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1 | use crate::utils::{span_lint, SpanlessEq}; |
2 | use if_chain::if_chain; | |
3 | use rustc_hir::{BinOpKind, Expr, ExprKind, QPath}; | |
4 | use rustc_lint::{LateContext, LateLintPass}; | |
5 | use rustc_session::{declare_lint_pass, declare_tool_lint}; | |
6 | ||
7 | declare_clippy_lint! { | |
8 | /// **What it does:** Detects classic underflow/overflow checks. | |
9 | /// | |
10 | /// **Why is this bad?** Most classic C underflow/overflow checks will fail in | |
11 | /// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead. | |
12 | /// | |
13 | /// **Known problems:** None. | |
14 | /// | |
15 | /// **Example:** | |
16 | /// ```rust | |
17 | /// # let a = 1; | |
18 | /// # let b = 2; | |
19 | /// a + b < a; | |
20 | /// ``` | |
21 | pub OVERFLOW_CHECK_CONDITIONAL, | |
22 | complexity, | |
23 | "overflow checks inspired by C which are likely to panic" | |
24 | } | |
25 | ||
26 | declare_lint_pass!(OverflowCheckConditional => [OVERFLOW_CHECK_CONDITIONAL]); | |
27 | ||
28 | impl<'tcx> LateLintPass<'tcx> for OverflowCheckConditional { | |
29 | // a + b < a, a > a + b, a < a - b, a - b > a | |
30 | fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { | |
31 | let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r); | |
32 | if_chain! { | |
33 | if let ExprKind::Binary(ref op, ref first, ref second) = expr.kind; | |
34 | if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = first.kind; | |
35 | if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.kind; | |
36 | if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.kind; | |
37 | if let ExprKind::Path(QPath::Resolved(_, ref path3)) = second.kind; | |
38 | if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); | |
39 | if cx.typeck_results().expr_ty(ident1).is_integral(); | |
40 | if cx.typeck_results().expr_ty(ident2).is_integral(); | |
41 | then { | |
42 | if let BinOpKind::Lt = op.node { | |
43 | if let BinOpKind::Add = op2.node { | |
44 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, | |
45 | "you are trying to use classic C overflow conditions that will fail in Rust"); | |
46 | } | |
47 | } | |
48 | if let BinOpKind::Gt = op.node { | |
49 | if let BinOpKind::Sub = op2.node { | |
50 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, | |
51 | "you are trying to use classic C underflow conditions that will fail in Rust"); | |
52 | } | |
53 | } | |
54 | } | |
55 | } | |
56 | ||
57 | if_chain! { | |
58 | if let ExprKind::Binary(ref op, ref first, ref second) = expr.kind; | |
59 | if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = second.kind; | |
60 | if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.kind; | |
61 | if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.kind; | |
62 | if let ExprKind::Path(QPath::Resolved(_, ref path3)) = first.kind; | |
63 | if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); | |
64 | if cx.typeck_results().expr_ty(ident1).is_integral(); | |
65 | if cx.typeck_results().expr_ty(ident2).is_integral(); | |
66 | then { | |
67 | if let BinOpKind::Gt = op.node { | |
68 | if let BinOpKind::Add = op2.node { | |
69 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, | |
70 | "you are trying to use classic C overflow conditions that will fail in Rust"); | |
71 | } | |
72 | } | |
73 | if let BinOpKind::Lt = op.node { | |
74 | if let BinOpKind::Sub = op2.node { | |
75 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, | |
76 | "you are trying to use classic C underflow conditions that will fail in Rust"); | |
77 | } | |
78 | } | |
79 | } | |
80 | } | |
81 | } | |
82 | } |