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use crate::utils::{in_macro, snippet_with_applicability, span_lint_and_sugg};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use syntax::ast::{Expr, ExprKind, UnOp};
declare_clippy_lint! {
/// **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,ignore
/// let a = f(*&mut b);
/// let c = *&d;
/// ```
pub DEREF_ADDROF,
complexity,
"use of `*&` or `*&mut` in an expression"
}
declare_lint_pass!(DerefAddrOf => [DEREF_ADDROF]);
fn without_parens(mut e: &Expr) -> &Expr {
while let ExprKind::Paren(ref child_e) = e.kind {
e = child_e;
}
e
}
impl EarlyLintPass for DerefAddrOf {
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
if_chain! {
if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.kind;
if let ExprKind::AddrOf(_, _, ref addrof_target) = without_parens(deref_target).kind;
if !in_macro(addrof_target.span);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
DEREF_ADDROF,
e.span,
"immediately dereferencing a reference",
"try this",
format!("{}", snippet_with_applicability(cx, addrof_target.span, "_", &mut applicability)),
applicability,
);
}
}
}
}
declare_clippy_lint! {
/// **What it does:** Checks for references in expressions that use
/// auto dereference.
///
/// **Why is this bad?** The reference is a no-op and is automatically
/// dereferenced by the compiler and makes the code less clear.
///
/// **Example:**
/// ```rust
/// struct Point(u32, u32);
/// let point = Point(30, 20);
/// let x = (&point).0;
/// ```
pub REF_IN_DEREF,
complexity,
"Use of reference in auto dereference expression."
}
declare_lint_pass!(RefInDeref => [REF_IN_DEREF]);
impl EarlyLintPass for RefInDeref {
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
if_chain! {
if let ExprKind::Field(ref object, _) = e.kind;
if let ExprKind::Paren(ref parened) = object.kind;
if let ExprKind::AddrOf(_, _, ref inner) = parened.kind;
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
REF_IN_DEREF,
object.span,
"Creating a reference that is immediately dereferenced.",
"try this",
snippet_with_applicability(cx, inner.span, "_", &mut applicability).to_string(),
applicability,
);
}
}
}
}
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