1 use crate::consts::{constant, Constant};
2 use clippy_utils::diagnostics::span_lint;
3 use clippy_utils::{method_chain_args, sext};
4 use if_chain::if_chain;
5 use rustc_hir::{Expr, ExprKind};
6 use rustc_lint::LateContext;
7 use rustc_middle::ty::{self, Ty};
9 use super::CAST_SIGN_LOSS;
11 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
12 if should_lint(cx, cast_op, cast_from, cast_to) {
18 "casting `{}` to `{}` may lose the sign of the value",
25 fn should_lint(cx: &LateContext<'_>, cast_op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) -> bool {
26 match (cast_from.is_integral(), cast_to.is_integral()) {
28 if !cast_from.is_signed() || cast_to.is_signed() {
32 // Don't lint for positive constants.
33 let const_val = constant(cx, &cx.typeck_results(), cast_op);
35 if let Some((Constant::Int(n), _)) = const_val;
36 if let ty::Int(ity) = *cast_from.kind();
37 if sext(cx.tcx, n, ity) >= 0;
43 // Don't lint for the result of methods that always return non-negative values.
44 if let ExprKind::MethodCall(ref path, _, _, _) = cast_op.kind {
45 let mut method_name = path.ident.name.as_str();
46 let allowed_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
49 if method_name == "unwrap";
50 if let Some(arglist) = method_chain_args(cast_op, &["unwrap"]);
51 if let ExprKind::MethodCall(ref inner_path, _, _, _) = &arglist[0][0].kind;
53 method_name = inner_path.ident.name.as_str();
57 if allowed_methods.iter().any(|&name| method_name == name) {
65 (false, true) => !cast_to.is_signed(),