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Add lint [single_range_in_vec_init]
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‎CHANGELOG.md

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@@ -5164,6 +5164,7 @@ Released 2018-09-13
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[`single_element_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_element_loop
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[`single_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_match
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[`single_match_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_match_else
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[`single_range_in_vec_init`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_range_in_vec_init
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[`size_of_in_element_count`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_in_element_count
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[`size_of_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_ref
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[`skip_while_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#skip_while_next

‎clippy_lints/src/declared_lints.rs

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@@ -569,6 +569,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
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crate::significant_drop_tightening::SIGNIFICANT_DROP_TIGHTENING_INFO,
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crate::single_char_lifetime_names::SINGLE_CHAR_LIFETIME_NAMES_INFO,
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crate::single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS_INFO,
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crate::single_range_in_vec_init::SINGLE_RANGE_IN_VEC_INIT_INFO,
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crate::size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT_INFO,
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crate::size_of_ref::SIZE_OF_REF_INFO,
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crate::slow_vector_initialization::SLOW_VECTOR_INITIALIZATION_INFO,

‎clippy_lints/src/lib.rs

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@@ -288,6 +288,7 @@ mod shadow;
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mod significant_drop_tightening;
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mod single_char_lifetime_names;
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mod single_component_path_imports;
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mod single_range_in_vec_init;
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mod size_of_in_element_count;
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mod size_of_ref;
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mod slow_vector_initialization;
@@ -1045,6 +1046,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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});
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let stack_size_threshold = conf.stack_size_threshold;
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store.register_late_pass(move |_| Box::new(large_stack_frames::LargeStackFrames::new(stack_size_threshold)));
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store.register_late_pass(|_| Box::new(single_range_in_vec_init::SingleRangeInVecInit));
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// add lints here, do not remove this comment, it's used in `new_lint`
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}
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‎clippy_lints/src/single_range_in_vec_init.rs

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@@ -0,0 +1,153 @@
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use clippy_utils::{
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diagnostics::span_lint_and_then,
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get_trait_def_id,
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higher::VecArgs,
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macros::root_macro_call_first_node,
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source::{snippet_opt, snippet_with_applicability},
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ty::implements_trait,
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};
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use rustc_ast::{LitIntType, LitKind, UintTy};
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, LangItem, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use std::fmt::{self, Display, Formatter};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for `Vec` or array initializations that contain only one range.
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///
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/// ### Why is this bad?
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/// This is almost always incorrect, as it will result in a `Vec` that has only element. Almost
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/// always, the programmer intended for it to include all elements in the range or for the end
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/// of the range to be the length instead.
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///
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/// ### Example
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/// ```rust
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/// let x = [0..200];
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/// ```
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/// Use instead:
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/// ```rust
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/// // If it was intended to include every element in the range...
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/// let x = (0..200).collect::<Vec<i32>>();
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/// // ...Or if 200 was meant to be the len
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/// let x = [0; 200];
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/// ```
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#[clippy::version = "1.72.0"]
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pub SINGLE_RANGE_IN_VEC_INIT,
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suspicious,
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"checks for initialization of `Vec` or arrays which consist of a single range"
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}
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declare_lint_pass!(SingleRangeInVecInit => [SINGLE_RANGE_IN_VEC_INIT]);
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enum SuggestedType {
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Vec,
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Array,
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}
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impl SuggestedType {
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fn starts_with(&self) -> &'static str {
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if matches!(self, SuggestedType::Vec) {
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"vec!"
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} else {
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"["
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}
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}
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fn ends_with(&self) -> &'static str {
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if matches!(self, SuggestedType::Vec) { "" } else { "]" }
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}
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}
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impl Display for SuggestedType {
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fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
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if matches!(&self, SuggestedType::Vec) {
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write!(f, "a `Vec`")
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} else {
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write!(f, "an array")
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}
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}
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}
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impl LateLintPass<'_> for SingleRangeInVecInit {
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fn check_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
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// inner_expr: `vec![0..200]` or `[0..200]`
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// ^^^^^^ ^^^^^^^
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// span: `vec![0..200]` or `[0..200]`
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// ^^^^^^^^^^^^ ^^^^^^^^
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// kind: What to print, an array or a `Vec`
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let (inner_expr, span, kind) = if let ExprKind::Array([inner_expr]) = expr.kind
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&& !expr.span.from_expansion()
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{
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(inner_expr, expr.span, SuggestedType::Array)
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} else if let Some(macro_call) = root_macro_call_first_node(cx, expr)
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&& let Some(VecArgs::Vec([expr])) = VecArgs::hir(cx, expr)
85+
{
86+
(expr, macro_call.span, SuggestedType::Vec)
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} else {
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return;
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};
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let ExprKind::Struct(QPath::LangItem(lang_item, ..), [start, end], None) = inner_expr.kind else {
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return;
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};
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if matches!(lang_item, LangItem::Range)
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&& let ty = cx.typeck_results().expr_ty(start.expr)
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&& let Some(snippet) = snippet_opt(cx, span)
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// `is_from_proc_macro` will skip any `vec![]`. Let's not!
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&& snippet.starts_with(kind.starts_with())
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&& snippet.ends_with(kind.ends_with())
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{
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let mut app = Applicability::MaybeIncorrect;
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let start_snippet = snippet_with_applicability(cx, start.span, "...", &mut app);
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let end_snippet = snippet_with_applicability(cx, end.span, "...", &mut app);
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let should_emit_every_value = if let Some(step_def_id) = get_trait_def_id(cx, &["core", "iter", "Step"])
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&& implements_trait(cx, ty, step_def_id, &[])
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{
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true
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} else {
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false
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};
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let should_emit_of_len = if let Some(copy_def_id) = cx.tcx.lang_items().copy_trait()
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&& implements_trait(cx, ty, copy_def_id, &[])
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&& let ExprKind::Lit(lit_kind) = end.expr.kind
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&& let LitKind::Int(.., suffix_type) = lit_kind.node
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&& let LitIntType::Unsigned(UintTy::Usize) | LitIntType::Unsuffixed = suffix_type
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{
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true
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} else {
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false
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};
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if should_emit_every_value || should_emit_of_len {
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span_lint_and_then(
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cx,
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SINGLE_RANGE_IN_VEC_INIT,
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span,
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&format!("{kind} of `Range` that is only one element"),
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|diag| {
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if should_emit_every_value {
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diag.span_suggestion(
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span,
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"if you wanted a `Vec` that contains every value in the range, try",
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format!("({start_snippet}..{end_snippet}).collect::<std::vec::Vec<{ty}>>()"),
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app,
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);
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}
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if should_emit_of_len {
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diag.span_suggestion(
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inner_expr.span,
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format!("if you wanted {kind} of len {end_snippet}, try"),
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format!("{start_snippet}; {end_snippet}"),
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app,
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);
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}
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},
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);
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}
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}
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}
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}

