arduino refusing to compile

Hi,
I’m trying to compile code onto my Arduino Mega 2560, but it’s not working. The weird bit is that this happened all of a sudden, as I was compiling code just this morning.

Here is the error message:

Arduino: 1.6.10 (Windows 10), Board: "Arduino Mega ADK"

C:\Users\Ben\AppData\Local\Temp\ccRtNWoc.ltrans0.ltrans.o: In function `main':

ccRtNWoc.ltrans0.o:(.text.startup+0xe0): undefined reference to `setup'

collect2.exe: error: ld returned 1 exit status

exit status 1
Error compiling for board Arduino Mega ADK.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Thanks!

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