clippy_lints/src/mem_forget.rs

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