This error can be caused by an unclosed set of brackets.
int main {
doSomething {}
doSomething else {
}
Not so easy to spot, even in this 4 line example.
This error, in a 150 line main function, caused the bewildering error: "static declaration of ‘savePair’ follows non-static declaration". There was nothing wrong with my definition of function savePair, it was that unclosed bracket.