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1 | use clippy_utils::diagnostics::span_lint; |
2 | use clippy_utils::SpanlessEq; | |
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3 | use rustc_hir::{BinOpKind, Expr, ExprKind, QPath}; |
4 | use rustc_lint::{LateContext, LateLintPass}; | |
4b012472 | 5 | use rustc_session::declare_lint_pass; |
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6 | |
7 | declare_clippy_lint! { | |
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8 | /// ### What it does |
9 | /// Detects classic underflow/overflow checks. | |
f20569fa | 10 | /// |
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11 | /// ### Why is this bad? |
12 | /// Most classic C underflow/overflow checks will fail in | |
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13 | /// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead. |
14 | /// | |
94222f64 | 15 | /// ### Example |
ed00b5ec | 16 | /// ```no_run |
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17 | /// # let a = 1; |
18 | /// # let b = 2; | |
19 | /// a + b < a; | |
20 | /// ``` | |
a2a8927a | 21 | #[clippy::version = "pre 1.29.0"] |
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22 | pub OVERFLOW_CHECK_CONDITIONAL, |
23 | complexity, | |
24 | "overflow checks inspired by C which are likely to panic" | |
25 | } | |
26 | ||
27 | declare_lint_pass!(OverflowCheckConditional => [OVERFLOW_CHECK_CONDITIONAL]); | |
28 | ||
c295e0f8 XL |
29 | const OVERFLOW_MSG: &str = "you are trying to use classic C overflow conditions that will fail in Rust"; |
30 | const UNDERFLOW_MSG: &str = "you are trying to use classic C underflow conditions that will fail in Rust"; | |
31 | ||
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32 | impl<'tcx> LateLintPass<'tcx> for OverflowCheckConditional { |
33 | // a + b < a, a > a + b, a < a - b, a - b > a | |
34 | fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { | |
35 | let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r); | |
4b012472 FG |
36 | if let ExprKind::Binary(ref op, first, second) = expr.kind |
37 | && let ExprKind::Binary(ref op2, ident1, ident2) = first.kind | |
38 | && let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind | |
39 | && let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind | |
40 | && let ExprKind::Path(QPath::Resolved(_, path3)) = second.kind | |
41 | && (eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0])) | |
42 | && cx.typeck_results().expr_ty(ident1).is_integral() | |
43 | && cx.typeck_results().expr_ty(ident2).is_integral() | |
44 | { | |
45 | if op.node == BinOpKind::Lt && op2.node == BinOpKind::Add { | |
46 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG); | |
47 | } | |
48 | if op.node == BinOpKind::Gt && op2.node == BinOpKind::Sub { | |
49 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG); | |
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50 | } |
51 | } | |
52 | ||
4b012472 FG |
53 | if let ExprKind::Binary(ref op, first, second) = expr.kind |
54 | && let ExprKind::Binary(ref op2, ident1, ident2) = second.kind | |
55 | && let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind | |
56 | && let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind | |
57 | && let ExprKind::Path(QPath::Resolved(_, path3)) = first.kind | |
58 | && (eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0])) | |
59 | && cx.typeck_results().expr_ty(ident1).is_integral() | |
60 | && cx.typeck_results().expr_ty(ident2).is_integral() | |
61 | { | |
62 | if op.node == BinOpKind::Gt && op2.node == BinOpKind::Add { | |
63 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG); | |
64 | } | |
65 | if op.node == BinOpKind::Lt && op2.node == BinOpKind::Sub { | |
66 | span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG); | |
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67 | } |
68 | } | |
69 | } | |
70 | } |