Macro try_expression 

macro_rules! try_expression {
    ($x:expr $(,)?) => { ... };
    ($x:block $(,)?) => { ... };
}

Unwraps an Expression or propagates its error.

This macro mirrors the standard try macro but operates on Expressions rather than Results. If the given Expression is the Defined variant, then the expression (of the macro) is the accompanying value. Otherwise, the error in the Undefined variant is converted via From and returned in the constructed Expression.