enum_derive cannot contain more than 24 variants due to recursion limit

[kennytm]

Test case:

custom_derive! {
    #[derive(Debug, PartialEq, EnumFromStr)]
    pub enum HugeEnum {
        Case0, Case1, Case2, Case3, Case4, Case5, Case6, Case7, Case8, Case9,
        Case10, Case11, Case12, Case13, Case14, Case15, Case16, Case17, Case18, Case19,
        Case20, Case21, Case22, Case23, Case24, Case25, Case26, Case27, Case28, Case29,
        Case30, Case31, Case32, Case33, Case34, Case35, Case36, Case37, Case38, Case39,
        Case40, Case41, Case42, Case43, Case44, Case45, Case46, Case47, Case48, Case49,
        Case50, Case51, Case52, Case53, Case54, Case55, Case56, Case57, Case58, Case59,
        Case60, Case61, Case62, Case63, Case64, Case65, Case66, Case67, Case68, Case69,
        Case70, Case71, Case72, Case73, Case74, Case75, Case76, Case77, Case78, Case79,
        Case80, Case81, Case82, Case83, Case84, Case85, Case86, Case87, Case88, Case89,
        Case90, Case91, Case92, Case93, Case94, Case95, Case96, Case97, Case98, Case99,
    }
}

In version 0.1.6, with Rust 1.8.0 – 1.10.0, this fails with:

<enum_derive macros>:17:1: 19:32 error: recursion limit reached while expanding the macro `enum_derive_util`
<enum_derive macros>:17 enum_derive_util ! {
                        ^

cc rust-lang/rust#22552

[DanielKeep]

Apologies for the long hiatus.

There's nothing I can do about this. I'd need either procedural macros (but I refuse to sacrifice working on stable) or for macro_rules! to learn how to do tail call optimisation.

You have to raise the recursion limit and hope you don't hit a more fundemental limit in the compiler (like blowing the actual call stack).

[lambda-fairy]

For anyone else who runs across this issue, the workaround is to add

#![recursion_limit = "1000"]

to the top of your crate.