taiki-e · bors · Apr 13, 2021 · Apr 13, 2021 · Apr 13, 2021
diff --git a/pin-project-internal/src/pin_project/derive.rs b/pin-project-internal/src/pin_project/derive.rs
@@ -3,7 +3,7 @@ use quote::{format_ident, quote, quote_spanned, ToTokens};
 use syn::{
     parse_quote, token, visit_mut::VisitMut, Attribute, Data, DataEnum, DeriveInput, Error, Field,
     Fields, FieldsNamed, FieldsUnnamed, Generics, Ident, Index, Lifetime, LifetimeDef, Meta,
-    MetaList, NestedMeta, Result, Token, Type, Variant, Visibility, WhereClause,
+    MetaList, MetaNameValue, NestedMeta, Result, Token, Type, Variant, Visibility, WhereClause,
 };
 
 use super::{
@@ -326,7 +326,7 @@ fn parse_struct<'a>(
     generate: &mut GenerateTokens,
 ) -> Result<()> {
     // Do this first for a better error message.
-    let packed_check = ensure_not_packed(&cx.orig, fields)?;
+    let packed_check = ensure_not_packed(&cx.orig, Some(fields))?;
 
     validate_struct(cx.orig.ident, fields)?;
 
@@ -414,8 +414,12 @@ fn parse_enum<'a>(
         ));
     }
 
-    // We don't need to check for `#[repr(packed)]`,
-    // since it does not apply to enums.
+    // #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
+    // However, we should not rely on the behavior of rustc that rejects this.
+    // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
+    //
+    // Do this first for a better error message.
+    ensure_not_packed(&cx.orig, None)?;
 
     validate_enum(*brace_token, variants)?;
 
@@ -996,28 +1000,45 @@ fn make_proj_impl(
 /// * Checks the attributes of structs to ensure there is no `[repr(packed)]`.
 /// * Generates a function that borrows fields without an unsafe block and
 ///   forbidding `unaligned_references` lint.
-fn ensure_not_packed(orig: &OriginalType<'_>, fields: &Fields) -> Result<TokenStream> {
+fn ensure_not_packed(orig: &OriginalType<'_>, fields: Option<&Fields>) -> Result<TokenStream> {
     for meta in orig.attrs.iter().filter_map(|attr| attr.parse_meta().ok()) {
         if let Meta::List(list) = meta {
             if list.path.is_ident("repr") {
                 for repr in list.nested.iter() {
                     match repr {
                         NestedMeta::Meta(Meta::Path(path))
                         | NestedMeta::Meta(Meta::List(MetaList { path, .. }))
-                            if path.is_ident("packed") =>
-                        {
-                            return Err(error!(
-                                repr,
-                                "#[pin_project] attribute may not be used on #[repr(packed)] types"
-                            ));
+                        | NestedMeta::Meta(Meta::NameValue(MetaNameValue { path, .. })) => {
+                            if path.is_ident("packed") {
+                                let msg = if fields.is_none() {
+                                    // #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
+                                    // However, we should not rely on the behavior of rustc that rejects this.
+                                    // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
+                                    "#[repr(packed)] attribute should be applied to a struct or union"
+                                } else if let NestedMeta::Meta(Meta::NameValue(..)) = repr {
+                                    // #[repr(packed = "")] is not valid format of #[repr(packed)] and will be
+                                    // rejected by rustc.
+                                    // However, we should not rely on the behavior of rustc that rejects this.
+                                    // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
+                                    "#[repr(packed)] attribute should not be name-value pair"
+                                } else {
+                                    "#[pin_project] attribute may not be used on #[repr(packed)] types"
+                                };
+                                return Err(error!(repr, msg));
+                            }
                         }
-                        _ => {}
+                        NestedMeta::Lit(..) => {}
                     }
                 }
             }
         }
     }
 
+    let fields = match fields {
+        Some(fields) => fields,
+        None => return Ok(TokenStream::new()),
+    };
+
     // Workaround for https://github.com/taiki-e/pin-project/issues/32
     // Through the tricky use of proc macros, it's possible to bypass
     // the above check for the `repr` attribute.

diff --git a/tests/ui/cfg/packed_sneaky-span-issue-1.rs b/tests/ui/cfg/packed_sneaky-span-issue-1.rs
@@ -2,9 +2,8 @@ use auxiliary_macro::hidden_repr;
 use pin_project::pin_project;
 
