Rust issue #13681 minimal trigger

build.sh

#!/bin/bash

BUILD_DIR=./build
rm -rf "$BUILD_DIR"
mkdir -p "$BUILD_DIR"

RUST_ARGS=(-A dead-code -g -L "$BUILD_DIR" --out-dir="$BUILD_DIR")

echo "Building l" &&
	rustc "${RUST_ARGS[@]}" l.rs &&
echo "Building C" &&
	rustc "${RUST_ARGS[@]}" -Z lto C.rs

C.rs

extern crate l;
pub struct C;
pub fn p() -> C {
    C
}
fn main() { }

l.rs

#![crate_type = "rlib"]
struct S;
impl S {
    fn f(&mut self) {  }
}

singledelta-test.sh

./build.sh 2>&1 | tee /tmp/build.log | grep -q 'Ty == resolve(Ty.getRef()) && "type was not uniqued'