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Auto merge of #11673 - y21:issue11672, r=Manishearth

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[`unnecessary_lazy_eval`]: reduce applicability if closure has return type annotation

Fixes #11672

We already check if closure parameters don't have type annotations and reduce the applicability to `MaybeIncorrect` if they do, since those help type inference and removing them breaks code. We didn't do this for return type annotations however. This PR adds it. This doesn't change it to produce a fix that will compile, but it will prevent rustfix from auto-applying it.

(In general I'm not sure if we can suggest a fix that will compile. In this specific example, it might be possible to suggest `&[] as &[u8]`, but as-casts won't always work, e.g. `Default::default() as &[u8]` is a compile error, so just reducing applicability should be a safe fix in any case for now)

changelog: [`unnecessary_lazy_eval`]: reduce applicability to `MaybeIncorrect` if closure has return type annotation
This commit is contained in:
bors 2023-10-16 16:27:01 +00:00
commit 9f27b1562c
6 changed files with 85 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
clippy_lints/src/methods/unnecessary_lazy_eval.rs
View File

@ -2,6 +2,7 @@ use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{eager_or_lazy, is_from_proc_macro, usage};
use hir::FnRetTy;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
@ -27,7 +28,7 @@ pub(super) fn check<'tcx>(
let is_bool = cx.typeck_results().expr_ty(recv).is_bool();
if is_option || is_result || is_bool {
if let hir::ExprKind::Closure(&hir::Closure { body, .. }) = arg.kind {
if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl, .. }) = arg.kind {
let body = cx.tcx.hir().body(body);
let body_expr = &body.value;
@ -48,7 +49,14 @@ pub(super) fn check<'tcx>(
.iter()
// bindings are checked to be unused above
.all(|param| matches!(param.pat.kind, hir::PatKind::Binding(..) | hir::PatKind::Wild))
{
&& matches!(
fn_decl.output,
FnRetTy::DefaultReturn(_)
| FnRetTy::Return(hir::Ty {
kind: hir::TyKind::Infer,
..
})
) {
Applicability::MachineApplicable
} else {
// replacing the lambda may break type inference

3
tests/ui/unnecessary_lazy_eval.fixed
View File

@ -5,6 +5,7 @@
#![allow(clippy::map_identity)]
#![allow(clippy::needless_borrow)]
#![allow(clippy::unnecessary_literal_unwrap)]
#![allow(clippy::unit_arg)]
use std::ops::Deref;
@ -76,6 +77,8 @@ fn main() {
let _ = opt.ok_or(2);
let _ = nested_tuple_opt.unwrap_or(Some((1, 2)));
let _ = cond.then_some(astronomers_pi);
let _ = true.then_some({});
let _ = true.then_some({});
// Should lint - Builtin deref
let r = &1;

3
tests/ui/unnecessary_lazy_eval.rs
View File

@ -5,6 +5,7 @@
#![allow(clippy::map_identity)]
#![allow(clippy::needless_borrow)]
#![allow(clippy::unnecessary_literal_unwrap)]
#![allow(clippy::unit_arg)]
use std::ops::Deref;
@ -76,6 +77,8 @@ fn main() {
let _ = opt.ok_or_else(|| 2);
let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
let _ = cond.then(|| astronomers_pi);
let _ = true.then(|| -> _ {});
let _ = true.then(|| {});
// Should lint - Builtin deref
let r = &1;

