1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::in_macro;
3 use clippy_utils::source::{snippet_opt, snippet_with_applicability};
4 use clippy_utils::sugg::Sugg;
5 use if_chain::if_chain;
6 use rustc_ast::ast::{Expr, ExprKind, Mutability, UnOp};
7 use rustc_errors::Applicability;
8 use rustc_lint::{EarlyContext, EarlyLintPass};
9 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 use rustc_span::BytePos;
12 declare_clippy_lint! {
14 /// Checks for usage of `*&` and `*&mut` in expressions.
16 /// ### Why is this bad?
17 /// Immediately dereferencing a reference is no-op and
18 /// makes the code less clear.
20 /// ### Known problems
21 /// Multiple dereference/addrof pairs are not handled so
22 /// the suggested fix for `x = **&&y` is `x = *&y`, which is still incorrect.
27 /// let a = f(*&mut b);
36 "use of `*&` or `*&mut` in an expression"
39 declare_lint_pass!(DerefAddrOf => [DEREF_ADDROF]);
41 fn without_parens(mut e: &Expr) -> &Expr {
42 while let ExprKind::Paren(ref child_e) = e.kind {
48 impl EarlyLintPass for DerefAddrOf {
49 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
51 if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.kind;
52 if let ExprKind::AddrOf(_, ref mutability, ref addrof_target) = without_parens(deref_target).kind;
53 if !in_macro(addrof_target.span);
55 let mut applicability = Applicability::MachineApplicable;
56 let sugg = if e.span.from_expansion() {
57 if let Ok(macro_source) = cx.sess.source_map().span_to_snippet(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 #[allow(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 #[allow(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",
106 declare_clippy_lint! {
108 /// Checks for references in expressions that use
109 /// auto dereference.
111 /// ### Why is this bad?
112 /// The reference is a no-op and is automatically
113 /// dereferenced by the compiler and makes the code less clear.
117 /// struct Point(u32, u32);
118 /// let point = Point(30, 20);
119 /// let x = (&point).0;
123 /// # struct Point(u32, u32);
124 /// # let point = Point(30, 20);
129 "Use of reference in auto dereference expression."
132 declare_lint_pass!(RefInDeref => [REF_IN_DEREF]);
134 impl EarlyLintPass for RefInDeref {
135 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
137 if let ExprKind::Field(ref object, _) = e.kind;
138 if let ExprKind::Paren(ref parened) = object.kind;
139 if let ExprKind::AddrOf(_, _, ref inner) = parened.kind;
141 let applicability = if inner.span.from_expansion() {
142 Applicability::MaybeIncorrect
144 Applicability::MachineApplicable
146 let sugg = Sugg::ast(cx, inner, "_").maybe_par();
151 "creating a reference that is immediately dereferenced",