Merge #244

244: Deprecate project* attributes r=taiki-e a=taiki-e

This deprecates `#[project]`, `#[project_ref]`, and `#[project_replace]` attributes in favor of the naming of projected type.

Closes #225


Co-authored-by: Taiki Endo <te316e89@gmail.com>

CHANGELOG.md

@@ -6,6 +6,33 @@ This project adheres to [Semantic Versioning](https://semver.org).
 
 ## [Unreleased]
 
+* [Deprecated `#[project]`, `#[project_ref]`, and `#[project_replace]` attributes due to some unfixable limitations.][244]
+
+ Consider naming the projected type by passing an argument with the same name as the method to the #[pin_project] attribute instead.
+
+ ```rust
+ use pin_project::pin_project;
+ use std::pin::Pin;
+
+ #[pin_project(project = EnumProj)]
+ enum Enum<T> {
+ Variant(#[pin] T),
+ }
+
+ fn func<T>(x: Pin<&mut Enum<T>>) {
+ match x.project() {
+ EnumProj::Variant(y) => {
+ let _: Pin<&mut T> = y;
+ }
+ }
+ }
+ ```
+
+ See [#225][225] for more details.
+
+[225]: https://github.com/taiki-e/pin-project/pull/225
+[244]: https://github.com/taiki-e/pin-project/pull/244
+
 ## [0.4.20] - 2020-06-07
 
 * [You can now use project_replace argument without Replace argument.][243]

pin-project-internal/build.rs

@@ -9,11 +9,17 @@ fn main() {
  None => return,
  };
 
- // Underscore const names stabilized in Rust 1.37:
- // https://github.com/rust-lang/rust/pull/61347/
+ // Underscore const names requires Rust 1.37:
+ // https://github.com/rust-lang/rust/pull/61347
  if minor >= 37 {
  println!("cargo:rustc-cfg=underscore_consts");
  }
+
+ // #[deprecated] on proc-macro requires Rust 1.40:
+ // https://github.com/rust-lang/rust/pull/65666
+ if minor >= 40 {
+ println!("cargo:rustc-cfg=deprecated_proc_macro");
+ }
 }
 
 fn rustc_minor_version() -> Option<u32> {

pin-project-internal/src/lib.rs

@@ -546,6 +546,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 /// ## Examples
 ///
 /// ```rust
+/// # #![allow(deprecated)]
 /// use pin_project::{pin_project, project};
 /// use std::pin::Pin;
 ///
@@ -576,6 +577,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 /// ## Examples
 ///
 /// ```rust
+/// # #![allow(deprecated)]
 /// use pin_project::{pin_project, project};
 /// use std::pin::Pin;
 ///
@@ -616,6 +618,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 /// ## Examples
 ///
 /// ```rust
+/// # #![allow(deprecated)]
 /// use pin_project::{pin_project, project};
 /// use std::pin::Pin;
 ///
@@ -650,6 +653,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 /// ## Examples
 ///
 /// ```rust
+/// # #![allow(deprecated)]
 /// # mod dox {
 /// use pin_project::pin_project;
 ///
@@ -676,6 +680,16 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 /// }
 /// # }
 /// ```
+#[cfg_attr(
+ deprecated_proc_macro,
+ deprecated(
+ since = "0.4.21",
+ note = "consider naming projected type by passing `project` \
+ argument to #[pin_project] attribute instead, see release note \
+ <https://github.com/taiki-e/pin-project/releases/tag/v0.4.21> \
+ for details"
+ )
+)]
 #[proc_macro_attribute]
 pub fn project(args: TokenStream, input: TokenStream) -> TokenStream {
  let input = syn::parse_macro_input!(input);
@@ -691,6 +705,16 @@ pub fn project(args: TokenStream, input: TokenStream) -> TokenStream {
 /// See [`#[project]`][`project`] attribute for more details.
 ///
 /// [`project`]: ./attr.project.html
+#[cfg_attr(
+ deprecated_proc_macro,
+ deprecated(
+ since = "0.4.21",
+ note = "consider naming projected type by passing `project_ref` \
+ argument to #[pin_project] attribute instead, see release note \
+ <https://github.com/taiki-e/pin-project/releases/tag/v0.4.21> \
+ for details"
+ )
+)]
 #[proc_macro_attribute]
 pub fn project_ref(args: TokenStream, input: TokenStream) -> TokenStream {
  let input = syn::parse_macro_input!(input);
@@ -706,6 +730,16 @@ pub fn project_ref(args: TokenStream, input: TokenStream) -> TokenStream {
 /// See [`#[project]`][`project`] attribute for more details.
 ///
 /// [`project`]: ./attr.project.html
+#[cfg_attr(
+ deprecated_proc_macro,
+ deprecated(
+ since = "0.4.21",
+ note = "consider naming projected type by passing `project_replace` \
+ argument to #[pin_project] attribute instead, see release note \
+ <https://github.com/taiki-e/pin-project/releases/tag/v0.4.21> \
+ for details"
+ )
+)]
 #[proc_macro_attribute]
 pub fn project_replace(args: TokenStream, input: TokenStream) -> TokenStream {
  let input = syn::parse_macro_input!(input);

