test macro hygiene

[Stargateur]

I have a trait that have a map method, it's look the macro use imported item from user code.

error[E0034]: multiple applicable items in scope
   --> network\src\tcp.rs:469:3
    |
469 |   #[test_log::test]
    |   ^^^^^^^^^^^^^^^^^ multiple `map` found
    |
    = note: candidate #1 is defined in an impl of the trait `binator_utils::Utils` for the type `T`
    = note: candidate #2 is defined in an impl of the trait `Iterator` for the type `std::str::Split<'a, P>`
    = note: this error originates in the attribute macro `test_log::test` (in Nightly builds, run with -Z macro-backtrace for more info)
help: disambiguate the associated function for candidate #1
    |
469 |   binator_utils::Utils::map(#[test_log::test], #[test_log::test])
    |
help: disambiguate the associated function for candidate #2
    |
469 |   Iterator::map(#[test_log::test], #[test_log::test])
    |

[d-e-s-o]

Can you provide a minimal example illustrating the issue?

[Stargateur]

Yes, sorry.

test-log = { version = "0.2", features = ["trace"] }
env_logger = "0.9"
tracing = {version = "0.1", default-features = false}
tracing-subscriber = {version = "0.3", default-features = false, features = ["env-filter", "fmt"]}

trait Foo: Sized {
    fn map(self) -> Self {
        self
    }
}

impl<T> Foo for T {}

#[cfg(test)]
mod tests {
    use super::*;

    #[test_log::test]
    fn foo() {
        42.map();
    }
}

error[E0034]: multiple applicable items in scope
  --> src\bin\lol.rs:15:5
   |
15 |     #[test_log::test]
   |     ^^^^^^^^^^^^^^^^^ multiple `map` found
   |
note: candidate #1 is defined in an impl of the trait `Foo` for the type `T`
  --> src\bin\lol.rs:4:5
   |
4  |     fn map(self) -> Self {
   |     ^^^^^^^^^^^^^^^^^^^^
   = note: candidate #2 is defined in an impl of the trait `Iterator` for the type `std::str::Split<'a, P>`
   = note: this error originates in the attribute macro `test_log::test` (in Nightly builds, run with -Z macro-backtrace for more info)
help: disambiguate the associated function for candidate #1
   |
15 |     Foo::map(#[test_log::test], #[test_log::test])
   |
help: disambiguate the associated function for candidate #2
   |
15 |     Iterator::map(#[test_log::test], #[test_log::test])
   |

cause

test-log/src/lib.rs

Line 120 in 3b60bc9

.map(|filter| match filter.trim() {

I believe #15 (comment) would help on this matter. But unsure, I don't know much about proc macro. rust-lang/rust#54727 is about proc macro hygiene.

[d-e-s-o]

Interestingly, it's not even that the proc macro is polluting your namespace, it's that you are polluting the proc macro's namespace from what I understand. It's reasonably easy to fix in this case, even in a generic manner.

Happy to be proven wrong, but I am not convinced that #15 (comment) has any bearing on the issue. All it suggests is putting the proc macro logic into a different crate and then importing the macros through this crate. That shouldn't have any impact on method resolution or really much of the compilation process.

[d-e-s-o]

Should be fixed now. Let me know if you encounter any problems with the fix. Should be able to cut a release in the next few days or so. Thanks for reporting this issue!