94
tests/ui/unnecessary_lazy_eval.stderr
View File

@ -1,5 +1,5 @@
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:68:13
--> $DIR/unnecessary_lazy_eval.rs:69:13
|
LL | let _ = opt.unwrap_or_else(|| 2);
| ^^^^--------------------
@ -10,7 +10,7 @@ LL | let _ = opt.unwrap_or_else(|| 2);
= help: to override `-D warnings` add `#[allow(clippy::unnecessary_lazy_evaluations)]`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:69:13
--> $DIR/unnecessary_lazy_eval.rs:70:13
|
LL | let _ = opt.unwrap_or_else(|| astronomers_pi);
| ^^^^---------------------------------
@ -18,7 +18,7 @@ LL | let _ = opt.unwrap_or_else(|| astronomers_pi);
| help: use `unwrap_or(..)` instead: `unwrap_or(astronomers_pi)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:70:13
--> $DIR/unnecessary_lazy_eval.rs:71:13
|
LL | let _ = opt.unwrap_or_else(|| ext_str.some_field);
| ^^^^-------------------------------------
@ -26,7 +26,7 @@ LL | let _ = opt.unwrap_or_else(|| ext_str.some_field);
| help: use `unwrap_or(..)` instead: `unwrap_or(ext_str.some_field)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:72:13
--> $DIR/unnecessary_lazy_eval.rs:73:13
|
LL | let _ = opt.and_then(|_| ext_opt);
| ^^^^---------------------
@ -34,7 +34,7 @@ LL | let _ = opt.and_then(|_| ext_opt);
| help: use `and(..)` instead: `and(ext_opt)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:73:13
--> $DIR/unnecessary_lazy_eval.rs:74:13
|
LL | let _ = opt.or_else(|| ext_opt);
| ^^^^-------------------
@ -42,7 +42,7 @@ LL | let _ = opt.or_else(|| ext_opt);
| help: use `or(..)` instead: `or(ext_opt)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:74:13
--> $DIR/unnecessary_lazy_eval.rs:75:13
|
LL | let _ = opt.or_else(|| None);
| ^^^^----------------
@ -50,7 +50,7 @@ LL | let _ = opt.or_else(|| None);
| help: use `or(..)` instead: `or(None)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:75:13
--> $DIR/unnecessary_lazy_eval.rs:76:13
|
LL | let _ = opt.get_or_insert_with(|| 2);
| ^^^^------------------------
@ -58,7 +58,7 @@ LL | let _ = opt.get_or_insert_with(|| 2);
| help: use `get_or_insert(..)` instead: `get_or_insert(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:76:13
--> $DIR/unnecessary_lazy_eval.rs:77:13
|
LL | let _ = opt.ok_or_else(|| 2);
| ^^^^----------------
@ -66,7 +66,7 @@ LL | let _ = opt.ok_or_else(|| 2);
| help: use `ok_or(..)` instead: `ok_or(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:77:13
--> $DIR/unnecessary_lazy_eval.rs:78:13
|
LL | let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
| ^^^^^^^^^^^^^^^^^-------------------------------
@ -74,15 +74,31 @@ LL | let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
| help: use `unwrap_or(..)` instead: `unwrap_or(Some((1, 2)))`
error: unnecessary closure used with `bool::then`
--> $DIR/unnecessary_lazy_eval.rs:78:13
--> $DIR/unnecessary_lazy_eval.rs:79:13
|
LL | let _ = cond.then(|| astronomers_pi);
| ^^^^^-----------------------
| |
| help: use `then_some(..)` instead: `then_some(astronomers_pi)`
error: unnecessary closure used with `bool::then`
--> $DIR/unnecessary_lazy_eval.rs:80:13
|
LL | let _ = true.then(|| -> _ {});
| ^^^^^----------------
| |
| help: use `then_some(..)` instead: `then_some({})`
error: unnecessary closure used with `bool::then`
--> $DIR/unnecessary_lazy_eval.rs:81:13
|
LL | let _ = true.then(|| {});
| ^^^^^-----------
| |
| help: use `then_some(..)` instead: `then_some({})`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:82:13
--> $DIR/unnecessary_lazy_eval.rs:85:13
|
LL | let _ = Some(1).unwrap_or_else(|| *r);
| ^^^^^^^^---------------------
@ -90,7 +106,7 @@ LL | let _ = Some(1).unwrap_or_else(|| *r);
| help: use `unwrap_or(..)` instead: `unwrap_or(*r)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:84:13
--> $DIR/unnecessary_lazy_eval.rs:87:13
|
LL | let _ = Some(1).unwrap_or_else(|| *b);
| ^^^^^^^^---------------------
@ -98,7 +114,7 @@ LL | let _ = Some(1).unwrap_or_else(|| *b);
| help: use `unwrap_or(..)` instead: `unwrap_or(*b)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:86:13
--> $DIR/unnecessary_lazy_eval.rs:89:13
|
LL | let _ = Some(1).as_ref().unwrap_or_else(|| &r);
| ^^^^^^^^^^^^^^^^^---------------------
@ -106,7 +122,7 @@ LL | let _ = Some(1).as_ref().unwrap_or_else(|| &r);
| help: use `unwrap_or(..)` instead: `unwrap_or(&r)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:87:13
