-    right: Expression;
-};
-
-// @public (undocumented)
-type And_2 = NodeBase_2 & {
-    type: 'and';
-    left: Expression_2;
-    right: Expression_2;
-};
-
-// @public (undocumented)
-const ARR: (arr: VArr['value']) => VArr;
-
-// @public (undocumented)
-type Arr = NodeBase & {
-    type: 'arr';
-    value: Expression[];
-};
-
-// Warning: (ae-forgotten-export) The symbol "ChainProp" needs to be exported by the entry point index.d.ts
-//
-// @public (undocumented)
-type Arr_2 = NodeBase_2 & ChainProp & {
-    type: 'arr';
-    value: Expression_2[];
-};
-
-// @public (undocumented)
-function assertArray(val: Value | null | undefined): asserts val is VArr;
-
-// @public (undocumented)
-function assertBoolean(val: Value | null | undefined): asserts val is VBool;
-
-// @public (undocumented)
-function assertFunction(val: Value | null | undefined): asserts val is VFn;
-
-// @public (undocumented)
-function assertNumber(val: Value | null | undefined): asserts val is VNum;
-
-// @public (undocumented)
-function assertObject(val: Value | null | undefined): asserts val is VObj;
-
-// @public (undocumented)
-function assertString(val: Value | null | undefined): asserts val is VStr;
-
-// @public (undocumented)
-type Assign = NodeBase & {
-    type: 'assign';
-    dest: Expression;
-    expr: Expression;
-};
-
-// @public (undocumented)
-type Assign_2 = NodeBase_2 & {
-    type: 'assign';
-    dest: Expression_2;
-    expr: Expression_2;
-};
-
-declare namespace Ast {
-    export {
-        isStatement,
-        isExpression,
-        Loc,
-        Node_2 as Node,
-        Statement,
-        Expression,
-        Namespace,
-        Meta,
-        Definition,
-        Attribute,
-        Return,
-        Each,
-        For,
-        Loop,
-        Break,
-        Continue,
-        AddAssign,
-        SubAssign,
-        Assign,
-        Not,
-        And,
-        Or,
-        If,
-        Fn,
-        Match,
-        Block,
-        Exists,
-        Tmpl,
-        Str,
-        Num,
-        Bool,
-        Null,
-        Obj,
-        Arr,
-        Identifier,
-        Call,
-        Index,
-        Prop,
-        TypeSource,
-        NamedTypeSource,
-        FnTypeSource
-    }
-}
-export { Ast }
-
-// @public (undocumented)
-type Attr_2 = {
-    attr?: {
-        name: string;
-        value: Value;
-    }[];
-};
-
-// @public (undocumented)
-type Attribute = NodeBase & {
-    type: 'attr';
-    name: string;
-    value: Expression;
-};
-
-// @public (undocumented)
-type Attribute_2 = NodeBase_2 & {
-    type: 'attr';
-    name: string;
-    value: Expression_2;
-};
-
-// @public (undocumented)
-type Block = NodeBase & {
-    type: 'block';
-    statements: (Statement | Expression)[];
-};
-
-// @public (undocumented)
-type Block_2 = NodeBase_2 & ChainProp & {
-    type: 'block';
-    statements: (Statement_2 | Expression_2)[];
-};
-
-// @public (undocumented)
-const BOOL: (bool: VBool['value']) => VBool;
-
-// @public (undocumented)
-type Bool = NodeBase & {
-    type: 'bool';
-    value: boolean;
-};
-
-// @public (undocumented)
-type Bool_2 = NodeBase_2 & ChainProp & {
-    type: 'bool';
-    value: boolean;
-};
-
-// @public (undocumented)
-const BREAK: () => Value;
-
-// @public (undocumented)
-type Break = NodeBase & {
-    type: 'break';
-};
-
-// @public (undocumented)
-type Break_2 = NodeBase_2 & {
-    type: 'break';
-};
-
-// @public (undocumented)
-function CALL(target: Call_2['target'], args: Call_2['args'], loc?: {
-    start: number;
-    end: number;
-}): Call_2;
-
-// @public (undocumented)
-type Call = NodeBase & {
-    type: 'call';
-    target: Expression;
-    args: Expression[];
-};
-
-// @public (undocumented)
-type Call_2 = NodeBase_2 & {
-    type: 'call';
-    target: Expression_2;
-    args: Expression_2[];
-};
-
-// @public (undocumented)
-type CallChain = NodeBase_2 & {
-    type: 'callChain';
-    args: Expression_2[];
-};
-
-// @public (undocumented)
-type ChainMember = CallChain | IndexChain | PropChain;
-
-// @public (undocumented)
-const CONTINUE: () => Value;
-
-// @public (undocumented)
-type Continue = NodeBase & {
-    type: 'continue';
-};
-
-// @public (undocumented)
-type Continue_2 = NodeBase_2 & {
-    type: 'continue';
-};
-
-declare namespace Cst {
-    export {
-        isStatement_2 as isStatement,
-        isExpression_2 as isExpression,
-        hasChainProp,
-        CALL,
-        INDEX,
-        PROP,
-        Node_3 as Node,
-        Statement_2 as Statement,
-        Expression_2 as Expression,
-        Namespace_2 as Namespace,
-        Meta_2 as Meta,
-        Definition_2 as Definition,
-        Attribute_2 as Attribute,
-        Return_2 as Return,
-        Each_2 as Each,
-        For_2 as For,
-        Loop_2 as Loop,
-        Break_2 as Break,
-        Continue_2 as Continue,
-        AddAssign_2 as AddAssign,
-        SubAssign_2 as SubAssign,
-        Assign_2 as Assign,
-        InfixOperator,
-        Infix,
-        Not_2 as Not,
-        And_2 as And,
-        Or_2 as Or,
-        If_2 as If,
-        Fn_2 as Fn,
-        Match_2 as Match,
-        Block_2 as Block,
-        Exists_2 as Exists,
-        Tmpl_2 as Tmpl,
-        Str_2 as Str,
-        Num_2 as Num,
-        Bool_2 as Bool,
-        Null_2 as Null,
-        Obj_2 as Obj,
-        Arr_2 as Arr,
-        Identifier_2 as Identifier,
-        ChainMember,
-        CallChain,
-        IndexChain,
-        PropChain,
-        Call_2 as Call,
-        Index_2 as Index,
-        Prop_2 as Prop,
-        TypeSource_2 as TypeSource,
-        NamedTypeSource_2 as NamedTypeSource,
-        FnTypeSource_2 as FnTypeSource
-    }
-}
-export { Cst }
-
-// @public (undocumented)
-type Definition = NodeBase & {
-    type: 'def';
-    name: string;
-    varType?: TypeSource;
-    expr: Expression;
-    mut: boolean;
-    attr: Attribute[];
-};
-
-// @public (undocumented)
-type Definition_2 = NodeBase_2 & {
-    type: 'def';
-    name: string;
-    varType?: TypeSource_2;
-    expr: Expression_2;
-    mut: boolean;
-    attr?: Attribute_2[];
-};
-
-// @public (undocumented)
-type Each = NodeBase & {
-    type: 'each';
-    var: string;
-    items: Expression;
-    for: Statement | Expression;
-};
-
