Merge pull request #868 from cramertj/master

Add lint for `mem::forget(_)`

CHANGELOG.md

@@ -2,7 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased
-* New lint: [`temporary_cstring_as_ptr`] and [`unsafe_removed_from_name`]
+* New lints: [`temporary_cstring_as_ptr`], [`unsafe_removed_from_name`], and [`mem_forget`]
 
 ## 0.0.63 — 2016-04-08
 * Rustup to *rustc 1.9.0-nightly (7979dd608 2016-04-07)*
@@ -135,6 +135,7 @@ All notable changes to this project will be documented in this file.
 [`match_overlapping_arm`]: https://github.com/Manishearth/rust-clippy/wiki#match_overlapping_arm
 [`match_ref_pats`]: https://github.com/Manishearth/rust-clippy/wiki#match_ref_pats
 [`match_same_arms`]: https://github.com/Manishearth/rust-clippy/wiki#match_same_arms
+[`mem_forget`]: https://github.com/Manishearth/rust-clippy/wiki#mem_forget
 [`min_max`]: https://github.com/Manishearth/rust-clippy/wiki#min_max
 [`modulo_one`]: https://github.com/Manishearth/rust-clippy/wiki#modulo_one
 [`mut_mut`]: https://github.com/Manishearth/rust-clippy/wiki#mut_mut

README.md

@@ -14,7 +14,7 @@ Table of contents:
 * [License](#license)
 
 ##Lints
-There are 143 lints included in this crate:
+There are 144 lints included in this crate:
 
 name                                                                                                                 | default | meaning
 ---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@@ -85,6 +85,7 @@ name
 [match_overlapping_arm](https://github.com/Manishearth/rust-clippy/wiki#match_overlapping_arm)                       | warn    | a match has overlapping arms
 [match_ref_pats](https://github.com/Manishearth/rust-clippy/wiki#match_ref_pats)                                     | warn    | a match or `if let` has all arms prefixed with `&`; the match expression can be dereferenced instead
 [match_same_arms](https://github.com/Manishearth/rust-clippy/wiki#match_same_arms)                                   | warn    | `match` with identical arm bodies
+[mem_forget](https://github.com/Manishearth/rust-clippy/wiki#mem_forget)                                             | allow   | `mem::forget` usage on `Drop` types is likely to cause memory leaks
 [min_max](https://github.com/Manishearth/rust-clippy/wiki#min_max)                                                   | warn    | `min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant
 [modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one)                                             | warn    | taking a number modulo 1, which always returns 0
 [mut_mut](https://github.com/Manishearth/rust-clippy/wiki#mut_mut)                                                   | allow   | usage of double-mut refs, e.g. `&mut &mut ...` (either copy'n'paste error, or shows a fundamental misunderstanding of references)

src/lib.rs

@@ -79,6 +79,7 @@ pub mod lifetimes;
 pub mod loops;
 pub mod map_clone;
 pub mod matches;
+pub mod mem_forget;
 pub mod methods;
 pub mod minmax;
 pub mod misc;
@@ -236,6 +237,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_early_lint_pass(box doc::Doc::new(conf.doc_valid_idents));
     reg.register_late_lint_pass(box neg_multiply::NegMultiply);
     reg.register_late_lint_pass(box unsafe_removed_from_name::UnsafeNameRemoval);
+    reg.register_late_lint_pass(box mem_forget::MemForget);
 
     reg.register_lint_group("clippy_pedantic", vec![
         array_indexing::INDEXING_SLICING,
@@ -243,6 +245,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
         enum_glob_use::ENUM_GLOB_USE,
         if_not_else::IF_NOT_ELSE,
         matches::SINGLE_MATCH_ELSE,
+        mem_forget::MEM_FORGET,
         methods::OPTION_UNWRAP_USED,
         methods::RESULT_UNWRAP_USED,
         methods::WRONG_PUB_SELF_CONVENTION,

src/mem_forget.rs

@@ -0,0 +1,44 @@
+use rustc::lint::*;
+use rustc::hir::{Expr, ExprCall, ExprPath};
+use utils::{match_def_path, paths, span_lint};
+
+/// **What it does:** This lint checks for usage of `std::mem::forget(t)` where `t` is `Drop`.
+///
+/// **Why is this bad?** `std::mem::forget(t)` prevents `t` from running its destructor, possibly causing leaks
+///
+/// **Known problems:** None.
+///
+/// **Example:** `mem::forget(Rc::new(55)))`
+declare_lint! {
+    pub MEM_FORGET,
+    Allow,
+    "`mem::forget` usage on `Drop` types is likely to cause memory leaks"
+}
+
+pub struct MemForget;
+
+impl LintPass for MemForget {
+    fn get_lints(&self) -> LintArray {
+        lint_array![MEM_FORGET]
+    }
+}
+
+impl LateLintPass for MemForget {
+    fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
+        if let ExprCall(ref path_expr, ref args) = e.node {
+            if let ExprPath(None, _) = path_expr.node {
+                let def_id = cx.tcx.def_map.borrow()[&path_expr.id].def_id();
+                if match_def_path(cx, def_id, &paths::MEM_FORGET) {
+                    let forgot_ty = cx.tcx.expr_ty(&args[0]);
+
+                    if match forgot_ty.ty_adt_def() {
+                        Some(def) => def.has_dtor(),
+                        _ => false
+                    } {
+                        span_lint(cx, MEM_FORGET, e.span, "usage of mem::forget on Drop type");
+                    }
+                }
+            }
+        }
+    }
+}

src/utils/paths.rs

@@ -20,6 +20,7 @@ pub const HASHMAP: [&'static str; 5] = ["std", "collections", "hash", "map", "Ha
 pub const HASH: [&'static str; 2] = ["hash", "Hash"];
 pub const IO_PRINT: [&'static str; 3] = ["std", "io", "_print"];
 pub const LINKED_LIST: [&'static str; 3] = ["collections", "linked_list", "LinkedList"];
+pub const MEM_FORGET: [&'static str; 3] = ["core", "mem", "forget"];
 pub const MUTEX: [&'static str; 4] = ["std", "sync", "mutex", "Mutex"];
 pub const OPEN_OPTIONS: [&'static str; 3] = ["std", "fs", "OpenOptions"];
 pub const OPTION: [&'static str; 3] = ["core", "option", "Option"];

tests/compile-fail/mem_forget.rs

@@ -0,0 +1,28 @@
+#![feature(plugin)]
+#![plugin(clippy)]
+
+use std::sync::Arc;
+use std::rc::Rc;
+
+use std::mem::forget as forgetSomething;
+use std::mem as memstuff;
+
+#[deny(mem_forget)]
+fn main() {
+    let five: i32 = 5;
+    forgetSomething(five);
+
+    let six: Arc<i32> = Arc::new(6);
+    memstuff::forget(six);
+    //~^ ERROR usage of mem::forget on Drop type
+
+    let seven: Rc<i32> = Rc::new(7);
+    std::mem::forget(seven);
+    //~^ ERROR usage of mem::forget on Drop type
+
+    let eight: Vec<i32> = vec![8];
+    forgetSomething(eight);
+    //~^ ERROR usage of mem::forget on Drop type
+
+    std::mem::forget(7);
+}