1 | // Original code (./struct-default.rs): |
2 | // |
3 | // ```rust |
4 | // #![allow(dead_code)] |
5 | // |
6 | // use pin_project::pin_project; |
7 | // |
8 | // #[pin_project] |
9 | // struct Struct<T, U> { |
10 | // #[pin] |
11 | // pinned: T, |
12 | // unpinned: U, |
13 | // } |
14 | // |
15 | // fn main() {} |
16 | // ``` |
17 | |
18 | #![allow (dead_code, unused_imports, unused_parens, unknown_lints, renamed_and_removed_lints)] |
19 | #![allow (clippy::needless_lifetimes)] |
20 | |
21 | use pin_project::pin_project ; |
22 | |
23 | // #[pin_project] |
24 | struct Struct<T, U> { |
25 | // #[pin] |
26 | pinned: T, |
27 | unpinned: U, |
28 | } |
29 | |
30 | const _: () = { |
31 | struct __StructProjection<'pin, T, U> |
32 | where |
33 | Struct<T, U>: 'pin, |
34 | { |
35 | pinned: ::pin_project::__private::Pin<&'pin mut (T)>, |
36 | unpinned: &'pin mut (U), |
37 | } |
38 | struct __StructProjectionRef<'pin, T, U> |
39 | where |
40 | Struct<T, U>: 'pin, |
41 | { |
42 | pinned: ::pin_project::__private::Pin<&'pin (T)>, |
43 | unpinned: &'pin (U), |
44 | } |
45 | |
46 | impl<T, U> Struct<T, U> { |
47 | fn project<'pin>( |
48 | self: ::pin_project::__private::Pin<&'pin mut Self>, |
49 | ) -> __StructProjection<'pin, T, U> { |
50 | unsafe { |
51 | let Self { pinned, unpinned } = self.get_unchecked_mut(); |
52 | __StructProjection { |
53 | pinned: ::pin_project::__private::Pin::new_unchecked(pinned), |
54 | unpinned, |
55 | } |
56 | } |
57 | } |
58 | fn project_ref<'pin>( |
59 | self: ::pin_project::__private::Pin<&'pin Self>, |
60 | ) -> __StructProjectionRef<'pin, T, U> { |
61 | unsafe { |
62 | let Self { pinned, unpinned } = self.get_ref(); |
63 | __StructProjectionRef { |
64 | pinned: ::pin_project::__private::Pin::new_unchecked(pinned), |
65 | unpinned, |
66 | } |
67 | } |
68 | } |
69 | } |
70 | |
71 | // Ensure that it's impossible to use pin projections on a #[repr(packed)] |
72 | // struct. |
73 | // |
74 | // Taking a reference to a packed field is UB, and applying |
75 | // `#[forbid(unaligned_references)]` makes sure that doing this is a hard error. |
76 | // |
77 | // If the struct ends up having #[repr(packed)] applied somehow, |
78 | // this will generate an (unfriendly) error message. Under all reasonable |
79 | // circumstances, we'll detect the #[repr(packed)] attribute, and generate |
80 | // a much nicer error above. |
81 | // |
82 | // See https://github.com/taiki-e/pin-project/pull/34 for more details. |
83 | #[forbid (unaligned_references, safe_packed_borrows)] |
84 | fn __assert_not_repr_packed<T, U>(this: &Struct<T, U>) { |
85 | let _ = &this.pinned; |
86 | let _ = &this.unpinned; |
87 | } |
88 | |
89 | // Automatically create the appropriate conditional `Unpin` implementation. |
90 | // |
91 | // Basically this is equivalent to the following code: |
92 | // |
93 | // ```rust |
94 | // impl<T, U> Unpin for Struct<T, U> where T: Unpin {} |
95 | // ``` |
96 | // |
97 | // However, if struct is public and there is a private type field, |
98 | // this would cause an E0446 (private type in public interface). |
99 | // |
100 | // When RFC 2145 is implemented (rust-lang/rust#48054), |
101 | // this will become a lint, rather then a hard error. |
102 | // |
103 | // As a workaround for this, we generate a new struct, containing all of |
104 | // the pinned fields from our #[pin_project] type. This struct is declared |
105 | // within a function, which makes it impossible to be named by user code. |
106 | // This guarantees that it will use the default auto-trait impl for Unpin - |
107 | // that is, it will implement Unpin iff all of its fields implement Unpin. |
108 | // This type can be safely declared as 'public', satisfying the privacy |
109 | // checker without actually allowing user code to access it. |
110 | // |
111 | // This allows users to apply the #[pin_project] attribute to types |
112 | // regardless of the privacy of the types of their fields. |
113 | // |
114 | // See also https://github.com/taiki-e/pin-project/pull/53. |
115 | struct __Struct<'pin, T, U> { |
116 | __pin_project_use_generics: ::pin_project::__private::AlwaysUnpin< |
117 | 'pin, |
118 | (::pin_project::__private::PhantomData<T>, ::pin_project::__private::PhantomData<U>), |
119 | >, |
120 | __field0: T, |
121 | } |
122 | impl<'pin, T, U> ::pin_project::__private::Unpin for Struct<T, U> where |
123 | __Struct<'pin, T, U>: ::pin_project::__private::Unpin |
124 | { |
125 | } |
126 | // A dummy impl of `UnsafeUnpin`, to ensure that the user cannot implement it. |
127 | // |
128 | // To ensure that users don't accidentally write a non-functional `UnsafeUnpin` |
129 | // impls, we emit one ourselves. If the user ends up writing an `UnsafeUnpin` |
130 | // impl, they'll get a "conflicting implementations of trait" error when |
131 | // coherence checks are run. |
132 | #[doc (hidden)] |
133 | unsafe impl<'pin, T, U> ::pin_project::UnsafeUnpin for Struct<T, U> where |
134 | __Struct<'pin, T, U>: ::pin_project::__private::Unpin |
135 | { |
136 | } |
137 | |
138 | // Ensure that struct does not implement `Drop`. |
139 | // |
140 | // If you attempt to provide an Drop impl, the blanket impl will |
141 | // then apply to your type, causing a compile-time error due to |
142 | // the conflict with the second impl. |
143 | trait StructMustNotImplDrop {} |
144 | #[allow (clippy::drop_bounds, drop_bounds)] |
145 | impl<T: ::pin_project::__private::Drop> StructMustNotImplDrop for T {} |
146 | impl<T, U> StructMustNotImplDrop for Struct<T, U> {} |
147 | // A dummy impl of `PinnedDrop`, to ensure that users don't accidentally |
148 | // write a non-functional `PinnedDrop` impls. |
149 | #[doc (hidden)] |
150 | impl<T, U> ::pin_project::__private::PinnedDrop for Struct<T, U> { |
151 | unsafe fn drop(self: ::pin_project::__private::Pin<&mut Self>) {} |
152 | } |
153 | }; |
154 | |
155 | fn main() {} |
156 | |