`Result!()` macro

The syntax of Result!() macro is Result!( OkType throws Err1, Err2, .. ), the underlying type of which is Result<OkType, Enum!(Err1, Err2, ..)>. However the Result!() macro is preferred over Enum!() because:

Enum!() is subject to changes on feature of log/env_log, while Result!() is not.
throws is cool, shorter and more clear than Enum!().

Use `Result!()` to enumerate the possible error types

in function signature:


#![allow(unused)]
fn main() {
#[cex] fn throws_never() -> Result!(i32) {/**/}

struct SomeError;

#[cex] fn foo() -> Result!( i32 throws String, &'static str, SomeError ) {/**/}
}

in closure's signature:


#![allow(unused)]
fn main() {
fn foo() {
    let _f = #[cex] || -> Result!( i32 throws String ) {/**/}
}
}

in the type annotation of a local let-binding:


#![allow(unused)]
fn main() {
fn foo() {
    #[cex] let v: Result!( i32 throws String ) = try {/**/};
}
}