105 lines
3.7 KiB
Rust
105 lines
3.7 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet_with_applicability;
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use rustc_ast::ast::{BinOpKind, Expr, ExprKind};
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use rustc_errors::Applicability;
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use rustc_lint::{EarlyContext, EarlyLintPass};
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use rustc_session::declare_lint_pass;
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use rustc_span::source_map::Spanned;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for operations where precedence may be unclear
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/// and suggests to add parentheses. Currently it catches the following:
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/// * mixed usage of arithmetic and bit shifting/combining operators without
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/// parentheses
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///
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/// ### Why is this bad?
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/// Not everyone knows the precedence of those operators by
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/// heart, so expressions like these may trip others trying to reason about the
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/// code.
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///
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/// ### Example
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/// * `1 << 2 + 3` equals 32, while `(1 << 2) + 3` equals 7
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#[clippy::version = "pre 1.29.0"]
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pub PRECEDENCE,
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complexity,
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"operations where precedence may be unclear"
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}
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declare_lint_pass!(Precedence => [PRECEDENCE]);
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impl EarlyLintPass for Precedence {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if expr.span.from_expansion() {
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return;
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}
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if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.kind {
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let span_sugg = |expr: &Expr, sugg, appl| {
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span_lint_and_sugg(
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cx,
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PRECEDENCE,
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expr.span,
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"operator precedence can trip the unwary",
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"consider parenthesizing your expression",
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sugg,
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appl,
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);
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};
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if !is_bit_op(op) {
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return;
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}
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let mut applicability = Applicability::MachineApplicable;
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match (is_arith_expr(left), is_arith_expr(right)) {
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(true, true) => {
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let sugg = format!(
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"({}) {} ({})",
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snippet_with_applicability(cx, left.span, "..", &mut applicability),
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op.as_str(),
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snippet_with_applicability(cx, right.span, "..", &mut applicability)
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);
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span_sugg(expr, sugg, applicability);
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},
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(true, false) => {
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let sugg = format!(
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"({}) {} {}",
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snippet_with_applicability(cx, left.span, "..", &mut applicability),
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op.as_str(),
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snippet_with_applicability(cx, right.span, "..", &mut applicability)
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);
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span_sugg(expr, sugg, applicability);
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},
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(false, true) => {
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let sugg = format!(
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"{} {} ({})",
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snippet_with_applicability(cx, left.span, "..", &mut applicability),
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op.as_str(),
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snippet_with_applicability(cx, right.span, "..", &mut applicability)
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);
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span_sugg(expr, sugg, applicability);
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},
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(false, false) => (),
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}
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}
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}
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}
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fn is_arith_expr(expr: &Expr) -> bool {
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match expr.kind {
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ExprKind::Binary(Spanned { node: op, .. }, _, _) => is_arith_op(op),
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_ => false,
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}
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}
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#[must_use]
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fn is_bit_op(op: BinOpKind) -> bool {
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use rustc_ast::ast::BinOpKind::{BitAnd, BitOr, BitXor, Shl, Shr};
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matches!(op, BitXor | BitAnd | BitOr | Shl | Shr)
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}
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#[must_use]
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fn is_arith_op(op: BinOpKind) -> bool {
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use rustc_ast::ast::BinOpKind::{Add, Div, Mul, Rem, Sub};
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matches!(op, Add | Sub | Mul | Div | Rem)
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}
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