Auto merge of #11129 - c410-f3r:lock-1, r=Manishearth

[significant_drop_tightening] Fix #11128

Fix #11128

```
changelog: [`significant_drop_tightening`]: Consider manual alias of the `drop` function.
```

Author: bors

clippy_lints/src/significant_drop_tightening.rs

@@ -7,11 +7,13 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_errors::Applicability;
 use rustc_hir::{
     self as hir,
+    def::{DefKind, Res},
     intravisit::{walk_expr, Visitor},
 };
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::ty::{subst::GenericArgKind, Ty, TypeAndMut};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::sym;
 use rustc_span::{symbol::Ident, Span, DUMMY_SP};
 use std::borrow::Cow;
 
@@ -333,7 +335,7 @@ impl<'ap, 'lc, 'others, 'stmt, 'tcx> Visitor<'tcx> for StmtsChecker<'ap, 'lc, 'o
                         }
                     },
                     hir::StmtKind::Semi(expr) => {
-                        if has_drop(expr, &apa.first_bind_ident) {
+                        if has_drop(expr, &apa.first_bind_ident, self.cx) {
                             apa.has_expensive_expr_after_last_attr = false;
                             apa.last_stmt_span = DUMMY_SP;
                             return;
@@ -430,11 +432,11 @@ fn dummy_stmt_expr<'any>(expr: &'any hir::Expr<'any>) -> hir::Stmt<'any> {
     }
 }
 
-fn has_drop(expr: &hir::Expr<'_>, first_bind_ident: &Ident) -> bool {
+fn has_drop(expr: &hir::Expr<'_>, first_bind_ident: &Ident, lcx: &LateContext<'_>) -> bool {
     if let hir::ExprKind::Call(fun, args) = expr.kind
         && let hir::ExprKind::Path(hir::QPath::Resolved(_, fun_path)) = &fun.kind
-        && let [fun_ident, ..] = fun_path.segments
-        && fun_ident.ident.name == rustc_span::sym::drop
+        && let Res::Def(DefKind::Fn, did) = fun_path.res
+        && lcx.tcx.is_diagnostic_item(sym::mem_drop, did)
         && let [first_arg, ..] = args
         && let hir::ExprKind::Path(hir::QPath::Resolved(_, arg_path)) = &first_arg.kind
         && let [first_arg_ps, .. ] = arg_path.segments

tests/ui/significant_drop_tightening.fixed

@@ -28,6 +28,29 @@ pub fn issue_10413() {
     }
 }
 
+pub fn issue_11128() {
+    use std::mem::drop as unlock;
+
+    struct Foo {
+        droppable: Option<Vec<i32>>,
+        mutex: Mutex<Vec<i32>>,
+    }
+
+    impl Drop for Foo {
+        fn drop(&mut self) {
+            if let Some(droppable) = self.droppable.take() {
+                let lock = self.mutex.lock().unwrap();
+                let idx_opt = lock.iter().copied().find(|el| Some(el) == droppable.first());
+                if let Some(idx) = idx_opt {
+                    let local_droppable = vec![lock.first().copied().unwrap_or_default()];
+                    unlock(lock);
+                    drop(local_droppable);
+                }
+            }
+        }
+    }
+}
+
 pub fn path_return_can_be_ignored() -> i32 {
     let mutex = Mutex::new(1);
     let lock = mutex.lock().unwrap();

tests/ui/significant_drop_tightening.rs

@@ -27,6 +27,29 @@ pub fn issue_10413() {
     }
 }
 
+pub fn issue_11128() {
+    use std::mem::drop as unlock;
+
+    struct Foo {
+        droppable: Option<Vec<i32>>,
+        mutex: Mutex<Vec<i32>>,
+    }
+
+    impl Drop for Foo {
+        fn drop(&mut self) {
+            if let Some(droppable) = self.droppable.take() {
+                let lock = self.mutex.lock().unwrap();
+                let idx_opt = lock.iter().copied().find(|el| Some(el) == droppable.first());
+                if let Some(idx) = idx_opt {
+                    let local_droppable = vec![lock.first().copied().unwrap_or_default()];
+                    unlock(lock);
+                    drop(local_droppable);
+                }
+            }
+        }
+    }
+}
+
 pub fn path_return_can_be_ignored() -> i32 {
     let mutex = Mutex::new(1);
     let lock = mutex.lock().unwrap();

tests/ui/significant_drop_tightening.stderr

@@ -23,7 +23,7 @@ LL +     drop(lock);
    |
 
 error: temporary with significant `Drop` can be early dropped
-  --> $DIR/significant_drop_tightening.rs:56:13
+  --> $DIR/significant_drop_tightening.rs:79:13
    |
 LL | /     {
 LL | |         let mutex = Mutex::new(1i32);
@@ -43,7 +43,7 @@ LL +         drop(lock);
    |
 
 error: temporary with significant `Drop` can be early dropped
-  --> $DIR/significant_drop_tightening.rs:77:13
+  --> $DIR/significant_drop_tightening.rs:100:13
    |
 LL | /     {
 LL | |         let mutex = Mutex::new(1i32);
@@ -67,7 +67,7 @@ LL +
    |
 
 error: temporary with significant `Drop` can be early dropped
-  --> $DIR/significant_drop_tightening.rs:83:17
+  --> $DIR/significant_drop_tightening.rs:106:17
    |
 LL | /     {
 LL | |         let mutex = Mutex::new(vec![1i32]);