Merge taiki-e#94 taiki-e#96

94: Remove "project_attr" feature and always enable #[project] attribute r=taiki-e a=taiki-e

Closes taiki-e#82

96: Determine the visibility based on the original type r=taiki-e a=taiki-e

The visibility of the projected type and projection method is based on the original type. However, if the visibility of the original type is `pub`, the visibility of the projected type and the projection method is `pub(crate)`.

Closes taiki-e#81


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

Author: bors[bot]

Cargo.toml

@@ -18,8 +18,6 @@ all-features = true
 members = ["pin-project-internal"]
 
 [features]
-# Enable to use `project` attribute.
-project_attr = ["pin-project-internal/project_attr"]
 # Enable to allow using this crate as a renamed dependency
 renamed = ["pin-project-internal/renamed"]
 

examples/pinned_drop-expanded.rs

@@ -33,13 +33,15 @@ pub struct Foo<'a, T> {
 
 #[allow(clippy::mut_mut)]
 #[allow(dead_code)]
-struct __FooProjection<'_pin, 'a, T> {
+pub(crate) struct __FooProjection<'_pin, 'a, T> {
     was_dropped: &'_pin mut &'a mut bool,
     field: ::core::pin::Pin<&'_pin mut T>,
 }
 
 impl<'a, T> Foo<'a, T> {
-    fn project<'_pin>(self: ::core::pin::Pin<&'_pin mut Self>) -> __FooProjection<'_pin, 'a, T> {
+    pub(crate) fn project<'_pin>(
+        self: ::core::pin::Pin<&'_pin mut Self>,
+    ) -> __FooProjection<'_pin, 'a, T> {
         unsafe {
             let Foo { was_dropped, field } = self.get_unchecked_mut();
             __FooProjection {

examples/unsafe_unpin-expanded.rs

@@ -28,13 +28,15 @@ pub struct Foo<T, U> {
 
 #[allow(clippy::mut_mut)]
 #[allow(dead_code)]
-struct __FooProjection<'_pin, T, U> {
+pub(crate) struct __FooProjection<'_pin, T, U> {
     pinned: ::core::pin::Pin<&'_pin mut T>,
     unpinned: &'_pin mut U,
 }
 
 impl<T, U> Foo<T, U> {
-    fn project<'_pin>(self: ::core::pin::Pin<&'_pin mut Self>) -> __FooProjection<'_pin, T, U> {
+    pub(crate) fn project<'_pin>(
+        self: ::core::pin::Pin<&'_pin mut Self>,
+    ) -> __FooProjection<'_pin, T, U> {
         unsafe {
             let Foo { pinned, unpinned } = self.get_unchecked_mut();
             __FooProjection { pinned: ::core::pin::Pin::new_unchecked(pinned), unpinned: unpinned }

pin-project-internal/Cargo.toml

@@ -17,15 +17,13 @@ all-features = true
 proc-macro = true
 
 [features]
-# Enable to use `project` attribute.
-project_attr = ["syn/visit-mut"]
 # Enable to allow using the crate with a renamed 'pin-project' dependency
 renamed = ["proc-macro-crate", "serde", "lazy_static"]
 
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = { version = "1.0", features = ["full"] }
+syn = { version = "1.0", features = ["full", "visit-mut"] }
 
 proc-macro-crate = { version = "0.1.4", optional = true }
 # Required until a new toml-rs release is made with https://github.com/alexcrichton/toml-rs/pull/311,

pin-project-internal/src/lib.rs

@@ -19,7 +19,6 @@ mod utils;
 
 mod pin_project;
 mod pinned_drop;
-#[cfg(feature = "project_attr")]
 mod project;
 
