rust-clippy/clippy_lints/src/overflow_check_conditional.rs

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use rustc::lint::*;
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use rustc::{declare_lint, lint_array};
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use if_chain::if_chain;
use rustc::hir::*;
use crate::utils::{span_lint, SpanlessEq};
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/// **What it does:** Detects classic underflow/overflow checks.
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///
/// **Why is this bad?** Most classic C underflow/overflow checks will fail in
/// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead.
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///
/// **Known problems:** None.
///
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/// **Example:**
/// ```rust
/// a + b < a
/// ```
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declare_clippy_lint! {
pub OVERFLOW_CHECK_CONDITIONAL,
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complexity,
"overflow checks inspired by C which are likely to panic"
}
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#[derive(Copy, Clone)]
pub struct OverflowCheckConditional;
impl LintPass for OverflowCheckConditional {
fn get_lints(&self) -> LintArray {
lint_array!(OVERFLOW_CHECK_CONDITIONAL)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for OverflowCheckConditional {
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// a + b < a, a > a + b, a < a - b, a - b > a
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r);
if_chain! {
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if let ExprKind::Binary(ref op, ref first, ref second) = expr.node;
if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = first.node;
if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.node;
if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.node;
if let ExprKind::Path(QPath::Resolved(_, ref path3)) = second.node;
if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]);
if cx.tables.expr_ty(ident1).is_integral();
if cx.tables.expr_ty(ident2).is_integral();
then {
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if let BinOpKind::Lt = op.node {
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if let BinOpKind::Add = op2.node {
span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
"You are trying to use classic C overflow conditions that will fail in Rust.");
}
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}
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if let BinOpKind::Gt = op.node {
if let BinOpKind::Sub = op2.node {
span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
"You are trying to use classic C underflow conditions that will fail in Rust.");
}
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}
}
}
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if_chain! {
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if let ExprKind::Binary(ref op, ref first, ref second) = expr.node;
if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = second.node;
if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.node;
if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.node;
if let ExprKind::Path(QPath::Resolved(_, ref path3)) = first.node;
if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]);
if cx.tables.expr_ty(ident1).is_integral();
if cx.tables.expr_ty(ident2).is_integral();
then {
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if let BinOpKind::Gt = op.node {
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if let BinOpKind::Add = op2.node {
span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
"You are trying to use classic C overflow conditions that will fail in Rust.");
}
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}
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if let BinOpKind::Lt = op.node {
if let BinOpKind::Sub = op2.node {
span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
"You are trying to use classic C underflow conditions that will fail in Rust.");
}
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}
}
}
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}
}