move to drop_forget_ref

Author: Centri3

clippy_lints/src/declared_lints.rs

@@ -140,6 +140,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::double_parens::DOUBLE_PARENS_INFO,
     crate::drop_forget_ref::DROP_NON_DROP_INFO,
     crate::drop_forget_ref::FORGET_NON_DROP_INFO,
+    crate::drop_forget_ref::MEM_FORGET_INFO,
     crate::drop_forget_ref::UNDROPPED_MANUALLY_DROPS_INFO,
     crate::duplicate_mod::DUPLICATE_MOD_INFO,
     crate::else_if_without_else::ELSE_IF_WITHOUT_ELSE_INFO,
@@ -310,7 +311,6 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::matches::TRY_ERR_INFO,
     crate::matches::WILDCARD_ENUM_MATCH_ARM_INFO,
     crate::matches::WILDCARD_IN_OR_PATTERNS_INFO,
-    crate::mem_forget::MEM_FORGET_INFO,
     crate::mem_replace::MEM_REPLACE_OPTION_WITH_NONE_INFO,
     crate::mem_replace::MEM_REPLACE_WITH_DEFAULT_INFO,
     crate::mem_replace::MEM_REPLACE_WITH_UNINIT_INFO,

clippy_lints/src/drop_forget_ref.rs

@@ -6,6 +6,7 @@ use rustc_hir::{Arm, Expr, ExprKind, LangItem, Node};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::sym;
+use std::borrow::Cow;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -76,6 +77,27 @@ declare_clippy_lint! {
     "use of safe `std::mem::drop` function to drop a std::mem::ManuallyDrop, which will not drop the inner value"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for usage of `std::mem::forget(t)` where `t` is
+    /// `Drop` or has a field that implements `Drop`.
+    ///
+    /// ### Why is this bad?
+    /// `std::mem::forget(t)` prevents `t` from running its
+    /// destructor, possibly causing leaks.
+    ///
+    /// ### Example
+    /// ```rust
+    /// # use std::mem;
+    /// # use std::rc::Rc;
+    /// mem::forget(Rc::new(55))
+    /// ```
+    #[clippy::version = "pre 1.29.0"]
+    pub MEM_FORGET,
+    restriction,
+    "`mem::forget` usage on `Drop` types, likely to cause memory leaks"
+}
+
 const DROP_NON_DROP_SUMMARY: &str = "call to `std::mem::drop` with a value that does not implement `Drop`. \
                                  Dropping such a type only extends its contained lifetimes";
 const FORGET_NON_DROP_SUMMARY: &str = "call to `std::mem::forget` with a value that does not implement `Drop`. \
@@ -84,7 +106,8 @@ const FORGET_NON_DROP_SUMMARY: &str = "call to `std::mem::forget` with a value t
 declare_lint_pass!(DropForgetRef => [
     DROP_NON_DROP,
     FORGET_NON_DROP,
-    UNDROPPED_MANUALLY_DROPS
+    UNDROPPED_MANUALLY_DROPS,
+    MEM_FORGET,
 ]);
 
 impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
@@ -121,18 +144,29 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
                         || drop_is_single_call_in_arm
                         ) =>
                 {
-                    (DROP_NON_DROP, DROP_NON_DROP_SUMMARY)
-                },
-                sym::mem_forget if !arg_ty.needs_drop(cx.tcx, cx.param_env) => {
-                    (FORGET_NON_DROP, FORGET_NON_DROP_SUMMARY)
+                    (DROP_NON_DROP, DROP_NON_DROP_SUMMARY.into())
                 },
+                sym::mem_forget => {
+                    if arg_ty.needs_drop(cx.tcx, cx.param_env) {
+                        (MEM_FORGET, Cow::Owned(format!(
+                            "usage of `mem::forget` on {}",
+                            if arg_ty.ty_adt_def().map_or(false, |def| def.has_dtor(cx.tcx)) {
+                                "`Drop` type"
+                            } else {
+                                "type with `Drop` fields"
+                            }
+                        )))
+                    } else {
+                        (FORGET_NON_DROP, FORGET_NON_DROP_SUMMARY.into())
+                    }
+                }
                 _ => return,
             };
             span_lint_and_note(
                 cx,
                 lint,
                 expr.span,
-                msg,
+                &msg,
                 Some(arg.span),
                 &format!("argument has type `{arg_ty}`"),
             );

clippy_lints/src/lib.rs

@@ -196,7 +196,6 @@ mod manual_strip;
 mod map_unit_fn;
 mod match_result_ok;
 mod matches;
-mod mem_forget;
 mod mem_replace;
 mod methods;
 mod min_ident_chars;
@@ -744,7 +743,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     let missing_docs_in_crate_items = conf.missing_docs_in_crate_items;
     store.register_late_pass(move |_| Box::new(doc::DocMarkdown::new(doc_valid_idents.clone())));
     store.register_late_pass(|_| Box::new(neg_multiply::NegMultiply));
-    store.register_late_pass(|_| Box::new(mem_forget::MemForget));
     store.register_late_pass(|_| Box::new(let_if_seq::LetIfSeq));
     store.register_late_pass(|_| Box::new(mixed_read_write_in_expression::EvalOrderDependence));
     store.register_late_pass(move |_| Box::new(missing_doc::MissingDoc::new(missing_docs_in_crate_items)));

clippy_lints/src/mem_forget.rs

@@ -4,25 +4,48 @@ error: usage of `mem::forget` on `Drop` type
 LL |     memstuff::forget(six);
    |     ^^^^^^^^^^^^^^^^^^^^^
    |
+note: argument has type `std::sync::Arc<i32>`
+  --> $DIR/mem_forget.rs:14:22
+   |
+LL |     memstuff::forget(six);
+   |                      ^^^
    = note: `-D clippy::mem-forget` implied by `-D warnings`
 
 error: usage of `mem::forget` on `Drop` type
   --> $DIR/mem_forget.rs:17:5
    |
 LL |     std::mem::forget(seven);
    |     ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: argument has type `std::rc::Rc<i32>`
+  --> $DIR/mem_forget.rs:17:22
+   |
+LL |     std::mem::forget(seven);
+   |                      ^^^^^
 
 error: usage of `mem::forget` on `Drop` type
   --> $DIR/mem_forget.rs:20:5
    |
 LL |     forgetSomething(eight);
    |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: argument has type `std::vec::Vec<i32>`
+  --> $DIR/mem_forget.rs:20:21
+   |
+LL |     forgetSomething(eight);
+   |                     ^^^^^
 
 error: usage of `mem::forget` on type with `Drop` fields
   --> $DIR/mem_forget.rs:23:5
    |
 LL |     std::mem::forget(string);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: argument has type `std::string::String`
+  --> $DIR/mem_forget.rs:23:22
+   |
+LL |     std::mem::forget(string);
+   |                      ^^^^^^
 
 error: aborting due to 4 previous errors