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_middle::ty::TyS;
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
9 use rustc_span::symbol::sym;
11 declare_clippy_lint! {
13 /// Checks for no-op uses of Option::{as_deref,as_deref_mut},
14 /// for example, `Option<&T>::as_deref()` returns the same type.
16 /// ### Why is this bad?
17 /// Redundant code and improving readability.
22 /// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
24 /// Could be written as:
29 #[clippy::version = "1.57.0"]
30 pub NEEDLESS_OPTION_AS_DEREF,
32 "no-op use of `deref` or `deref_mut` method to `Option`."
35 declare_lint_pass!(OptionNeedlessDeref=> [
36 NEEDLESS_OPTION_AS_DEREF,
39 impl<'tcx> LateLintPass<'tcx> for OptionNeedlessDeref {
40 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
41 if expr.span.from_expansion() {
44 let typeck = cx.typeck_results();
45 let outer_ty = typeck.expr_ty(expr);
48 if is_type_diagnostic_item(cx,outer_ty,sym::Option);
49 if let ExprKind::MethodCall(path, _, [sub_expr], _) = expr.kind;
50 let symbol = path.ident.as_str();
51 if symbol=="as_deref" || symbol=="as_deref_mut";
52 if TyS::same_type( outer_ty, typeck.expr_ty(sub_expr) );
56 NEEDLESS_OPTION_AS_DEREF,
58 "derefed type is same as origin",
60 snippet_opt(cx,sub_expr.span).unwrap(),
61 Applicability::MachineApplicable