src/tools/clippy/tests/ui/indexing_slicing_index.rs

#![feature(inline_const)]
#![warn(clippy::indexing_slicing)]
// We also check the out_of_bounds_indexing lint here, because it lints similar things and
// we want to avoid false positives.
#![warn(clippy::out_of_bounds_indexing)]
#![allow(
    unconditional_panic,
    clippy::no_effect,
    clippy::unnecessary_operation,
    clippy::useless_vec
)]

const ARR: [i32; 2] = [1, 2];
const REF: &i32 = &ARR[idx()]; // This should be linted, since `suppress-restriction-lint-in-const` default is false.
//~^ ERROR: indexing may panic
const REF_ERR: &i32 = &ARR[idx4()]; // Ok, let rustc handle const contexts.
//~^ ERROR: indexing may panic

const fn idx() -> usize {
    1
}
const fn idx4() -> usize {
    4
}

fn main() {
    let x = [1, 2, 3, 4];
    let index: usize = 1;
    x[index];
    //~^ ERROR: indexing may panic
    // Ok, let rustc's `unconditional_panic` lint handle `usize` indexing on arrays.
    x[4];
    // Ok, let rustc's `unconditional_panic` lint handle `usize` indexing on arrays.
    x[1 << 3];

    // Ok, should not produce stderr.
    x[0];
    // Ok, should not produce stderr.
    x[3];
    // Ok, should not produce stderr.
    x[const { idx() }];
    // Ok, let rustc's `unconditional_panic` lint handle `usize` indexing on arrays.
    x[const { idx4() }];
    // This should be linted, since `suppress-restriction-lint-in-const` default is false.
    const { &ARR[idx()] };
    //~^ ERROR: indexing may panic
    // This should be linted, since `suppress-restriction-lint-in-const` default is false.
    const { &ARR[idx4()] };
    //~^ ERROR: indexing may panic

    let y = &x;
    // Ok, referencing shouldn't affect this lint. See the issue 6021
    y[0];
    // Ok, rustc will handle references too.
    y[4];

    let v = vec![0; 5];
    v[0];
    //~^ ERROR: indexing may panic
    v[10];
    //~^ ERROR: indexing may panic
    v[1 << 3];
    //~^ ERROR: indexing may panic

    // Out of bounds
    const N: usize = 15;
    // In bounds
    const M: usize = 3;
    // Ok, let rustc's `unconditional_panic` lint handle `usize` indexing on arrays.
    x[N];
    // Ok, should not produce stderr.
    x[M];
    v[N];
    //~^ ERROR: indexing may panic
    v[M];
    //~^ ERROR: indexing may panic
}