How to preserve the exact inferred type while ensuring the type conforms to another type in TypeScri-CodePudding

Is it possible to get the inferred type from an object when a type already is defined? Example:

type Foo = { [key: string]: string };

const foo: Foo = {
    lorem: 'ipsum',
    hello: 'world',
} as const;

type T = typeof foo;

/* Actual type:

type T = {
    [key: string]: string;
};
*/

/* Wanted type:

type T = {
    readonly lorem: 'ipsum';
    readonly hello: 'world';
};
*/

CodePudding user response：

You can use the new TypeScript 4.9 feature satisfies:

type Foo = { [key: string]: string };

const foo = {
    lorem: 'ipsum',
    hello: 'world',
} as const satisfies Foo;

type T = typeof foo;

/*
type T = {
    readonly lorem: 'ipsum';
    readonly hello: 'world';
};
*/