Can't say much without your code but I would advise to check if your function is returning a Boolean value.
looking at the error you're getting it sounds like you're not returning a bool.
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bool Pacman::CollisionCheck(int x1, int y1, int width1, int height1, int x2, int y2, int width2, int height2)
{
bool status;
statement;
statement;
statement;
return status;
}