 use proc_macro::TokenStream;
@@ -45,6 +44,10 @@ use syn::parse::Nothing;
 /// # }
 /// ```
 ///
+/// The visibility of the projected type and projection method is based on the
+/// original type. However, if the visibility of the original type is `pub`,
+/// the visibility of the projected type and the projection method is `pub(crate)`.
+///
 /// If you want to call the `project` method multiple times or later use the
 /// original Pin type, it needs to use [`.as_mut()`][`Pin::as_mut`] to avoid
 /// consuming the `Pin`.
@@ -265,30 +268,23 @@ use syn::parse::Nothing;
 ///
 /// ### Enums
 ///
-/// `pin_project` also supports enums, but to use it ergonomically, you need
-/// to use the [`project`] attribute.
-///
-/// *This attribute is only available if pin-project is built
-/// with the `"project_attr"` feature.*
+/// `pin_project` also supports enums, but to use it, you need to use with the
+/// [`project`] attribute.
 ///
 /// The attribute at the expression position is not stable, so you need to use
 /// a dummy `#[project]` attribute for the function.
 ///
 /// ```rust
-/// # #[cfg(feature = "project_attr")]
 /// use pin_project::{project, pin_project};
-/// # #[cfg(feature = "project_attr")]
 /// use std::pin::Pin;
 ///
-/// # #[cfg(feature = "project_attr")]
 /// #[pin_project]
 /// enum Foo<A, B, C> {
 ///     Tuple(#[pin] A, B),
 ///     Struct { field: C },
 ///     Unit,
 /// }
 ///
-/// # #[cfg(feature = "project_attr")]
 /// impl<A, B, C> Foo<A, B, C> {
 ///     #[project] // Nightly does not need a dummy attribute to the function.
 ///     fn baz(self: Pin<&mut Self>) {
@@ -368,9 +364,6 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 // TODO: Move this doc into pin-project crate when https://github.com/rust-lang/rust/pull/62855 merged.
 /// An attribute to provide way to refer to the projected type.
 ///
-/// *This attribute is available if pin-project is built with the
-/// `"project_attr"` feature.*
-///
 /// The following three syntaxes are supported.
 ///
 /// ## `impl` blocks
@@ -479,7 +472,6 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 ///     }
 /// }
 /// ```
-#[cfg(feature = "project_attr")]
 #[proc_macro_attribute]
 pub fn project(args: TokenStream, input: TokenStream) -> TokenStream {
     let _: Nothing = syn::parse_macro_input!(args);

pin-project-internal/src/pin_project/attribute.rs

@@ -7,7 +7,8 @@ use syn::{
 };
 
 use crate::utils::{
-    self, collect_cfg, crate_path, proj_ident, proj_lifetime_name, VecExt, DEFAULT_LIFETIME_NAME,
+    self, collect_cfg, crate_path, determine_visibility, proj_ident, proj_lifetime_name, VecExt,
+    DEFAULT_LIFETIME_NAME,
 };
 
 use super::PIN;
@@ -16,15 +17,15 @@ pub(super) fn parse_attribute(args: TokenStream, mut item: Item) -> Result<Token
     let cx;
     let proj_items = match &mut item {
         Item::Struct(item) => {
-            cx = Context::new(args, &mut item.attrs, &item.ident, &item.generics)?;
+            cx = Context::new(args, &mut item.attrs, &item.ident, &item.vis, &item.generics)?;
 
             let packed_check = ensure_not_packed(&item)?;
             let mut proj_items = cx.parse_struct(item)?;
             proj_items.extend(packed_check);
             proj_items
         }
         Item::Enum(item) => {
-            cx = Context::new(args, &mut item.attrs, &item.ident, &item.generics)?;
+            cx = Context::new(args, &mut item.attrs, &item.ident, &item.vis, &item.generics)?;
 
             // We don't need to check for '#[repr(packed)]',
             // since it does not apply to enums.
@@ -96,6 +97,9 @@ struct Context {
     /// Name of the projected type.
     proj_ident: Ident,
 
+    /// Visibility of the original type.
+    vis: Visibility,
+
     /// Generics of the original type.
     generics: Generics,
 
@@ -114,6 +118,7 @@ impl Context {
         args: TokenStream,
         attrs: &mut Vec<Attribute>,
         orig_ident: &Ident,
+        vis: &Visibility,
         generics: &Generics,
     ) -> Result<Self> {
         let Args { pinned_drop, unsafe_unpin } = syn::parse2(args)?;
@@ -133,6 +138,7 @@ impl Context {
             crate_path,
             orig_ident: orig_ident.clone(),
             proj_ident: proj_ident(orig_ident),
+            vis: determine_visibility(vis),
             generics: generics.clone(),
             lifetime,
             unsafe_unpin,
@@ -258,7 +264,7 @@ impl Context {
 
