1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::source::{snippet_opt, snippet_with_applicability};
3 use if_chain::if_chain;
4 use rustc_ast::ast::{Expr, ExprKind, Mutability, UnOp};
5 use rustc_errors::Applicability;
6 use rustc_lint::{EarlyContext, EarlyLintPass};
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
8 use rustc_span::BytePos;
10 declare_clippy_lint! {
12 /// Checks for usage of `*&` and `*&mut` in expressions.
14 /// ### Why is this bad?
15 /// Immediately dereferencing a reference is no-op and
16 /// makes the code less clear.
18 /// ### Known problems
19 /// Multiple dereference/addrof pairs are not handled so
20 /// the suggested fix for `x = **&&y` is `x = *&y`, which is still incorrect.
25 /// let a = f(*&mut b);
32 #[clippy::version = "pre 1.29.0"]
35 "use of `*&` or `*&mut` in an expression"
38 declare_lint_pass!(DerefAddrOf => [DEREF_ADDROF]);
40 fn without_parens(mut e: &Expr) -> &Expr {
41 while let ExprKind::Paren(ref child_e) = e.kind {
47 impl EarlyLintPass for DerefAddrOf {
48 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
50 if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.kind;
51 if let ExprKind::AddrOf(_, ref mutability, ref addrof_target) = without_parens(deref_target).kind;
52 if deref_target.span.ctxt() == e.span.ctxt();
53 if !addrof_target.span.from_expansion();
55 let mut applicability = Applicability::MachineApplicable;
56 let sugg = if e.span.from_expansion() {
57 if let Some(macro_source) = snippet_opt(cx, e.span) {
58 // Remove leading whitespace from the given span
59 // e.g: ` $visitor` turns into `$visitor`
60 let trim_leading_whitespaces = |span| {
61 snippet_opt(cx, span).and_then(|snip| {
62 #[expect(clippy::cast_possible_truncation)]
63 snip.find(|c: char| !c.is_whitespace()).map(|pos| {
64 span.lo() + BytePos(pos as u32)
66 }).map_or(span, |start_no_whitespace| e.span.with_lo(start_no_whitespace))
69 let mut generate_snippet = |pattern: &str| {
70 #[expect(clippy::cast_possible_truncation)]
71 macro_source.rfind(pattern).map(|pattern_pos| {
72 let rpos = pattern_pos + pattern.len();
73 let span_after_ref = e.span.with_lo(BytePos(e.span.lo().0 + rpos as u32));
74 let span = trim_leading_whitespaces(span_after_ref);
75 snippet_with_applicability(cx, span, "_", &mut applicability)
79 if *mutability == Mutability::Mut {
80 generate_snippet("mut")
85 Some(snippet_with_applicability(cx, e.span, "_", &mut applicability))
88 Some(snippet_with_applicability(cx, addrof_target.span, "_", &mut applicability))
90 if let Some(sugg) = sugg {
95 "immediately dereferencing a reference",