-// @public (undocumented)
-type Each_2 = NodeBase_2 & {
-    type: 'each';
-    var: string;
-    items: Expression_2;
-    for: Statement_2 | Expression_2;
-};
-
-// @public (undocumented)
-function eq(a: Value, b: Value): boolean;
-
-declare namespace errors {
-    export {
-        AiScriptError,
-        SyntaxError_2 as SyntaxError,
-        TypeError_2 as TypeError,
-        RuntimeError,
-        IndexOutOfRangeError
-    }
-}
-export { errors }
-
-// @public (undocumented)
-type Exists = NodeBase & {
-    type: 'exists';
-    identifier: Identifier;
-};
-
-// @public (undocumented)
-type Exists_2 = NodeBase_2 & ChainProp & {
-    type: 'exists';
-    identifier: Identifier_2;
-};
-
-// @public (undocumented)
-function expectAny(val: Value | null | undefined): asserts val is Value;
-
-// @public (undocumented)
-type Expression = If | Fn | Match | Block | Exists | Tmpl | Str | Num | Bool | Null | Obj | Arr | Not | And | Or | Identifier | Call | Index | Prop;
-
-// @public (undocumented)
-type Expression_2 = Infix | Not_2 | And_2 | Or_2 | If_2 | Fn_2 | Match_2 | Block_2 | Exists_2 | Tmpl_2 | Str_2 | Num_2 | Bool_2 | Null_2 | Obj_2 | Arr_2 | Identifier_2 | Call_2 | // IR
-Index_2 | // IR
-Prop_2;
-
-// @public (undocumented)
-const FALSE: {
-    type: "bool";
-    value: boolean;
-};
-
-// @public (undocumented)
-const FN: (args: VFn['args'], statements: VFn['statements'], scope: VFn['scope']) => VFn;
-
-// @public (undocumented)
-type Fn = NodeBase & {
-    type: 'fn';
-    args: {
-        name: string;
-        argType?: TypeSource;
-    }[];
-    retType?: TypeSource;
-    children: (Statement | Expression)[];
-};
-
-// @public (undocumented)
-type Fn_2 = NodeBase_2 & ChainProp & {
-    type: 'fn';
-    args: {
-        name: string;
-        argType?: TypeSource_2;
-    }[];
-    retType?: TypeSource_2;
-    children: (Statement_2 | Expression_2)[];
-};
-
-// @public (undocumented)
-const FN_NATIVE: (fn: VFn['native']) => VFn;
-
-// @public (undocumented)
-type FnTypeSource = NodeBase & {
-    type: 'fnTypeSource';
-    args: TypeSource[];
-    result: TypeSource;
-};
-
-// @public (undocumented)
-type FnTypeSource_2 = NodeBase_2 & {
-    type: 'fnTypeSource';
-    args: TypeSource_2[];
-    result: TypeSource_2;
-};
-
-// @public (undocumented)
-type For = NodeBase & {
-    type: 'for';
-    var?: string;
-    from?: Expression;
-    to?: Expression;
-    times?: Expression;
-    for: Statement | Expression;
-};
-
-// @public (undocumented)
-type For_2 = NodeBase_2 & {
-    type: 'for';
-    var?: string;
-    from?: Expression_2;
-    to?: Expression_2;
-    times?: Expression_2;
-    for: Statement_2 | Expression_2;
-};
-
-// @public (undocumented)
-function getLangVersion(input: string): string | null;
-
-// @public (undocumented)
-function hasChainProp<T extends Node_3>(x: T): x is T & ChainProp;
-
-// @public (undocumented)
-type Identifier = NodeBase & {
-    type: 'identifier';
-    name: string;
-};
-
-// @public (undocumented)
-type Identifier_2 = NodeBase_2 & ChainProp & {
-    type: 'identifier';
-    name: string;
-};
-
-// @public (undocumented)
-type If = NodeBase & {
-    type: 'if';
-    cond: Expression;
-    then: Statement | Expression;
-    elseif: {
-        cond: Expression;
-        then: Statement | Expression;
-    }[];
-    else?: Statement | Expression;
-};
-
-// @public (undocumented)
-type If_2 = NodeBase_2 & {
-    type: 'if';
-    cond: Expression_2;
-    then: Statement_2 | Expression_2;
-    elseif: {
-        cond: Expression_2;
-        then: Statement_2 | Expression_2;
-    }[];
-    else?: Statement_2 | Expression_2;
-};
-
-// @public (undocumented)
-function INDEX(target: Index_2['target'], index: Index_2['index'], loc?: {
-    start: number;
-    end: number;
-}): Index_2;
-
-// @public (undocumented)
-type Index = NodeBase & {
-    type: 'index';
-    target: Expression;
-    index: Expression;
-};
-
-// @public (undocumented)
-type Index_2 = NodeBase_2 & {
-    type: 'index';
-    target: Expression_2;
-    index: Expression_2;
-};
-
-// @public (undocumented)
-type IndexChain = NodeBase_2 & {
-    type: 'indexChain';
-    index: Expression_2;
-};
-
-// @public (undocumented)
-class IndexOutOfRangeError extends RuntimeError {
-    constructor(message: string, info?: any);
-}
-
-// @public (undocumented)
-type Infix = NodeBase_2 & {
-    type: 'infix';
-    operands: Expression_2[];
-    operators: InfixOperator[];
-};
-
-// @public (undocumented)
-type InfixOperator = '||' | '&&' | '==' | '!=' | '<=' | '>=' | '<' | '>' | '+' | '-' | '*' | '^' | '/' | '%';
-
-// @public (undocumented)
-export class Interpreter {
-    constructor(vars: Record<string, Value>, opts?: {
-        in?(q: string): Promise<string>;
-        out?(value: Value): void;
-        log?(type: string, params: Record<string, any>): void;
-        maxStep?: number;
-    });
-    // (undocumented)
-    abort(): void;
-    // (undocumented)
-    static collectMetadata(script?: Ast.Node[]): Map<any, any> | undefined;
-    // (undocumented)
-    exec(script?: Ast.Node[]): Promise<void>;
-    // (undocumented)
-    execFn(fn: VFn, args: Value[]): Promise<Value>;
-    // (undocumented)
-    registerAbortHandler(handler: () => void): void;
-    // (undocumented)
-    scope: Scope;
-    // (undocumented)
-    stepCount: number;
-    // (undocumented)
-    unregisterAbortHandler(handler: () => void): void;
-}
-
-// @public (undocumented)
-function isArray(val: Value): val is VArr;
-
-// @public (undocumented)
-function isBoolean(val: Value): val is VBool;
-
-// @public (undocumented)
-function isExpression(x: Node_2): x is Expression;
-
-// @public (undocumented)
-function isExpression_2(x: Node_3): x is Expression_2;
-
-// @public (undocumented)
-function isFunction(val: Value): val is VFn;
-
-// @public (undocumented)
-function isNumber(val: Value): val is VNum;
-
-// @public (undocumented)
-function isObject(val: Value): val is VObj;
-
-// @public (undocumented)
-function isStatement(x: Node_2): x is Statement;
-
-// @public (undocumented)
-function isStatement_2(x: Node_3): x is Statement_2;
-
-// @public (undocumented)
-function isString(val: Value): val is VStr;
-
-// @public (undocumented)
