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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::paths;
   3 use clippy_utils::source::snippet_with_macro_callsite;
   4 use clippy_utils::ty::{is_type_diagnostic_item, match_type};
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_lint::LateContext;
   8 use rustc_middle::ty;
   9 use rustc_span::symbol::{sym, Symbol};
  10
  11 use super::CLONE_ON_REF_PTR;
  12
  13 pub(super) fn check(
  14     cx: &LateContext<'_>,
  15     expr: &hir::Expr<'_>,
  16     method_name: Symbol,
  17     receiver: &hir::Expr<'_>,
  18     args: &[hir::Expr<'_>],
  19 ) {
  20     if !(args.is_empty() && method_name == sym::clone) {
  21         return;
  22     }
  23     let arg = receiver;
  24     let obj_ty = cx.typeck_results().expr_ty(arg).peel_refs();
  25
  26     if let ty::Adt(_, subst) = obj_ty.kind() {
  27         let caller_type = if is_type_diagnostic_item(cx, obj_ty, sym::Rc) {
  28             "Rc"
  29         } else if is_type_diagnostic_item(cx, obj_ty, sym::Arc) {
  30             "Arc"
  31         } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
  32             "Weak"
  33         } else {
  34             return;
  35         };
  36
  37         let snippet = snippet_with_macro_callsite(cx, arg.span, "..");
  38
  39         span_lint_and_sugg(
  40             cx,
  41             CLONE_ON_REF_PTR,
  42             expr.span,
  43             "using `.clone()` on a ref-counted pointer",
  44             "try this",
  45             format!("{}::<{}>::clone(&{})", caller_type, subst.type_at(0), snippet),
  46             Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
  47         );
  48     }
  49 }