     /// Creates an implementation of the projection method.
     fn make_proj_impl(&self, proj_body: &TokenStream) -> TokenStream {
-        let Context { proj_ident, orig_ident, lifetime, .. } = &self;
+        let Context { proj_ident, orig_ident, vis, lifetime, .. } = self;
 
         let proj_generics = self.proj_generics();
         let proj_ty_generics = proj_generics.split_for_impl().1;
@@ -267,7 +273,7 @@ impl Context {
 
         quote! {
             impl #impl_generics #orig_ident #ty_generics #where_clause {
-                fn project<#lifetime>(
+                #vis fn project<#lifetime>(
                     self: ::core::pin::Pin<&#lifetime mut Self>,
                 ) -> #proj_ident #proj_ty_generics {
                     unsafe {
@@ -385,14 +391,14 @@ impl Context {
             Fields::Unit => unreachable!(),
         };
 
-        let Context { orig_ident, proj_ident, .. } = &self;
+        let Context { orig_ident, proj_ident, vis, .. } = self;
         let proj_generics = self.proj_generics();
         let where_clause = item.generics.split_for_impl().2;
 
         let mut proj_items = quote! {
             #[allow(clippy::mut_mut)] // This lint warns `&mut &mut <ty>`.
             #[allow(dead_code)] // This lint warns unused fields/variants.
-            struct #proj_ident #proj_generics #where_clause #proj_fields
+            #vis struct #proj_ident #proj_generics #where_clause #proj_fields
         };
 
         let proj_body = quote! {
@@ -410,14 +416,14 @@ impl Context {
 
         let (proj_variants, proj_arms) = self.visit_variants(item)?;
 
-        let proj_ident = &self.proj_ident;
+        let Context { proj_ident, vis, .. } = &self;
         let proj_generics = self.proj_generics();
         let where_clause = item.generics.split_for_impl().2;
 
         let mut proj_items = quote! {
             #[allow(clippy::mut_mut)] // This lint warns `&mut &mut <ty>`.
             #[allow(dead_code)] // This lint warns unused fields/variants.
-            enum #proj_ident #proj_generics #where_clause {
+            #vis enum #proj_ident #proj_generics #where_clause {
                 #(#proj_variants,)*
             }
         };
@@ -466,13 +472,13 @@ impl Context {
         let mut proj_pat = Vec::with_capacity(fields.len());
         let mut proj_body = Vec::with_capacity(fields.len());
         let mut proj_fields = Vec::with_capacity(fields.len());
-        for Field { attrs, ident, ty, .. } in fields {
+        for Field { attrs, vis, ident, ty, .. } in fields {
             let cfg = collect_cfg(attrs);
             if self.find_pin_attr(attrs)? {
                 let lifetime = &self.lifetime;
                 proj_fields.push(quote! {
                     #(#cfg)*
-                    #ident: ::core::pin::Pin<&#lifetime mut #ty>
+                    #vis #ident: ::core::pin::Pin<&#lifetime mut #ty>
                 });
                 proj_body.push(quote! {
                     #(#cfg)*
@@ -482,7 +488,7 @@ impl Context {
                 let lifetime = &self.lifetime;
                 proj_fields.push(quote! {
                     #(#cfg)*
-                    #ident: &#lifetime mut #ty
+                    #vis #ident: &#lifetime mut #ty
                 });
                 proj_body.push(quote! {
                     #(#cfg)*
@@ -508,7 +514,7 @@ impl Context {
         let mut proj_pat = Vec::with_capacity(fields.len());
         let mut proj_body = Vec::with_capacity(fields.len());
         let mut proj_fields = Vec::with_capacity(fields.len());
-        for (i, Field { attrs, ty, .. }) in fields.iter_mut().enumerate() {
+        for (i, Field { attrs, vis, ty, .. }) in fields.iter_mut().enumerate() {
             let id = format_ident!("_x{}", i);
             let cfg = collect_cfg(attrs);
             if !cfg.is_empty() {
@@ -521,15 +527,15 @@ impl Context {
             if self.find_pin_attr(attrs)? {
                 let lifetime = &self.lifetime;
                 proj_fields.push(quote! {
-                    ::core::pin::Pin<&#lifetime mut #ty>
+                    #vis ::core::pin::Pin<&#lifetime mut #ty>
                 });
                 proj_body.push(quote! {
                     ::core::pin::Pin::new_unchecked(#id)
                 });
             } else {
                 let lifetime = &self.lifetime;
                 proj_fields.push(quote! {
-                    &#lifetime mut #ty
+                    #vis &#lifetime mut #ty
                 });
                 proj_body.push(quote! {
                     #id

