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Auto merge of #12562 - m-rph:12501, r=y21

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Allow `filter_map_identity` when the closure is typed

This extends the `filter_map_identity` lint to support typed closures.

For untyped closures, we know that the program compiles, and therefore we can safely suggest using flatten.

For typed closures, they may participate in type resolution. In this case we use `Applicability::MaybeIncorrect`.

Details:
https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/Should.20.60filter_map_identity.60.20lint.20when.20closures.20are.20typed.3F

changelog: `filter_map_identity` will now suggest using flatten for typed closures.

r? `@y21` && `@Centri3`
This commit is contained in:
bors 2024-03-31 12:16:01 +00:00
commit 797d50dfe6
4 changed files with 288 additions and 36 deletions
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18
clippy_lints/src/methods/filter_map_identity.rs
View File

@ -1,5 +1,5 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::{is_expr_untyped_identity_function, is_trait_method};
use clippy_utils::{is_expr_identity_function, is_expr_untyped_identity_function, is_trait_method};
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
@ -7,8 +7,20 @@ use rustc_span::{sym, Span};
use super::FILTER_MAP_IDENTITY;
fn is_identity(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Applicability> {
if is_expr_untyped_identity_function(cx, expr) {
return Some(Applicability::MachineApplicable);
}
if is_expr_identity_function(cx, expr) {
return Some(Applicability::Unspecified);
}
None
}
pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, filter_map_arg: &hir::Expr<'_>, filter_map_span: Span) {
if is_trait_method(cx, expr, sym::Iterator) && is_expr_untyped_identity_function(cx, filter_map_arg) {
if is_trait_method(cx, expr, sym::Iterator)
&& let Some(applicability) = is_identity(cx, filter_map_arg)
{
span_lint_and_sugg(
cx,
FILTER_MAP_IDENTITY,
@ -16,7 +28,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, filter_map_arg:
"use of `filter_map` with an identity function",
"try",
"flatten()".to_string(),
Applicability::MachineApplicable,
applicability,
);
}
}

86
tests/ui/filter_map_identity.fixed
View File

@ -1,17 +1,83 @@
#![allow(unused_imports, clippy::needless_return)]
#![allow(unused_imports, clippy::needless_return, clippy::useless_vec)]
#![warn(clippy::filter_map_identity)]
#![feature(stmt_expr_attributes)]
use std::option::Option;
struct NonCopy;
use std::convert::identity;
fn non_copy_vec() -> Vec<Option<NonCopy>> {
todo!()
}
fn copy_vec<T: Copy>() -> Vec<Option<T>> {
todo!()
}
fn copy_vec_non_inferred() -> Vec<Option<i32>> {
todo!()
}
fn opaque<T: Default>() -> impl IntoIterator<Item = Option<T>> {
vec![Some(T::default())]
}
fn main() {
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.flatten();
{
// into_iter
copy_vec_non_inferred().into_iter().flatten();
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().flatten();
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().flatten();
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().flatten();
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().flatten();
//~^ ERROR: use of
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.flatten();
non_copy_vec().into_iter().flatten();
//~^ ERROR: use of
non_copy_vec().into_iter().flatten();
//~^ ERROR: use of
use std::convert::identity;
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.flatten();
non_copy_vec().into_iter().flatten();
//~^ ERROR: use of
non_copy_vec().into_iter().flatten();
//~^ ERROR: use of
non_copy_vec().into_iter().flatten();
//~^ ERROR: use of
non_copy_vec().into_iter().flatten();
//~^ ERROR: use of
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.flatten();
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
// we are forced to pass the type in the call.
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
#[rustfmt::skip]
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
#[rustfmt::skip]
copy_vec::<i32>().into_iter().flatten();
//~^ ERROR: use of
// note, the compiler requires that we pass the type to `opaque`. This is mostly for reference,
// it behaves the same as copy_vec.
opaque::<i32>().into_iter().flatten();
//~^ ERROR: use of
}
}

