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Regression in procedural macros emitting macro_rules macros #39889
Description
my-macro/src/lib.rs
extern crate proc_macro;
use proc_macro::TokenStream;
#[proc_macro_derive(Useless)]
pub fn demo(_input: TokenStream) -> TokenStream {
let rules = r#"
macro_rules! id {
($($tt:tt)*) => { $($tt)* };
}
"#;
rules.parse().unwrap()
}testing/src/main.rs
#[macro_use]
extern crate my_macro;
#[derive(Useless)]
struct _S;
pub fn main() {
println!("{}", id!(true));
}rustup run nightly-2017-02-13 cargo run
true
rustup run nightly-2017-02-16 cargo run
error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
--> src/main.rs:4:10
|
4 | #[derive(Useless)]
| ^^^^^^^
error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
--> src/main.rs:4:10
|
4 | #[derive(Useless)]
| ^^^^^^^
error: aborting due to 2 previous errors
cc @jseyfried who touched macro expansion recently
Activity
jseyfried commentedon Feb 28, 2017
@dtolnay Sorry for the delay! This will get fixed by #39419 (added a regression test).
Rollup merge of rust-lang#39419 - jseyfried:simplify_tokentree, r=nrc
Auto merge of #39419 - jseyfried:simplify_tokentree, r=nrc