Arduino IDE inserts forward declaration

mySketch.ino

/*
#line 1 "mySketch.ino"
*/
#include <SPI.h>
/*
#include "Arduino.h"
void foo(TwoWire bar);
void setup();
void loop();
#line 2
*/
int a=0;
#include <Wire.h>
int b=0;
void foo(TwoWire bar){
}
void setup(){
}
void loop(){
}

//mySketch:3: error: variable or field 'foo' declared void
//mySketch:3: error: 'TwoWire' was not declared in this scope