-function jsToVal(val: any): Value;
-
-// @public
-type Loc = {
-    start: number;
-    end: number;
-};
-
-// @public (undocumented)
-type Loop = NodeBase & {
-    type: 'loop';
-    statements: (Statement | Expression)[];
-};
-
-// @public (undocumented)
-type Loop_2 = NodeBase_2 & {
-    type: 'loop';
-    statements: (Statement_2 | Expression_2)[];
-};
-
-// @public (undocumented)
-type Match = NodeBase & {
-    type: 'match';
-    about: Expression;
-    qs: {
-        q: Expression;
-        a: Statement | Expression;
-    }[];
-    default?: Statement | Expression;
-};
-
-// @public (undocumented)
-type Match_2 = NodeBase_2 & ChainProp & {
-    type: 'match';
-    about: Expression_2;
-    qs: {
-        q: Expression_2;
-        a: Statement_2 | Expression_2;
-    }[];
-    default?: Statement_2 | Expression_2;
-};
-
-// @public (undocumented)
-type Meta = NodeBase & {
-    type: 'meta';
-    name: string | null;
-    value: Expression;
-};
-
-// @public (undocumented)
-type Meta_2 = NodeBase_2 & {
-    type: 'meta';
-    name: string | null;
-    value: Expression_2;
-};
-
-// @public (undocumented)
-type NamedTypeSource = NodeBase & {
-    type: 'namedTypeSource';
-    name: string;
-    inner?: TypeSource;
-};
-
-// @public (undocumented)
-type NamedTypeSource_2 = NodeBase_2 & {
-    type: 'namedTypeSource';
-    name: string;
-    inner?: TypeSource_2;
-};
-
-// @public (undocumented)
-type Namespace = NodeBase & {
-    type: 'ns';
-    name: string;
-    members: (Definition | Namespace)[];
-};
-
-// @public (undocumented)
-type Namespace_2 = NodeBase_2 & {
-    type: 'ns';
-    name: string;
-    members: (Definition_2 | Namespace_2)[];
-};
-
-// @public (undocumented)
-type Node_2 = Namespace | Meta | Statement | Expression | TypeSource;
-
-// @public
-type Node_3 = Namespace_2 | Meta_2 | Statement_2 | Expression_2 | ChainMember | TypeSource_2;
-
-// @public (undocumented)
-type Not = NodeBase & {
-    type: 'not';
-    expr: Expression;
-};
-
-// @public (undocumented)
-type Not_2 = NodeBase_2 & {
-    type: 'not';
-    expr: Expression_2;
-};
-
-// @public (undocumented)
-const NULL: {
-    type: "null";
-};
-
-// @public (undocumented)
-type Null = NodeBase & {
-    type: 'null';
-};
-
-// @public (undocumented)
-type Null_2 = NodeBase_2 & ChainProp & {
-    type: 'null';
-};
-
-// @public (undocumented)
-const NUM: (num: VNum['value']) => VNum;
-
-// @public (undocumented)
-type Num = NodeBase & {
-    type: 'num';
-    value: number;
-};
-
-// @public (undocumented)
-type Num_2 = NodeBase_2 & ChainProp & {
-    type: 'num';
-    value: number;
-};
-
-// @public (undocumented)
-const OBJ: (obj: VObj['value']) => VObj;
-
-// @public (undocumented)
-type Obj = NodeBase & {
-    type: 'obj';
-    value: Map<string, Expression>;
-};
-
-// @public (undocumented)
-type Obj_2 = NodeBase_2 & ChainProp & {
-    type: 'obj';
-    value: Map<string, Expression_2>;
-};
-
-// @public (undocumented)
-type Or = NodeBase & {
-    type: 'or';
-    left: Expression;
-    right: Expression;
-};
-
-// @public (undocumented)
-type Or_2 = NodeBase_2 & {
-    type: 'or';
-    left: Expression_2;
-    right: Expression_2;
-};
-
-// @public (undocumented)
-export class Parser {
-    constructor();
-    // (undocumented)
-    addPlugin(type: PluginType, plugin: ParserPlugin): void;
-    // (undocumented)
-    static parse(input: string): Ast.Node[];
-    // (undocumented)
-    parse(input: string): Ast.Node[];
-}
-
-// @public (undocumented)
-export type ParserPlugin = (nodes: Cst.Node[]) => Cst.Node[];
-
-// @public (undocumented)
-export type PluginType = 'validate' | 'transform';
-
-// @public (undocumented)
-function PROP(target: Prop_2['target'], name: Prop_2['name'], loc?: {
-    start: number;
-    end: number;
-}): Prop_2;
-
-// @public (undocumented)
-type Prop = NodeBase & {
-    type: 'prop';
-    target: Expression;
-    name: string;
-};
-
-// @public (undocumented)
-type Prop_2 = NodeBase_2 & {
-    type: 'prop';
-    target: Expression_2;
-    name: string;
-};
-
-// @public (undocumented)
-type PropChain = NodeBase_2 & {
-    type: 'propChain';
-    name: string;
-};
-
-// @public (undocumented)
-function reprValue(value: Value, literalLike?: boolean, processedObjects?: Set<object>): string;
-
-// @public (undocumented)
-const RETURN: (v: VReturn['value']) => Value;
-
-// @public (undocumented)
-type Return = NodeBase & {
-    type: 'return';
-    expr: Expression;
-};
-
-// @public (undocumented)
-type Return_2 = NodeBase_2 & {
-    type: 'return';
-    expr: Expression_2;
-};
-
-// @public (undocumented)
-class RuntimeError extends AiScriptError {
-    constructor(message: string, info?: any);
-}
-
-// @public (undocumented)
-export class Scope {
-    constructor(layerdStates?: Scope['layerdStates'], parent?: Scope, name?: Scope['name']);
-    add(name: string, val: Value): void;
-    assign(name: string, val: Value): void;
-    // (undocumented)
-    createChildScope(states?: Map<string, Value>, name?: Scope['name']): Scope;
-    exists(name: string): boolean;
-    get(name: string): Value;
-    getAll(): Map<string, Value>;
-    // (undocumented)
-    name: string;
-    // (undocumented)
-    opts: {
-        log?(type: string, params: Record<string, any>): void;
-        onUpdated?(name: string, value: Value): void;
-    };
-}
-
-// @public (undocumented)
-type Statement = Definition | Return | Each | For | Loop | Break | Continue | Assign | AddAssign | SubAssign;
-
-// @public (undocumented)
-type Statement_2 = Definition_2 | Return_2 | Attribute_2 | // AST
-Each_2 | For_2 | Loop_2 | Break_2 | Continue_2 | Assign_2 | AddAssign_2 | SubAssign_2;
-
-// @public (undocumented)
-const STR: (str: VStr['value']) => VStr;
-
-// @public (undocumented)
-type Str = NodeBase & {
-    type: 'str';
-    value: string;
-};
-
-// @public (undocumented)
-type Str_2 = NodeBase_2 & ChainProp & {
-    type: 'str';
-    value: string;
-};
-
-// @public (undocumented)
-type SubAssign = NodeBase & {
-    type: 'subAssign';
-    dest: Expression;
-    expr: Expression;
-};
-
-// @public (undocumented)
-type SubAssign_2 = NodeBase_2 & {
-    type: 'subAssign';
-    dest: Expression_2;
-    expr: Expression_2;
-};
-
-// @public (undocumented)
