Macro rerast_macros::replace_pattern

macro_rules! replace_pattern {
    ($a:pat = $at:ident => $b:pat = $bt:ident) => { ... };
}

Replaces a pattern with another pattern. A placeholder is required in order to specify the types of the search and replacement pattern. Although they can be the same if you're replacing a pattern with another of the same type.

Examples

fn some_foo_to_result_foo(p1: Option<Foo>, p2: Result<Foo, ()>) {
    replace_pattern!(Some(f1) = p1 => Result::Ok(f1) = p2);
    replace_pattern!(None = p1 => Result::Err(()) = p2);
}

This will transform:

match f() {
    Some(Foo(x)) => x,
    None => 0,
}

Into:

match f() {
    Result::Ok(Foo(x)) => x,
    Result::Err(()) => 0,
}