Preserve type aliases on implement interface

From https://github.com/microsoft/vscode/issues/90061

TypeScript Version: 3.8.1-rc

Search Terms:

• quick fix
• implement interface

Repo

export type UrlString = string;
export type UUID = string;

export interface I_IdToUrlMapper {
	mapIdToUrl(id: UUID): UrlString
	mapUrlToId(url: UrlString): UUID
}

export class IdToUrlMapper implements I_IdToUrlMapper {

}

Run implement interface on IdToUrlMapper

Expected behavior:
Type aliases are preserved

export class IdToUrlMapper implements I_IdToUrlMapper {
    mapIdToUrl(id: UUID): UrlString {
        throw new Error("Method not implemented.");
    }
    mapUrlToId(url: UrlString): UUID {
        throw new Error("Method not implemented.");
    }
}

Actual behavior:
Both methods use string:

export class IdToUrlMapper implements I_IdToUrlMapper {
    mapIdToUrl(id: string): string {
        throw new Error("Method not implemented.");
    }
    mapUrlToId(url: string): string {
        throw new Error("Method not implemented.");
    }
}

Related Issues

• https://github.com/microsoft/TypeScript/issues/34778

Comienza con la corrección rápida “implement interface” del TypeScript language-service usando el ejemplo reproducido de IdToUrlMapper. Compara las firmas de método generadas con la salida esperada y verifica que los alias de tipo como UUID y UrlString se conserven en lugar de reducirse a string.