clippy_lints/src/mem_forget.rs

   1 use rustc::lint::*;
   2 use rustc::{declare_lint, lint_array};
   3 use rustc::hir::{Expr, ExprKind};
   4 use crate::utils::{match_def_path, opt_def_id, paths, span_lint};
   5
   6 /// **What it does:** Checks for usage of `std::mem::forget(t)` where `t` is
   7 /// `Drop`.
   8 ///
   9 /// **Why is this bad?** `std::mem::forget(t)` prevents `t` from running its
  10 /// destructor, possibly causing leaks.
  11 ///
  12 /// **Known problems:** None.
  13 ///
  14 /// **Example:**
  15 /// ```rust
  16 /// mem::forget(Rc::new(55)))
  17 /// ```
  18 declare_clippy_lint! {
  19     pub MEM_FORGET,
  20     restriction,
  21     "`mem::forget` usage on `Drop` types, likely to cause memory leaks"
  22 }
  23
  24 pub struct MemForget;
  25
  26 impl LintPass for MemForget {
  27     fn get_lints(&self) -> LintArray {
  28         lint_array![MEM_FORGET]
  29     }
  30 }
  31
  32 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemForget {
  33     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
  34         if let ExprKind::Call(ref path_expr, ref args) = e.node {
  35             if let ExprKind::Path(ref qpath) = path_expr.node {
  36                 if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path_expr.hir_id)) {
  37                     if match_def_path(cx.tcx, def_id, &paths::MEM_FORGET) {
  38                         let forgot_ty = cx.tables.expr_ty(&args[0]);
  39
  40                         if match forgot_ty.ty_adt_def() {
  41                             Some(def) => def.has_dtor(cx.tcx),
  42                             _ => false,
  43                         } {
  44                             span_lint(cx, MEM_FORGET, e.span, "usage of mem::forget on Drop type");
  45                         }
  46                     }
  47                 }
  48             }
  49         }
  50     }
  51 }