1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::source::snippet_opt;
3 use clippy_utils::ty::is_type_diagnostic_item;
4 use rustc_errors::Applicability;
5 use rustc_hir::{Expr, ExprKind};
6 use rustc_lint::{LateContext, LateLintPass};
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
8 use rustc_span::symbol::sym;
10 declare_clippy_lint! {
12 /// Checks for no-op uses of Option::{as_deref,as_deref_mut},
13 /// for example, `Option<&T>::as_deref()` returns the same type.
15 /// ### Why is this bad?
16 /// Redundant code and improving readability.
21 /// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
23 /// Could be written as:
28 #[clippy::version = "1.57.0"]
29 pub NEEDLESS_OPTION_AS_DEREF,
31 "no-op use of `deref` or `deref_mut` method to `Option`."
34 declare_lint_pass!(OptionNeedlessDeref=> [
35 NEEDLESS_OPTION_AS_DEREF,
38 impl<'tcx> LateLintPass<'tcx> for OptionNeedlessDeref {
39 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
40 if expr.span.from_expansion() {
43 let typeck = cx.typeck_results();
44 let outer_ty = typeck.expr_ty(expr);
47 if is_type_diagnostic_item(cx,outer_ty,sym::Option);
48 if let ExprKind::MethodCall(path, [sub_expr], _) = expr.kind;
49 let symbol = path.ident.as_str();
50 if symbol == "as_deref" || symbol == "as_deref_mut";
51 if outer_ty == typeck.expr_ty(sub_expr);
55 NEEDLESS_OPTION_AS_DEREF,
57 "derefed type is same as origin",
59 snippet_opt(cx,sub_expr.span).unwrap(),
60 Applicability::MachineApplicable