Compile Error if i add #include <ESP8266WiFi.h> to readwrite example scetch

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INSTRUCTIONS

Basic Infos

[x] This issue complies with the issue POLICY doc.
[x] I have read the documentation at readthedocs and the issue is not addressed there.
[x] I have tested that the issue is present in current master branch (aka latest git).
[x] I have searched the issue tracker for a similar issue.
[x] If there is a stack dump, I have decoded it.
[x] I have filled out all fields below.

Platform

Hardware: [ESP-12|
Core Version: [2.7.1]
Development Env: [Arduino IDE]
Operating System: [Windows]

Settings in IDE

Module: [Lolin Wemos D1 r2 & mini]
Flash Mode: [dio]
Flash Size: [4MB]
lwip Variant: [v2 Lower Memory]
Reset Method: [ck|nodemcu]
Flash Frequency: [40Mhz]
CPU Frequency: [80Mhz]
Upload Using: [SERIAL]
Upload Speed: [115200]

Problem Description

I open the readwrite example and upload it. All works fine. but if i add #include then i get this error: ReadWrite:50:3: error: 'myFile' was not declared in this scope myFile = SD.open("test.txt", FILE_WRITE); exit status 1 reference to 'File' is ambiguous

i have nothing other changed except the one include line.

How can i solve this?

MCVE Sketch


#include <ESP8266WiFi.h> 
#include <SPI.h>
//#include <SD.h>
#include "SdFat.h"

using namespace sdfat;

SdFat SD;

#define SD_CS_PIN SS
File myFile;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  Serial.print("Initializing SD card...");

  if (!SD.begin(SD_CS_PIN)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  myFile = SD.open("test.txt", FILE_WRITE);

  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("testing 1, 2, 3.");
    // close the file:
    myFile.close();
    Serial.println("done.");
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }

  // re-open the file for reading:
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");

    // read from the file until there's nothing else in it:
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    // close the file:
    myFile.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void loop() {
  // nothing happens after setup
}

Debug Messages

Debug messages go here

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