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single_element_loop: handle arrays for Edition2021

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also handle `.iter_mut()`, `.into_iter()`,
and wrapping in parens if necessary
This commit is contained in:
Peter Jaszkowiak 2022-04-01 00:04:19 -06:00
parent 8ebe766695
commit 3bbb3e3329
4 changed files with 172 additions and 16 deletions
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70
clippy_lints/src/loops/single_element_loop.rs
View File

@ -2,9 +2,12 @@ use super::SINGLE_ELEMENT_LOOP;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, snippet_with_applicability};
use if_chain::if_chain;
use rustc_ast::util::parser::PREC_PREFIX;
use rustc_ast::Mutability;
use rustc_errors::Applicability;
use rustc_hir::{BorrowKind, Expr, ExprKind, Pat};
use rustc_hir::{is_range_literal, BorrowKind, Expr, ExprKind, Pat};
use rustc_lint::LateContext;
use rustc_span::edition::Edition;
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
@ -13,31 +16,84 @@ pub(super) fn check<'tcx>(
body: &'tcx Expr<'_>,
expr: &'tcx Expr<'_>,
) {
let arg_expr = match arg.kind {
ExprKind::AddrOf(BorrowKind::Ref, _, ref_arg) => ref_arg,
ExprKind::MethodCall(method, [arg], _) if method.ident.name == rustc_span::sym::iter => arg,
let (arg_expression, prefix) = match arg.kind {
ExprKind::AddrOf(
BorrowKind::Ref,
Mutability::Not,
Expr {
kind: ExprKind::Array([arg]),
..
},
) => (arg, "&"),
ExprKind::AddrOf(
BorrowKind::Ref,
Mutability::Mut,
Expr {
kind: ExprKind::Array([arg]),
..
},
) => (arg, "&mut "),
ExprKind::MethodCall(
method,
[
Expr {
kind: ExprKind::Array([arg]),
..
},
],
_,
) if method.ident.name == rustc_span::sym::iter => (arg, "&"),
ExprKind::MethodCall(
method,
[
Expr {
kind: ExprKind::Array([arg]),
..
},
],
_,
) if method.ident.name.as_str() == "iter_mut" => (arg, "&mut "),
ExprKind::MethodCall(
method,
[
Expr {
kind: ExprKind::Array([arg]),
..
},
],
_,
) if method.ident.name == rustc_span::sym::into_iter => (arg, ""),
// Only check for arrays edition 2021 or later, as this case will trigger a compiler error otherwise.
ExprKind::Array([arg]) if cx.tcx.sess.edition() >= Edition::Edition2021 => (arg, ""),
_ => return,
};
if_chain! {
if let ExprKind::Array([arg_expression]) = arg_expr.kind;
if let ExprKind::Block(block, _) = body.kind;
if !block.stmts.is_empty();
then {
let mut applicability = Applicability::MachineApplicable;
let pat_snip = snippet_with_applicability(cx, pat.span, "..", &mut applicability);
let arg_snip = snippet_with_applicability(cx, arg_expression.span, "..", &mut applicability);
let mut arg_snip = snippet_with_applicability(cx, arg_expression.span, "..", &mut applicability);
let mut block_str = snippet_with_applicability(cx, block.span, "..", &mut applicability).into_owned();
block_str.remove(0);
block_str.pop();
let indent = " ".repeat(indent_of(cx, block.stmts[0].span).unwrap_or(0));
// Reference iterator from `&(mut) []` or `[].iter(_mut)()`.
if !prefix.is_empty() && (
// Precedence of internal expression is less than or equal to precedence of `&expr`.
arg_expression.precedence().order() <= PREC_PREFIX || is_range_literal(arg_expression)
) {
arg_snip = format!("({arg_snip})").into();
}
span_lint_and_sugg(
cx,
SINGLE_ELEMENT_LOOP,
expr.span,
"for loop over a single element",
"try",
format!("{{\n{}let {} = &{};{}}}", indent, pat_snip, arg_snip, block_str),
format!("{{\n{indent}let {pat_snip} = {prefix}{arg_snip};{block_str}}}"),
applicability,
)
}

24
tests/ui/single_element_loop.fixed
View File

@ -6,11 +6,31 @@ fn main() {
let item1 = 2;
{
let item = &item1;
println!("{}", item);
dbg!(item);
}
{
let item = &item1;
println!("{:?}", item);
dbg!(item);
}
{
let item = &(0..5);
dbg!(item);
}
{
let item = &mut (0..5);
dbg!(item);
}
{
let item = 0..5;
dbg!(item);
}
{
let item = 0..5;
dbg!(item);
}
}

20
tests/ui/single_element_loop.rs
View File

@ -5,10 +5,26 @@
fn main() {
let item1 = 2;
for item in &[item1] {
println!("{}", item);
dbg!(item);
}
for item in [item1].iter() {
println!("{:?}", item);
dbg!(item);
}
for item in &[0..5] {
dbg!(item);
}
for item in [0..5].iter_mut() {
dbg!(item);
}
for item in [0..5] {
dbg!(item);
}
for item in [0..5].into_iter() {
dbg!(item);
}
}

74
tests/ui/single_element_loop.stderr
View File

@ -2,7 +2,7 @@ error: for loop over a single element
--> $DIR/single_element_loop.rs:7:5
|
LL | / for item in &[item1] {
LL | | println!("{}", item);
LL | | dbg!(item);
LL | | }
| |_____^
|
@ -11,7 +11,7 @@ help: try
|
LL ~ {
LL + let item = &item1;
LL + println!("{}", item);
LL + dbg!(item);
LL + }
|
@ -19,7 +19,7 @@ error: for loop over a single element
--> $DIR/single_element_loop.rs:11:5
|
LL | / for item in [item1].iter() {
LL | | println!("{:?}", item);
LL | | dbg!(item);
LL | | }
| |_____^
|
@ -27,9 +27,73 @@ help: try
|
LL ~ {
LL + let item = &item1;
LL + println!("{:?}", item);
LL + dbg!(item);
LL + }
|
error: aborting due to 2 previous errors
error: for loop over a single element
--> $DIR/single_element_loop.rs:15:5
|
LL | / for item in &[0..5] {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = &(0..5);
LL + dbg!(item);
LL + }
|
error: for loop over a single element
--> $DIR/single_element_loop.rs:19:5
|
LL | / for item in [0..5].iter_mut() {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = &mut (0..5);
LL + dbg!(item);
LL + }
|
error: for loop over a single element
--> $DIR/single_element_loop.rs:23:5
|
LL | / for item in [0..5] {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = 0..5;
LL + dbg!(item);
LL + }
|
error: for loop over a single element
--> $DIR/single_element_loop.rs:27:5
|
LL | / for item in [0..5].into_iter() {
LL | | dbg!(item);
LL | | }
| |_____^
|
help: try
|
LL ~ {
LL + let item = 0..5;
LL + dbg!(item);
LL + }
|
error: aborting due to 6 previous errors