1 use crate::utils::sugg::Sugg;
2 use crate::utils::{in_macro, snippet_opt, snippet_with_applicability, span_lint_and_sugg};
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! {
11 /// **What it does:** Checks for usage of `*&` and `*&mut` in expressions.
13 /// **Why is this bad?** Immediately dereferencing a reference is no-op and
14 /// makes the code less clear.
16 /// **Known problems:** Multiple dereference/addrof pairs are not handled so
17 /// the suggested fix for `x = **&&y` is `x = *&y`, which is still incorrect.
22 /// let a = f(*&mut b);
31 "use of `*&` or `*&mut` in an expression"
34 declare_lint_pass!(DerefAddrOf => [DEREF_ADDROF]);
36 fn without_parens(mut e: &Expr) -> &Expr {
37 while let ExprKind::Paren(ref child_e) = e.kind {
43 impl EarlyLintPass for DerefAddrOf {
44 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
46 if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.kind;
47 if let ExprKind::AddrOf(_, ref mutability, ref addrof_target) = without_parens(deref_target).kind;
48 if !in_macro(addrof_target.span);
50 let mut applicability = Applicability::MachineApplicable;
51 let sugg = if e.span.from_expansion() {
52 if let Ok(macro_source) = cx.sess.source_map().span_to_snippet(e.span) {
53 // Remove leading whitespace from the given span
54 // e.g: ` $visitor` turns into `$visitor`
55 let trim_leading_whitespaces = |span| {
56 snippet_opt(cx, span).and_then(|snip| {
57 #[allow(clippy::cast_possible_truncation)]
58 snip.find(|c: char| !c.is_whitespace()).map(|pos| {
59 span.lo() + BytePos(pos as u32)
61 }).map_or(span, |start_no_whitespace| e.span.with_lo(start_no_whitespace))
64 let mut generate_snippet = |pattern: &str| {
65 #[allow(clippy::cast_possible_truncation)]
66 macro_source.rfind(pattern).map(|pattern_pos| {
67 let rpos = pattern_pos + pattern.len();
68 let span_after_ref = e.span.with_lo(BytePos(e.span.lo().0 + rpos as u32));
69 let span = trim_leading_whitespaces(span_after_ref);
70 snippet_with_applicability(cx, span, "_", &mut applicability)
74 if *mutability == Mutability::Mut {
75 generate_snippet("mut")
80 Some(snippet_with_applicability(cx, e.span, "_", &mut applicability))
83 Some(snippet_with_applicability(cx, addrof_target.span, "_", &mut applicability))
85 if let Some(sugg) = sugg {
90 "immediately dereferencing a reference",
101 declare_clippy_lint! {
102 /// **What it does:** Checks for references in expressions that use
103 /// auto dereference.
105 /// **Why is this bad?** The reference is a no-op and is automatically
106 /// dereferenced by the compiler and makes the code less clear.
110 /// struct Point(u32, u32);
111 /// let point = Point(30, 20);
112 /// let x = (&point).0;
116 "Use of reference in auto dereference expression."
119 declare_lint_pass!(RefInDeref => [REF_IN_DEREF]);
121 impl EarlyLintPass for RefInDeref {
122 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
124 if let ExprKind::Field(ref object, _) = e.kind;
125 if let ExprKind::Paren(ref parened) = object.kind;
126 if let ExprKind::AddrOf(_, _, ref inner) = parened.kind;
128 let applicability = if inner.span.from_expansion() {
129 Applicability::MaybeIncorrect
131 Applicability::MachineApplicable
133 let sugg = Sugg::ast(cx, inner, "_").maybe_par();
138 "creating a reference that is immediately dereferenced",