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use crate::rule_prelude::*;
declare_lint! {
#[derive(Default)]
NoCompareNegZero,
errors,
"no-compare-neg-zero"
}
#[typetag::serde]
impl CstRule for NoCompareNegZero {
fn check_node(&self, node: &SyntaxNode, ctx: &mut RuleCtx) -> Option<()> {
if node.try_to::<ast::BinExpr>()?.comparison() {
let bin = node.to::<ast::BinExpr>();
let op = bin.op_token().unwrap();
if let Some(expr) = bin
.lhs()
.filter(|e| unsafe_comparison(e))
.and_then(|_| bin.rhs())
{
issue_err(expr, ctx, op.clone());
}
if let Some(expr) = bin
.rhs()
.filter(|e| unsafe_comparison(e))
.and_then(|_| bin.lhs())
{
issue_err(expr, ctx, op)
}
}
None
}
}
fn issue_err(expr: ast::Expr, ctx: &mut RuleCtx, op: SyntaxToken) {
let err = ctx
.err(
"no-compare-neg-zero",
"Comparison against `-0` with `{}` yields unexpected behavior",
)
.primary(
op,
"...because this comparison passes for both `-0` and `+0`",
)
.note(format!(
"help: try using this: `{}`",
color(&format!("Object.is({}, -0)", expr.syntax().text()))
));
ctx.add_err(err);
}
fn unsafe_comparison(expr: &ast::Expr) -> bool {
expr.syntax().text() == "-0"
}
rule_tests! {
NoCompareNegZero::default(),
err: {
"x == -0",
"x != -0",
"x === -0",
"-0 === -0",
"-0 == x",
"-0 >= 1",
"x < -0",
"x !== -0"
},
ok: {
"x === 0",
"0 === 0",
"Object.is(x, -0)"
}
}