You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test.rs
    path of file: ./repos/lalrpop/lalrpop/src/lr1/trace/shift
    
    the code of the file until where you have to start completion: use crate::grammar::repr::*;
use crate::lr1::build_states;
use crate::lr1::core::*;
use crate::lr1::first::FirstSets;
use crate::lr1::tls::Lr1Tls;
use crate::test_util::{expect_debug, normalized_grammar};
use crate::tls::Tls;
use string_cache::DefaultAtom as Atom;

use super::super::Tracer;

fn nt(t: &str) -> NonterminalString {
    NonterminalString(Atom::from(t))
}

#[test]
fn shift_backtrace_1() {
    // This grammar yields a S/R conflict. Is it `(int -> int) -> int`
    // or `int -> (int -> int)`?

    let _tls = Tls::test();
    let grammar = normalized_grammar(
        r#"
grammar;
pub Ty: () = {
    "int" => (),
    "bool" => (),
    <t1:Ty> "->" <t2:Ty> => (),
};
"#,
    );
    let _lr1_tls = Lr1Tls::install(grammar.terminals.clone());
    let first_sets = FirstSets::new(&grammar);
    let err = build_states(&grammar, nt("Ty")).unwrap_err();
    let conflict = err.conflicts[0].clone();
    println!("conflict={:?}", conflict);

    // Gin up the LR0 item involved in the shift/reduce conflict:
    //
    //     Ty = Ty (*) -> Ty (shift)
    //
    // from the item that we can reduce:
    //
    //     Ty = Ty -> Ty (*) (reduce)

    assert!(conflict.production.symbols.len() == 3);
    let item = Item::lr0(conflict.production, 1);
    println!("item={:?}", item);
    let tracer = Tracer::new(&first_sets, &err.states);
    let graph = tracer.backtrace_shift(conflict.state, item);
    expect_debug(
        &graph,
        r#"
[
    (Nonterminal(Ty) -([], Some(Ty), ["->", T
    
fn shift_backtrace_1() {
    // This grammar yields a S/R conflict. Is it `(int -> int) -> int`
    // or `int -> (int -> int)`?

    let _tls = Tls::test();
    let grammar = normalized_grammar(
        r#"
grammar;
pub Ty: () = {
    "int" => (),
    "bool" => (),
    <t1:Ty> "->" <t2:Ty> => (),
};
"#,
    );
    let _lr1_tls = Lr1Tls::install(grammar.terminals.clone());
    let first_sets = FirstSets::new(&grammar);
    let err = build_states(&grammar, nt("Ty")).unwrap_err();
    let conflict = err.conflicts[0].clone();
    println!("conflict={:?}", conflict);

    // Gin up the LR0 item involved in the shift/reduce conflict:
    //
    //     Ty = Ty (*) -> Ty (shift)
    //
    // from the item that we can reduce:
    //
    //     Ty = Ty -> Ty (*) (reduce)

    assert!(conflict.production.symbols.len() == 3);
    let item = Item::lr0(conflict.production, 1);
    println!("item={:?}", item);
    let tracer = Tracer::new(&first_sets, &err.states);
    let graph = tracer.backtrace_shift(conflict.state, item);
    expect_debug(
        &graph,
        r#"
[
    (Nonterminal(Ty) -([], Some(Ty), ["->", Ty])-> Nonterminal(Ty)),
    (Nonterminal(Ty) -([Ty], Some("->"), [Ty])-> Item(Ty = Ty (*) "->" Ty)),
    (Item(Ty = Ty "->" (*) Ty) -([Ty, "->"], Some(Ty), [])-> Nonterminal(Ty))
]
"#
        .trim(),
    );

    let list: Vec<_> = graph
        .lr0_examples(item)
        .map(|example| example.paint_unstyled())
        .collect();
    expect_debug(
        list,
        r#"
[
    [
        "  Ty "->" Ty "->" Ty",
        "  │       └─Ty─────┤",
        "  └─Ty─────────────┘"
    ]
]
"#
        .trim(),
    );
}