71 lines
3.2 KiB
Rust
71 lines
3.2 KiB
Rust
use clippy_utils::diagnostics::span_lint;
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use clippy_utils::SpanlessEq;
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use rustc_hir::{BinOpKind, Expr, ExprKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::declare_lint_pass;
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declare_clippy_lint! {
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/// ### What it does
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/// Detects classic underflow/overflow checks.
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///
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/// ### Why is this bad?
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/// Most classic C underflow/overflow checks will fail in
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/// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead.
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///
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/// ### Example
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/// ```no_run
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/// # let a = 1;
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/// # let b = 2;
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/// a + b < a;
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub OVERFLOW_CHECK_CONDITIONAL,
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complexity,
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"overflow checks inspired by C which are likely to panic"
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}
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declare_lint_pass!(OverflowCheckConditional => [OVERFLOW_CHECK_CONDITIONAL]);
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const OVERFLOW_MSG: &str = "you are trying to use classic C overflow conditions that will fail in Rust";
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const UNDERFLOW_MSG: &str = "you are trying to use classic C underflow conditions that will fail in Rust";
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impl<'tcx> LateLintPass<'tcx> for OverflowCheckConditional {
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// a + b < a, a > a + b, a < a - b, a - b > a
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r);
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if let ExprKind::Binary(ref op, first, second) = expr.kind
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&& let ExprKind::Binary(ref op2, ident1, ident2) = first.kind
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&& let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind
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&& let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind
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&& let ExprKind::Path(QPath::Resolved(_, path3)) = second.kind
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&& (eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]))
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&& cx.typeck_results().expr_ty(ident1).is_integral()
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&& cx.typeck_results().expr_ty(ident2).is_integral()
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{
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if op.node == BinOpKind::Lt && op2.node == BinOpKind::Add {
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span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG);
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}
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if op.node == BinOpKind::Gt && op2.node == BinOpKind::Sub {
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span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG);
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}
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}
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if let ExprKind::Binary(ref op, first, second) = expr.kind
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&& let ExprKind::Binary(ref op2, ident1, ident2) = second.kind
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&& let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind
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&& let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind
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&& let ExprKind::Path(QPath::Resolved(_, path3)) = first.kind
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&& (eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]))
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&& cx.typeck_results().expr_ty(ident1).is_integral()
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&& cx.typeck_results().expr_ty(ident2).is_integral()
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{
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if op.node == BinOpKind::Gt && op2.node == BinOpKind::Add {
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span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG);
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}
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if op.node == BinOpKind::Lt && op2.node == BinOpKind::Sub {
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span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG);
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}
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}
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}
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}
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