Macro_rules! defining macro_rules!

[anon80458984]

Based on https://github.com/rust-lang/rust/pull/34925 it seems it is possible for macro_rules! to define new macros within itself.

Are there any cool examples of what can be done with this technique ?

(No, I don't have a problem I need solved. I am just curious what is possible.)

[vague]

@anon80458984

any cool examples of what can be done with this technique ?

I'd suggest reading this thread where steffahn put foward a macro of that kind well using patterns.

Generic referencing enum inner data

I was thinking of a macro like macro_rules! Foo { ($p:pat) => { Foo::Bar($p) | Foo::Bink($p) } } or perhaps something like enum Baz { Variant1 { x: u32, y: String, z: bool, }, Variant2 { x: u32, z: bool, qux: fn(), } } macro_rules! Baz { ($($field:ident $(: $p:pat)?,)* ..) => { Baz::Variant1{ $($field $(: $p)?,)* .. } | Baz::Variant2{ $($field $(: $p)?,)* .. } } } (playground) Maybe a macro to c…