[−][src]Attribute Macro some_error::some_error
#[some_error]
A Macro for allowing Anonymous Sum Types in the error of the returned result.
The function this is attached to must return a type in the form of Result<T, E1 + E2 + ...>
.
Example:
use std::io; use some_error::*; #[derive(Debug, Clone, Copy)] struct NotZeroError(u32); #[some_error] fn my_func() -> Result<(), io::Error + NotZeroError>{ let x = 3; if x != 0 { Err(NotZeroError(x))?; } Ok(()) } fn main() { match my_func() { Ok(_) => { println!("Worked ok!"); } Err(my_func::NotZeroError(NotZeroError(x))) => { println!("{} is not zero!!", x); } Err(my_func::io::Error(io_err)) => { println!("io error: {:?}", io_err); } } }
More Info
- The type of the anonymous sum type can be referenced via
function_name::Error
. - All variants of the anonymous sum type can be accessed via
function_name::<path>
- For example if you use the return type
Result<(), fmt::Error + i32>
the variants will be namedfunction_name::fmt::Error
andfunction_name::i32
and can be used as patterns to match against (see the above example)
- For example if you use the return type