From 9655231eb825500d69738382f791374660311390 Mon Sep 17 00:00:00 2001 From: Quinn Sinclair Date: Mon, 25 Mar 2024 23:29:34 +0100 Subject: [PATCH 1/2] 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 --- .../src/methods/filter_map_identity.rs | 18 ++- tests/ui/filter_map_identity.fixed | 86 +++++++++-- tests/ui/filter_map_identity.rs | 86 +++++++++-- tests/ui/filter_map_identity.stderr | 134 ++++++++++++++++-- 4 files changed, 288 insertions(+), 36 deletions(-) diff --git a/clippy_lints/src/methods/filter_map_identity.rs b/clippy_lints/src/methods/filter_map_identity.rs index 8291c373f371..15b11a731c98 100644 --- a/clippy_lints/src/methods/filter_map_identity.rs +++ b/clippy_lints/src/methods/filter_map_identity.rs @@ -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 { + if is_expr_untyped_identity_function(cx, expr) { + return Some(Applicability::MachineApplicable); + } + if is_expr_identity_function(cx, expr) { + return Some(Applicability::MaybeIncorrect); + } + 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, ); } } diff --git a/tests/ui/filter_map_identity.fixed b/tests/ui/filter_map_identity.fixed index ad438afaca77..f3f6848e5f92 100644 --- a/tests/ui/filter_map_identity.fixed +++ b/tests/ui/filter_map_identity.fixed @@ -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> { + todo!() +} + +fn copy_vec() -> Vec> { + todo!() +} + +fn copy_vec_non_inferred() -> Vec> { + todo!() +} + +fn opaque() -> impl IntoIterator> { + 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 + + 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 + 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::().into_iter().flatten(); + //~^ ERROR: use of + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + 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(); + // we are forced to pass the type in the call. + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + #[rustfmt::skip] + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of + #[rustfmt::skip] + copy_vec::().into_iter().flatten(); + //~^ ERROR: use of - let iterator = vec![Some(1), None, Some(2)].into_iter(); - let _ = iterator.flatten(); + // note, the compiler requires that we pass the type to `opaque`. This is mostly for reference, + // it behaves the same as copy_vec. + opaque::().into_iter().flatten(); + //~^ ERROR: use of + } } diff --git a/tests/ui/filter_map_identity.rs b/tests/ui/filter_map_identity.rs index d7423276872a..b9aa9c05be89 100644 --- a/tests/ui/filter_map_identity.rs +++ b/tests/ui/filter_map_identity.rs @@ -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> { + todo!() +} + +fn copy_vec() -> Vec> { + todo!() +} + +fn copy_vec_non_inferred() -> Vec> { + todo!() +} + +fn opaque() -> impl IntoIterator> { + 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 + + non_copy_vec().into_iter().filter_map(|x| x); + //~^ ERROR: use of + non_copy_vec().into_iter().filter_map(|x| x); + //~^ ERROR: use of + + 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(std::convert::identity); + copy_vec::().into_iter().filter_map(|x: Option<_>| x); + //~^ ERROR: use of + copy_vec::().into_iter().filter_map(|x: Option<_>| x); + //~^ ERROR: use of + copy_vec::().into_iter().filter_map(|x: Option<_>| return x); + //~^ ERROR: use of + copy_vec::().into_iter().filter_map(|x: Option<_>| return x); + //~^ ERROR: use of - use std::convert::identity; - let iterator = vec![Some(1), None, Some(2)].into_iter(); - let _ = iterator.filter_map(identity); + // we are forced to pass the type in the call. + copy_vec::().into_iter().filter_map(|x: Option| x); + //~^ ERROR: use of + copy_vec::().into_iter().filter_map(|x: Option| x); + //~^ ERROR: use of + copy_vec::().into_iter().filter_map(|x: Option| return x); + //~^ ERROR: use of + copy_vec::().into_iter().filter_map(|x: Option| return x); + //~^ ERROR: use of + #[rustfmt::skip] + copy_vec::().into_iter().filter_map(|x: Option| -> Option {{ x }}); + //~^ ERROR: use of + #[rustfmt::skip] + copy_vec::().into_iter().filter_map(|x: Option| -> Option {{ return x }}); + //~^ ERROR: use of - let iterator = vec![Some(1), None, Some(2)].into_iter(); - let _ = iterator.filter_map(|x| return x); + // note, the compiler requires that we pass the type to `opaque`. This is mostly for reference, + // it behaves the same as copy_vec. + opaque::().into_iter().filter_map(|x| x); + //~^ ERROR: use of + } } diff --git a/tests/ui/filter_map_identity.stderr b/tests/ui/filter_map_identity.stderr index 5aa46ad6d237..55068db4e9d0 100644 --- a/tests/ui/filter_map_identity.stderr +++ b/tests/ui/filter_map_identity.stderr @@ -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::().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::().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::().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::().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::().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:65:39 + | +LL | copy_vec::().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:67:39 + | +LL | copy_vec::().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:69:39 + | +LL | copy_vec::().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:72:43 + | +LL | copy_vec::().into_iter().filter_map(|x: Option| -> Option {{ x }}); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()` + +error: use of `filter_map` with an identity function + --> tests/ui/filter_map_identity.rs:75:43 + | +LL | copy_vec::().into_iter().filter_map(|x: Option| -> Option {{ return x }}); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `flatten()` + +error: use of `filter_map` with an identity function + --> tests/ui/filter_map_identity.rs:80:37 + | +LL | opaque::().into_iter().filter_map(|x| x); + | ^^^^^^^^^^^^^^^^^ help: try: `flatten()` + +error: aborting due to 22 previous errors From 60937bf2dbf68e36c078087b3a0dc01d6857465a Mon Sep 17 00:00:00 2001 From: Quinn Sinclair Date: Tue, 26 Mar 2024 18:59:09 +0100 Subject: [PATCH 2/2] :adjust applicability for typed identity closures in `filter_map_identity` --- clippy_lints/src/methods/filter_map_identity.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/clippy_lints/src/methods/filter_map_identity.rs b/clippy_lints/src/methods/filter_map_identity.rs index 15b11a731c98..999df875c753 100644 --- a/clippy_lints/src/methods/filter_map_identity.rs +++ b/clippy_lints/src/methods/filter_map_identity.rs @@ -12,7 +12,7 @@ fn is_identity(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option