 #[pin_project]
-#[hidden_repr(packed)]
+#[hidden_repr(packed)] //~ ERROR may not be used on #[repr(packed)] types
 struct S {
-    //~^ ERROR may not be used on #[repr(packed)] types
     #[cfg(not(any()))]
     #[pin]
     f: u32,

diff --git a/tests/ui/cfg/packed_sneaky-span-issue-1.stderr b/tests/ui/cfg/packed_sneaky-span-issue-1.stderr
@@ -1,11 +1,5 @@
 error: #[pin_project] attribute may not be used on #[repr(packed)] types
-  --> $DIR/packed_sneaky-span-issue-1.rs:6:1
-   |
-6  | / struct S {
-7  | |     //~^ ERROR may not be used on #[repr(packed)] types
-8  | |     #[cfg(not(any()))]
-9  | |     #[pin]
-...  |
-13 | |     f: u8,
-14 | | }
-   | |_^
+ --> $DIR/packed_sneaky-span-issue-1.rs:5:15
+  |
+5 | #[hidden_repr(packed)] //~ ERROR may not be used on #[repr(packed)] types
+  |               ^^^^^^
diff --git a/tests/ui/cfg/packed_sneaky-span-issue-2.rs b/tests/ui/cfg/packed_sneaky-span-issue-2.rs
@@ -2,9 +2,8 @@ use auxiliary_macro::hidden_repr;
 use pin_project::pin_project;
 
 #[pin_project]
-#[hidden_repr(packed)]
+#[hidden_repr(packed)] //~ ERROR may not be used on #[repr(packed)] types
 struct S {
-    //~^ ERROR may not be used on #[repr(packed)] types
     #[cfg(any())]
     #[pin]
     f: u32,

diff --git a/tests/ui/cfg/packed_sneaky-span-issue-2.stderr b/tests/ui/cfg/packed_sneaky-span-issue-2.stderr
@@ -1,11 +1,5 @@
 error: #[pin_project] attribute may not be used on #[repr(packed)] types
-  --> $DIR/packed_sneaky-span-issue-2.rs:6:1
-   |
-6  | / struct S {
-7  | |     //~^ ERROR may not be used on #[repr(packed)] types
-8  | |     #[cfg(any())]
-9  | |     #[pin]
-...  |
-13 | |     f: u8,
-14 | | }
-   | |_^
+ --> $DIR/packed_sneaky-span-issue-2.rs:5:15
+  |
+5 | #[hidden_repr(packed)] //~ ERROR may not be used on #[repr(packed)] types
+  |               ^^^^^^
diff --git a/tests/ui/cfg/unsupported.stderr b/tests/ui/cfg/unsupported.stderr
@@ -1,7 +1,8 @@
 error: #[pin_project] attribute may not be used on structs with zero fields
- --> $DIR/unsupported.rs:4:1
+ --> $DIR/unsupported.rs:4:10
   |
-4 | / struct S {
+4 |   struct S {
+  |  __________^
 5 | |     //~^ ERROR may not be used on structs with zero fields
 6 | |     #[cfg(any())]
 7 | |     #[pin]

diff --git a/tests/ui/not_unpin/conflict-unpin.stderr b/tests/ui/not_unpin/conflict-unpin.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Foo<_, _>`:
+error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Foo<_, _>`
   --> $DIR/conflict-unpin.rs:3:15
    |
 3  | #[pin_project(!Unpin)] //~ ERROR E0119
@@ -7,7 +7,7 @@ error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type
 10 | impl<T, U> Unpin for Foo<T, U> where T: Unpin {}
    | --------------------------------------------- first implementation here
 
-error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Bar<_, _>`:
+error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Bar<_, _>`
   --> $DIR/conflict-unpin.rs:12:15
    |
 12 | #[pin_project(!Unpin)] //~ ERROR E0119
@@ -16,7 +16,7 @@ error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type
 19 | impl<T, U> Unpin for Bar<T, U> {}
    | ------------------------------ first implementation here
 
