clippy_lints/src/types/box_vec.rs

   1 use rustc_hir::{self as hir, def_id::DefId, QPath};
   2 use rustc_lint::LateContext;
   3 use rustc_span::symbol::sym;
   4
   5 use crate::utils::{is_ty_param_diagnostic_item, span_lint_and_help};
   6
   7 use super::BOX_VEC;
   8
   9 pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, qpath: &QPath<'_>, def_id: DefId) -> bool {
  10     if Some(def_id) == cx.tcx.lang_items().owned_box() {
  11         if is_ty_param_diagnostic_item(cx, qpath, sym::vec_type).is_some() {
  12             span_lint_and_help(
  13                 cx,
  14                 BOX_VEC,
  15                 hir_ty.span,
  16                 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
  17                 None,
  18                 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation",
  19             );
  20             return true;
  21         }
  22     }
  23     false
  24 }