oppi.li
Lints and suggestions for the Nix programming language
mightyiam.tngl.sh
1use crate::{Metadata, Report, Rule, Suggestion, make};
2
3use macros::lint;
4use rnix::{
5 NodeOrToken, SyntaxElement, SyntaxKind,
6 ast::{BinOpKind, Expr, UnaryOp, UnaryOpKind},
7};
8use rowan::ast::AstNode as _;
9
10/// ## What it does
11/// Checks for boolean expressions that can be simplified.
12///
13/// ## Why is this bad?
14/// Complex booleans affect readibility.
15///
16/// ## Example
17/// ```nix
18/// if !(x == y) then 0 else 1
19/// ```
20///
21/// Use `!=` instead:
22///
23/// ```nix
24/// if x != y then 0 else 1
25/// ```
26#[lint(
27 name = "bool_simplification",
28 note = "This boolean expression can be simplified",
29 code = 18,
30 match_with = SyntaxKind::NODE_UNARY_OP
31)]
32struct BoolSimplification;
33
34impl Rule for BoolSimplification {
35 fn validate(&self, node: &SyntaxElement) -> Option<Report> {
36 let NodeOrToken::Node(node) = node else {
37 return None;
38 };
39
40 let unary_expr = UnaryOp::cast(node.clone())?;
41
42 if unary_expr.operator() != Some(UnaryOpKind::Invert) {
43 return None;
44 }
45
46 let value_expr = unary_expr.expr()?;
47
48 let Expr::Paren(paren_expr) = value_expr else {
49 return None;
50 };
51
52 let inner_expr = paren_expr.expr()?;
53
54 let Expr::BinOp(bin_expr) = inner_expr else {
55 return None;
56 };
57
58 let Some(BinOpKind::Equal) = bin_expr.operator() else {
59 return None;
60 };
61
62 let at = node.text_range();
63 let message = "Try `!=` instead of `!(... == ...)`";
64
65 let lhs = bin_expr.lhs()?;
66 let rhs = bin_expr.rhs()?;
67 let replacement = make::binary(lhs.syntax(), "!=", rhs.syntax())
68 .syntax()
69 .clone();
70 Some(
71 self.report()
72 .suggest(at, message, Suggestion::with_replacement(at, replacement)),
73 )
74 }
75}