Refactoring: Extract to interface

[DanielRosenwasser]

The "extract to type alias" code fix is great, however, a lot of people (myself included) prefer interfaces for object types rather than type aliases.

Extract to interface should work only on an intersection type with some number of anonymous object types, named object types, and type references.

Examples

// before
let x: { hello: string, world: string };

// after
interface NewType {
    hello: string;
    world: string;
}

let x: NewType;

// before
let x: { hello: string, world: string } & Record<string, string>;

// after
interface NewType extends Record<string, string> {
    hello: string;
    world: string;
}

let x: NewType;

Related issues:

• Suggestion: Refactor extract to type alias/typedef #23869
• add codefix for extracting an interface from an object literal #13082

[DanielRosenwasser]

P.S. it's okay if the refactoring results in a type that doesn't actually type-check as long as it does "the right thing" 90% of the time - don't over-do it (e.g. running on { hello: number } & Record<string, string>)

[Kingwl]

Extract to interface should work only on an intersection type with some number of anonymous object types, named object types, and type references.

I prefer deny refactor if there are any type reference(and not a type literal) in the selection

[DanielRosenwasser]

That's fine (and understandable) - I think it's a reasonable first step for the refactoring, and it would likely hit most of the cases.