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use crate::{Metadata, Report, Rule, Suggestion};
use if_chain::if_chain;
use macros::lint;
use rnix::{
types::{EntryHolder, LetIn, TypedNode},
NodeOrToken, SyntaxElement, SyntaxKind,
};
/// ## What it does
/// Checks for `let-in` expressions which create no new bindings.
///
/// ## Why is this bad?
/// `let-in` expressions that create no new bindings are useless.
/// These are probably remnants from debugging or editing expressions.
///
/// ## Example
///
/// ```
/// let in pkgs.statix
/// ```
///
/// Preserve only the body of the `let-in` expression:
///
/// ```
/// pkgs.statix
/// ```
#[lint(
name = "empty let-in",
note = "Useless let-in expression",
code = 2,
match_with = SyntaxKind::NODE_LET_IN
)]
struct EmptyLetIn;
impl Rule for EmptyLetIn {
fn validate(&self, node: &SyntaxElement) -> Option<Report> {
if_chain! {
if let NodeOrToken::Node(node) = node;
if let Some(let_in_expr) = LetIn::cast(node.clone());
let entries = let_in_expr.entries();
let inherits = let_in_expr.inherits();
if entries.count() == 0;
if inherits.count() == 0;
if let Some(body) = let_in_expr.body();
then {
let at = node.text_range();
let replacement = body;
let message = "This let-in expression has no entries";
Some(self.report().suggest(at, message, Suggestion::new(at, replacement)))
} else {
None
}
}
}
}
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