pin-project-internal/src/utils.rs

@@ -1,4 +1,4 @@
-use quote::format_ident;
+use quote::{format_ident, quote_spanned};
 use syn::{
     punctuated::Punctuated,
     token::{self, Comma},
@@ -12,7 +12,7 @@ pub(crate) fn proj_ident(ident: &Ident) -> Ident {
     format_ident!("__{}Projection", ident)
 }
 
-/// Determine the lifetime names. Ensure it doesn't overlap with any existing lifetime names.
+/// Determines the lifetime names. Ensure it doesn't overlap with any existing lifetime names.
 pub(crate) fn proj_lifetime_name(
     lifetime_name: &mut String,
     generics: &Punctuated<GenericParam, Comma>,
@@ -52,6 +52,18 @@ pub(crate) fn proj_generics(generics: &mut Generics, lifetime: Lifetime) {
     );
 }
 
+/// Determines the visibility of the projected type and projection method.
+pub(crate) fn determine_visibility(vis: &Visibility) -> Visibility {
+    if let Visibility::Public(token) = vis {
+        syn::parse2(quote_spanned! { token.pub_token.span =>
+            pub(crate)
+        })
+        .unwrap()
+    } else {
+        vis.clone()
+    }
+}
+
 pub(crate) fn collect_cfg(attrs: &[Attribute]) -> Vec<Attribute> {
     attrs.iter().filter(|attr| attr.path.is_ident("cfg")).cloned().collect()
 }

src/lib.rs

@@ -57,7 +57,6 @@ pub use pin_project_internal::pin_project;
 #[doc(hidden)]
 pub use pin_project_internal::pinned_drop;
 
-#[cfg(feature = "project_attr")]
 #[doc(hidden)]
 pub use pin_project_internal::project;
 

tests/compiletest.rs

@@ -1,6 +1,5 @@
 #![cfg(compiletest)]
 #![cfg(pin_project_show_unpin_struct)]
-#![cfg(feature = "project_attr")]
 #![warn(rust_2018_idioms, single_use_lifetimes)]
 
 use std::{env, path::PathBuf};

tests/pin_project.rs

@@ -240,10 +240,6 @@ fn combine() {
     unsafe impl<T: Unpin> UnsafeUnpin for Foo<T> {}
 }
 
-// This 'allow' is unrelated to the code
-// generated by pin-project - it's just to
-// allow us to put a private enum in a public enum
-#[allow(private_in_public)]
 #[test]
 fn private_type_in_public_type() {
     #[pin_project]
@@ -253,15 +249,6 @@ fn private_type_in_public_type() {
     }
 
     struct PrivateStruct<T>(T);
-
-    #[pin_project]
-    pub enum PublicEnum {
-        Variant(#[pin] PrivateEnum),
-    }
-
-    enum PrivateEnum {
-        OtherVariant(u8),
-    }
 }
 
 #[test]
@@ -320,3 +307,19 @@ fn lifetime_project() {
         }
     }
 }
+
+mod visibility {
+    use pin_project::pin_project;
+
+    #[pin_project]
+    pub(crate) struct A {
+        pub b: u8,
+    }
+}
+
+#[test]
+fn visibility() {
+    let mut x = visibility::A { b: 0 };
+    let x = Pin::new(&mut x).project();
+    let _: &mut u8 = x.b;
+}