rust-clippy/clippy_lints/src/precedence.rs
2020-04-17 10:12:30 +02:00

164 lines
5.9 KiB
Rust

use crate::utils::{snippet_with_applicability, span_lint_and_sugg};
use rustc_ast::ast::{BinOpKind, Expr, ExprKind, LitKind, UnOp};
use rustc_errors::Applicability;
use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Spanned;
const ODD_FUNCTIONS_WHITELIST: [&str; 14] = [
"asin",
"asinh",
"atan",
"atanh",
"cbrt",
"fract",
"round",
"signum",
"sin",
"sinh",
"tan",
"tanh",
"to_degrees",
"to_radians",
];
declare_clippy_lint! {
/// **What it does:** Checks for operations where precedence may be unclear
/// and suggests to add parentheses. Currently it catches the following:
/// * mixed usage of arithmetic and bit shifting/combining operators without
/// parentheses
/// * a "negative" numeric literal (which is really a unary `-` followed by a
/// numeric literal)
/// followed by a method call
///
/// **Why is this bad?** Not everyone knows the precedence of those operators by
/// heart, so expressions like these may trip others trying to reason about the
/// code.
///
/// **Known problems:** None.
///
/// **Example:**
/// * `1 << 2 + 3` equals 32, while `(1 << 2) + 3` equals 7
/// * `-1i32.abs()` equals -1, while `(-1i32).abs()` equals 1
pub PRECEDENCE,
complexity,
"operations where precedence may be unclear"
}
declare_lint_pass!(Precedence => [PRECEDENCE]);
impl EarlyLintPass for Precedence {
fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
if expr.span.from_expansion() {
return;
}
if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.kind {
let span_sugg = |expr: &Expr, sugg, appl| {
span_lint_and_sugg(
cx,
PRECEDENCE,
expr.span,
"operator precedence can trip the unwary",
"consider parenthesizing your expression",
sugg,
appl,
);
};
if !is_bit_op(op) {
return;
}
let mut applicability = Applicability::MachineApplicable;
match (is_arith_expr(left), is_arith_expr(right)) {
(true, true) => {
let sugg = format!(
"({}) {} ({})",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(true, false) => {
let sugg = format!(
"({}) {} {}",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(false, true) => {
let sugg = format!(
"{} {} ({})",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(false, false) => (),
}
}
if let ExprKind::Unary(UnOp::Neg, ref rhs) = expr.kind {
if let ExprKind::MethodCall(ref path_segment, ref args) = rhs.kind {
let path_segment_str = path_segment.ident.name.as_str();
if let Some(slf) = args.first() {
if let ExprKind::Lit(ref lit) = slf.kind {
match lit.kind {
LitKind::Int(..) | LitKind::Float(..) => {
if ODD_FUNCTIONS_WHITELIST
.iter()
.any(|odd_function| **odd_function == *path_segment_str)
{
return;
}
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
PRECEDENCE,
expr.span,
"unary minus has lower precedence than method call",
"consider adding parentheses to clarify your intent",
format!(
"-({})",
snippet_with_applicability(cx, rhs.span, "..", &mut applicability)
),
applicability,
);
},
_ => (),
}
}
}
}
}
}
}
fn is_arith_expr(expr: &Expr) -> bool {
match expr.kind {
ExprKind::Binary(Spanned { node: op, .. }, _, _) => is_arith_op(op),
_ => false,
}
}
#[must_use]
fn is_bit_op(op: BinOpKind) -> bool {
use rustc_ast::ast::BinOpKind::{BitAnd, BitOr, BitXor, Shl, Shr};
match op {
BitXor | BitAnd | BitOr | Shl | Shr => true,
_ => false,
}
}
#[must_use]
fn is_arith_op(op: BinOpKind) -> bool {
use rustc_ast::ast::BinOpKind::{Add, Div, Mul, Rem, Sub};
match op {
Add | Sub | Mul | Div | Rem => true,
_ => false,
}
}