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Auto merge of #8616 - pitaj:single_element_loop_arrays, r=llogiq
single_element_loop: handle arrays for Edition2021 changelog: [`single_element_loop`] handle arrays in Edition 2021, handle `.iter_mut()` and `.into_iter()`, and wrap in parens if necessary
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commit
f6b29923c6
4 changed files with 172 additions and 16 deletions
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@ -2,9 +2,12 @@ use super::SINGLE_ELEMENT_LOOP;
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::{indent_of, snippet_with_applicability};
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use if_chain::if_chain;
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use rustc_ast::util::parser::PREC_PREFIX;
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use rustc_ast::Mutability;
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use rustc_errors::Applicability;
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use rustc_hir::{BorrowKind, Expr, ExprKind, Pat};
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use rustc_hir::{is_range_literal, BorrowKind, Expr, ExprKind, Pat};
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use rustc_lint::LateContext;
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use rustc_span::edition::Edition;
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pub(super) fn check<'tcx>(
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cx: &LateContext<'tcx>,
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@ -13,31 +16,84 @@ pub(super) fn check<'tcx>(
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body: &'tcx Expr<'_>,
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expr: &'tcx Expr<'_>,
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) {
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let arg_expr = match arg.kind {
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ExprKind::AddrOf(BorrowKind::Ref, _, ref_arg) => ref_arg,
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ExprKind::MethodCall(method, [arg], _) if method.ident.name == rustc_span::sym::iter => arg,
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let (arg_expression, prefix) = match arg.kind {
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ExprKind::AddrOf(
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BorrowKind::Ref,
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Mutability::Not,
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Expr {
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kind: ExprKind::Array([arg]),
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..
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},
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) => (arg, "&"),
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ExprKind::AddrOf(
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BorrowKind::Ref,
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Mutability::Mut,
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Expr {
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kind: ExprKind::Array([arg]),
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..
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},
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) => (arg, "&mut "),
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ExprKind::MethodCall(
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method,
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[
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Expr {
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kind: ExprKind::Array([arg]),
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..
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},
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],
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_,
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) if method.ident.name == rustc_span::sym::iter => (arg, "&"),
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ExprKind::MethodCall(
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method,
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[
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Expr {
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kind: ExprKind::Array([arg]),
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..
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},
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],
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_,
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) if method.ident.name.as_str() == "iter_mut" => (arg, "&mut "),
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ExprKind::MethodCall(
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method,
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[
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Expr {
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kind: ExprKind::Array([arg]),
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..
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},
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],
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_,
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) if method.ident.name == rustc_span::sym::into_iter => (arg, ""),
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// Only check for arrays edition 2021 or later, as this case will trigger a compiler error otherwise.
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ExprKind::Array([arg]) if cx.tcx.sess.edition() >= Edition::Edition2021 => (arg, ""),
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_ => return,
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};
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if_chain! {
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if let ExprKind::Array([arg_expression]) = arg_expr.kind;
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if let ExprKind::Block(block, _) = body.kind;
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if !block.stmts.is_empty();
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then {
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let mut applicability = Applicability::MachineApplicable;
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let pat_snip = snippet_with_applicability(cx, pat.span, "..", &mut applicability);
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let arg_snip = snippet_with_applicability(cx, arg_expression.span, "..", &mut applicability);
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let mut arg_snip = snippet_with_applicability(cx, arg_expression.span, "..", &mut applicability);
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let mut block_str = snippet_with_applicability(cx, block.span, "..", &mut applicability).into_owned();
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block_str.remove(0);
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block_str.pop();
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let indent = " ".repeat(indent_of(cx, block.stmts[0].span).unwrap_or(0));
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// Reference iterator from `&(mut) []` or `[].iter(_mut)()`.
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if !prefix.is_empty() && (
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// Precedence of internal expression is less than or equal to precedence of `&expr`.
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arg_expression.precedence().order() <= PREC_PREFIX || is_range_literal(arg_expression)
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) {
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arg_snip = format!("({arg_snip})").into();
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}
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span_lint_and_sugg(
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cx,
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SINGLE_ELEMENT_LOOP,
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expr.span,
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"for loop over a single element",
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"try",
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format!("{{\n{}let {} = &{};{}}}", indent, pat_snip, arg_snip, block_str),
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format!("{{\n{indent}let {pat_snip} = {prefix}{arg_snip};{block_str}}}"),
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applicability,
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)
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}
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@ -6,11 +6,31 @@ fn main() {
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let item1 = 2;
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{
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let item = &item1;
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println!("{}", item);
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dbg!(item);
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}
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{
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let item = &item1;
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println!("{:?}", item);
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dbg!(item);
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}
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{
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let item = &(0..5);
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dbg!(item);
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}
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{
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let item = &mut (0..5);
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dbg!(item);
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}
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{
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let item = 0..5;
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dbg!(item);
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}
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{
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let item = 0..5;
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dbg!(item);
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}
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}
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@ -5,10 +5,26 @@
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fn main() {
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let item1 = 2;
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for item in &[item1] {
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println!("{}", item);
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dbg!(item);
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}
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for item in [item1].iter() {
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println!("{:?}", item);
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dbg!(item);
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}
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for item in &[0..5] {
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dbg!(item);
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}
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for item in [0..5].iter_mut() {
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dbg!(item);
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}
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for item in [0..5] {
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dbg!(item);
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}
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for item in [0..5].into_iter() {
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dbg!(item);
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}
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}
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@ -2,7 +2,7 @@ error: for loop over a single element
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--> $DIR/single_element_loop.rs:7:5
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LL | / for item in &[item1] {
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LL | | println!("{}", item);
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LL | | dbg!(item);
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LL | | }
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| |_____^
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@ -11,7 +11,7 @@ help: try
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LL ~ {
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LL + let item = &item1;
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LL + println!("{}", item);
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LL + dbg!(item);
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LL + }
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@ -19,7 +19,7 @@ error: for loop over a single element
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--> $DIR/single_element_loop.rs:11:5
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LL | / for item in [item1].iter() {
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LL | | println!("{:?}", item);
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LL | | dbg!(item);
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LL | | }
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| |_____^
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@ -27,9 +27,73 @@ help: try
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LL ~ {
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LL + let item = &item1;
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LL + println!("{:?}", item);
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LL + dbg!(item);
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LL + }
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error: aborting due to 2 previous errors
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error: for loop over a single element
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--> $DIR/single_element_loop.rs:15:5
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LL | / for item in &[0..5] {
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LL | | dbg!(item);
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LL | | }
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| |_____^
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help: try
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LL ~ {
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LL + let item = &(0..5);
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LL + dbg!(item);
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LL + }
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error: for loop over a single element
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--> $DIR/single_element_loop.rs:19:5
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LL | / for item in [0..5].iter_mut() {
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LL | | dbg!(item);
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LL | | }
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| |_____^
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help: try
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LL ~ {
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LL + let item = &mut (0..5);
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LL + dbg!(item);
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LL + }
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error: for loop over a single element
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--> $DIR/single_element_loop.rs:23:5
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LL | / for item in [0..5] {
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LL | | dbg!(item);
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LL | | }
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| |_____^
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help: try
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LL ~ {
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LL + let item = 0..5;
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LL + dbg!(item);
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LL + }
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error: for loop over a single element
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--> $DIR/single_element_loop.rs:27:5
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LL | / for item in [0..5].into_iter() {
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LL | | dbg!(item);
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LL | | }
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| |_____^
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help: try
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LL ~ {
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LL + let item = 0..5;
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LL + dbg!(item);
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LL + }
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error: aborting due to 6 previous errors
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