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Auto merge of rust-lang#8933 - DennisOSRM:needless_braces_range_literal, r=dswij
Add new lint [`needless_parens_on_range_literals`] changelog: Adds a new lint [`needless_parens_on_range_literals`] to warn on needless braces on literals in a range statement For example, the lint would catch ```log error: needless parenthesis on range literals can be removed --> $DIR/needless_parens_on_range_literals.rs:8:13 | LL | let _ = ('a')..=('z'); | ^^^^^ help: try: `'a'` | = note: `-D clippy::needless-parens-on-range-literals` implied by `-D warnings` ```
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‎CHANGELOG.md‎

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@@ -3605,6 +3605,7 @@ Released 2018-09-13
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[`needless_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_match
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[`needless_option_as_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_option_as_deref
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[`needless_option_take`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_option_take
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[`needless_parens_on_range_literals`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_parens_on_range_literals
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[`needless_pass_by_value`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_value
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[`needless_question_mark`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_question_mark
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[`needless_range_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_range_loop

‎clippy_lints/src/lib.register_all.rs‎

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@@ -242,6 +242,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
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LintId::of(needless_bool::NEEDLESS_BOOL),
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LintId::of(needless_borrowed_ref::NEEDLESS_BORROWED_REFERENCE),
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LintId::of(needless_late_init::NEEDLESS_LATE_INIT),
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LintId::of(needless_parens_on_range_literals::NEEDLESS_PARENS_ON_RANGE_LITERALS),
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LintId::of(needless_question_mark::NEEDLESS_QUESTION_MARK),
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LintId::of(needless_update::NEEDLESS_UPDATE),
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LintId::of(neg_cmp_op_on_partial_ord::NEG_CMP_OP_ON_PARTIAL_ORD),

‎clippy_lints/src/lib.register_lints.rs‎

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@@ -408,6 +408,7 @@ store.register_lints(&[
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needless_continue::NEEDLESS_CONTINUE,
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needless_for_each::NEEDLESS_FOR_EACH,
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needless_late_init::NEEDLESS_LATE_INIT,
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needless_parens_on_range_literals::NEEDLESS_PARENS_ON_RANGE_LITERALS,
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needless_pass_by_value::NEEDLESS_PASS_BY_VALUE,
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needless_question_mark::NEEDLESS_QUESTION_MARK,
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needless_update::NEEDLESS_UPDATE,

‎clippy_lints/src/lib.register_style.rs‎

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@@ -91,6 +91,7 @@ store.register_group(true, "clippy::style", Some("clippy_style"), vec![
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LintId::of(mut_mutex_lock::MUT_MUTEX_LOCK),
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LintId::of(mut_reference::UNNECESSARY_MUT_PASSED),
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LintId::of(needless_late_init::NEEDLESS_LATE_INIT),
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LintId::of(needless_parens_on_range_literals::NEEDLESS_PARENS_ON_RANGE_LITERALS),
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LintId::of(neg_multiply::NEG_MULTIPLY),
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LintId::of(new_without_default::NEW_WITHOUT_DEFAULT),
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LintId::of(non_copy_const::BORROW_INTERIOR_MUTABLE_CONST),

‎clippy_lints/src/lib.rs‎

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@@ -315,6 +315,7 @@ mod needless_borrowed_ref;
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mod needless_continue;
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mod needless_for_each;
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mod needless_late_init;
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mod needless_parens_on_range_literals;
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mod needless_pass_by_value;
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mod needless_question_mark;
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mod needless_update;
@@ -746,6 +747,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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store.register_early_pass(|| Box::new(collapsible_if::CollapsibleIf));
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store.register_early_pass(|| Box::new(items_after_statements::ItemsAfterStatements));
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store.register_early_pass(|| Box::new(precedence::Precedence));
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store.register_late_pass(|| Box::new(needless_parens_on_range_literals::NeedlessParensOnRangeLiterals));
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store.register_early_pass(|| Box::new(needless_continue::NeedlessContinue));
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store.register_early_pass(|| Box::new(redundant_else::RedundantElse));
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store.register_late_pass(|| Box::new(create_dir::CreateDir));

