1 use crate::utils::{snippet_with_applicability, span_lint_and_sugg};
2 use if_chain::if_chain;
3 use rustc_ast::ast::{BinOpKind, Expr, ExprKind, LitKind, UnOp};
4 use rustc_errors::Applicability;
5 use rustc_lint::{EarlyContext, EarlyLintPass};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
7 use rustc_span::source_map::Spanned;
9 const ALLOWED_ODD_FUNCTIONS: [&str; 14] = [
26 declare_clippy_lint! {
27 /// **What it does:** Checks for operations where precedence may be unclear
28 /// and suggests to add parentheses. Currently it catches the following:
29 /// * mixed usage of arithmetic and bit shifting/combining operators without
31 /// * a "negative" numeric literal (which is really a unary `-` followed by a
33 /// followed by a method call
35 /// **Why is this bad?** Not everyone knows the precedence of those operators by
36 /// heart, so expressions like these may trip others trying to reason about the
39 /// **Known problems:** None.
42 /// * `1 << 2 + 3` equals 32, while `(1 << 2) + 3` equals 7
43 /// * `-1i32.abs()` equals -1, while `(-1i32).abs()` equals 1
46 "operations where precedence may be unclear"
49 declare_lint_pass!(Precedence => [PRECEDENCE]);
51 impl EarlyLintPass for Precedence {
52 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
53 if expr.span.from_expansion() {
57 if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.kind {
58 let span_sugg = |expr: &Expr, sugg, appl| {
63 "operator precedence can trip the unwary",
64 "consider parenthesizing your expression",
73 let mut applicability = Applicability::MachineApplicable;
74 match (is_arith_expr(left), is_arith_expr(right)) {
78 snippet_with_applicability(cx, left.span, "..", &mut applicability),
80 snippet_with_applicability(cx, right.span, "..", &mut applicability)
82 span_sugg(expr, sugg, applicability);
87 snippet_with_applicability(cx, left.span, "..", &mut applicability),
89 snippet_with_applicability(cx, right.span, "..", &mut applicability)
91 span_sugg(expr, sugg, applicability);
96 snippet_with_applicability(cx, left.span, "..", &mut applicability),
98 snippet_with_applicability(cx, right.span, "..", &mut applicability)
100 span_sugg(expr, sugg, applicability);
102 (false, false) => (),
106 if let ExprKind::Unary(UnOp::Neg, operand) = &expr.kind {
107 let mut arg = operand;
109 let mut all_odd = true;
110 while let ExprKind::MethodCall(path_segment, args, _) = &arg.kind {
111 let path_segment_str = path_segment.ident.name.as_str();
112 all_odd &= ALLOWED_ODD_FUNCTIONS
114 .any(|odd_function| **odd_function == *path_segment_str);
115 arg = args.first().expect("A method always has a receiver.");
120 if let ExprKind::Lit(lit) = &arg.kind;
121 if let LitKind::Int(..) | LitKind::Float(..) = &lit.kind;
123 let mut applicability = Applicability::MachineApplicable;
128 "unary minus has lower precedence than method call",
129 "consider adding parentheses to clarify your intent",
132 snippet_with_applicability(cx, operand.span, "..", &mut applicability)
142 fn is_arith_expr(expr: &Expr) -> bool {
144 ExprKind::Binary(Spanned { node: op, .. }, _, _) => is_arith_op(op),
150 fn is_bit_op(op: BinOpKind) -> bool {
151 use rustc_ast::ast::BinOpKind::{BitAnd, BitOr, BitXor, Shl, Shr};
152 matches!(op, BitXor | BitAnd | BitOr | Shl | Shr)
156 fn is_arith_op(op: BinOpKind) -> bool {
157 use rustc_ast::ast::BinOpKind::{Add, Div, Mul, Rem, Sub};
158 matches!(op, Add | Sub | Mul | Div | Rem)