`error: cannot determine resolution for the macro` itself is not stably triggering on 1.97.1

[shirok1]

src/lib.rs

#[cfg(feature = "env-first")]
pub mod env;

// This declaration-before-`env` order is part of the rustc regression.
pub mod interface {
    mod wasm {
        #[allow(unused_imports)]
        use crate::env::{self};

        #[cfg(not(feature = "qualified-env"))]
        include!(concat!(env!("OUT_DIR"), "/wit/dom_export.rs"));

        #[cfg(feature = "qualified-env")]
        include!(concat!(core::env!("OUT_DIR"), "/wit/dom_export.rs"));

        // This child scope survives and drives rustc's `dom_import` suggestion.
        pub mod dom_import {
            include!(concat!(env!("OUT_DIR"), "/wit/dom_import.rs"));
        }

        #[allow(dead_code)]
        struct DomExport;
        impl dom_export::DomExport for DomExport {}
    }

    pub use wasm::*;
}

#[cfg(not(feature = "env-first"))]
pub mod env;

src/env.rs

#[derive(Default)]
#[allow(dead_code)]
pub struct BusinessData;

build.rs

use std::{env, fs, path::PathBuf};

fn main() {
    let output = PathBuf::from(env::var_os("OUT_DIR").unwrap()).join("wit");
    fs::create_dir_all(&output).unwrap();

    fs::write(
        output.join("dom_export.rs"),
        "pub mod dom_export { pub trait DomExport {} }\n",
    )
    .unwrap();
    fs::write(
        output.join("dom_import.rs"),
        "pub mod dom_import { pub trait DomImport {} }\n",
    )
    .unwrap();
}

Building:

$ cargo +1.96.1 build
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.17s

$ cargo +1.97.1 build
error: cannot determine resolution for the macro `env`
  --> src/lib.rs:11:26
   |
11 |         include!(concat!(env!("OUT_DIR"), "/wit/dom_export.rs"));
   |                          ^^^
   |
   = note: import resolution is stuck, try simplifying macro imports

error[E0433]: cannot find module or crate `dom_export` in this scope
  --> src/lib.rs:23:14
   |
23 |         impl dom_export::DomExport for DomExport {}
   |              ^^^^^^^^^^ use of unresolved module or unlinked crate `dom_export`
   |
help: there is a crate or module with a similar name
   |
23 -         impl dom_export::DomExport for DomExport {}
23 +         impl dom_import::DomExport for DomExport {}
   |

For more information about this error, try `rustc --explain E0433`.
error: could not compile `xxx` (lib) due to 2 previous errors

$ cargo +1.97.1 build --features env-first
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.06s

$ cargo +1.97.1 build  --features qualified-env
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.00s

If error: cannot determine resolution for the macro is an intended feature of 1.97, it should not be affected by the mod declaring order

Workaround: fully qualify to core::env! or just don't name the mod env and import it

Detail version:

$ rustc +1.97.1 -vV
rustc 1.97.1 (8bab26f4f 2026-07-14)
binary: rustc
commit-hash: 8bab26f4f68e0e26f0bb7960be334d5b520ea452
commit-date: 2026-07-14
host: aarch64-apple-darwin
release: 1.97.1
LLVM version: 22.1.6

$ rustc +1.96.1 -vV
rustc 1.96.1 (31fca3adb 2026-06-26)
binary: rustc
commit-hash: 31fca3adb283cc9dfd56b49cdee9a96eb9c96ffd
commit-date: 2026-06-26
host: aarch64-apple-darwin
release: 1.96.1
LLVM version: 22.1.2

Disclosure: this minimal reproduce is generated with GPT-5.6 Sol from diagnose log

[apiraino]

bisection leads to b1b06b8

cc @mu001999 @petrochenkov for an opinion

[mu001999]

Reduced:

pub mod interface {
    use crate::env::{self};

    include!(concat!(env!()));
}

pub mod env {
    #[derive(Default)] // Comment this line will suppress the error
    pub struct BusinessData;
}

[petrochenkov]

It would be good to have the reproduction further minimized (single file, and without non-essential parts).
And then debug what's going on.

The concat!(env!("OUT_DIR"), "/wit/dom_export.rs") part is eager expansion.
If something in eager expansion cannot be fully resolved yet, then we should retry it later, this was already implemented, at least partially.
If the retrying in eager expansion is not fully implemented, we could get order-dependent results.