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use clippy_utils::diagnostics::span_lint;
use clippy_utils::macros::{find_assert_eq_args, root_macro_call_first_node};
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::LateContext;
use super::UNIT_CMP;
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
if expr.span.from_expansion() {
if let Some(macro_call) = root_macro_call_first_node(cx, expr) {
let macro_name = cx.tcx.item_name(macro_call.def_id);
let result = match macro_name.as_str() {
"assert_eq" | "debug_assert_eq" => "succeed",
"assert_ne" | "debug_assert_ne" => "fail",
_ => return,
};
let Some((left, _, _)) = find_assert_eq_args(cx, expr, macro_call.expn) else {
return;
};
if !cx.typeck_results().expr_ty(left).is_unit() {
return;
}
span_lint(
cx,
UNIT_CMP,
macro_call.span,
&format!("`{macro_name}` of unit values detected. This will always {result}"),
);
}
return;
}
if let ExprKind::Binary(ref cmp, left, _) = expr.kind {
let op = cmp.node;
if op.is_comparison() && cx.typeck_results().expr_ty(left).is_unit() {
let result = match op {
BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
_ => "false",
};
span_lint(
cx,
UNIT_CMP,
expr.span,
&format!(
"{}-comparison of unit values detected. This will always be {result}",
op.as_str()
),
);
}
}
}
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