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use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint;
use clippy_utils::{method_chain_args, sext};
use if_chain::if_chain;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use super::CAST_SIGN_LOSS;
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
if should_lint(cx, cast_op, cast_from, cast_to) {
span_lint(
cx,
CAST_SIGN_LOSS,
expr.span,
&format!(
"casting `{}` to `{}` may lose the sign of the value",
cast_from, cast_to
),
);
}
}
fn should_lint(cx: &LateContext<'_>, cast_op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) -> bool {
match (cast_from.is_integral(), cast_to.is_integral()) {
(true, true) => {
if !cast_from.is_signed() || cast_to.is_signed() {
return false;
}
// Don't lint for positive constants.
let const_val = constant(cx, cx.typeck_results(), cast_op);
if_chain! {
if let Some((Constant::Int(n), _)) = const_val;
if let ty::Int(ity) = *cast_from.kind();
if sext(cx.tcx, n, ity) >= 0;
then {
return false;
}
}
// Don't lint for the result of methods that always return non-negative values.
if let ExprKind::MethodCall(path, ..) = cast_op.kind {
let mut method_name = path.ident.name.as_str();
let allowed_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
if_chain! {
if method_name == "unwrap";
if let Some(arglist) = method_chain_args(cast_op, &["unwrap"]);
if let ExprKind::MethodCall(inner_path, ..) = &arglist[0].0.kind;
then {
method_name = inner_path.ident.name.as_str();
}
}
if allowed_methods.iter().any(|&name| method_name == name) {
return false;
}
}
true
},
(false, true) => !cast_to.is_signed(),
(_, _) => false,
}
}
|