src/lib.rs

@@ -55,12 +55,15 @@ pub use pin_project_internal::pin_project;
 #[doc(inline)]
 pub use pin_project_internal::pinned_drop;
 
+#[allow(deprecated)]
 #[doc(inline)]
 pub use pin_project_internal::project;
 
+#[allow(deprecated)]
 #[doc(inline)]
 pub use pin_project_internal::project_ref;
 
+#[allow(deprecated)]
 #[doc(inline)]
 pub use pin_project_internal::project_replace;
 

tests/project.rs

@@ -1,5 +1,6 @@
 #![warn(rust_2018_idioms, single_use_lifetimes)]
 #![allow(dead_code)]
+#![allow(deprecated)]
 
 // Ceurrently, `#[attr] if true {}` doesn't even *parse* on MSRV,
 // which means that it will error even behind a `#[rustversion::since(..)]`

tests/project_ref.rs

@@ -1,5 +1,6 @@
 #![warn(rust_2018_idioms, single_use_lifetimes)]
 #![allow(dead_code)]
+#![allow(deprecated)]
 
 use pin_project::{pin_project, project_ref};
 use std::pin::Pin;

tests/project_replace.rs

@@ -1,5 +1,6 @@
 #![warn(rust_2018_idioms, single_use_lifetimes)]
 #![allow(dead_code)]
+#![allow(deprecated)]
 
 use pin_project::{pin_project, project_replace};
 use std::{marker::PhantomData, pin::Pin};

tests/ui/project/ambiguous-let.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)]
+
 use pin_project::{pin_project, project};
 
 #[pin_project]

tests/ui/project/ambiguous-let.stderr

@@ -1,5 +1,5 @@
 error: Both initializer expression and pattern are replaceable, you need to split the initializer expression into separate let bindings to avoid ambiguity
- --> $DIR/ambiguous-let.rs:16:9
+ --> $DIR/ambiguous-let.rs:18:9
  |
-16 | let Struct(x) = match Pin::new(&mut foo).project() {
+18 | let Struct(x) = match Pin::new(&mut foo).project() {
  | ^^^^^^^^^

tests/ui/project/deprecated.rs

@@ -0,0 +1,8 @@
+#![deny(deprecated)]
+
+use pin_project::{project, project_ref, project_replace};
+
+#[project]
+#[project_ref]
+#[project_replace]
+fn main() {}

tests/ui/project/deprecated.stderr

@@ -0,0 +1,23 @@
+error: use of deprecated item 'project': consider naming projected type by passing `project` argument to #[pin_project] attribute instead, see release note <https://github.com/taiki-e/pin-project/releases/tag/v0.4.21> for details
+ --> $DIR/deprecated.rs:5:3
+ |
+5 | #[project]
+ | ^^^^^^^
+ |
+note: the lint level is defined here
+ --> $DIR/deprecated.rs:1:9
+ |
+1 | #![deny(deprecated)]
+ | ^^^^^^^^^^
+
+error: use of deprecated item 'project_ref': consider naming projected type by passing `project_ref` argument to #[pin_project] attribute instead, see release note <https://github.com/taiki-e/pin-project/releases/tag/v0.4.21> for details
+ --> $DIR/deprecated.rs:6:3
+ |
+6 | #[project_ref]
+ | ^^^^^^^^^^^
+
+error: use of deprecated item 'project_replace': consider naming projected type by passing `project_replace` argument to #[pin_project] attribute instead, see release note <https://github.com/taiki-e/pin-project/releases/tag/v0.4.21> for details
+ --> $DIR/deprecated.rs:7:3
+ |
+7 | #[project_replace]
+ | ^^^^^^^^^^^^^^^

tests/ui/project/invalid.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)]
+
 mod argument {
  use pin_project::{pin_project, project};