Should async: false force return a type "string" instead of "string | Promise<string>"?

[Jakobud]

I am using marked with default options. Async is false by default. When using it in TypeScript I get

Type 'string | Promise<string>' is not assignable to type 'string'

It seems that the type signature should return string when async: false and Promise<string> when async: true.

Am I misunderstanding something about this?

[UziTech]

Yes, you are missing that typescript cannot know if an extension changes async to true

marked.use({async: true});

marked.parse(...) // returns Promise<string>

[Jakobud]

Oh yeah I guess that makes sense because the change happens at runtime. Doh! Thanks