Stack overflow in rustdoc using enum_primitive with a big enum

[nstoddard]

Running cargo doc on the following code results in a stack overflow:

#[macro_use] extern crate enum_primitive;

enum_from_primitive! {
pub enum Test {
    A1,A2,A3,A4,A5,A6,
    B1,B2,B3,B4,B5,B6,
    C1,C2,C3,C4,C5,C6,
    D1,D2,D3,D4,D5,D6,
    E1,E2,E3,E4,E5,E6,
    F1,F2,F3,F4,F5,F6,
    G1,G2,G3,G4,G5,G6,
    H1,H2,H3,H4,H5,H6,
    I1,I2,I3,I4,I5,I6,
    J1,J2,J3,J4,J5,J6,
    K1,K2,K3,K4,K5,K6,
    L1,L2,L3,L4,L5,L6,
    M1,M2,M3,M4,M5,M6,
    N1,N2,N3,N4,N5,N6,
    O1,O2,O3,O4,O5,O6,
    P1,P2,P3,P4,P5,P6,
    Q1,Q2,Q3,Q4,Q5,Q6,
    R1,R2,R3,R4,R5,R6,
    S1,S2,S3,S4,S5,S6,
    T1,T2,T3,T4,T5,T6,
    U1,U2,U3,U4,U5,U6,
    V1,V2,V3,V4,V5,V6,
    W1,W2,W3,W4,W5,W6,
    X1,X2,X3,X4,X5,X6,
    Y1,Y2,Y3,Y4,Y5,Y6,
    Z1,Z2,Z3,Z4,Z5,Z6,
}
}

thread '<unknown>' has overflowed its stack
Could not document `enum-test`.

With significantly fewer enum variants, it works. If I remove the use of enum_from_primitive!, it works.

This is breaking cargo doc on one of my PRs (PistonDevelopers/glfw-rs#316).

[mitaa]

This seems to be fixed.

[nstoddard]

In my tests, you now need to have around 460+ enum variants in order to get the stack overflow. Can we assume nobody will ever have that many?

[sanmai-NL]

@alexcrichton: should a test still be written for this?
Panicking is not correct, better would be that the number of variants is limited explicitly and that this is documented. Better still if there is no limit, of course.

[alexcrichton]

In theory yeah if there's something that overflowed previously and no longer does, we should have a test for that :)

[steveklabnik]

Triage: not aware of a test yet