From https://github.com/Microsoft/TypeScript/issues/11054 ``` ts interface FolderContentItem{ type: 'folder' | 'file'; } let a:FolderContentItem[] = []; a = [1,2,3,4,5].map(v=>({type:'folder'})) ``` Today this is an error without casting `"folder"` to the literal type. We have a contextual type coming from `a` that is not being used.