-error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Baz<_, _>`:
+error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Baz<_, _>`
   --> $DIR/conflict-unpin.rs:21:15
    |
 21 | #[pin_project(!Unpin)] //~ ERROR E0119

diff --git a/tests/ui/not_unpin/impl-unsafe-unpin.stderr b/tests/ui/not_unpin/impl-unsafe-unpin.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Foo<_, _>`:
+error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Foo<_, _>`
   --> $DIR/impl-unsafe-unpin.rs:3:1
    |
 3  | #[pin_project(!Unpin)] //~ ERROR E0119
@@ -9,7 +9,7 @@ error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` fo
    |
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Bar<_, _>`:
+error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Bar<_, _>`
   --> $DIR/impl-unsafe-unpin.rs:12:1
    |
 12 | #[pin_project(!Unpin)] //~ ERROR E0119
@@ -20,7 +20,7 @@ error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` fo
    |
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Baz<_, _>`:
+error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Baz<_, _>`
   --> $DIR/impl-unsafe-unpin.rs:21:1
    |
 21 | #[pin_project(!Unpin)] //~ ERROR E0119

diff --git a/tests/ui/pin_project/add-pinned-field.stderr b/tests/ui/pin_project/add-pinned-field.stderr
@@ -7,7 +7,12 @@ error[E0277]: `PhantomPinned` cannot be unpinned
 21 |     is_unpin::<Foo>(); //~ ERROR E0277
    |     ^^^^^^^^^^^^^^^ within `__Foo<'_>`, the trait `Unpin` is not implemented for `PhantomPinned`
    |
-   = note: required because it appears within the type `__Foo<'_>`
+   = note: consider using `Box::pin`
+note: required because it appears within the type `__Foo<'_>`
+  --> $DIR/add-pinned-field.rs:8:8
+   |
+8  | struct Foo {
+   |        ^^^
    = note: required because of the requirements on the impl of `Unpin` for `Foo`
 
 error[E0277]: `PhantomPinned` cannot be unpinned
@@ -19,5 +24,10 @@ error[E0277]: `PhantomPinned` cannot be unpinned
 22 |     is_unpin::<Bar>(); //~ ERROR E0277
    |     ^^^^^^^^^^^^^^^ within `__Bar<'_>`, the trait `Unpin` is not implemented for `PhantomPinned`
    |
-   = note: required because it appears within the type `__Bar<'_>`
+   = note: consider using `Box::pin`
+note: required because it appears within the type `__Bar<'_>`
+  --> $DIR/add-pinned-field.rs:15:8
+   |
+15 | struct Bar {
+   |        ^^^
    = note: required because of the requirements on the impl of `Unpin` for `Bar`
diff --git a/tests/ui/pin_project/conflict-drop.stderr b/tests/ui/pin_project/conflict-drop.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `_::FooMustNotImplDrop` for type `Foo<_, _>`:
+error[E0119]: conflicting implementations of trait `_::FooMustNotImplDrop` for type `Foo<_, _>`
  --> $DIR/conflict-drop.rs:5:1
   |
 5 | #[pin_project] //~ ERROR E0119
@@ -9,7 +9,7 @@ error[E0119]: conflicting implementations of trait `_::FooMustNotImplDrop` for t
   |
   = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `std::ops::Drop` for type `Bar<_, _>`:
+error[E0119]: conflicting implementations of trait `std::ops::Drop` for type `Bar<_, _>`
   --> $DIR/conflict-drop.rs:16:15
    |
 16 | #[pin_project(PinnedDrop)] //~ ERROR E0119

diff --git a/tests/ui/pin_project/conflict-unpin.stderr b/tests/ui/pin_project/conflict-unpin.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Foo<_, _>`:
+error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Foo<_, _>`
   --> $DIR/conflict-unpin.rs:5:1
    |
 5  | #[pin_project] //~ ERROR E0119
@@ -9,7 +9,7 @@ error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type
    |
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Bar<_, _>`:
+error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Bar<_, _>`
   --> $DIR/conflict-unpin.rs:17:1
    |
 17 | #[pin_project] //~ ERROR E0119
@@ -20,7 +20,7 @@ error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type
    |
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Baz<_, _>`:
+error[E0119]: conflicting implementations of trait `std::marker::Unpin` for type `Baz<_, _>`
   --> $DIR/conflict-unpin.rs:27:1
    |
 27 | #[pin_project] //~ ERROR E0119

