clippy_lints/src/types/redundant_allocation.rs

   1 use rustc_errors::Applicability;
   2 use rustc_hir::{self as hir, def_id::DefId, LangItem, QPath, TyKind};
   3 use rustc_lint::LateContext;
   4 use rustc_span::symbol::sym;
   5
   6 use crate::utils::{
   7     get_qpath_generic_tys, is_ty_param_diagnostic_item, is_ty_param_lang_item, snippet_with_applicability,
   8     span_lint_and_sugg,
   9 };
  10
  11 use super::{utils, REDUNDANT_ALLOCATION};
  12
  13 pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, qpath: &QPath<'_>, def_id: DefId) -> bool {
  14     if Some(def_id) == cx.tcx.lang_items().owned_box() {
  15         if let Some(span) = utils::match_borrows_parameter(cx, qpath) {
  16             let mut applicability = Applicability::MachineApplicable;
  17             span_lint_and_sugg(
  18                 cx,
  19                 REDUNDANT_ALLOCATION,
  20                 hir_ty.span,
  21                 "usage of `Box<&T>`",
  22                 "try",
  23                 snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
  24                 applicability,
  25             );
  26             return true;
  27         }
  28     }
  29
  30     if cx.tcx.is_diagnostic_item(sym::Rc, def_id) {
  31         if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::Rc) {
  32             let mut applicability = Applicability::MachineApplicable;
  33             span_lint_and_sugg(
  34                 cx,
  35                 REDUNDANT_ALLOCATION,
  36                 hir_ty.span,
  37                 "usage of `Rc<Rc<T>>`",
  38                 "try",
  39                 snippet_with_applicability(cx, ty.span, "..", &mut applicability).to_string(),
  40                 applicability,
  41             );
  42             true
  43         } else if let Some(ty) = is_ty_param_lang_item(cx, qpath, LangItem::OwnedBox) {
  44             let qpath = match &ty.kind {
  45                 TyKind::Path(qpath) => qpath,
  46                 _ => return false,
  47             };
  48             let inner_span = match get_qpath_generic_tys(qpath).next() {
  49                 Some(ty) => ty.span,
  50                 None => return false,
  51             };
  52             let mut applicability = Applicability::MachineApplicable;
  53             span_lint_and_sugg(
  54                 cx,
  55                 REDUNDANT_ALLOCATION,
  56                 hir_ty.span,
  57                 "usage of `Rc<Box<T>>`",
  58                 "try",
  59                 format!(
  60                     "Rc<{}>",
  61                     snippet_with_applicability(cx, inner_span, "..", &mut applicability)
  62                 ),
  63                 applicability,
  64             );
  65             true
  66         } else if let Some(span) = utils::match_borrows_parameter(cx, qpath) {
  67             let mut applicability = Applicability::MachineApplicable;
  68             span_lint_and_sugg(
  69                 cx,
  70                 REDUNDANT_ALLOCATION,
  71                 hir_ty.span,
  72                 "usage of `Rc<&T>`",
  73                 "try",
  74                 snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
  75                 applicability,
  76             );
  77             true
  78         } else {
  79             false
  80         }
  81     } else {
  82         false
  83     }
  84 }