Closed
Description
openedon Sep 18, 2020
Context:
input of proc_macro_attribute have invalid (null) span for some input.
I test spans with this code:
#[proc_macro_attribute]
pub fn bar(_attr: proc_macro::TokenStream, item: proc_macro::TokenStream) -> proc_macro::TokenStream {
for tt in item.clone().into_iter() {
println!("tt: {}: {:?}", tt, tt.span());
}
item
}Failing inputs:
1- inner doc (this is fixed by #76130 )
#[ressai_proc::bar]
pub mod inner_doc {
//! With this documentation line removed span are working.
}prints
tt: pub: #0 bytes(0..0)
tt: mod: #0 bytes(0..0)
tt: inner_doc: #0 bytes(0..0)
tt: {
//! With this documentation line removed span are working.
}: #0 bytes(0..0)
removing the inner doc makes the token tree having non-null spans.
2- another path attribute (with two path segment) (this one is now fixed in rustc 1.49.0-nightly (ffa2e7a 2020-10-24))
#[ressai_proc::bar]
#[ressai_proc::bar]
pub mod another_attribute {
}prints
tt: #: #0 bytes(0..0)
tt: [ressai_proc :: bar]: #0 bytes(0..0)
tt: pub: #0 bytes(0..0)
tt: mod: #0 bytes(0..0)
tt: another_attribute: #0 bytes(0..0)
tt: { }: #0 bytes(0..0)
tt: pub: #0 bytes(0..0)
tt: mod: #0 bytes(0..0)
tt: another_attribute: #0 bytes(0..0)
tt: { }: #0 bytes(0..0)
note that this slightly modified input will give non-null spans:
use ressai_proc::bar;
#[ressai_proc::bar]
#[bar]
pub mod another_attribute_but_successful {
}3 - some method on associated type: (this is fixed by #78980)
#[ressai_proc::bar]
mod foo {
trait Config {
type Origin: From<u32>;
}
struct A<T>(T);
impl<T: Config> A<T> {
fn foo() {
<T as Config>::Origin::from(3);
}
}
}This will output:
Compiling ressai-proc v0.1.0 (/home/thiolliere/Developpement/ressai-procedural/ressai-proc)
tt: mod: #0 bytes(0..0)
tt: foo: #0 bytes(0..0)
tt: {
trait Config { type Origin : From < u32 > ; } struct A < T > (T) ; impl <
T : Config > A < T > { fn foo() { < T as Config > :: from(3) ; } }
}: #0 bytes(0..0)
error[E0576]: cannot find method or associated constant `from` in trait `Config`
So the rust error message is not pointing the failing code. All span are 0.
Meta
cargo rustc -- --version --verbose:
rustc 1.49.0-nightly (ffa2e7ae8 2020-10-24)
binary: rustc
commit-hash: ffa2e7ae8fbf9badc035740db949b9dae271c29f
commit-date: 2020-10-24
host: x86_64-unknown-linux-gnu
release: 1.49.0-nightly
LLVM version: 11.0
EDIT: related #43081
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