Macro rustc_ap_rustc_data_structures::enum_from_u32

macro_rules! enum_from_u32 {
    ($(#[$attr:meta])* pub enum $name:ident {
        $($variant:ident = $e:expr,)*
    }) => { ... };
    ($(#[$attr:meta])* pub enum $name:ident {
        $($variant:ident,)*
    }) => { ... };
}