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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{snippet_opt, trim_span};
use rustc_ast::ast::{Expr, ExprKind};
use rustc_errors::Applicability;
use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// ### What it does
/// Checks for empty `else` branches.
///
/// ### Why is this bad?
/// An empty else branch does nothing and can be removed.
///
/// ### Example
/// ```rust
///# fn check() -> bool { true }
/// if check() {
/// println!("Check successful!");
/// } else {
/// }
/// ```
/// Use instead:
/// ```rust
///# fn check() -> bool { true }
/// if check() {
/// println!("Check successful!");
/// }
/// ```
#[clippy::version = "1.71.0"]
pub NEEDLESS_ELSE,
style,
"empty else branch"
}
declare_lint_pass!(NeedlessElse => [NEEDLESS_ELSE]);
impl EarlyLintPass for NeedlessElse {
fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
if let ExprKind::If(_, then_block, Some(else_clause)) = &expr.kind
&& let ExprKind::Block(block, _) = &else_clause.kind
&& !expr.span.from_expansion()
&& !else_clause.span.from_expansion()
&& block.stmts.is_empty()
&& let Some(trimmed) = expr.span.trim_start(then_block.span)
&& let span = trim_span(cx.sess().source_map(), trimmed)
&& let Some(else_snippet) = snippet_opt(cx, span)
// Ignore else blocks that contain comments or #[cfg]s
&& !else_snippet.contains(['/', '#'])
{
span_lint_and_sugg(
cx,
NEEDLESS_ELSE,
span,
"this `else` branch is empty",
"you can remove it",
String::new(),
Applicability::MachineApplicable,
);
}
}
}
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