Macro generic_error 

macro_rules! generic_error {
    ($msg:literal $(,)?) => { ... };
    ($err:expr $(,)?) => { ... };
    ($fmt:expr, $($arg:tt)*) => { ... };
}

Macro for constructing a generic error.

The resulting value evaluates to GenericError, and can be construct from a string literal, a format string (with arguments accepted, in the same order as std::format!), or a value which implements Debug and Display, such as an existing error that implements std::error::Error.

When the value given implements std::error::Error, the source of the existing error value will be used as the source of the error created by this macro.