-use rustc::ty;
-use rustc_hir::*;
+use if_chain::if_chain;
+use rustc_hir::{BinOp, BinOpKind, Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
declare_lint_pass!(IdentityOp => [IDENTITY_OP]);
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityOp {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
+impl<'tcx> LateLintPass<'tcx> for IdentityOp {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
if e.span.from_expansion() {
return;
}
- if let ExprKind::Binary(ref cmp, ref left, ref right) = e.kind {
+ if let ExprKind::Binary(cmp, ref left, ref right) = e.kind {
+ if is_allowed(cx, cmp, left, right) {
+ return;
+ }
match cmp.node {
BinOpKind::Add | BinOpKind::BitOr | BinOpKind::BitXor => {
check(cx, left, 0, e.span, right.span);
}
}
+fn is_allowed(cx: &LateContext<'_>, cmp: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> bool {
+ // `1 << 0` is a common pattern in bit manipulation code
+ if_chain! {
+ if let BinOpKind::Shl = cmp.node;
+ if let Some(Constant::Int(0)) = constant_simple(cx, cx.typeck_results(), right);
+ if let Some(Constant::Int(1)) = constant_simple(cx, cx.typeck_results(), left);
+ then {
+ return true;
+ }
+ }
+
+ false
+}
+
#[allow(clippy::cast_possible_wrap)]
-fn check(cx: &LateContext<'_, '_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {
- if let Some(Constant::Int(v)) = constant_simple(cx, cx.tables, e) {
- let check = match cx.tables.expr_ty(e).kind {
+fn check(cx: &LateContext<'_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {
+ if let Some(Constant::Int(v)) = constant_simple(cx, cx.typeck_results(), e) {
+ let check = match *cx.typeck_results().expr_ty(e).kind() {
ty::Int(ity) => unsext(cx.tcx, -1_i128, ity),
ty::Uint(uty) => clip(cx.tcx, !0, uty),
_ => return,