ICE: librustc_resolve/lib.rs:2853: unexpected definition for an identifier in pattern: Mod(DefId(10/0:0))

[eddyb]

Reported by @Manishearth in #52923 (comment):

   Compiling clippy_lints v0.0.212 (file:///home/manishearth/mozilla/Wall/rust-clippy/clippy_lints)
thread 'main' panicked at 'librustc_resolve/lib.rs:2853: unexpected definition for an identifier in pattern: Mod(DefId(10/0:0))', librustc/util/bug.rs:47:26
note: Run with `RUST_BACKTRACE=1` for a backtrace.

error: internal compiler error: unexpected panic

Minimal reproduction (with --edition=2018):

fn main() {
    use std;
    let std = "std";
    println!("{}", std);
}