Closed
Description
This is a strange one to summarize. As best as I have been able to tell: the compiler ICEs with "no index for a field" if two derived functions each independently acknowledge the existence of a field that is not visible to them.
In any case, here is as far as I got minimizing this one:
#!/bin/sh
cargo new --lib repro
cargo new --lib repro_derive
echo >repro/src/lib.rs '
#[macro_use]
extern crate repro_derive;
#[derive(Derive)]
struct Restricted {
pub(in restricted) field: usize,
}
mod restricted {}
fn main() {}
'
echo >>repro/Cargo.toml '
repro_derive = { path = "../repro_derive" }
'
echo >repro_derive/src/lib.rs '
extern crate proc_macro;
use proc_macro::TokenStream;
#[proc_macro_derive(Derive)]
pub fn derive(_: TokenStream) -> TokenStream {
let code = "
fn one(r: Restricted) {
r.field;
}
fn two(r: Restricted) {
r.field;
}
";
code.parse().unwrap()
}
'
echo >>repro_derive/Cargo.toml '
[lib]
proc-macro = true
'
cargo build --manifest-path repro/Cargo.tomlReasonable error message on stable and beta. But on nightly:
error: visibilities can only be restricted to ancestor modules
--> src/lib.rs:7:12
|
7 | pub(in restricted) field: usize,
| ^^^^^^^^^^
error[E0616]: field `field` of struct `Restricted` is private
--> src/lib.rs:5:10
|
5 | #[derive(Derive)]
| ^^^^^^
thread 'main' panicked at 'no index for a field', libcore/option.rs:914:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0616`.
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
Mentioning @petrochenkov who added the panicking function in #49718.