I have the following function :

let templateLoader = (onDidFinishLoad : Function, onDidFailLoad : Function) =>

    (url : string) : Promise<void> => 

        new Promise(    

            (resolve,reject) => {

                mainWindow.loadURL(url);

                mainWindow.webContents.once(

                    'did-finish-load',

                    () => { 

                        onDidFinishLoad(resolve);

                    }  

                );  

                mainWindow.webContents.once(

                    'did-fail-load', 

                    (event,errorCode,errorDescription) => {  

                        onDidFailLoad(reject,errorDescription); 

                    }  

                );   

            } 

        ); 

I've got the following compilation error:

ERROR in [at-loader] ./app/loaders.ts:9:9
TS2322: Type 'Promise {}' is not assignable to type
Promise void. Type '{}' is not assignable to type 'void'.