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Reduce false-positives for needless_pass_by_value lint

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Excluding a type whose reference also fulfills the trait bound.
This commit is contained in:
sinkuu 2017-10-08 10:23:41 +09:00
parent 12a7d1489a
commit bf97cd0338
3 changed files with 108 additions and 77 deletions
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19
tests/ui/needless_pass_by_value.rs
View file

@ -4,6 +4,9 @@
#![warn(needless_pass_by_value)]
#![allow(dead_code, single_match, if_let_redundant_pattern_matching, many_single_char_names)]
use std::borrow::Borrow;
use std::convert::AsRef;
// `v` should be warned
// `w`, `x` and `y` are allowed (moved or mutated)
fn foo<T: Default>(v: Vec<T>, w: Vec<T>, mut x: Vec<T>, y: Vec<T>) -> Vec<T> {
@ -25,10 +28,11 @@ fn bar(x: String, y: Wrapper) {
assert_eq!(y.0.len(), 42);
}
// U implements `Borrow<U>`, but should be warned correctly
fn test_borrow_trait<T: std::borrow::Borrow<str>, U>(t: T, u: U) {
// V implements `Borrow<V>`, but should be warned correctly
fn test_borrow_trait<T: Borrow<str>, U: AsRef<str>, V>(t: T, u: U, v: V) {
println!("{}", t.borrow());
consume(&u);
println!("{}", u.as_ref());
consume(&v);
}
// ok
@ -59,4 +63,13 @@ fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
println!("{}", t);
}
trait Foo {}
// `S: Serialize` can be passed by value
trait Serialize {}
impl<'a, T> Serialize for &'a T where T: Serialize {}
impl Serialize for i32 {}
fn test_blanket_ref<T: Foo, S: Serialize>(_foo: T, _serializable: S) {}
fn main() {}

56
tests/ui/needless_pass_by_value.stderr
View file

@ -1,58 +1,64 @@
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:9:23
|
9 | fn foo<T: Default>(v: Vec<T>, w: Vec<T>, mut x: Vec<T>, y: Vec<T>) -> Vec<T> {
| ^^^^^^ help: consider changing the type to: `&[T]`
|
= note: `-D needless-pass-by-value` implied by `-D warnings`
--> $DIR/needless_pass_by_value.rs:12:23
|
12 | fn foo<T: Default>(v: Vec<T>, w: Vec<T>, mut x: Vec<T>, y: Vec<T>) -> Vec<T> {
| ^^^^^^ help: consider changing the type to: `&[T]`
|
= note: `-D needless-pass-by-value` implied by `-D warnings`
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:23:11
--> $DIR/needless_pass_by_value.rs:26:11
|
23 | fn bar(x: String, y: Wrapper) {
26 | fn bar(x: String, y: Wrapper) {
| ^^^^^^ help: consider changing the type to: `&str`
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:23:22
--> $DIR/needless_pass_by_value.rs:26:22
|
23 | fn bar(x: String, y: Wrapper) {
26 | fn bar(x: String, y: Wrapper) {
| ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:29:63
--> $DIR/needless_pass_by_value.rs:32:71
|
29 | fn test_borrow_trait<T: std::borrow::Borrow<str>, U>(t: T, u: U) {
| ^ help: consider taking a reference instead: `&U`
32 | fn test_borrow_trait<T: Borrow<str>, U: AsRef<str>, V>(t: T, u: U, v: V) {
| ^ help: consider taking a reference instead: `&V`
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:40:18
--> $DIR/needless_pass_by_value.rs:44:18
|
40 | fn test_match(x: Option<Option<String>>, y: Option<Option<String>>) {
44 | fn test_match(x: Option<Option<String>>, y: Option<Option<String>>) {
| ^^^^^^^^^^^^^^^^^^^^^^
|
help: consider taking a reference instead
|
40 | fn test_match(x: &Option<Option<String>>, y: Option<Option<String>>) {
41 | match *x {
44 | fn test_match(x: &Option<Option<String>>, y: Option<Option<String>>) {
45 | match *x {
|
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:53:24
--> $DIR/needless_pass_by_value.rs:57:24
|
53 | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
57 | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
| ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:53:36
--> $DIR/needless_pass_by_value.rs:57:36
|
53 | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
57 | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
| ^^^^^^^
|
help: consider taking a reference instead
|
53 | fn test_destructure(x: Wrapper, y: &Wrapper, z: Wrapper) {
54 | let Wrapper(s) = z; // moved
55 | let Wrapper(ref t) = *y; // not moved
56 | let Wrapper(_) = *y; // still not moved
57 | fn test_destructure(x: Wrapper, y: &Wrapper, z: Wrapper) {
58 | let Wrapper(s) = z; // moved
59 | let Wrapper(ref t) = *y; // not moved
60 | let Wrapper(_) = *y; // still not moved
|
error: this argument is passed by value, but not consumed in the function body
--> $DIR/needless_pass_by_value.rs:73:49
|
73 | fn test_blanket_ref<T: Foo, S: Serialize>(_foo: T, _serializable: S) {}
| ^ help: consider taking a reference instead: `&T`