fix invalid code generated due to empty anyOf array

src/generator.ts

@@ -174,6 +174,9 @@ function generateRawType(ast: AST, options: Options): string {
     case 'ARRAY':
       return (() => {
         const type = generateType(ast.params, options)
+        if (!type) {
+          return 'never'
+        }
         return type.endsWith('"') ? '(' + type + ')[]' : type + '[]'
       })()
     case 'BOOLEAN':
@@ -289,6 +292,9 @@ function generateRawType(ast: AST, options: Options): string {
 function generateSetOperation(ast: TIntersection | TUnion, options: Options): string {
   const members = (ast as TUnion).params.map(_ => generateType(_, options))
   const separator = ast.type === 'UNION' ? '|' : '&'
+  if (!members.length) {
+    return 'never'
+  }
   return members.length === 1 ? members[0] : '(' + members.join(' ' + separator + ' ') + ')'
 }
 

test/__snapshots__/test/test.ts.md

@@ -947,6 +947,27 @@ Generated by [AVA](https://avajs.dev).
     }␊
     `
 
+## emptySet.js
+
+> Expected output to match snapshot for e2e test: emptySet.js
+
+    `/* eslint-disable */␊
+    /**␊
+     * This file was automatically generated by json-schema-to-typescript.␊
+     * DO NOT MODIFY IT BY HAND. Instead, modify the source JSONSchema file,␊
+     * and run json-schema-to-typescript to regenerate this file.␊
+     */␊
+    ␊
+    export interface EmptySet {␊
+      a?: never;␊
+      b?: never;␊
+      c?: never;␊
+      d?: {␊
+        [k: string]: unknown;␊
+      };␊
+    }␊
+    `
+
 ## enum.2.js
 
 > Expected output to match snapshot for e2e test: enum.2.js

test/e2e/emptySet.ts

@@ -0,0 +1,10 @@
+export const input = {
+  type: 'object',
+  properties: {
+    a: {anyOf: []},
+    b: {oneOf: []},
+    c: {allOf: []},
+    d: {multipleOf: []},
+  },
+  additionalProperties: false,
+}