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use crate::{make, session::SessionInfo, Metadata, Report, Rule, Suggestion};
use if_chain::if_chain;
use macros::lint;
use rnix::{
types::{BinOp, BinOpKind, Paren, TypedNode, UnaryOp, UnaryOpKind, Wrapper},
NodeOrToken, SyntaxElement, SyntaxKind,
};
/// ## What it does
/// Checks for boolean expressions that can be simplified.
///
/// ## Why is this bad?
/// Complex booleans affect readibility.
///
/// ## Example
/// ```nix
/// if !(x == y) then 0 else 1
/// ```
///
/// Use `!=` instead:
///
/// ```nix
/// if x != y then 0 else 1
/// ```
#[lint(
name = "bool_simplification",
note = "This boolean expression can be simplified",
code = 18,
match_with = SyntaxKind::NODE_UNARY_OP
)]
struct BoolSimplification;
impl Rule for BoolSimplification {
fn validate(&self, node: &SyntaxElement, _sess: &SessionInfo) -> Option<Report> {
if_chain! {
if let NodeOrToken::Node(node) = node;
if let Some(unary_expr) = UnaryOp::cast(node.clone());
if unary_expr.operator() == UnaryOpKind::Invert;
if let Some(value_expr) = unary_expr.value();
if let Some(paren_expr) = Paren::cast(value_expr.clone());
if let Some(inner_expr) = paren_expr.inner();
if let Some(bin_expr) = BinOp::cast(inner_expr);
if let Some(BinOpKind::Equal) = bin_expr.operator();
then {
let at = node.text_range();
let message = "Try `!=` instead of `!(... == ...)`";
let lhs = bin_expr.lhs()?;
let rhs = bin_expr.rhs()?;
let replacement = make::binary(&lhs, "!=", &rhs).node().clone();
Some(
self.report()
.suggest(at, message, Suggestion::new(at, replacement)),
)
} else {
None
}
}
}
}
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