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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::is_diag_trait_item;
   3 use clippy_utils::source::snippet_with_context;
   4 use if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_lint::LateContext;
   8 use rustc_middle::ty::{self, print::with_forced_trimmed_paths};
   9 use rustc_span::sym;
  10
  11 use super::SUSPICIOUS_TO_OWNED;
  12
  13 pub fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>) -> bool {
  14     if_chain! {
  15         if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
  16         if is_diag_trait_item(cx, method_def_id, sym::ToOwned);
  17         let input_type = cx.typeck_results().expr_ty(expr);
  18         if let ty::Adt(adt, _) = cx.typeck_results().expr_ty(expr).kind();
  19         if cx.tcx.is_diagnostic_item(sym::Cow, adt.did());
  20         then {
  21             let mut app = Applicability::MaybeIncorrect;
  22             let recv_snip = snippet_with_context(cx, recv.span, expr.span.ctxt(), "..", &mut app).0;
  23             span_lint_and_sugg(
  24                 cx,
  25                 SUSPICIOUS_TO_OWNED,
  26                 expr.span,
  27                 &with_forced_trimmed_paths!(format!(
  28                     "this `to_owned` call clones the {input_type} itself and does not cause the {input_type} contents to become owned"
  29                 )),
  30                 "consider using, depending on intent",
  31                 format!("{recv_snip}.clone()` or `{recv_snip}.into_owned()"),
  32                 app,
  33             );
  34             return true;
  35         }
  36     }
  37     false
  38 }