86
tests/ui/filter_map_identity.rs
View File

@ -1,17 +1,83 @@
#![allow(unused_imports, clippy::needless_return)]
#![allow(unused_imports, clippy::needless_return, clippy::useless_vec)]
#![warn(clippy::filter_map_identity)]
#![feature(stmt_expr_attributes)]
use std::option::Option;
struct NonCopy;
use std::convert::identity;
fn non_copy_vec() -> Vec<Option<NonCopy>> {
todo!()
}
fn copy_vec<T: Copy>() -> Vec<Option<T>> {
todo!()
}
fn copy_vec_non_inferred() -> Vec<Option<i32>> {
todo!()
}
fn opaque<T: Default>() -> impl IntoIterator<Item = Option<T>> {
vec![Some(T::default())]
}
fn main() {
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.filter_map(|x| x);
{
// into_iter
copy_vec_non_inferred().into_iter().filter_map(|x| x);
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().filter_map(std::convert::identity);
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().filter_map(identity);
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().filter_map(|x| return x);
//~^ ERROR: use of
copy_vec_non_inferred().into_iter().filter_map(|x| return x);
//~^ ERROR: use of
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.filter_map(std::convert::identity);
non_copy_vec().into_iter().filter_map(|x| x);
//~^ ERROR: use of
non_copy_vec().into_iter().filter_map(|x| x);
//~^ ERROR: use of
use std::convert::identity;
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.filter_map(identity);
non_copy_vec().into_iter().filter_map(std::convert::identity);
//~^ ERROR: use of
non_copy_vec().into_iter().filter_map(identity);
//~^ ERROR: use of
non_copy_vec().into_iter().filter_map(|x| return x);
//~^ ERROR: use of
non_copy_vec().into_iter().filter_map(|x| return x);
//~^ ERROR: use of
let iterator = vec![Some(1), None, Some(2)].into_iter();
let _ = iterator.filter_map(|x| return x);
copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| x);
//~^ ERROR: use of
copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| x);
//~^ ERROR: use of
copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| return x);
//~^ ERROR: use of
copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| return x);
//~^ ERROR: use of
// we are forced to pass the type in the call.
copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| x);
//~^ ERROR: use of
copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| x);
//~^ ERROR: use of
copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| return x);
//~^ ERROR: use of
copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| return x);
//~^ ERROR: use of
#[rustfmt::skip]
copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| -> Option<i32> {{ x }});
//~^ ERROR: use of
#[rustfmt::skip]
copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| -> Option<i32> {{ return x }});
//~^ ERROR: use of
// note, the compiler requires that we pass the type to `opaque`. This is mostly for reference,
// it behaves the same as copy_vec.
opaque::<i32>().into_iter().filter_map(|x| x);
//~^ ERROR: use of
}
}

134
tests/ui/filter_map_identity.stderr
View File

@ -1,29 +1,137 @@
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:6:22
--> tests/ui/filter_map_identity.rs:28:45
|
LL | let _ = iterator.filter_map(|x| x);
| ^^^^^^^^^^^^^^^^^ help: try: `flatten()`
LL | copy_vec_non_inferred().into_iter().filter_map(|x| x);
| ^^^^^^^^^^^^^^^^^ help: try: `flatten()`
|
= note: `-D clippy::filter-map-identity` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::filter_map_identity)]`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:9:22
--> tests/ui/filter_map_identity.rs:30:45
|
LL | let _ = iterator.filter_map(std::convert::identity);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
LL | copy_vec_non_inferred().into_iter().filter_map(std::convert::identity);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:13:22
--> tests/ui/filter_map_identity.rs:32:45
|
LL | let _ = iterator.filter_map(identity);
| ^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
LL | copy_vec_non_inferred().into_iter().filter_map(identity);
| ^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:16:22
--> tests/ui/filter_map_identity.rs:34:45
|
LL | let _ = iterator.filter_map(|x| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
LL | copy_vec_non_inferred().into_iter().filter_map(|x| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: aborting due to 4 previous errors
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:36:45
|
LL | copy_vec_non_inferred().into_iter().filter_map(|x| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:39:36
|
LL | non_copy_vec().into_iter().filter_map(|x| x);
| ^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:41:36
|
LL | non_copy_vec().into_iter().filter_map(|x| x);
| ^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:44:36
|
LL | non_copy_vec().into_iter().filter_map(std::convert::identity);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:46:36
|
LL | non_copy_vec().into_iter().filter_map(identity);
| ^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:48:36
|
LL | non_copy_vec().into_iter().filter_map(|x| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:50:36
|
LL | non_copy_vec().into_iter().filter_map(|x| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:53:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:55:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:57:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:59:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<_>| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:63:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:65:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:67:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:69:39
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| return x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:72:43
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| -> Option<i32> {{ x }});
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:75:43
|
LL | copy_vec::<i32>().into_iter().filter_map(|x: Option<i32>| -> Option<i32> {{ return x }});
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: use of `filter_map` with an identity function
--> tests/ui/filter_map_identity.rs:80:37
|
LL | opaque::<i32>().into_iter().filter_map(|x| x);
| ^^^^^^^^^^^^^^^^^ help: try: `flatten()`
error: aborting due to 22 previous errors