-class SyntaxError_2 extends AiScriptError {
-    constructor(message: string, info?: any);
-}
-
-// @public (undocumented)
-type Tmpl = NodeBase & {
-    type: 'tmpl';
-    tmpl: (string | Expression)[];
-};
-
-// @public (undocumented)
-type Tmpl_2 = NodeBase_2 & ChainProp & {
-    type: 'tmpl';
-    tmpl: (string | Expression_2)[];
-};
-
-// @public (undocumented)
-const TRUE: {
-    type: "bool";
-    value: boolean;
-};
-
-// @public (undocumented)
-class TypeError_2 extends AiScriptError {
-    constructor(message: string, info?: any);
-}
-
-// @public (undocumented)
-type TypeSource = NamedTypeSource | FnTypeSource;
-
-// @public (undocumented)
-type TypeSource_2 = NamedTypeSource_2 | FnTypeSource_2;
-
-// @public (undocumented)
-const unWrapRet: (v: Value) => Value;
-
-declare namespace utils {
-    export {
-        expectAny,
-        assertBoolean,
-        assertFunction,
-        assertString,
-        assertNumber,
-        assertObject,
-        assertArray,
-        isBoolean,
-        isFunction,
-        isString,
-        isNumber,
-        isObject,
-        isArray,
-        eq,
-        valToString,
-        valToJs,
-        jsToVal,
-        getLangVersion,
-        reprValue
-    }
-}
-export { utils }
-
-// @public (undocumented)
-function valToJs(val: Value): any;
-
-// @public (undocumented)
-function valToString(val: Value, simple?: boolean): string;
-
-// @public (undocumented)
-type Value = (VNull | VBool | VNum | VStr | VArr | VObj | VFn | VReturn | VBreak | VContinue) & Attr_2;
-
-declare namespace values {
-    export {
-        VNull,
-        VBool,
-        VNum,
-        VStr,
-        VArr,
-        VObj,
-        VFn,
-        VReturn,
-        VBreak,
-        VContinue,
-        Attr_2 as Attr,
-        Value,
-        NULL,
-        TRUE,
-        FALSE,
-        NUM,
-        STR,
-        BOOL,
-        OBJ,
-        ARR,
-        FN,
-        FN_NATIVE,
-        RETURN,
-        BREAK,
-        CONTINUE,
-        unWrapRet
-    }
-}
-export { values }
-
-// @public (undocumented)
-type VArr = {
-    type: 'arr';
-    value: Value[];
-};
-
-// @public (undocumented)
-type VBool = {
-    type: 'bool';
-    value: boolean;
-};
-
-// @public (undocumented)
-type VBreak = {
-    type: 'break';
-    value: null;
-};
-
-// @public (undocumented)
-type VContinue = {
-    type: 'continue';
-    value: null;
-};
-
-// @public (undocumented)
-type VFn = {
-    type: 'fn';
-    args?: string[];
-    statements?: Node_2[];
-    native?: (args: (Value | undefined)[], opts: {
-        call: (fn: VFn, args: Value[]) => Promise<Value>;
-        registerAbortHandler: (handler: () => void) => void;
-        unregisterAbortHandler: (handler: () => void) => void;
-    }) => Value | Promise<Value> | void;
-    scope?: Scope;
-};
-
-// @public (undocumented)
-type VNull = {
-    type: 'null';
-};
-
-// @public (undocumented)
-type VNum = {
-    type: 'num';
-    value: number;
-};
-
-// @public (undocumented)
-type VObj = {
-    type: 'obj';
-    value: Map<string, Value>;
-};
-
-// @public (undocumented)
-type VReturn = {
-    type: 'return';
-    value: Value;
-};
-
-// @public (undocumented)
-type VStr = {
-    type: 'str';
-    value: string;
-};
-
-// (No @packageDocumentation comment for this package)
-
-```
+## API Report File for "@syuilo/aiscript"
+
+> Do not edit this file. It is a report generated by [API Extractor](https://api-extractor.com/).
+
+```ts
+
+// Warning: (ae-forgotten-export) The symbol "NodeBase" needs to be exported by the entry point index.d.ts
+//
+// @public (undocumented)
+type AddAssign = NodeBase & {
+    type: 'addAssign';
+    dest: Expression;
+    expr: Expression;
+};
+
+// Warning: (ae-forgotten-export) The symbol "NodeBase_2" needs to be exported by the entry point index.d.ts
+//
+// @public (undocumented)
+type AddAssign_2 = NodeBase_2 & {
+    type: 'addAssign';
+    dest: Expression_2;
+    expr: Expression_2;
+};
+
+// @public (undocumented)
+abstract class AiScriptError extends Error {
+    constructor(message: string, info?: any);
+    // (undocumented)
+    info?: any;
+}
+
+// @public (undocumented)
+type And = NodeBase & {
+    type: 'and';
+    left: Expression;
+    right: Expression;
+};
+
+// @public (undocumented)
+type And_2 = NodeBase_2 & {
+    type: 'and';
+    left: Expression_2;
+    right: Expression_2;
+};
+
+// @public (undocumented)
+const ARR: (arr: VArr['value']) => VArr;
+
+// @public (undocumented)
+type Arr = NodeBase & {
+    type: 'arr';
+    value: Expression[];
+};
+
+// Warning: (ae-forgotten-export) The symbol "ChainProp" needs to be exported by the entry point index.d.ts
+//
+// @public (undocumented)
+type Arr_2 = NodeBase_2 & ChainProp & {
+    type: 'arr';
+    value: Expression_2[];
+};
+
+// @public (undocumented)
+function assertArray(val: Value | null | undefined): asserts val is VArr;
+
+// @public (undocumented)
+function assertBoolean(val: Value | null | undefined): asserts val is VBool;
+
+// @public (undocumented)
+function assertFunction(val: Value | null | undefined): asserts val is VFn;
+
+// @public (undocumented)
+function assertNumber(val: Value | null | undefined): asserts val is VNum;
+
+// @public (undocumented)
+function assertObject(val: Value | null | undefined): asserts val is VObj;
+
+// @public (undocumented)
+function assertString(val: Value | null | undefined): asserts val is VStr;
+
+// @public (undocumented)
+type Assign = NodeBase & {
+    type: 'assign';
+    dest: Expression;
+    expr: Expression;
+};
+
+// @public (undocumented)
+type Assign_2 = NodeBase_2 & {
+    type: 'assign';
+    dest: Expression_2;
+    expr: Expression_2;
+};
+
+declare namespace Ast {
+    export {
+        isStatement,
+        isExpression,
+        Loc,
+        Node_2 as Node,
+        Statement,
+        Expression,
+        Namespace,
+        Meta,
+        Definition,
+        Attribute,
+        Return,
+        Each,
+        For,
+        Loop,
+        Break,
+        Continue,
+        AddAssign,
+        SubAssign,
+        Assign,
+        Not,
+        And,
+        Or,
+        If,
+        Fn,
+        Match,
+        Block,
+        Exists,
+        Tmpl,
+        Str,
+        Num,
