pub static PROC_MACRO_DERIVE_RESOLUTION_FALLBACK: &Lint
Expand description
The proc_macro_derive_resolution_fallback
lint detects proc macro
derives using inaccessible names from parent modules.
§Example
ⓘ
// foo.rs
#![crate_type = "proc-macro"]
extern crate proc_macro;
use proc_macro::*;
#[proc_macro_derive(Foo)]
pub fn foo1(a: TokenStream) -> TokenStream {
drop(a);
"mod __bar { static mut BAR: Option<Something> = None; }".parse().unwrap()
}
ⓘ
// bar.rs
#[macro_use]
extern crate foo;
struct Something;
#[derive(Foo)]
struct Another;
fn main() {}
This will produce:
warning: cannot find type `Something` in this scope
--> src/main.rs:8:10
|
8 | #[derive(Foo)]
| ^^^ names from parent modules are not accessible without an explicit import
|
= note: `#[warn(proc_macro_derive_resolution_fallback)]` on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #50504 <https://github.com/rust-lang/rust/issues/50504>
§Explanation
If a proc-macro generates a module, the compiler unintentionally allowed items in that module to refer to items in the crate root without importing them. This is a future-incompatible lint to transition this to a hard error in the future. See issue #50504 for more details.