[PATCH 1/7] rust: pin-init: internal: error on duplicate `#[pin]` attribute

[Gary Guo <gary@garyguo.net>]

From: Luiz Georg <luizgngeorg@gmail.com>

Duplicated `#[pin]` has no effect, thus error if misused.

Reported-by: Mohamad Alsadhan <mo@sdhn.cc>
Closes: https://github.com/Rust-for-Linux/pin-init/issues/119
Signed-off-by: Luiz Georg <luizgngeorg@gmail.com>
[ Reworded commit message, and change the logic so code generation still
  continue after reporting error - Gary ]
Signed-off-by: Gary Guo <gary@garyguo.net>
---
 rust/pin-init/internal/src/pin_data.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/rust/pin-init/internal/src/pin_data.rs b/rust/pin-init/internal/src/pin_data.rs
index 9fbbd25bcaac..263f67300727 100644
--- a/rust/pin-init/internal/src/pin_data.rs
+++ b/rust/pin-init/internal/src/pin_data.rs
@@ -85,7 +85,10 @@ pub(crate) fn pin_data(
         .map(|field| {
             let len = field.attrs.len();
             field.attrs.retain(|a| !a.path().is_ident("pin"));
-            let pinned = len != field.attrs.len();
+            let pinned_count = len - field.attrs.len();
+            if pinned_count > 1 {
+                dcx.error(&field, "#[pin] attribute specified more than once");
+            }
 
             let cfg_attrs = field
                 .attrs
@@ -95,7 +98,7 @@ pub(crate) fn pin_data(
 
             FieldInfo {
                 field: &*field,
-                pinned,
+                pinned: pinned_count != 0,
                 cfg_attrs,
             }
         })

-- 
2.54.0