src/tools/clippy/clippy_lints/src/mem_forget.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use rustc_hir::{Expr, ExprKind};
   3 use rustc_lint::{LateContext, LateLintPass};
   4 use rustc_session::{declare_lint_pass, declare_tool_lint};
   5 use rustc_span::sym;
   6
   7 declare_clippy_lint! {
   8     /// ### What it does
   9     /// Checks for usage of `std::mem::forget(t)` where `t` is
  10     /// `Drop`.
  11     ///
  12     /// ### Why is this bad?
  13     /// `std::mem::forget(t)` prevents `t` from running its
  14     /// destructor, possibly causing leaks.
  15     ///
  16     /// ### Example
  17     /// ```rust
  18     /// # use std::mem;
  19     /// # use std::rc::Rc;
  20     /// mem::forget(Rc::new(55))
  21     /// ```
  22     #[clippy::version = "pre 1.29.0"]
  23     pub MEM_FORGET,
  24     restriction,
  25     "`mem::forget` usage on `Drop` types, likely to cause memory leaks"
  26 }
  27
  28 declare_lint_pass!(MemForget => [MEM_FORGET]);
  29
  30 impl<'tcx> LateLintPass<'tcx> for MemForget {
  31     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
  32         if let ExprKind::Call(path_expr, [ref first_arg, ..]) = e.kind {
  33             if let ExprKind::Path(ref qpath) = path_expr.kind {
  34                 if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id() {
  35                     if cx.tcx.is_diagnostic_item(sym::mem_forget, def_id) {
  36                         let forgot_ty = cx.typeck_results().expr_ty(first_arg);
  37
  38                         if forgot_ty.ty_adt_def().map_or(false, |def| def.has_dtor(cx.tcx)) {
  39                             span_lint(cx, MEM_FORGET, e.span, "usage of `mem::forget` on `Drop` type");
  40                         }
  41                     }
  42                 }
  43             }
  44         }
  45     }
  46 }