除了@JDB和@adsy提供的答案之外，您还可以使用extends来实现您的目标：

type StringOrArrayString<T extends PromptOptions> = T extends {input: TextType} ? string : string[];

function foo<T extends PromptOptions>(name: string, options: T): StringOrArrayString<T> {
  // ...
}

检查这个Playground

使用函数重载。

const TextInputTypes = [
    "text",
    "number",
    "password",
    "email",
    "tel",
    "url",
    "search",
    "color",
    "date",
    "time",
    "datetime-local",
    "month",
    "week",
    "range",
    "file",
] as const;
const CheckboxTypes = ["checkbox", "radio"];
const SelectTypes = ["select"] as const;
type TextType = (typeof TextInputTypes)[number];
type CheckType = (typeof CheckboxTypes)[number] | (typeof SelectTypes)[number];
type InputType = TextType | CheckType;

type PromptOptions<T extends InputType> = {
    input: T;
    placeholder: string;
    entries: { value: string; text: string }[];
};

const isCheckboxType = (typeString: string): typeString is CheckType => (CheckboxTypes as string[]).includes(typeString)

function foo (name: string, options: PromptOptions<TextType>): string
function foo (name: string, options: PromptOptions<CheckType>): string[]
function foo (name: string, options: PromptOptions<TextType | CheckType>): string | string[]  {
  if (CheckboxTypes.includes(options.input as CheckType)) {
    // TODO
    return ''
  }

  // transformToDocument
  return []
}

const arrayExample = foo('test', {input: 'select', placeholder: 'test', entries: []})
const stringExample = foo('test', {input: 'text', placeholder: 'test', entries: []})

使用函数重载。

可以使用函数重载检测input属性的类型，然后返回string或string[]。请注意，这需要将匿名函数（const foo = () => {}）更改为命名函数（function foo() {}）。

function isTextType(inputType:string):inputType is typeof TextInputTypes[number] {
    return (TextInputTypes as readonly string[]).includes(inputType);
}

type PromptOptions = {
    placeholder: string;
    entries: { value: string; text: string }[];
}
type TextTypePromptOptions = PromptOptions & {
    input: TextType;
};
type CheckTypePromptOptions = PromptOptions & {
    input: CheckType;
}

function foo(name:string, options:TextTypePromptOptions):string;
function foo(name:string, options:CheckTypePromptOptions):string[];
function foo(name:string, options:TextTypePromptOptions|CheckTypePromptOptions):string|string[] {
    if (isTextType(options.input)) {
        return "";
    } else {
        return [];
    }
}

// const result1: string
const result1 = foo("", { placeholder: "", entries: [], input: "text" });
// const result2: string[]
const result2 = foo("", { placeholder: "", entries: [], input: "radio" });

对于像您这样的简单情况，这很容易阅读和理解，但是如果您有许多这样的参数，那么写出所有可能的重载可能会有点乏味。