1 use if_chain::if_chain;
2 use rustc_hir::{BinOp, BinOpKind, Expr, ExprKind};
3 use rustc_lint::{LateContext, LateLintPass};
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
6 use rustc_span::source_map::Span;
8 use crate::consts::{constant_simple, Constant};
9 use crate::utils::{clip, snippet, span_lint, unsext};
11 declare_clippy_lint! {
12 /// **What it does:** Checks for identity operations, e.g., `x + 0`.
14 /// **Why is this bad?** This code can be removed without changing the
15 /// meaning. So it just obscures what's going on. Delete it mercilessly.
17 /// **Known problems:** None.
22 /// x / 1 + 0 * 1 - 0 | 0;
26 "using identity operations, e.g., `x + 0` or `y / 1`"
29 declare_lint_pass!(IdentityOp => [IDENTITY_OP]);
31 impl<'tcx> LateLintPass<'tcx> for IdentityOp {
32 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
33 if e.span.from_expansion() {
36 if let ExprKind::Binary(cmp, ref left, ref right) = e.kind {
37 if is_allowed(cx, cmp, left, right) {
41 BinOpKind::Add | BinOpKind::BitOr | BinOpKind::BitXor => {
42 check(cx, left, 0, e.span, right.span);
43 check(cx, right, 0, e.span, left.span);
45 BinOpKind::Shl | BinOpKind::Shr | BinOpKind::Sub => check(cx, right, 0, e.span, left.span),
47 check(cx, left, 1, e.span, right.span);
48 check(cx, right, 1, e.span, left.span);
50 BinOpKind::Div => check(cx, right, 1, e.span, left.span),
51 BinOpKind::BitAnd => {
52 check(cx, left, -1, e.span, right.span);
53 check(cx, right, -1, e.span, left.span);
61 fn is_allowed(cx: &LateContext<'_>, cmp: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> bool {
62 // `1 << 0` is a common pattern in bit manipulation code
64 if let BinOpKind::Shl = cmp.node;
65 if let Some(Constant::Int(0)) = constant_simple(cx, cx.typeck_results(), right);
66 if let Some(Constant::Int(1)) = constant_simple(cx, cx.typeck_results(), left);
75 #[allow(clippy::cast_possible_wrap)]
76 fn check(cx: &LateContext<'_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {
77 if let Some(Constant::Int(v)) = constant_simple(cx, cx.typeck_results(), e) {
78 let check = match *cx.typeck_results().expr_ty(e).kind() {
79 ty::Int(ity) => unsext(cx.tcx, -1_i128, ity),
80 ty::Uint(uty) => clip(cx.tcx, !0, uty),
94 "the operation is ineffective. Consider reducing it to `{}`",
95 snippet(cx, arg, "..")