/** Useful to flatten the type output to improve type hints shown in editors. And also to transform an interface into a type to aide with assignability. @example ``` import type {Simplify} from 'type-fest'; type PositionProps = { top: number; left: number; }; type SizeProps = { width: number; height: number; }; // In your editor, hovering over `Props` will show a flattened object with all the properties. type Props = Simplify; ``` Sometimes it is desired to pass a value as a function argument that has a different type. At first inspection it may seem assignable, and then you discover it is not because the `value`'s type definition was defined as an interface. In the following example, `fn` requires an argument of type `Record`. If the value is defined as a literal, then it is assignable. And if the `value` is defined as type using the `Simplify` utility the value is assignable. But if the `value` is defined as an interface, it is not assignable because the interface is not sealed and elsewhere a non-string property could be added to the interface. If the type definition must be an interface (perhaps it was defined in a third-party npm package), then the `value` can be defined as `const value: Simplify = ...`. Then `value` will be assignable to the `fn` argument. Or the `value` can be cast as `Simplify` if you can't re-declare the `value`. @example ``` import type {Simplify} from 'type-fest'; interface SomeInterface { foo: number; bar?: string; baz: number | undefined; } type SomeType = { foo: number; bar?: string; baz: number | undefined; }; const literal = {foo: 123, bar: 'hello', baz: 456}; const someType: SomeType = literal; const someInterface: SomeInterface = literal; function fn(object: Record): void {} fn(literal); // Good: literal object type is sealed fn(someType); // Good: type is sealed fn(someInterface); // Error: Index signature for type 'string' is missing in type 'someInterface'. Because `interface` can be re-opened fn(someInterface as Simplify); // Good: transform an `interface` into a `type` ``` @link https://github.com/microsoft/TypeScript/issues/15300 @see SimplifyDeep @category Object */ export type Simplify = {[KeyType in keyof T]: T[KeyType]} & {};