--> $DIR/unnecessary_lazy_eval.rs:90:13
|
LL | let _ = Some(1).as_ref().unwrap_or_else(|| &b);
| ^^^^^^^^^^^^^^^^^---------------------
@ -114,7 +130,7 @@ LL | let _ = Some(1).as_ref().unwrap_or_else(|| &b);
| help: use `unwrap_or(..)` instead: `unwrap_or(&b)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:90:13
--> $DIR/unnecessary_lazy_eval.rs:93:13
|
LL | let _ = Some(10).unwrap_or_else(|| 2);
| ^^^^^^^^^--------------------
@ -122,7 +138,7 @@ LL | let _ = Some(10).unwrap_or_else(|| 2);
| help: use `unwrap_or(..)` instead: `unwrap_or(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:91:13
--> $DIR/unnecessary_lazy_eval.rs:94:13
|
LL | let _ = Some(10).and_then(|_| ext_opt);
| ^^^^^^^^^---------------------
@ -130,7 +146,7 @@ LL | let _ = Some(10).and_then(|_| ext_opt);
| help: use `and(..)` instead: `and(ext_opt)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:92:28
--> $DIR/unnecessary_lazy_eval.rs:95:28
|
LL | let _: Option<usize> = None.or_else(|| ext_opt);
| ^^^^^-------------------
@ -138,7 +154,7 @@ LL | let _: Option<usize> = None.or_else(|| ext_opt);
| help: use `or(..)` instead: `or(ext_opt)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:93:13
--> $DIR/unnecessary_lazy_eval.rs:96:13
|
LL | let _ = None.get_or_insert_with(|| 2);
| ^^^^^------------------------
@ -146,7 +162,7 @@ LL | let _ = None.get_or_insert_with(|| 2);
| help: use `get_or_insert(..)` instead: `get_or_insert(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:94:35
--> $DIR/unnecessary_lazy_eval.rs:97:35
|
LL | let _: Result<usize, usize> = None.ok_or_else(|| 2);
| ^^^^^----------------
@ -154,7 +170,7 @@ LL | let _: Result<usize, usize> = None.ok_or_else(|| 2);
| help: use `ok_or(..)` instead: `ok_or(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:95:28
--> $DIR/unnecessary_lazy_eval.rs:98:28
|
LL | let _: Option<usize> = None.or_else(|| None);
| ^^^^^----------------
@ -162,7 +178,7 @@ LL | let _: Option<usize> = None.or_else(|| None);
| help: use `or(..)` instead: `or(None)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:98:13
--> $DIR/unnecessary_lazy_eval.rs:101:13
|
LL | let _ = deep.0.unwrap_or_else(|| 2);
| ^^^^^^^--------------------
@ -170,7 +186,7 @@ LL | let _ = deep.0.unwrap_or_else(|| 2);
| help: use `unwrap_or(..)` instead: `unwrap_or(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:99:13
--> $DIR/unnecessary_lazy_eval.rs:102:13
|
LL | let _ = deep.0.and_then(|_| ext_opt);
| ^^^^^^^---------------------
@ -178,7 +194,7 @@ LL | let _ = deep.0.and_then(|_| ext_opt);
| help: use `and(..)` instead: `and(ext_opt)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:100:13
--> $DIR/unnecessary_lazy_eval.rs:103:13
|
LL | let _ = deep.0.or_else(|| None);
| ^^^^^^^----------------
@ -186,7 +202,7 @@ LL | let _ = deep.0.or_else(|| None);
| help: use `or(..)` instead: `or(None)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:101:13
--> $DIR/unnecessary_lazy_eval.rs:104:13
|
LL | let _ = deep.0.get_or_insert_with(|| 2);
| ^^^^^^^------------------------
@ -194,7 +210,7 @@ LL | let _ = deep.0.get_or_insert_with(|| 2);
| help: use `get_or_insert(..)` instead: `get_or_insert(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:102:13
--> $DIR/unnecessary_lazy_eval.rs:105:13
|
LL | let _ = deep.0.ok_or_else(|| 2);
| ^^^^^^^----------------
@ -202,7 +218,7 @@ LL | let _ = deep.0.ok_or_else(|| 2);
| help: use `ok_or(..)` instead: `ok_or(2)`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:132:28
--> $DIR/unnecessary_lazy_eval.rs:135:28
|
LL | let _: Option<usize> = None.or_else(|| Some(3));
| ^^^^^-------------------
@ -210,7 +226,7 @@ LL | let _: Option<usize> = None.or_else(|| Some(3));
| help: use `or(..)` instead: `or(Some(3))`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:133:13
--> $DIR/unnecessary_lazy_eval.rs:136:13
|
LL | let _ = deep.0.or_else(|| Some(3));
| ^^^^^^^-------------------
@ -218,7 +234,7 @@ LL | let _ = deep.0.or_else(|| Some(3));
| help: use `or(..)` instead: `or(Some(3))`
error: unnecessary closure used to substitute value for `Option::None`
--> $DIR/unnecessary_lazy_eval.rs:134:13
--> $DIR/unnecessary_lazy_eval.rs:137:13
|
LL | let _ = opt.or_else(|| Some(3));
| ^^^^-------------------
@ -226,7 +242,7 @@ LL | let _ = opt.or_else(|| Some(3));
