From c208c8c8e6eeec6f0e1fc1105271692e586be755 Mon Sep 17 00:00:00 2001
From: Taiki Endo <te316e89@gmail.com>
Date: Mon, 11 May 2020 09:17:40 +0900
Subject: [PATCH] Prevent user call `__drop_inner`

---
 examples/pinned_drop-expanded.rs                      |  3 +++
 pin-project-internal/src/pinned_drop.rs               | 11 +++++++----
 .../expand/tests/expand/pinned_drop-enum.expanded.rs  |  1 +
 .../tests/expand/pinned_drop-struct.expanded.rs       |  1 +
 .../tests/expand/pinned_drop-tuple_struct.expanded.rs |  1 +
 5 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/examples/pinned_drop-expanded.rs b/examples/pinned_drop-expanded.rs
index 9bee33bc..583bf111 100644
--- a/examples/pinned_drop-expanded.rs
+++ b/examples/pinned_drop-expanded.rs
@@ -142,6 +142,9 @@ impl<T> ::pin_project::__private::PinnedDrop for Struct<'_, T> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]
         fn __drop_inner<T>(__self: Pin<&mut Struct<'_, T>>) {
+            // Added `__drop_inner` function to prevent user call outer `__drop_inner`.
+            fn __drop_inner() {}
+
             **__self.project().was_dropped = true;
         }
         __drop_inner(self);
diff --git a/pin-project-internal/src/pinned_drop.rs b/pin-project-internal/src/pinned_drop.rs
index 8a6f18d8..ebe79ffe 100644
--- a/pin-project-internal/src/pinned_drop.rs
+++ b/pin-project-internal/src/pinned_drop.rs
@@ -53,10 +53,10 @@ fn parse_method(method: &ImplItemMethod) -> Result<()> {
     match method.sig.inputs.len() {
         1 => {}
         0 => return Err(Error::new(method.sig.paren_token.span, INVALID_ARGUMENT)),
-        _ => return Err(error!(&method.sig.inputs, INVALID_ARGUMENT)),
+        _ => return Err(error!(method.sig.inputs, INVALID_ARGUMENT)),
     }
 
-    if let Some(FnArg::Typed(pat)) = &method.sig.receiver() {
+    if let Some(FnArg::Typed(pat)) = method.sig.receiver() {
         // (mut) self: <path>
         if let Some(path) = get_ty_path(&pat.ty) {
             let ty = path.segments.last().unwrap();
@@ -149,6 +149,7 @@ fn parse(item: &mut ItemImpl) -> Result<()> {
 //
 // unsafe fn drop(self: Pin<&mut Self>) {
 //     fn __drop_inner<T>(__self: Pin<&mut Foo<'_, T>>) {
+//         fn __drop_inner() {}
 //         // something
 //     }
 //     __drop_inner(self);
@@ -160,14 +161,16 @@ fn expand_item(item: &mut ItemImpl) {
     let mut drop_inner = method.clone();
 
     // `fn drop(mut self: Pin<&mut Self>)` -> `fn __drop_inner<T>(mut __self: Pin<&mut Receiver>)`
-    drop_inner.sig.ident = Ident::new("__drop_inner", drop_inner.sig.ident.span());
+    let ident = Ident::new("__drop_inner", drop_inner.sig.ident.span());
+    // Add `__drop_inner` function to prevent user call outer `__drop_inner`.
+    drop_inner.block.stmts.insert(0, parse_quote!(fn #ident() {}));
+    drop_inner.sig.ident = ident;
     drop_inner.sig.generics = item.generics.clone();
     if let FnArg::Typed(arg) = &mut drop_inner.sig.inputs[0] {
         if let Pat::Ident(ident) = &mut *arg.pat {
             prepend_underscore_to_self(&mut ident.ident);
         }
     }
-
     let mut visitor = ReplaceReceiver(&item.self_ty);
     visitor.visit_signature_mut(&mut drop_inner.sig);
     visitor.visit_block_mut(&mut drop_inner.block);
diff --git a/tests/expand/tests/expand/pinned_drop-enum.expanded.rs b/tests/expand/tests/expand/pinned_drop-enum.expanded.rs
index d445f5f0..f29a9dc3 100644
--- a/tests/expand/tests/expand/pinned_drop-enum.expanded.rs
+++ b/tests/expand/tests/expand/pinned_drop-enum.expanded.rs
@@ -105,6 +105,7 @@ impl<T, U> ::pin_project::__private::PinnedDrop for Enum<T, U> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]
         fn __drop_inner<T, U>(__self: Pin<&mut Enum<T, U>>) {
+            fn __drop_inner() {}
             let _this = __self;
         }
         __drop_inner(self);
diff --git a/tests/expand/tests/expand/pinned_drop-struct.expanded.rs b/tests/expand/tests/expand/pinned_drop-struct.expanded.rs
index b103d095..ec43e13b 100644
--- a/tests/expand/tests/expand/pinned_drop-struct.expanded.rs
+++ b/tests/expand/tests/expand/pinned_drop-struct.expanded.rs
@@ -82,6 +82,7 @@ impl<T, U> ::pin_project::__private::PinnedDrop for Struct<T, U> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]
         fn __drop_inner<T, U>(__self: Pin<&mut Struct<T, U>>) {
+            fn __drop_inner() {}
             let _this = __self;
         }
         __drop_inner(self);
diff --git a/tests/expand/tests/expand/pinned_drop-tuple_struct.expanded.rs b/tests/expand/tests/expand/pinned_drop-tuple_struct.expanded.rs
index 1d9dbfb0..1177dd6f 100644
--- a/tests/expand/tests/expand/pinned_drop-tuple_struct.expanded.rs
+++ b/tests/expand/tests/expand/pinned_drop-tuple_struct.expanded.rs
@@ -73,6 +73,7 @@ impl<T, U> ::pin_project::__private::PinnedDrop for TupleStruct<T, U> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]
         fn __drop_inner<T, U>(__self: Pin<&mut TupleStruct<T, U>>) {
+            fn __drop_inner() {}
             let _this = __self;
         }
         __drop_inner(self);