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//! Test that dead code warnings are issued for superfluous assignments of fields or variables to
//! themselves (issue #75356).
//!
//! # History of this test (to aid relanding of a fixed version of #81473)
//!
//! - Original lint request was about self-assignments not triggering sth like `dead_code`.
//! - `dead_code` lint expansion for self-assignments was implemented in #87129.
//! - Unfortunately implementation components of #87129 had to be disabled as part of reverts
//! #86212, #83171 (to revert #81473) to address regressions #81626 and #81658.
//! - Re-enabled in current version to properly detect self-assignments.
//@ check-pass
#![allow(unused_assignments)]
#![warn(dead_code)]
fn main() {
let mut x = 0;
x = x;
//~^ WARNING: useless assignment of variable of type `i32` to itself
x = (x);
//~^ WARNING: useless assignment of variable of type `i32` to itself
x = {x};
// block expressions don't count as self-assignments
struct S<'a> { f: &'a str }
let mut s = S { f: "abc" };
s = s;
//~^ WARNING: useless assignment of variable of type `S<'_>` to itself
s.f = s.f;
//~^ WARNING: useless assignment of field of type `&str` to itself
struct N0 { x: Box<i32> }
struct N1 { n: N0 }
struct N2(N1);
struct N3 { n: N2 };
let mut n3 = N3 { n: N2(N1 { n: N0 { x: Box::new(42) } }) };
n3.n.0.n.x = n3.n.0.n.x;
//~^ WARNING: useless assignment of field of type `Box<i32>` to itself
let mut t = (1, ((2, 3, (4, 5)),));
t.1.0.2.1 = t.1.0.2.1;
//~^ WARNING: useless assignment of field of type `i32` to itself
let mut y = 0;
macro_rules! assign_to_y {
($cur:expr) => {{
y = $cur;
}};
}
assign_to_y!(y);
// self-assignments in macro expansions are not reported either
}
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