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) {
  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;
  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         } else if let Some(ty) = is_ty_param_lang_item(cx, qpath, LangItem::OwnedBox) {
  43             let qpath = match &ty.kind {
  44                 TyKind::Path(qpath) => qpath,
  45                 _ => return,
  46             };
  47             let inner_span = match get_qpath_generic_tys(qpath).next() {
  48                 Some(ty) => ty.span,
  49                 None => return,
  50             };
  51             let mut applicability = Applicability::MachineApplicable;
  52             span_lint_and_sugg(
  53                 cx,
  54                 REDUNDANT_ALLOCATION,
  55                 hir_ty.span,
  56                 "usage of `Rc<Box<T>>`",
  57                 "try",
  58                 format!(
  59                     "Rc<{}>",
  60                     snippet_with_applicability(cx, inner_span, "..", &mut applicability)
  61                 ),
  62                 applicability,
  63             );
  64         } else if let Some(span) = utils::match_borrows_parameter(cx, qpath) {
  65             let mut applicability = Applicability::MachineApplicable;
  66             span_lint_and_sugg(
  67                 cx,
  68                 REDUNDANT_ALLOCATION,
  69                 hir_ty.span,
  70                 "usage of `Rc<&T>`",
  71                 "try",
  72                 snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
  73                 applicability,
  74             );
  75             return; // don't recurse into the type
  76         }
  77     }
  78 }