+        Bool,
+        Null,
+        Obj,
+        Arr,
+        Identifier,
+        Call,
+        Index,
+        Prop,
+        TypeSource,
+        NamedTypeSource,
+        FnTypeSource
+    }
+}
+export { Ast }
+
+// @public (undocumented)
+type Attr_2 = {
+    attr?: {
+        name: string;
+        value: Value;
+    }[];
+};
+
+// @public (undocumented)
+type Attribute = NodeBase & {
+    type: 'attr';
+    name: string;
+    value: Expression;
+};
+
+// @public (undocumented)
+type Attribute_2 = NodeBase_2 & {
+    type: 'attr';
+    name: string;
+    value: Expression_2;
+};
+
+// @public (undocumented)
+type Block = NodeBase & {
+    type: 'block';
+    statements: (Statement | Expression)[];
+};
+
+// @public (undocumented)
+type Block_2 = NodeBase_2 & ChainProp & {
+    type: 'block';
+    statements: (Statement_2 | Expression_2)[];
+};
+
+// @public (undocumented)
+const BOOL: (bool: VBool['value']) => VBool;
+
+// @public (undocumented)
+type Bool = NodeBase & {
+    type: 'bool';
+    value: boolean;
+};
+
+// @public (undocumented)
+type Bool_2 = NodeBase_2 & ChainProp & {
+    type: 'bool';
+    value: boolean;
+};
+
+// @public (undocumented)
+const BREAK: () => Value;
+
+// @public (undocumented)
+type Break = NodeBase & {
+    type: 'break';
+};
+
+// @public (undocumented)
+type Break_2 = NodeBase_2 & {
+    type: 'break';
+};
+
+// @public (undocumented)
+function CALL(target: Call_2['target'], args: Call_2['args'], loc?: {
+    start: number;
+    end: number;
+}): Call_2;
+
+// @public (undocumented)
+type Call = NodeBase & {
+    type: 'call';
+    target: Expression;
+    args: Expression[];
+};
+
+// @public (undocumented)
+type Call_2 = NodeBase_2 & {
+    type: 'call';
+    target: Expression_2;
+    args: Expression_2[];
+};
+
+// @public (undocumented)
+type CallChain = NodeBase_2 & {
+    type: 'callChain';
+    args: Expression_2[];
+};
+
+// @public (undocumented)
+type ChainMember = CallChain | IndexChain | PropChain;
+
+// @public (undocumented)
+const CONTINUE: () => Value;
+
+// @public (undocumented)
+type Continue = NodeBase & {
+    type: 'continue';
+};
+
+// @public (undocumented)
+type Continue_2 = NodeBase_2 & {
+    type: 'continue';
+};
+
+declare namespace Cst {
+    export {
+        isStatement_2 as isStatement,
+        isExpression_2 as isExpression,
+        hasChainProp,
+        CALL,
+        INDEX,
+        PROP,
+        Node_3 as Node,
+        Statement_2 as Statement,
+        Expression_2 as Expression,
+        Namespace_2 as Namespace,
+        Meta_2 as Meta,
+        Definition_2 as Definition,
+        Attribute_2 as Attribute,
+        Return_2 as Return,
+        Each_2 as Each,
+        For_2 as For,
+        Loop_2 as Loop,
+        Break_2 as Break,
+        Continue_2 as Continue,
+        AddAssign_2 as AddAssign,
+        SubAssign_2 as SubAssign,
+        Assign_2 as Assign,
+        InfixOperator,
+        Infix,
+        Not_2 as Not,
+        And_2 as And,
+        Or_2 as Or,
+        If_2 as If,
+        Fn_2 as Fn,
+        Match_2 as Match,
+        Block_2 as Block,
+        Exists_2 as Exists,
+        Tmpl_2 as Tmpl,
+        Str_2 as Str,
+        Num_2 as Num,
+        Bool_2 as Bool,
+        Null_2 as Null,
+        Obj_2 as Obj,
+        Arr_2 as Arr,
+        Identifier_2 as Identifier,
+        ChainMember,
+        CallChain,
+        IndexChain,
+        PropChain,
+        Call_2 as Call,
+        Index_2 as Index,
+        Prop_2 as Prop,
+        TypeSource_2 as TypeSource,
+        NamedTypeSource_2 as NamedTypeSource,
+        FnTypeSource_2 as FnTypeSource
+    }
+}
+export { Cst }
+
+// @public (undocumented)
+type Definition = NodeBase & {
+    type: 'def';
+    name: string;
+    varType?: TypeSource;
+    expr: Expression;
+    mut: boolean;
+    attr: Attribute[];
+};
+
+// @public (undocumented)
+type Definition_2 = NodeBase_2 & {
+    type: 'def';
+    name: string;
+    varType?: TypeSource_2;
+    expr: Expression_2;
+    mut: boolean;
+    attr?: Attribute_2[];
+};
+
+// @public (undocumented)
+type Each = NodeBase & {
+    type: 'each';
+    var: string;
+    items: Expression;
+    for: Statement | Expression;
+};
+
+// @public (undocumented)
+type Each_2 = NodeBase_2 & {
+    type: 'each';
+    var: string;
+    items: Expression_2;
+    for: Statement_2 | Expression_2;
+};
+
+// @public (undocumented)
+function eq(a: Value, b: Value): boolean;
+
+// @public (undocumented)
+const ERROR: (name: string, info?: Value) => Value;
+
+declare namespace errors {
+    export {
+        AiScriptError,
+        SyntaxError_2 as SyntaxError,
+        TypeError_2 as TypeError,
+        RuntimeError,
+        IndexOutOfRangeError
+    }
+}
+export { errors }
+
+// @public (undocumented)
+type Exists = NodeBase & {
+    type: 'exists';
+    identifier: Identifier;
+};
+
+// @public (undocumented)
+type Exists_2 = NodeBase_2 & ChainProp & {
+    type: 'exists';
+    identifier: Identifier_2;
+};
+
+// @public (undocumented)
+function expectAny(val: Value | null | undefined): asserts val is Value;
+
+// @public (undocumented)
+type Expression = If | Fn | Match | Block | Exists | Tmpl | Str | Num | Bool | Null | Obj | Arr | Not | And | Or | Identifier | Call | Index | Prop;
+
+// @public (undocumented)
+type Expression_2 = Infix | Not_2 | And_2 | Or_2 | If_2 | Fn_2 | Match_2 | Block_2 | Exists_2 | Tmpl_2 | Str_2 | Num_2 | Bool_2 | Null_2 | Obj_2 | Arr_2 | Identifier_2 | Call_2 | // IR
+Index_2 | // IR
+Prop_2;
+
+// @public (undocumented)
+const FALSE: {
+    type: "bool";
+    value: boolean;
+};
+
+// @public (undocumented)
+const FN: (args: VFn['args'], statements: VFn['statements'], scope: VFn['scope']) => VFn;
+
+// @public (undocumented)
+type Fn = NodeBase & {
+    type: 'fn';
+    args: {
+        name: string;
+        argType?: TypeSource;
+    }[];
+    retType?: TypeSource;
+    children: (Statement | Expression)[];
+};
+
+// @public (undocumented)
+type Fn_2 = NodeBase_2 & ChainProp & {
+    type: 'fn';
+    args: {
+        name: string;
+        argType?: TypeSource_2;
+    }[];
+    retType?: TypeSource_2;
+    children: (Statement_2 | Expression_2)[];
+};
+
+// @public (undocumented)
