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Auto merge of #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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| use clippy_utils::{ | ||
| diagnostics::span_lint_and_then, | ||
| higher, | ||
| source::{snippet, snippet_with_applicability}, | ||
| }; | ||
|
|
||
| use rustc_ast::ast; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::{Expr, ExprKind}; | ||
|
|
||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
|
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||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// The lint checks for parenthesis on literals in range statements that are | ||
| /// superfluous. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// Having superfluous parenthesis makes the code less readable | ||
| /// overhead when reading. | ||
| /// | ||
| /// ### Example | ||
| /// | ||
| /// ```rust | ||
| /// for i in (0)..10 { | ||
| /// println!("{i}"); | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// Use instead: | ||
| /// | ||
| /// ```rust | ||
| /// for i in 0..10 { | ||
| /// println!("{i}"); | ||
| /// } | ||
| /// ``` | ||
| #[clippy::version = "1.63.0"] | ||
| pub NEEDLESS_PARENS_ON_RANGE_LITERALS, | ||
| style, | ||
| "needless parenthesis on range literals can be removed" | ||
| } | ||
|
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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 { | ||
| snippet.starts_with('(') && snippet.ends_with(')') | ||
| } | ||
|
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||
| fn check_for_parens(cx: &LateContext<'_>, e: &Expr<'_>, is_start: bool) { | ||
| if is_start && | ||
| let ExprKind::Lit(ref literal) = e.kind && | ||
| let ast::LitKind::Float(_sym, ast::LitFloatType::Unsuffixed) = literal.node | ||
| { | ||
| // don't check floating point literals on the start expression of a range | ||
| return; | ||
| } | ||
| if_chain! { | ||
| if let ExprKind::Lit(ref literal) = e.kind; | ||
| // the indicator that parenthesis surround the literal is that the span of the expression and the literal differ | ||
| if (literal.span.data().hi - literal.span.data().lo) != (e.span.data().hi - e.span.data().lo); | ||
| // inspect the source code of the expression for parenthesis | ||
| if snippet_enclosed_in_parenthesis(&snippet(cx, e.span, "")); | ||
| then { | ||
| let mut applicability = Applicability::MachineApplicable; | ||
| span_lint_and_then(cx, NEEDLESS_PARENS_ON_RANGE_LITERALS, e.span, | ||
| "needless parenthesis on range literals can be removed", | ||
| |diag| { | ||
| let suggestion = snippet_with_applicability(cx, literal.span, "_", &mut applicability); | ||
| diag.span_suggestion(e.span, "try", suggestion, applicability); | ||
| }); | ||
| } | ||
| } | ||
| } | ||
|
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||
| impl<'tcx> LateLintPass<'tcx> for NeedlessParensOnRangeLiterals { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { | ||
| if let Some(higher::Range { start, end, .. }) = higher::Range::hir(expr) { | ||
| if let Some(start) = start { | ||
| check_for_parens(cx, start, true); | ||
| } | ||
| if let Some(end) = end { | ||
| check_for_parens(cx, end, false); | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,14 @@ | ||
| // run-rustfix | ||
| // edition:2018 | ||
|
|
||
| #![warn(clippy::needless_parens_on_range_literals)] | ||
| #![allow(clippy::almost_complete_letter_range)] | ||
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| fn main() { | ||
| let _ = 'a'..='z'; | ||
| let _ = 'a'..'z'; | ||
| let _ = (1.)..2.; | ||
| let _ = (1.)..2.; | ||
| let _ = 'a'..; | ||
| let _ = ..'z'; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,14 @@ | ||
| // run-rustfix | ||
| // edition:2018 | ||
|
|
||
| #![warn(clippy::needless_parens_on_range_literals)] | ||
| #![allow(clippy::almost_complete_letter_range)] | ||
|
|
||
| fn main() { | ||
| let _ = ('a')..=('z'); | ||
| let _ = 'a'..('z'); | ||
| let _ = (1.)..2.; | ||
| let _ = (1.)..(2.); | ||
| let _ = ('a')..; | ||
| let _ = ..('z'); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| 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` | ||
|
|
||
| error: needless parenthesis on range literals can be removed | ||
| --> $DIR/needless_parens_on_range_literals.rs:8:21 | ||
| | | ||
| LL | let _ = ('a')..=('z'); | ||
| | ^^^^^ help: try: `'z'` | ||
|
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||
| error: needless parenthesis on range literals can be removed | ||
| --> $DIR/needless_parens_on_range_literals.rs:9:18 | ||
| | | ||
| LL | let _ = 'a'..('z'); | ||
| | ^^^^^ help: try: `'z'` | ||
|
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||
| error: needless parenthesis on range literals can be removed | ||
| --> $DIR/needless_parens_on_range_literals.rs:11:19 | ||
| | | ||
| LL | let _ = (1.)..(2.); | ||
| | ^^^^ help: try: `2.` | ||
|
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||
| error: needless parenthesis on range literals can be removed | ||
| --> $DIR/needless_parens_on_range_literals.rs:12:13 | ||
| | | ||
| LL | let _ = ('a')..; | ||
| | ^^^^^ help: try: `'a'` | ||
|
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||
| error: needless parenthesis on range literals can be removed | ||
| --> $DIR/needless_parens_on_range_literals.rs:13:15 | ||
| | | ||
| LL | let _ = ..('z'); | ||
| | ^^^^^ help: try: `'z'` | ||
|
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||
| error: aborting due to 6 previous errors | ||
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|