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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};
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"
}
declare_lint_pass!(NeedlessParensOnRangeLiterals => [NEEDLESS_PARENS_ON_RANGE_LITERALS]);
fn snippet_enclosed_in_parenthesis(snippet: &str) -> bool {
snippet.starts_with('(') && snippet.ends_with(')')
}
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);
});
}
}
}
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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