diff --git a/tests/ui/pin_project/impl-unsafe-unpin.stderr b/tests/ui/pin_project/impl-unsafe-unpin.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Foo<_, _>`:
+error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Foo<_, _>`
   --> $DIR/impl-unsafe-unpin.rs:3:1
    |
 3  | #[pin_project] //~ ERROR E0119
@@ -9,7 +9,7 @@ error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` fo
    |
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Bar<_, _>`:
+error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Bar<_, _>`
   --> $DIR/impl-unsafe-unpin.rs:12:1
    |
 12 | #[pin_project] //~ ERROR E0119
@@ -20,7 +20,7 @@ error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` fo
    |
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Baz<_, _>`:
+error[E0119]: conflicting implementations of trait `pin_project::UnsafeUnpin` for type `Baz<_, _>`
   --> $DIR/impl-unsafe-unpin.rs:21:1
    |
 21 | #[pin_project] //~ ERROR E0119

diff --git a/tests/ui/pin_project/overlapping_unpin_struct.stderr b/tests/ui/pin_project/overlapping_unpin_struct.stderr
@@ -7,5 +7,10 @@ error[E0277]: `PhantomPinned` cannot be unpinned
 18 |     is_unpin::<S<PhantomPinned>>(); //~ ERROR E0277
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ within `_::__S<'_, PhantomPinned>`, the trait `Unpin` is not implemented for `PhantomPinned`
    |
-   = note: required because it appears within the type `_::__S<'_, PhantomPinned>`
+   = note: consider using `Box::pin`
+note: required because it appears within the type `_::__S<'_, PhantomPinned>`
+  --> $DIR/overlapping_unpin_struct.rs:6:8
+   |
+6  | struct S<T> {
+   |        ^
    = note: required because of the requirements on the impl of `Unpin` for `S<PhantomPinned>`
diff --git a/tests/ui/pin_project/packed-enum.rs b/tests/ui/pin_project/packed-enum.rs
@@ -1,5 +1,9 @@
 use pin_project::pin_project;
 
+// #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
+// However, we should not rely on the behavior of rustc that rejects this.
+// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
+
 #[repr(packed)] //~ ERROR E0517
 enum E1 {
     V(()),

diff --git a/tests/ui/pin_project/packed-enum.stderr b/tests/ui/pin_project/packed-enum.stderr
@@ -1,30 +1,42 @@
+error: #[repr(packed)] attribute should be applied to a struct or union
+  --> $DIR/packed-enum.rs:13:8
+   |
+13 | #[repr(packed)] //~ ERROR E0517
+   |        ^^^^^^
+
+error: #[repr(packed)] attribute should be applied to a struct or union
+  --> $DIR/packed-enum.rs:18:8
+   |
+18 | #[repr(packed)] //~ ERROR E0517
+   |        ^^^^^^
+
 error[E0517]: attribute should be applied to a struct or union
- --> $DIR/packed-enum.rs:3:8
-  |
-3 |   #[repr(packed)] //~ ERROR E0517
-  |          ^^^^^^
-4 | / enum E1 {
-5 | |     V(()),
-6 | | }
-  | |_- not a struct or union
+  --> $DIR/packed-enum.rs:7:8
+   |
+7  |   #[repr(packed)] //~ ERROR E0517
+   |          ^^^^^^
+8  | / enum E1 {
+9  | |     V(()),
+10 | | }
+   | |_- not a struct or union
 
 error[E0517]: attribute should be applied to a struct or union
-  --> $DIR/packed-enum.rs:9:8
+  --> $DIR/packed-enum.rs:13:8
    |
-9  |   #[repr(packed)] //~ ERROR E0517
+13 |   #[repr(packed)] //~ ERROR E0517
    |          ^^^^^^
-10 | / enum E2 {
-11 | |     V(()),
-12 | | }
+14 | / enum E2 {
+15 | |     V(()),
+16 | | }
    | |_- not a struct or union
 
 error[E0517]: attribute should be applied to a struct or union
-  --> $DIR/packed-enum.rs:14:8
+  --> $DIR/packed-enum.rs:18:8
    |
-14 |   #[repr(packed)] //~ ERROR E0517
+18 |   #[repr(packed)] //~ ERROR E0517
    |          ^^^^^^
-15 |   #[pin_project]
-16 | / enum E3 {
-17 | |     V(()),
-18 | | }
+19 |   #[pin_project]
+20 | / enum E3 {
+21 | |     V(()),
+22 | | }
    | |_- not a struct or union