+const FN_NATIVE: (fn: VFn['native']) => VFn;
+
+// @public (undocumented)
+type FnTypeSource = NodeBase & {
+    type: 'fnTypeSource';
+    args: TypeSource[];
+    result: TypeSource;
+};
+
+// @public (undocumented)
+type FnTypeSource_2 = NodeBase_2 & {
+    type: 'fnTypeSource';
+    args: TypeSource_2[];
+    result: TypeSource_2;
+};
+
+// @public (undocumented)
+type For = NodeBase & {
+    type: 'for';
+    var?: string;
+    from?: Expression;
+    to?: Expression;
+    times?: Expression;
+    for: Statement | Expression;
+};
+
+// @public (undocumented)
+type For_2 = NodeBase_2 & {
+    type: 'for';
+    var?: string;
+    from?: Expression_2;
+    to?: Expression_2;
+    times?: Expression_2;
+    for: Statement_2 | Expression_2;
+};
+
+// @public (undocumented)
+function getLangVersion(input: string): string | null;
+
+// @public (undocumented)
+function hasChainProp<T extends Node_3>(x: T): x is T & ChainProp;
+
+// @public (undocumented)
+type Identifier = NodeBase & {
+    type: 'identifier';
+    name: string;
+};
+
+// @public (undocumented)
+type Identifier_2 = NodeBase_2 & ChainProp & {
+    type: 'identifier';
+    name: string;
+};
+
+// @public (undocumented)
+type If = NodeBase & {
+    type: 'if';
+    cond: Expression;
+    then: Statement | Expression;
+    elseif: {
+        cond: Expression;
+        then: Statement | Expression;
+    }[];
+    else?: Statement | Expression;
+};
+
+// @public (undocumented)
+type If_2 = NodeBase_2 & {
+    type: 'if';
+    cond: Expression_2;
+    then: Statement_2 | Expression_2;
+    elseif: {
+        cond: Expression_2;
+        then: Statement_2 | Expression_2;
+    }[];
+    else?: Statement_2 | Expression_2;
+};
+
+// @public (undocumented)
+function INDEX(target: Index_2['target'], index: Index_2['index'], loc?: {
+    start: number;
+    end: number;
+}): Index_2;
+
+// @public (undocumented)
+type Index = NodeBase & {
+    type: 'index';
+    target: Expression;
+    index: Expression;
+};
+
+// @public (undocumented)
+type Index_2 = NodeBase_2 & {
+    type: 'index';
+    target: Expression_2;
+    index: Expression_2;
+};
+
+// @public (undocumented)
+type IndexChain = NodeBase_2 & {
+    type: 'indexChain';
+    index: Expression_2;
+};
+
+// @public (undocumented)
+class IndexOutOfRangeError extends RuntimeError {
+    constructor(message: string, info?: any);
+}
+
+// @public (undocumented)
+type Infix = NodeBase_2 & {
+    type: 'infix';
+    operands: Expression_2[];
+    operators: InfixOperator[];
+};
+
+// @public (undocumented)
+type InfixOperator = '||' | '&&' | '==' | '!=' | '<=' | '>=' | '<' | '>' | '+' | '-' | '*' | '^' | '/' | '%';
+
+// @public (undocumented)
+export class Interpreter {
+    constructor(vars: Record<string, Value>, opts?: {
+        in?(q: string): Promise<string>;
+        out?(value: Value): void;
+        log?(type: string, params: Record<string, any>): void;
+        maxStep?: number;
+    });
+    // (undocumented)
+    abort(): void;
+    // (undocumented)
+    static collectMetadata(script?: Ast.Node[]): Map<any, any> | undefined;
+    // (undocumented)
+    exec(script?: Ast.Node[]): Promise<void>;
+    // (undocumented)
+    execFn(fn: VFn, args: Value[]): Promise<Value>;
+    // (undocumented)
+    registerAbortHandler(handler: () => void): void;
+    // (undocumented)
+    scope: Scope;
+    // (undocumented)
+    stepCount: number;
+    // (undocumented)
+    unregisterAbortHandler(handler: () => void): void;
+}
+
+// @public (undocumented)
+function isArray(val: Value): val is VArr;
+
+// @public (undocumented)
+function isBoolean(val: Value): val is VBool;
+
+// @public (undocumented)
+function isExpression(x: Node_2): x is Expression;
+
+// @public (undocumented)
+function isExpression_2(x: Node_3): x is Expression_2;
+
+// @public (undocumented)
+function isFunction(val: Value): val is VFn;
+
+// @public (undocumented)
+function isNumber(val: Value): val is VNum;
+
+// @public (undocumented)
+function isObject(val: Value): val is VObj;
+
+// @public (undocumented)
+function isStatement(x: Node_2): x is Statement;
+
+// @public (undocumented)
+function isStatement_2(x: Node_3): x is Statement_2;
+
+// @public (undocumented)
+function isString(val: Value): val is VStr;
+
+// @public (undocumented)
+function jsToVal(val: any): Value;
+
+// @public
+type Loc = {
+    start: number;
+    end: number;
+};
+
+// @public (undocumented)
+type Loop = NodeBase & {
+    type: 'loop';
+    statements: (Statement | Expression)[];
+};
+
+// @public (undocumented)
+type Loop_2 = NodeBase_2 & {
+    type: 'loop';
+    statements: (Statement_2 | Expression_2)[];
+};
+
+// @public (undocumented)
+type Match = NodeBase & {
+    type: 'match';
+    about: Expression;
+    qs: {
+        q: Expression;
+        a: Statement | Expression;
+    }[];
+    default?: Statement | Expression;
+};
+
+// @public (undocumented)
+type Match_2 = NodeBase_2 & ChainProp & {
+    type: 'match';
+    about: Expression_2;
+    qs: {
+        q: Expression_2;
+        a: Statement_2 | Expression_2;
+    }[];
+    default?: Statement_2 | Expression_2;
+};
+
+// @public (undocumented)
+type Meta = NodeBase & {
+    type: 'meta';
+    name: string | null;
+    value: Expression;
+};
+
+// @public (undocumented)
+type Meta_2 = NodeBase_2 & {
+    type: 'meta';
+    name: string | null;
+    value: Expression_2;
+};
+
+// @public (undocumented)
+type NamedTypeSource = NodeBase & {
+    type: 'namedTypeSource';
+    name: string;
+    inner?: TypeSource;
+};
+
+// @public (undocumented)
+type NamedTypeSource_2 = NodeBase_2 & {
+    type: 'namedTypeSource';
+    name: string;
+    inner?: TypeSource_2;
+};
+
+// @public (undocumented)
+type Namespace = NodeBase & {
+    type: 'ns';
+    name: string;
+    members: (Definition | Namespace)[];
+};
+
+// @public (undocumented)
+type Namespace_2 = NodeBase_2 & {
+    type: 'ns';
+    name: string;
+    members: (Definition_2 | Namespace_2)[];
+};
+
+// @public (undocumented)
+type Node_2 = Namespace | Meta | Statement | Expression | TypeSource;
+
+// @public
+type Node_3 = Namespace_2 | Meta_2 | Statement_2 | Expression_2 | ChainMember | TypeSource_2;
+
+// @public (undocumented)
+type Not = NodeBase & {
