AP_HAL: AnalogSource: set_pin returns bool

libraries/AP_HAL/AnalogIn.h

@@ -9,7 +9,7 @@ class AP_HAL::AnalogSource {
 public:
     virtual float read_average() = 0;
     virtual float read_latest() = 0;
-    virtual void set_pin(uint8_t p) = 0;
+    virtual bool set_pin(uint8_t p) WARN_IF_UNUSED = 0;
 
     // return a voltage from 0.0 to 5.0V, scaled
     // against a reference voltage

libraries/AP_HAL/examples/AnalogIn/AnalogIn.cpp

@@ -46,7 +46,7 @@ void loop(void) {
     //increment the pin number
     pin = (pin+1) % 16;
     //set pin corresponding to the new pin value
-    chan->set_pin(pin);
+    IGNORE_RETURN(chan->set_pin(pin));
     //give a delay of 100ms
     hal.scheduler->delay(100);
 }