103 lines
3.4 KiB
Rust
103 lines
3.4 KiB
Rust
use clippy_utils::source::snippet;
|
|
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;
|
|
|
|
use crate::consts::{constant_simple, Constant};
|
|
use clippy_utils::diagnostics::span_lint;
|
|
use clippy_utils::{clip, unsext};
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for identity operations, e.g., `x + 0`.
|
|
///
|
|
/// **Why is this bad?** This code can be removed without changing the
|
|
/// meaning. So it just obscures what's going on. Delete it mercilessly.
|
|
///
|
|
/// **Known problems:** None.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// # let x = 1;
|
|
/// x / 1 + 0 * 1 - 0 | 0;
|
|
/// ```
|
|
pub IDENTITY_OP,
|
|
complexity,
|
|
"using identity operations, e.g., `x + 0` or `y / 1`"
|
|
}
|
|
|
|
declare_lint_pass!(IdentityOp => [IDENTITY_OP]);
|
|
|
|
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(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);
|
|
check(cx, right, 0, e.span, left.span);
|
|
},
|
|
BinOpKind::Shl | BinOpKind::Shr | BinOpKind::Sub => check(cx, right, 0, e.span, left.span),
|
|
BinOpKind::Mul => {
|
|
check(cx, left, 1, e.span, right.span);
|
|
check(cx, right, 1, e.span, left.span);
|
|
},
|
|
BinOpKind::Div => check(cx, right, 1, e.span, left.span),
|
|
BinOpKind::BitAnd => {
|
|
check(cx, left, -1, e.span, right.span);
|
|
check(cx, right, -1, e.span, left.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.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,
|
|
};
|
|
if match m {
|
|
0 => v == 0,
|
|
-1 => v == check,
|
|
1 => v == 1,
|
|
_ => unreachable!(),
|
|
} {
|
|
span_lint(
|
|
cx,
|
|
IDENTITY_OP,
|
|
span,
|
|
&format!(
|
|
"the operation is ineffective. Consider reducing it to `{}`",
|
|
snippet(cx, arg, "..")
|
|
),
|
|
);
|
|
}
|
|
}
|
|
}
|