+    type: 'not';
+    expr: Expression;
+};
+
+// @public (undocumented)
+type Not_2 = NodeBase_2 & {
+    type: 'not';
+    expr: Expression_2;
+};
+
+// @public (undocumented)
+const NULL: {
+    type: "null";
+};
+
+// @public (undocumented)
+type Null = NodeBase & {
+    type: 'null';
+};
+
+// @public (undocumented)
+type Null_2 = NodeBase_2 & ChainProp & {
+    type: 'null';
+};
+
+// @public (undocumented)
+const NUM: (num: VNum['value']) => VNum;
+
+// @public (undocumented)
+type Num = NodeBase & {
+    type: 'num';
+    value: number;
+};
+
+// @public (undocumented)
+type Num_2 = NodeBase_2 & ChainProp & {
+    type: 'num';
+    value: number;
+};
+
+// @public (undocumented)
+const OBJ: (obj: VObj['value']) => VObj;
+
+// @public (undocumented)
+type Obj = NodeBase & {
+    type: 'obj';
+    value: Map<string, Expression>;
+};
+
+// @public (undocumented)
+type Obj_2 = NodeBase_2 & ChainProp & {
+    type: 'obj';
+    value: Map<string, Expression_2>;
+};
+
+// @public (undocumented)
+type Or = NodeBase & {
+    type: 'or';
+    left: Expression;
+    right: Expression;
+};
+
+// @public (undocumented)
+type Or_2 = NodeBase_2 & {
+    type: 'or';
+    left: Expression_2;
+    right: Expression_2;
+};
+
+// @public (undocumented)
+export class Parser {
+    constructor();
+    // (undocumented)
+    addPlugin(type: PluginType, plugin: ParserPlugin): void;
+    // (undocumented)
+    static parse(input: string): Ast.Node[];
+    // (undocumented)
+    parse(input: string): Ast.Node[];
+}
+
+// @public (undocumented)
+export type ParserPlugin = (nodes: Cst.Node[]) => Cst.Node[];
+
+// @public (undocumented)
+export type PluginType = 'validate' | 'transform';
+
+// @public (undocumented)
+function PROP(target: Prop_2['target'], name: Prop_2['name'], loc?: {
+    start: number;
+    end: number;
+}): Prop_2;
+
+// @public (undocumented)
+type Prop = NodeBase & {
+    type: 'prop';
+    target: Expression;
+    name: string;
+};
+
+// @public (undocumented)
+type Prop_2 = NodeBase_2 & {
+    type: 'prop';
+    target: Expression_2;
+    name: string;
+};
+
+// @public (undocumented)
+type PropChain = NodeBase_2 & {
+    type: 'propChain';
+    name: string;
+};
+
+// @public (undocumented)
+function reprValue(value: Value, literalLike?: boolean, processedObjects?: Set<object>): string;
+
+// @public (undocumented)
+const RETURN: (v: VReturn['value']) => Value;
+
+// @public (undocumented)
+type Return = NodeBase & {
+    type: 'return';
+    expr: Expression;
+};
+
+// @public (undocumented)
+type Return_2 = NodeBase_2 & {
+    type: 'return';
+    expr: Expression_2;
+};
+
+// @public (undocumented)
+class RuntimeError extends AiScriptError {
+    constructor(message: string, info?: any);
+}
+
+// @public (undocumented)
+export class Scope {
+    constructor(layerdStates?: Scope['layerdStates'], parent?: Scope, name?: Scope['name']);
+    add(name: string, val: Value): void;
+    assign(name: string, val: Value): void;
+    // (undocumented)
+    createChildScope(states?: Map<string, Value>, name?: Scope['name']): Scope;
+    exists(name: string): boolean;
+    get(name: string): Value;
+    getAll(): Map<string, Value>;
+    // (undocumented)
+    name: string;
+    // (undocumented)
+    opts: {
+        log?(type: string, params: Record<string, any>): void;
+        onUpdated?(name: string, value: Value): void;
+    };
+}
+
+// @public (undocumented)
+type Statement = Definition | Return | Each | For | Loop | Break | Continue | Assign | AddAssign | SubAssign;
+
+// @public (undocumented)
+type Statement_2 = Definition_2 | Return_2 | Attribute_2 | // AST
+Each_2 | For_2 | Loop_2 | Break_2 | Continue_2 | Assign_2 | AddAssign_2 | SubAssign_2;
+
+// @public (undocumented)
+const STR: (str: VStr['value']) => VStr;
+
+// @public (undocumented)
+type Str = NodeBase & {
+    type: 'str';
+    value: string;
+};
+
+// @public (undocumented)
+type Str_2 = NodeBase_2 & ChainProp & {
+    type: 'str';
+    value: string;
+};
+
+// @public (undocumented)
+type SubAssign = NodeBase & {
+    type: 'subAssign';
+    dest: Expression;
+    expr: Expression;
+};
+
+// @public (undocumented)
+type SubAssign_2 = NodeBase_2 & {
+    type: 'subAssign';
+    dest: Expression_2;
+    expr: Expression_2;
+};
+
+// @public (undocumented)
+class SyntaxError_2 extends AiScriptError {
+    constructor(message: string, info?: any);
+}
+
+// @public (undocumented)
+type Tmpl = NodeBase & {
+    type: 'tmpl';
+    tmpl: (string | Expression)[];
+};
+
+// @public (undocumented)
+type Tmpl_2 = NodeBase_2 & ChainProp & {
+    type: 'tmpl';
+    tmpl: (string | Expression_2)[];
+};
+
+// @public (undocumented)
+const TRUE: {
+    type: "bool";
+    value: boolean;
+};
+
+// @public (undocumented)
+class TypeError_2 extends AiScriptError {
+    constructor(message: string, info?: any);
+}
+
+// @public (undocumented)
+type TypeSource = NamedTypeSource | FnTypeSource;
+
+// @public (undocumented)
+type TypeSource_2 = NamedTypeSource_2 | FnTypeSource_2;
+
+// @public (undocumented)
+const unWrapRet: (v: Value) => Value;
+
+declare namespace utils {
+    export {
+        expectAny,
+        assertBoolean,
+        assertFunction,
+        assertString,
+        assertNumber,
+        assertObject,
+        assertArray,
+        isBoolean,
+        isFunction,
+        isString,
+        isNumber,
+        isObject,
+        isArray,
+        eq,
+        valToString,
+        valToJs,
+        jsToVal,
+        getLangVersion,
+        reprValue
+    }
+}
+export { utils }
+
+// @public (undocumented)
+function valToJs(val: Value): any;
+
+// @public (undocumented)
+function valToString(val: Value, simple?: boolean): string;
+
+// @public (undocumented)
+type Value = (VNull | VBool | VNum | VStr | VArr | VObj | VFn | VReturn | VBreak | VContinue | VError) & Attr_2;
+
+declare namespace values {
+    export {
+        VNull,
+        VBool,
+        VNum,
+        VStr,
+        VArr,
+        VObj,
+        VFn,
+        VReturn,
+        VBreak,
+        VContinue,
+        VError,
+        Attr_2 as Attr,
+        Value,
+        NULL,
+        TRUE,
+        FALSE,
+        NUM,
+        STR,
+        BOOL,
+        OBJ,
+        ARR,
+        FN,
