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allow needless_option_take to report for more cases (#13684)
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changelog:
```
changelog: [`needless_option_take`]: now lints for all temporary expressions of type  Option<T>.
```

fixes #13671

In general, needless_option_take should report whenever take() is called
on a temporary value, not just when the temporary value is created by
as_ref().

Also, we stop emitting machine applicable fixes in these cases, since
sometimes the intention of the user is to actually clear the original
option, in cases such as `option.as_mut().take()`.
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Centri3 authored Dec 14, 2024
2 parents 5ac1805 + b8cd513 commit 6240710
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Showing 4 changed files with 146 additions and 40 deletions.
55 changes: 32 additions & 23 deletions clippy_lints/src/methods/needless_option_take.rs
Original file line number Diff line number Diff line change
@@ -1,30 +1,24 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::match_def_path;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::diagnostics::span_lint_and_note;
use clippy_utils::ty::is_type_diagnostic_item;
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_hir::{Expr, ExprKind, QPath};
use rustc_lint::LateContext;
use rustc_span::sym;

use super::NEEDLESS_OPTION_TAKE;

pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'tcx Expr<'_>) {
// Checks if expression type is equal to sym::Option and if the expr is not a syntactic place
if !recv.is_syntactic_place_expr() && is_expr_option(cx, recv) && has_expr_as_ref_path(cx, recv) {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
NEEDLESS_OPTION_TAKE,
expr.span,
"called `Option::take()` on a temporary value",
"try",
format!(
"{}",
snippet_with_applicability(cx, recv.span, "..", &mut applicability)
),
applicability,
);
if !recv.is_syntactic_place_expr() && is_expr_option(cx, recv) {
if let Some(function_name) = source_of_temporary_value(recv) {
span_lint_and_note(
cx,
NEEDLESS_OPTION_TAKE,
expr.span,
"called `Option::take()` on a temporary value",
None,
format!("`{function_name}` creates a temporary value, so calling take() has no effect"),
);
}
}
}

Expand All @@ -33,9 +27,24 @@ fn is_expr_option(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
is_type_diagnostic_item(cx, expr_type, sym::Option)
}

fn has_expr_as_ref_path(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
if let Some(ref_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
return match_def_path(cx, ref_id, &["core", "option", "Option", "as_ref"]);
/// Returns the string of the function call that creates the temporary.
/// When this function is called, we are reasonably certain that the `ExprKind` is either
/// `Call` or `MethodCall` because we already checked that the expression is not
/// `is_syntactic_place_expr()`.
fn source_of_temporary_value<'a>(expr: &'a Expr<'_>) -> Option<&'a str> {
match expr.peel_borrows().kind {
ExprKind::Call(function, _) => {
if let ExprKind::Path(QPath::Resolved(_, func_path)) = function.kind {
if !func_path.segments.is_empty() {
return Some(func_path.segments[0].ident.name.as_str());
}
}
if let ExprKind::Path(QPath::TypeRelative(_, func_path_segment)) = function.kind {
return Some(func_path_segment.ident.name.as_str());
}
None
},
ExprKind::MethodCall(path_segment, ..) => Some(path_segment.ident.name.as_str()),
_ => None,
}
false
}
13 changes: 0 additions & 13 deletions tests/ui/needless_option_take.fixed

This file was deleted.

47 changes: 46 additions & 1 deletion tests/ui/needless_option_take.rs
Original file line number Diff line number Diff line change
@@ -1,3 +1,15 @@
struct MyStruct;

impl MyStruct {
pub fn get_option() -> Option<Self> {
todo!()
}
}

fn return_option() -> Option<i32> {
todo!()
}

fn main() {
println!("Testing non erroneous option_take_on_temporary");
let mut option = Some(1);
Expand All @@ -7,7 +19,40 @@ fn main() {
let x = Some(3);
x.as_ref();

println!("Testing erroneous option_take_on_temporary");
let x = Some(3);
x.as_ref().take();
//~^ ERROR: called `Option::take()` on a temporary value

println!("Testing non erroneous option_take_on_temporary");
let mut x = Some(3);
let y = x.as_mut();

let mut x = Some(3);
let y = x.as_mut().take();
//~^ ERROR: called `Option::take()` on a temporary value
let y = x.replace(289).take();
//~^ ERROR: called `Option::take()` on a temporary value

let y = Some(3).as_mut().take();
//~^ ERROR: called `Option::take()` on a temporary value

let y = Option::as_mut(&mut x).take();
//~^ ERROR: called `Option::take()` on a temporary value

let x = return_option();
let x = return_option().take();
//~^ ERROR: called `Option::take()` on a temporary value

let x = MyStruct::get_option();
let x = MyStruct::get_option().take();
//~^ ERROR: called `Option::take()` on a temporary value

let mut my_vec = vec![1, 2, 3];
my_vec.push(4);
let y = my_vec.first();
let y = my_vec.first().take();
//~^ ERROR: called `Option::take()` on a temporary value

let y = my_vec.first().take();
//~^ ERROR: called `Option::take()` on a temporary value
}
71 changes: 68 additions & 3 deletions tests/ui/needless_option_take.stderr
Original file line number Diff line number Diff line change
@@ -1,11 +1,76 @@
error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:12:5
--> tests/ui/needless_option_take.rs:23:5
|
LL | x.as_ref().take();
| ^^^^^^^^^^^^^^^^^ help: try: `x.as_ref()`
| ^^^^^^^^^^^^^^^^^
|
= note: `as_ref` creates a temporary value, so calling take() has no effect
= note: `-D clippy::needless-option-take` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::needless_option_take)]`

error: aborting due to 1 previous error
error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:31:13
|
LL | let y = x.as_mut().take();
| ^^^^^^^^^^^^^^^^^
|
= note: `as_mut` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:33:13
|
LL | let y = x.replace(289).take();
| ^^^^^^^^^^^^^^^^^^^^^
|
= note: `replace` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:36:13
|
LL | let y = Some(3).as_mut().take();
| ^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `as_mut` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:39:13
|
LL | let y = Option::as_mut(&mut x).take();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `as_mut` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:43:13
|
LL | let x = return_option().take();
| ^^^^^^^^^^^^^^^^^^^^^^
|
= note: `return_option` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:47:13
|
LL | let x = MyStruct::get_option().take();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `get_option` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:53:13
|
LL | let y = my_vec.first().take();
| ^^^^^^^^^^^^^^^^^^^^^
|
= note: `first` creates a temporary value, so calling take() has no effect

error: called `Option::take()` on a temporary value
--> tests/ui/needless_option_take.rs:56:13
|
LL | let y = my_vec.first().take();
| ^^^^^^^^^^^^^^^^^^^^^
|
= note: `first` creates a temporary value, so calling take() has no effect

error: aborting due to 9 previous errors

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