rust/clippy_lints/src/reference.rs
2018-03-28 15:24:26 +02:00

55 lines
1.5 KiB
Rust

use syntax::ast::{Expr, ExprKind, UnOp};
use rustc::lint::*;
use utils::{snippet, span_lint_and_sugg};
/// **What it does:** Checks for usage of `*&` and `*&mut` in expressions.
///
/// **Why is this bad?** Immediately dereferencing a reference is no-op and
/// makes the code less clear.
///
/// **Known problems:** Multiple dereference/addrof pairs are not handled so
/// the suggested fix for `x = **&&y` is `x = *&y`, which is still incorrect.
///
/// **Example:**
/// ```rust
/// let a = f(*&mut b);
/// let c = *&d;
/// ```
declare_clippy_lint! {
pub DEREF_ADDROF,
complexity,
"use of `*&` or `*&mut` in an expression"
}
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(DEREF_ADDROF)
}
}
fn without_parens(mut e: &Expr) -> &Expr {
while let ExprKind::Paren(ref child_e) = e.node {
e = child_e;
}
e
}
impl EarlyLintPass for Pass {
fn check_expr(&mut self, cx: &EarlyContext, e: &Expr) {
if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.node {
if let ExprKind::AddrOf(_, ref addrof_target) = without_parens(deref_target).node {
span_lint_and_sugg(
cx,
DEREF_ADDROF,
e.span,
"immediately dereferencing a reference",
"try this",
format!("{}", snippet(cx, addrof_target.span, "_")),
);
}
}
}
}