clippy_lints/src/mem_forget.rs

   1 use crate::utils::{match_def_path, paths, qpath_res, span_lint};
   2 use rustc::lint::{LateContext, LateLintPass};
   3 use rustc_hir::{Expr, ExprKind};
   4 use rustc_session::{declare_lint_pass, declare_tool_lint};
   5
   6 declare_clippy_lint! {
   7     /// **What it does:** Checks for usage of `std::mem::forget(t)` where `t` is
   8     /// `Drop`.
   9     ///
  10     /// **Why is this bad?** `std::mem::forget(t)` prevents `t` from running its
  11     /// destructor, possibly causing leaks.
  12     ///
  13     /// **Known problems:** None.
  14     ///
  15     /// **Example:**
  16     /// ```rust
  17     /// # use std::mem;
  18     /// # use std::rc::Rc;
  19     /// mem::forget(Rc::new(55))
  20     /// ```
  21     pub MEM_FORGET,
  22     restriction,
  23     "`mem::forget` usage on `Drop` types, likely to cause memory leaks"
  24 }
  25
  26 declare_lint_pass!(MemForget => [MEM_FORGET]);
  27
  28 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemForget {
  29     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) {
  30         if let ExprKind::Call(ref path_expr, ref args) = e.kind {
  31             if let ExprKind::Path(ref qpath) = path_expr.kind {
  32                 if let Some(def_id) = qpath_res(cx, qpath, path_expr.hir_id).opt_def_id() {
  33                     if match_def_path(cx, def_id, &paths::MEM_FORGET) {
  34                         let forgot_ty = cx.tables.expr_ty(&args[0]);
  35
  36                         if forgot_ty.ty_adt_def().map_or(false, |def| def.has_dtor(cx.tcx)) {
  37                             span_lint(cx, MEM_FORGET, e.span, "usage of `mem::forget` on `Drop` type");
  38                         }
  39                     }
  40                 }
  41             }
  42         }
  43     }
  44 }