| help: use `or(..)` instead: `or(Some(3))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:140:13
--> $DIR/unnecessary_lazy_eval.rs:143:13
|
LL | let _ = res2.unwrap_or_else(|_| 2);
| ^^^^^---------------------
@ -234,7 +250,7 @@ LL | let _ = res2.unwrap_or_else(|_| 2);
| help: use `unwrap_or(..)` instead: `unwrap_or(2)`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:141:13
--> $DIR/unnecessary_lazy_eval.rs:144:13
|
LL | let _ = res2.unwrap_or_else(|_| astronomers_pi);
| ^^^^^----------------------------------
@ -242,7 +258,7 @@ LL | let _ = res2.unwrap_or_else(|_| astronomers_pi);
| help: use `unwrap_or(..)` instead: `unwrap_or(astronomers_pi)`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:142:13
--> $DIR/unnecessary_lazy_eval.rs:145:13
|
LL | let _ = res2.unwrap_or_else(|_| ext_str.some_field);
| ^^^^^--------------------------------------
@ -250,7 +266,7 @@ LL | let _ = res2.unwrap_or_else(|_| ext_str.some_field);
| help: use `unwrap_or(..)` instead: `unwrap_or(ext_str.some_field)`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:164:35
--> $DIR/unnecessary_lazy_eval.rs:167:35
|
LL | let _: Result<usize, usize> = res.and_then(|_| Err(2));
| ^^^^--------------------
@ -258,7 +274,7 @@ LL | let _: Result<usize, usize> = res.and_then(|_| Err(2));
| help: use `and(..)` instead: `and(Err(2))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:165:35
--> $DIR/unnecessary_lazy_eval.rs:168:35
|
LL | let _: Result<usize, usize> = res.and_then(|_| Err(astronomers_pi));
| ^^^^---------------------------------
@ -266,7 +282,7 @@ LL | let _: Result<usize, usize> = res.and_then(|_| Err(astronomers_pi));
| help: use `and(..)` instead: `and(Err(astronomers_pi))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:166:35
--> $DIR/unnecessary_lazy_eval.rs:169:35
|
LL | let _: Result<usize, usize> = res.and_then(|_| Err(ext_str.some_field));
| ^^^^-------------------------------------
@ -274,7 +290,7 @@ LL | let _: Result<usize, usize> = res.and_then(|_| Err(ext_str.some_field))
| help: use `and(..)` instead: `and(Err(ext_str.some_field))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:168:35
--> $DIR/unnecessary_lazy_eval.rs:171:35
|
LL | let _: Result<usize, usize> = res.or_else(|_| Ok(2));
| ^^^^------------------
@ -282,7 +298,7 @@ LL | let _: Result<usize, usize> = res.or_else(|_| Ok(2));
| help: use `or(..)` instead: `or(Ok(2))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:169:35
--> $DIR/unnecessary_lazy_eval.rs:172:35
|
LL | let _: Result<usize, usize> = res.or_else(|_| Ok(astronomers_pi));
| ^^^^-------------------------------
@ -290,7 +306,7 @@ LL | let _: Result<usize, usize> = res.or_else(|_| Ok(astronomers_pi));
| help: use `or(..)` instead: `or(Ok(astronomers_pi))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:170:35
--> $DIR/unnecessary_lazy_eval.rs:173:35
|
LL | let _: Result<usize, usize> = res.or_else(|_| Ok(ext_str.some_field));
| ^^^^-----------------------------------
@ -298,7 +314,7 @@ LL | let _: Result<usize, usize> = res.or_else(|_| Ok(ext_str.some_field));
| help: use `or(..)` instead: `or(Ok(ext_str.some_field))`
error: unnecessary closure used to substitute value for `Result::Err`
--> $DIR/unnecessary_lazy_eval.rs:171:35
--> $DIR/unnecessary_lazy_eval.rs:174:35
|
LL | let _: Result<usize, usize> = res.
| ___________________________________^
@ -312,5 +328,5 @@ LL | | or_else(|_| Ok(ext_str.some_field));
| |
| help: use `or(..)` instead: `or(Ok(ext_str.some_field))`
error: aborting due to 38 previous errors
error: aborting due to 40 previous errors

5
tests/ui/unnecessary_lazy_eval_unfixable.rs
View File

@ -25,3 +25,8 @@ fn main() {
let arr = [(Some(1),)];
Some(&0).and_then(|&i| arr[i].0);
}
fn issue11672() {
// Return type annotation helps type inference and removing it can break code
let _ = true.then(|| -> &[u8] { &[] });
}

10
tests/ui/unnecessary_lazy_eval_unfixable.stderr
View File

@ -25,5 +25,13 @@ LL | let _ = Ok(1).unwrap_or_else(|SomeStruct { .. }| 2);
| |
| help: use `unwrap_or(..)` instead: `unwrap_or(2)`
error: aborting due to 3 previous errors
error: unnecessary closure used with `bool::then`
--> $DIR/unnecessary_lazy_eval_unfixable.rs:31:13
|
LL | let _ = true.then(|| -> &[u8] { &[] });
| ^^^^^-------------------------
| |
| help: use `then_some(..)` instead: `then_some({ &[] })`
error: aborting due to 4 previous errors