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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet_with_context;
   3 use clippy_utils::ty::peel_mid_ty_refs;
   4 use clippy_utils::{is_diag_item_method, is_diag_trait_item};
   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_span::sym;
  10
  11 use super::IMPLICIT_CLONE;
  12
  13 pub fn check(cx: &LateContext<'_>, method_name: &str, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>) {
  14     if_chain! {
  15         if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
  16         if is_clone_like(cx, method_name, method_def_id);
  17         let return_type = cx.typeck_results().expr_ty(expr);
  18         let input_type = cx.typeck_results().expr_ty(recv);
  19         let (input_type, ref_count) = peel_mid_ty_refs(input_type);
  20         if let Some(ty_name) = input_type.ty_adt_def().map(|adt_def| cx.tcx.item_name(adt_def.did()));
  21         if return_type == input_type;
  22         then {
  23             let mut app = Applicability::MachineApplicable;
  24             let recv_snip = snippet_with_context(cx, recv.span, expr.span.ctxt(), "..", &mut app).0;
  25             span_lint_and_sugg(
  26                 cx,
  27                 IMPLICIT_CLONE,
  28                 expr.span,
  29                 &format!("implicitly cloning a `{}` by calling `{}` on its dereferenced type", ty_name, method_name),
  30                 "consider using",
  31                 if ref_count > 1 {
  32                     format!("({}{}).clone()", "*".repeat(ref_count - 1), recv_snip)
  33                 } else {
  34                     format!("{}.clone()", recv_snip)
  35                 },
  36                 app,
  37             );
  38         }
  39     }
  40 }
  41
  42 /// Returns true if the named method can be used to clone the receiver.
  43 /// Note that `to_string` is not flagged by `implicit_clone`. So other lints that call
  44 /// `is_clone_like` and that do flag `to_string` must handle it separately. See, e.g.,
  45 /// `is_to_owned_like` in `unnecessary_to_owned.rs`.
  46 pub fn is_clone_like(cx: &LateContext<'_>, method_name: &str, method_def_id: hir::def_id::DefId) -> bool {
  47     match method_name {
  48         "to_os_string" => is_diag_item_method(cx, method_def_id, sym::OsStr),
  49         "to_owned" => is_diag_trait_item(cx, method_def_id, sym::ToOwned),
  50         "to_path_buf" => is_diag_item_method(cx, method_def_id, sym::Path),
  51         "to_vec" => cx
  52             .tcx
  53             .impl_of_method(method_def_id)
  54             .filter(|&impl_did| cx.tcx.type_of(impl_did).is_slice() && cx.tcx.impl_trait_ref(impl_did).is_none())
  55             .is_some(),
  56         _ => false,
  57     }
  58 }