+        FN_NATIVE,
+        RETURN,
+        BREAK,
+        CONTINUE,
+        unWrapRet,
+        ERROR
+    }
+}
+export { values }
+
+// @public (undocumented)
+type VArr = {
+    type: 'arr';
+    value: Value[];
+};
+
+// @public (undocumented)
+type VBool = {
+    type: 'bool';
+    value: boolean;
+};
+
+// @public (undocumented)
+type VBreak = {
+    type: 'break';
+    value: null;
+};
+
+// @public (undocumented)
+type VContinue = {
+    type: 'continue';
+    value: null;
+};
+
+// @public (undocumented)
+type VError = {
+    type: 'error';
+    value: string;
+    info?: Value;
+};
+
+// @public (undocumented)
+type VFn = {
+    type: 'fn';
+    args?: string[];
+    statements?: Node_2[];
+    native?: (args: (Value | undefined)[], opts: {
+        call: (fn: VFn, args: Value[]) => Promise<Value>;
+        registerAbortHandler: (handler: () => void) => void;
+        unregisterAbortHandler: (handler: () => void) => void;
+    }) => Value | Promise<Value> | void;
+    scope?: Scope;
+};
+
+// @public (undocumented)
+type VNull = {
+    type: 'null';
+};
+
+// @public (undocumented)
+type VNum = {
+    type: 'num';
+    value: number;
+};
+
+// @public (undocumented)
+type VObj = {
+    type: 'obj';
+    value: Map<string, Value>;
+};
+
+// @public (undocumented)
+type VReturn = {
+    type: 'return';
+    value: Value;
+};
+
+// @public (undocumented)
+type VStr = {
+    type: 'str';
+    value: string;
+};
+
+// (No @packageDocumentation comment for this package)
+
+```
diff --git a/src/interpreter/lib/std.ts b/src/interpreter/lib/std.ts
index a7ffea54..f46e20b3 100644
--- a/src/interpreter/lib/std.ts
+++ b/src/interpreter/lib/std.ts
@@ -1,7 +1,7 @@
 /* eslint-disable no-empty-pattern */
 import { v4 as uuid } from 'uuid';
 import seedrandom from 'seedrandom';
-import { NUM, STR, FN_NATIVE, FALSE, TRUE, ARR, NULL, BOOL, OBJ } from '../value.js';
+import { NUM, STR, FN_NATIVE, FALSE, TRUE, ARR, NULL, BOOL, OBJ, ERROR } from '../value.js';
 import { assertNumber, assertString, assertBoolean, valToJs, jsToVal, assertFunction, assertObject, eq, expectAny, assertArray, reprValue } from '../util.js';
 import { RuntimeError } from '../../error.js';
 import type { Value } from '../value.js';
@@ -152,7 +152,11 @@ export const std: Record<string, Value> = {
 
 	'Json:parse': FN_NATIVE(([json]) => {
 		assertString(json);
-		return jsToVal(JSON.parse(json.value));
+		try {
+			return jsToVal(JSON.parse(json.value));
+		} catch (e) {
+			return ERROR('not_json');
+		}
 	}),
 
 	'Json:parsable': FN_NATIVE(([str]) => {
diff --git a/src/interpreter/primitive-props.ts b/src/interpreter/primitive-props.ts
index fdd51b22..3784f8d0 100644
--- a/src/interpreter/primitive-props.ts
+++ b/src/interpreter/primitive-props.ts
@@ -2,9 +2,9 @@ import { substring, length, indexOf, toArray } from 'stringz';
 import { RuntimeError } from '../error.js';
 import { assertArray, assertBoolean, assertFunction, assertNumber, assertString, expectAny } from './util.js';
 import { ARR, FALSE, FN_NATIVE, NULL, NUM, STR, TRUE } from './value.js';
-import type { Value, VArr, VFn, VNum, VStr } from './value.js';
+import type { Value, VArr, VFn, VNum, VStr, VError } from './value.js';
 
-type VWithPP = VNum|VStr|VArr;
+type VWithPP = VNum|VStr|VArr|VError;
 
 const PRIMITIVE_PROPS: {
 	[key in VWithPP['type']]: { [key: string]: (target: Value) => Value }
@@ -221,6 +221,12 @@ const PRIMITIVE_PROPS: {
 			return target;
 		}),
 	},
+
+	error: {
+		name: (target: VError): VStr => STR(target.value), 
+
+		info: (target: VError): Value => target.info ?? NULL,
+	},
 } as const;
 
 export function getPrimProp(target: Value, name: string): Value {
diff --git a/src/interpreter/value.ts b/src/interpreter/value.ts
index 44db6d51..420ccfb7 100644
--- a/src/interpreter/value.ts
+++ b/src/interpreter/value.ts
@@ -57,6 +57,12 @@ export type VContinue = {
 	value: null;
 };
 
+export type VError = {
+	type: 'error';
+	value: string;
+	info?: Value;
+};
+
 export type Attr = {
 	attr?: {
 		name: string;
@@ -64,7 +70,7 @@ export type Attr = {
 	}[];
 };
 
-export type Value = (VNull | VBool | VNum | VStr | VArr | VObj | VFn | VReturn | VBreak | VContinue) & Attr;
+export type Value = (VNull | VBool | VNum | VStr | VArr | VObj | VFn | VReturn | VBreak | VContinue | VError) & Attr;
 
 export const NULL = {
 	type: 'null' as const,
@@ -134,3 +140,9 @@ export const CONTINUE = (): Value => ({
 });
 
 export const unWrapRet = (v: Value): Value => v.type === 'return' ? v.value : v;
+
+export const ERROR = (name: string, info?: Value): Value => ({
+	type: 'error' as const,
+	value: name,
+	info: info,
+});
diff --git a/test/index.ts b/test/index.ts
index 6e4c977c..2da98120 100644
--- a/test/index.ts
+++ b/test/index.ts
@@ -5,7 +5,7 @@
 
 import * as assert from 'assert';
 import { Parser, Interpreter, utils, errors, Ast } from '../src';
-import { NUM, STR, NULL, ARR, OBJ, BOOL, TRUE, FALSE } from '../src/interpreter/value';
+import { NUM, STR, NULL, ARR, OBJ, BOOL, TRUE, FALSE, ERROR } from '../src/interpreter/value';
 import { RuntimeError } from '../src/error';
 
 const exe = (program: string): Promise<any> => new Promise((ok, err) => {
@@ -2762,32 +2762,33 @@ describe('std', () => {
 
 		test.concurrent('parsable', async () => {
 			[
-				'',
 				'null',
-				'hoge',
 				'"hoge"',
-				'[',
 				'[]',
-				'{}'
+				'{}',
 			].forEach(async (str) => {
 				const res = await exe(`
-					<: Json:parsable('${str}')
+					<: [
+						Json:parsable('${str}')
+						Json:stringify(Json:parse('${str}'))
+					]
 				`);
-				assert.deepEqual(res.type, 'bool');
-				if (res.value) {
-					await exe(`
-						<: Json:parse('${str}')
-					`);
-				} else {
-					try {
-						await exe(`
-							<: Json:parse('${str}')
-						`);
-					} catch (e) {
-						if (e instanceof SyntaxError) return;
-					}
-					assert.fail()
-				}
+				eq(res, ARR([TRUE, STR(str)]));
+			});
+		});
+		test.concurrent('unparsable', async () => {
+			[
+				'',
+				'hoge',
+				'[',
+			].forEach(async (str) => {
+				const res = await exe(`
+					<: [
+						Json:parsable('${str}')
+						Json:parse('${str}')
+					]
+				`);
+				eq(res, ARR([FALSE, ERROR('not_json')]));
 			});
 		});
 	});