Types of property 'responseType' are incompatible

Here is an approach if you don't want to remove <string> to keep your response strongly typed:

    const httpOptions = {
      headers: new HttpHeaders({
        'Accept': 'text/plain, */*',
        'Content-Type': 'application/json' // We send JSON
      }),
      responseType: 'text' as 'json'  // We accept plain text as response.
    };
    return this.http.post<string>(this.setBaseUrl, body, httpOptions);

Replace text with valid responseType according the data that you want to receive.

The version of post accepting responseType:'text' is not generic, since the result type is already clear (ie string)

this.http
.post(this.loginUrl, this.user, {responseType: 'text'}) // no generic parameter
.subscribe(
    (data) => this.success(data), // data is string
    (error) => this.failure(error)
);

I just ran into this particular issue today myself. After searching for a little and figuring that the responseType option should exist, I managed to get it work as below:

let requestOptions: Object = { 
    headers: new HttpHeaders().set('Authorization', 'Basic ' + credentials),
    responseType: 'text'
}    

return this.httpClient.get<any>(
                this.environment.tokenHost + this.environment.authenticationURL,
                requestOptions
            )
            .subscribe(result => {
                // do stuff
            });

Setting the responseType like that makes it work, compared to configuring it in the 'request' itself.

Regards.

Just remove "string" from your request. Try this:

this.http.post(this.loginUrl, this.user, {responseType: 'text'}).subscribe(
    (data) => this.success(data),
    (error) => this.failure(error)
);