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Auto merge of #7850 - ThibsG:PossibleCastTruncation5395, r=camsteffen

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Fix FP: no lint when cast is coming from `signum` method call for `cast_possible_truncation` lint

Fixes a FP when cast is coming from `signum` method call

fixes: #5395

changelog: [`cast_possible_truncation`] Fix FP when cast is coming from `signum` method call
This commit is contained in:
bors 2021-10-21 18:01:39 +00:00
commit c97a06d9af
3 changed files with 19 additions and 3 deletions
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12
clippy_lints/src/casts/cast_possible_truncation.rs
View file

@ -1,12 +1,20 @@
use clippy_utils::diagnostics::span_lint;
use clippy_utils::expr_or_init;
use clippy_utils::ty::is_isize_or_usize;
use rustc_hir::Expr;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, FloatTy, Ty};
use super::{utils, CAST_POSSIBLE_TRUNCATION};
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
// do not lint if cast comes from a `signum` function
if let ExprKind::MethodCall(path, ..) = expr_or_init(cx, cast_expr).kind {
if path.ident.name.as_str() == "signum" {
return;
}
}
let msg = match (cast_from.is_integral(), cast_to.is_integral()) {
(true, true) => {
let from_nbits = utils::int_ty_to_nbits(cast_from, cx.tcx);

2
clippy_lints/src/casts/mod.rs
View file

@ -427,7 +427,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
fn_to_numeric_cast::check(cx, expr, cast_expr, cast_from, cast_to);
fn_to_numeric_cast_with_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
cast_possible_truncation::check(cx, expr, cast_from, cast_to);
cast_possible_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
cast_possible_wrap::check(cx, expr, cast_from, cast_to);
cast_precision_loss::check(cx, expr, cast_from, cast_to);
cast_lossless::check(cx, expr, cast_expr, cast_from, cast_to);

8
tests/ui/cast.rs
View file

@ -92,4 +92,12 @@ fn main() {
(1i64).checked_rem_euclid(-1i64).unwrap() as u64;
(1i64).checked_rem_euclid(-1i64).unwrap() as u128;
(1isize).checked_rem_euclid(-1isize).unwrap() as usize;
// no lint for `cast_possible_truncation`
// with `signum` method call (see issue #5395)
let x: i64 = 5;
let _ = x.signum() as i32;
let s = x.signum();
let _ = s as i32;
}