‎tests/ui/single_element_loop.fixed

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@@ -1,6 +1,8 @@
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//@run-rustfix
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// Tests from for_loop.rs that don't have suggestions
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#![allow(clippy::single_range_in_vec_init)]
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#[warn(clippy::single_element_loop)]
57
fn main() {
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let item1 = 2;

‎tests/ui/single_element_loop.rs

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@@ -1,6 +1,8 @@
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//@run-rustfix
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// Tests from for_loop.rs that don't have suggestions
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#![allow(clippy::single_range_in_vec_init)]
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#[warn(clippy::single_element_loop)]
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fn main() {
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let item1 = 2;

‎tests/ui/single_element_loop.stderr

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@@ -1,5 +1,5 @@
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error: for loop over a single element
2-
--> $DIR/single_element_loop.rs:7:5
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--> $DIR/single_element_loop.rs:9:5
33
|
44
LL | / for item in &[item1] {
55
LL | | dbg!(item);
@@ -16,7 +16,7 @@ LL + }
1616
|
1717

1818
error: for loop over a single element
19-
--> $DIR/single_element_loop.rs:11:5
19+
--> $DIR/single_element_loop.rs:13:5
2020
|
2121
LL | / for item in [item1].iter() {
2222
LL | | dbg!(item);
@@ -32,7 +32,7 @@ LL + }
3232
|
3333

3434
error: for loop over a single element
35-
--> $DIR/single_element_loop.rs:15:5
35+
--> $DIR/single_element_loop.rs:17:5
3636
|
3737
LL | / for item in &[0..5] {
3838
LL | | dbg!(item);
@@ -48,7 +48,7 @@ LL + }
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|
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5050
error: for loop over a single element
51-
--> $DIR/single_element_loop.rs:19:5
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--> $DIR/single_element_loop.rs:21:5
5252
|
5353
LL | / for item in [0..5].iter_mut() {
5454
LL | | dbg!(item);
@@ -64,7 +64,7 @@ LL + }
6464
|
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6666
error: for loop over a single element
67-
--> $DIR/single_element_loop.rs:23:5
67+
--> $DIR/single_element_loop.rs:25:5
6868
|
6969
LL | / for item in [0..5] {
7070
LL | | dbg!(item);
@@ -80,7 +80,7 @@ LL + }
8080
|
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8282
error: for loop over a single element
83-
--> $DIR/single_element_loop.rs:27:5
83+
--> $DIR/single_element_loop.rs:29:5
8484
|
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LL | / for item in [0..5].into_iter() {
8686
LL | | dbg!(item);
@@ -96,7 +96,7 @@ LL + }
9696
|
9797

9898
error: for loop over a single element
99-
--> $DIR/single_element_loop.rs:46:5
99+
--> $DIR/single_element_loop.rs:48:5
100100
|
101101
LL | / for _ in [42] {
102102
LL | | let _f = |n: u32| {

‎tests/ui/single_range_in_vec_init.rs

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@@ -0,0 +1,58 @@
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//@aux-build:proc_macros.rs
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#![allow(clippy::no_effect, clippy::useless_vec, unused)]
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#![warn(clippy::single_range_in_vec_init)]
4+
#![feature(generic_arg_infer)]
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#[macro_use]
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extern crate proc_macros;
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macro_rules! a {
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() => {
11+
vec![0..200];
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};
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}
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fn awa<T: PartialOrd>(start: T, end: T) {
16+
[start..end];
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}
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fn awa_vec<T: PartialOrd>(start: T, end: T) {
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vec![start..end];
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}
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fn main() {
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// Lint
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[0..200];
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vec![0..200];
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[0u8..200];
28+
[0usize..200];
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[0..200usize];
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vec![0u8..200];
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vec![0usize..200];
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vec![0..200usize];
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// Only suggest collect
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[0..200isize];
35+
vec![0..200isize];
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// Do not lint
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[0..200, 0..100];
38+
vec![0..200, 0..100];
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[0.0..200.0];
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vec![0.0..200.0];
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// `Copy` is not implemented for `Range`, so this doesn't matter
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// [0..200; 2];
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// [vec!0..200; 2];
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45+
// Unfortunately skips any macros
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a!();
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48+
// Skip external macros and procedural macros
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external! {
50+
[0..200];
51+
vec![0..200];
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}
53+
with_span! {
54+
span
55+
[0..200];
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vec![0..200];
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}
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}

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