136 lines
2.8 KiB
Rust
136 lines
2.8 KiB
Rust
#![allow(unused)]
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#![warn(clippy::collection_is_never_read)]
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use std::collections::{HashMap, HashSet};
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fn main() {}
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fn not_a_collection() {
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// TODO: Expand `collection_is_never_read` beyond collections?
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let mut x = 10; // Ok
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x += 1;
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}
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fn no_access_at_all() {
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// Other lints should catch this.
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let x = vec![1, 2, 3]; // Ok
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}
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fn write_without_read() {
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// The main use case for `collection_is_never_read`.
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let mut x = HashMap::new(); // WARNING
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x.insert(1, 2);
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}
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fn read_without_write() {
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let mut x = vec![1, 2, 3]; // Ok
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let _ = x.len();
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}
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fn write_and_read() {
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let mut x = vec![1, 2, 3]; // Ok
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x.push(4);
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let _ = x.len();
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}
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fn write_after_read() {
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// TODO: Warn here, but this requires more extensive data flow analysis.
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let mut x = vec![1, 2, 3]; // Ok
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let _ = x.len();
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x.push(4); // Pointless
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}
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fn write_before_reassign() {
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// TODO: Warn here, but this requires more extensive data flow analysis.
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let mut x = HashMap::new(); // Ok
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x.insert(1, 2); // Pointless
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x = HashMap::new();
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let _ = x.len();
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}
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fn read_in_closure() {
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let mut x = HashMap::new(); // Ok
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x.insert(1, 2);
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let _ = || {
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let _ = x.len();
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};
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}
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fn write_in_closure() {
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let mut x = vec![1, 2, 3]; // WARNING
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let _ = || {
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x.push(4);
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};
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}
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fn read_in_format() {
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let mut x = HashMap::new(); // Ok
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x.insert(1, 2);
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format!("{x:?}");
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}
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fn shadowing_1() {
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let x = HashMap::<usize, usize>::new(); // Ok
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let _ = x.len();
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let mut x = HashMap::new(); // WARNING
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x.insert(1, 2);
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}
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fn shadowing_2() {
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let mut x = HashMap::new(); // WARNING
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x.insert(1, 2);
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let x = HashMap::<usize, usize>::new(); // Ok
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let _ = x.len();
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}
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#[allow(clippy::let_unit_value)]
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fn fake_read() {
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let mut x = vec![1, 2, 3]; // Ok
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x.reverse();
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// `collection_is_never_read` gets fooled, but other lints should catch this.
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let _: () = x.clear();
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}
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fn assignment() {
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let mut x = vec![1, 2, 3]; // WARNING
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let y = vec![4, 5, 6]; // Ok
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x = y;
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}
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#[allow(clippy::self_assignment)]
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fn self_assignment() {
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let mut x = vec![1, 2, 3]; // WARNING
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x = x;
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}
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fn method_argument_but_not_target() {
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struct MyStruct;
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impl MyStruct {
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fn my_method(&self, _argument: &[usize]) {}
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}
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let my_struct = MyStruct;
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let mut x = vec![1, 2, 3]; // Ok
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x.reverse();
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my_struct.my_method(&x);
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}
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fn insert_is_not_a_read() {
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let mut x = HashSet::new(); // WARNING
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x.insert(5);
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}
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fn insert_is_a_read() {
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let mut x = HashSet::new(); // Ok
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if x.insert(5) {
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println!("5 was inserted");
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}
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}
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fn not_read_if_return_value_not_used() {
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// `is_empty` does not modify the set, so it's a query. But since the return value is not used, the
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// lint does not consider it a read here.
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let x = vec![1, 2, 3]; // WARNING
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x.is_empty();
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}
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