Add test for issue 342

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

@@ -1084,12 +1084,6 @@ fn ensure_not_packed(orig: &OriginalType<'_>, fields: Option<&Fields>) -> Result
     // See also https://github.com/taiki-e/pin-project/pull/34.
     //
     // Note:
-    // - pin-project v0.4.3 or later (#135, v0.4.0-v0.4.2 are already yanked for
-    //   another reason) is internally proc-macro-derive, so they are not
-    //   affected by the problem that the struct definition is rewritten by
-    //   another macro after the #[pin_project] is expanded.
-    //   So this is probably no longer necessary, but it keeps it for now.
-    //
     // - Lint-based tricks aren't perfect, but they're much better than nothing:
     //   https://github.com/taiki-e/pin-project-lite/issues/26
     //

tests/auxiliary/macro/lib.rs

@@ -12,8 +12,17 @@ fn tokens2(tokens: TokenStream) -> proc_macro2::TokenStream {
 
 #[proc_macro_attribute]
 pub fn hidden_repr(args: TokenStream, input: TokenStream) -> TokenStream {
-    let (args, input) = (tokens2(args), tokens2(input));
-    quote!(#[repr(#args)] #input).into()
+    let args = tokens2(args);
+    let mut item = syn::parse_macro_input!(input as ItemStruct);
+    item.attrs.push(parse_quote!(#[repr(#args)]));
+    quote!(#item).into()
+}
+
+#[proc_macro_attribute]
+pub fn hidden_repr2(_args: TokenStream, input: TokenStream) -> TokenStream {
+    let mut item = syn::parse_macro_input!(input as ItemStruct);
+    item.attrs.push(parse_quote!(#[auxiliary_macro::hidden_repr(packed)] ));
+    quote!(#item).into()
 }
 
 #[proc_macro]

tests/ui/pin_project/packed_sneaky-1.rs

@@ -1,6 +1,6 @@
 use std::pin::Pin;
 
-use auxiliary_macro::hidden_repr;
+use auxiliary_macro::{hidden_repr, hidden_repr2};
 use pin_project::{pin_project, pinned_drop, UnsafeUnpin};
 
 #[pin_project] //~ ERROR may not be used on #[repr(packed)] types
@@ -10,6 +10,13 @@ struct A {
     f: u32,
 }
 
+#[hidden_repr2]
+#[pin_project] //~ ERROR may not be used on #[repr(packed)] types
+struct B {
+    #[pin]
+    f: u32,
+}
+
 #[pin_project(UnsafeUnpin)] //~ ERROR may not be used on #[repr(packed)] types
 #[hidden_repr(packed)]
 struct C {

tests/ui/pin_project/packed_sneaky-1.stderr

@@ -5,13 +5,21 @@ error: #[pin_project] attribute may not be used on #[repr(packed)] types
   |               ^^^^^^
 
 error: #[pin_project] attribute may not be used on #[repr(packed)] types
-  --> tests/ui/pin_project/packed_sneaky-1.rs:14:15
+  --> tests/ui/pin_project/packed_sneaky-1.rs:13:1
    |
-14 | #[hidden_repr(packed)]
+13 | #[hidden_repr2]
+   | ^^^^^^^^^^^^^^^
+   |
+   = note: this error originates in the attribute macro `hidden_repr2` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: #[pin_project] attribute may not be used on #[repr(packed)] types
+  --> tests/ui/pin_project/packed_sneaky-1.rs:21:15
+   |
+21 | #[hidden_repr(packed)]
    |               ^^^^^^
 
 error: #[pin_project] attribute may not be used on #[repr(packed)] types
-  --> tests/ui/pin_project/packed_sneaky-1.rs:23:15
+  --> tests/ui/pin_project/packed_sneaky-1.rs:30:15
    |
-23 | #[hidden_repr(packed)]
+30 | #[hidden_repr(packed)]
    |               ^^^^^^

tests/ui/pin_project/packed_sneaky-4.rs

@@ -0,0 +1,15 @@
+// https://github.com/taiki-e/pin-project/issues/342
+
+#![allow(unaligned_references)]
+
+use auxiliary_macro::hidden_repr2;
+use pin_project::pin_project;
+
+#[pin_project] //~ ERROR reference to packed field is unaligned
+#[hidden_repr2]
+struct A {
+    #[pin]
+    f: u32,
+}
+
+fn main() {}

tests/ui/pin_project/packed_sneaky-4.stderr

@@ -0,0 +1,16 @@
+error: reference to packed field is unaligned
+ --> tests/ui/pin_project/packed_sneaky-4.rs:8:1
+  |
+8 | #[pin_project] //~ ERROR reference to packed field is unaligned
+  | ^^^^^^^^^^^^^^
+  |
+note: the lint level is defined here
+ --> tests/ui/pin_project/packed_sneaky-4.rs:8:1
+  |
+8 | #[pin_project] //~ ERROR reference to packed field is unaligned
+  | ^^^^^^^^^^^^^^
+  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+  = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+  = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+  = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+  = note: this error originates in the derive macro `::pin_project::__private::__PinProjectInternalDerive` (in Nightly builds, run with -Z macro-backtrace for more info)