src/tools/clippy/clippy_lints/src/methods/option_as_ref_deref.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet;
   3 use clippy_utils::ty::is_type_diagnostic_item;
   4 use clippy_utils::{match_def_path, meets_msrv, msrvs, path_to_local_id, paths, peel_blocks};
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_lint::LateContext;
   9 use rustc_middle::ty;
  10 use rustc_semver::RustcVersion;
  11 use rustc_span::sym;
  12
  13 use super::OPTION_AS_REF_DEREF;
  14
  15 /// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
  16 pub(super) fn check<'tcx>(
  17     cx: &LateContext<'tcx>,
  18     expr: &hir::Expr<'_>,
  19     as_ref_recv: &hir::Expr<'_>,
  20     map_arg: &hir::Expr<'_>,
  21     is_mut: bool,
  22     msrv: Option<RustcVersion>,
  23 ) {
  24     if !meets_msrv(msrv, msrvs::OPTION_AS_DEREF) {
  25         return;
  26     }
  27
  28     let same_mutability = |m| (is_mut && m == &hir::Mutability::Mut) || (!is_mut && m == &hir::Mutability::Not);
  29
  30     let option_ty = cx.typeck_results().expr_ty(as_ref_recv);
  31     if !is_type_diagnostic_item(cx, option_ty, sym::Option) {
  32         return;
  33     }
  34
  35     let deref_aliases: [&[&str]; 9] = [
  36         &paths::DEREF_TRAIT_METHOD,
  37         &paths::DEREF_MUT_TRAIT_METHOD,
  38         &paths::CSTRING_AS_C_STR,
  39         &paths::OS_STRING_AS_OS_STR,
  40         &paths::PATH_BUF_AS_PATH,
  41         &paths::STRING_AS_STR,
  42         &paths::STRING_AS_MUT_STR,
  43         &paths::VEC_AS_SLICE,
  44         &paths::VEC_AS_MUT_SLICE,
  45     ];
  46
  47     let is_deref = match map_arg.kind {
  48         hir::ExprKind::Path(ref expr_qpath) => cx
  49             .qpath_res(expr_qpath, map_arg.hir_id)
  50             .opt_def_id()
  51             .map_or(false, |fun_def_id| {
  52                 deref_aliases.iter().any(|path| match_def_path(cx, fun_def_id, path))
  53             }),
  54         hir::ExprKind::Closure { body, .. } => {
  55             let closure_body = cx.tcx.hir().body(body);
  56             let closure_expr = peel_blocks(&closure_body.value);
  57
  58             match &closure_expr.kind {
  59                 hir::ExprKind::MethodCall(_, args, _) => {
  60                     if_chain! {
  61                         if args.len() == 1;
  62                         if path_to_local_id(&args[0], closure_body.params[0].pat.hir_id);
  63                         let adj = cx
  64                             .typeck_results()
  65                             .expr_adjustments(&args[0])
  66                             .iter()
  67                             .map(|x| &x.kind)
  68                             .collect::<Box<[_]>>();
  69                         if let [ty::adjustment::Adjust::Deref(None), ty::adjustment::Adjust::Borrow(_)] = *adj;
  70                         then {
  71                             let method_did = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id).unwrap();
  72                             deref_aliases.iter().any(|path| match_def_path(cx, method_did, path))
  73                         } else {
  74                             false
  75                         }
  76                     }
  77                 },
  78                 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, m, inner) if same_mutability(m) => {
  79                     if_chain! {
  80                         if let hir::ExprKind::Unary(hir::UnOp::Deref, inner1) = inner.kind;
  81                         if let hir::ExprKind::Unary(hir::UnOp::Deref, inner2) = inner1.kind;
  82                         then {
  83                             path_to_local_id(inner2, closure_body.params[0].pat.hir_id)
  84                         } else {
  85                             false
  86                         }
  87                     }
  88                 },
  89                 _ => false,
  90             }
  91         },
  92         _ => false,
  93     };
  94
  95     if is_deref {
  96         let current_method = if is_mut {
  97             format!(".as_mut().map({})", snippet(cx, map_arg.span, ".."))
  98         } else {
  99             format!(".as_ref().map({})", snippet(cx, map_arg.span, ".."))
 100         };
 101         let method_hint = if is_mut { "as_deref_mut" } else { "as_deref" };
 102         let hint = format!("{}.{}()", snippet(cx, as_ref_recv.span, ".."), method_hint);
 103         let suggestion = format!("try using {} instead", method_hint);
 104
 105         let msg = format!(
 106             "called `{0}` on an Option value. This can be done more directly \
 107             by calling `{1}` instead",
 108             current_method, hint
 109         );
 110         span_lint_and_sugg(
 111             cx,
 112             OPTION_AS_REF_DEREF,
 113             expr.span,
 114             &msg,
 115             &suggestion,
 116             hint,
 117             Applicability::MachineApplicable,
 118         );
 119     }
 120 }