incorrect type resolution during conflict checking from extern crate

I tried this code:

// sub-crate "inner":
pub trait TryFromBits: Sized {
    const BITS: u8;
    type Inner;
}
pub struct Bits<const N: u8>(<Self as TryFromBits>::Inner)
where
    Self: TryFromBits;
impl TryFromBits for Bits<4> {
    const BITS: u8 = 4;
    type Inner = u8;
}

// main crate
use inner::{Bits, TryFromBits};

pub struct Abcd {}
impl TryFromBits for Abcd {
    const BITS: u8 = 4;
    type Inner = <Bits<{ <Self as TryFromBits>::BITS }> as TryFromBits>::Inner; // should be `u8`
}
pub trait ConvFrom<Src>: Sized {}
impl<T> ConvFrom<T> for T {}
impl ConvFrom<<Self as TryFromBits>::Inner> for Abcd {}

I expected to see this happen: successful compilation

Instead, this happened: compile error

error[E0119]: conflicting implementations of trait `ConvFrom<Abcd>` for type `Abcd`
  --> src/main.rs:11:1
   |
10 | impl<T> ConvFrom<T> for T {}
   | ------------------------- first implementation here
11 | impl ConvFrom<<Self as TryFromBits>::Inner> for Abcd {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Abcd`

The compiler "thinks" <Abcd as TryFromBits>::Inner is Abcd but the actual type is u8.
Commenting-out the offending line and adding the following code confirms it:

fn main() {
    println!("{}", std::any::type_name::<<Abcd as TryFromBits>::Inner>());
}

minimal reproduction repository

Notes:

• this only happens if Bits struct is defined in extern crate - the code compiles fine within single crate
• does not seem to be a regression, reproducible back to 1.56 (haven't tested any further)

Meta

rustc --version --verbose:

rustc --version --verbose
rustc 1.98.0-nightly (cb46fbb8c 2026-06-08)
binary: rustc
commit-hash: cb46fbb8c6ea799c6fba9188ed889275c35a8c28
commit-date: 2026-06-08
host: x86_64-unknown-linux-gnu
release: 1.98.0-nightly
LLVM version: 22.1.6

Start by building the minimal reproduction repository linked in the issue and compare the extern-crate case with the single-crate case. The reported example is in src/main.rs; inspect rustc's trait conflict-checking and type-resolution paths to trace why the associated type is treated as Abcd rather than u8. Done means the reproduction compiles successfully while the existing conflict diagnostics remain correct.