‎clippy_lints/src/needless_parens_on_range_literals.rs‎

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use clippy_utils::{
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diagnostics::span_lint_and_then,
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higher,
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source::{snippet, snippet_with_applicability},
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};
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use rustc_ast::ast;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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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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declare_clippy_lint! {
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/// ### What it does
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/// The lint checks for parenthesis on literals in range statements that are
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/// superfluous.
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///
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/// ### Why is this bad?
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/// Having superfluous parenthesis makes the code less readable
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/// overhead when reading.
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///
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/// ### Example
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///
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/// ```rust
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/// for i in (0)..10 {
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/// println!("{i}");
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/// }
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/// ```
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///
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/// Use instead:
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///
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/// ```rust
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/// for i in 0..10 {
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/// println!("{i}");
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/// }
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/// ```
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#[clippy::version = "1.63.0"]
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pub NEEDLESS_PARENS_ON_RANGE_LITERALS,
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style,
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"needless parenthesis on range literals can be removed"
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}
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declare_lint_pass!(NeedlessParensOnRangeLiterals => [NEEDLESS_PARENS_ON_RANGE_LITERALS]);
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fn snippet_enclosed_in_parenthesis(snippet: &str) -> bool {
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snippet.starts_with('(') && snippet.ends_with(')')
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}
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fn check_for_parens(cx: &LateContext<'_>, e: &Expr<'_>, is_start: bool) {
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if is_start &&
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let ExprKind::Lit(ref literal) = e.kind &&
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let ast::LitKind::Float(_sym, ast::LitFloatType::Unsuffixed) = literal.node
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{
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// don't check floating point literals on the start expression of a range
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return;
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}
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if_chain! {
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if let ExprKind::Lit(ref literal) = e.kind;
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// the indicator that parenthesis surround the literal is that the span of the expression and the literal differ
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if (literal.span.data().hi - literal.span.data().lo) != (e.span.data().hi - e.span.data().lo);
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// inspect the source code of the expression for parenthesis
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if snippet_enclosed_in_parenthesis(&snippet(cx, e.span, ""));
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then {
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_then(cx, NEEDLESS_PARENS_ON_RANGE_LITERALS, e.span,
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"needless parenthesis on range literals can be removed",
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|diag| {
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let suggestion = snippet_with_applicability(cx, literal.span, "_", &mut applicability);
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diag.span_suggestion(e.span, "try", suggestion, applicability);
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});
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}
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}
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}
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impl<'tcx> LateLintPass<'tcx> for NeedlessParensOnRangeLiterals {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let Some(higher::Range { start, end, .. }) = higher::Range::hir(expr) {
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if let Some(start) = start {
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check_for_parens(cx, start, true);
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}
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if let Some(end) = end {
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check_for_parens(cx, end, false);
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}
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}
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}
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}

‎tests/ui/almost_complete_letter_range.fixed‎

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#![feature(stmt_expr_attributes)]
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#![warn(clippy::almost_complete_letter_range)]
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#![allow(ellipsis_inclusive_range_patterns)]
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#![allow(clippy::needless_parens_on_range_literals)]
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macro_rules! a {
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() => {

‎tests/ui/almost_complete_letter_range.rs‎

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#![feature(stmt_expr_attributes)]
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#![warn(clippy::almost_complete_letter_range)]
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#![allow(ellipsis_inclusive_range_patterns)]
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#![allow(clippy::needless_parens_on_range_literals)]
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macro_rules! a {
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() => {

‎tests/ui/almost_complete_letter_range.stderr‎

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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:19:17
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--> $DIR/almost_complete_letter_range.rs:20:17
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|
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LL | let _ = ('a') ..'z';
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| ^^^^^^--^^^
@@ -9,87 +9,87 @@ LL | let _ = ('a') ..'z';
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= note: `-D clippy::almost-complete-letter-range` implied by `-D warnings`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:20:17
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--> $DIR/almost_complete_letter_range.rs:21:17
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|
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LL | let _ = 'A' .. ('Z');
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| ^^^^--^^^^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:26:13
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--> $DIR/almost_complete_letter_range.rs:27:13
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|
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LL | let _ = (b'a')..(b'z');
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| ^^^^^^--^^^^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:27:13
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--> $DIR/almost_complete_letter_range.rs:28:13
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|
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LL | let _ = b'A'..b'Z';
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| ^^^^--^^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:32:13
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--> $DIR/almost_complete_letter_range.rs:33:13
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|
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LL | let _ = a!()..'z';
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| ^^^^--^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:35:9
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--> $DIR/almost_complete_letter_range.rs:36:9
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|
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LL | b'a'..b'z' if true => 1,
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| ^^^^--^^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:36:9
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--> $DIR/almost_complete_letter_range.rs:37:9
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|
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LL | b'A'..b'Z' if true => 2,
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| ^^^^--^^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:43:9
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--> $DIR/almost_complete_letter_range.rs:44:9
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|
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LL | 'a'..'z' if true => 1,
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| ^^^--^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:44:9
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--> $DIR/almost_complete_letter_range.rs:45:9
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|
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LL | 'A'..'Z' if true => 2,
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| ^^^--^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:54:9
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--> $DIR/almost_complete_letter_range.rs:55:9
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|
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LL | 'a'..'z' => 1,
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| ^^^--^^^
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| |
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| help: use an inclusive range: `...`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:61:13
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--> $DIR/almost_complete_letter_range.rs:62:13
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|
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LL | let _ = 'a'..'z';
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| ^^^--^^^
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| |
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| help: use an inclusive range: `..=`
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error: almost complete ascii letter range
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--> $DIR/almost_complete_letter_range.rs:63:9
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--> $DIR/almost_complete_letter_range.rs:64:9
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|
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LL | 'a'..'z' => 1,
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| ^^^--^^^

‎tests/ui/needless_parens_on_range_literals.fixed‎

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// run-rustfix
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// edition:2018
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#![warn(clippy::needless_parens_on_range_literals)]
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#![allow(clippy::almost_complete_letter_range)]
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fn main() {
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let _ = 'a'..='z';
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let _ = 'a'..'z';
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let _ = (1.)..2.;
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let _ = (1.)..2.;
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let _ = 'a'..;
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let _ = ..'z';
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}

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