Force muliple repr hint to be hard error

The consideraton is this will be unsafe in our environmnt. In rust, it is possible that users would allow that error, thinking it shouldn't lead to unsafe behavior. Signed-off-by: Ahmed Abdelraoof <[email protected]>
oddcoder · Aug 16, 2024 · 28cea8d · 28cea8d
1 parent 02c564f
commit 28cea8d
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Showing 2 changed files with 19 additions and 4 deletions.
diff --git a/safe-discriminant-derive/src/lib.rs b/safe-discriminant-derive/src/lib.rs
@@ -26,12 +26,21 @@ fn get_enum_repr_prim(attrs: &[Attribute], error_span: Span) -> Result<Path> {
         if !attr.path().is_ident("repr") {
             continue;
         }
-        let _ = attr.parse_nested_meta(|meta| {
-            if is_prim(&meta.path) {
-                prim = Some(meta.path);
+        attr.parse_nested_meta(|meta| {
+            if !is_prim(&meta.path) {
+                return Ok(());
             }
+            if prim.is_some() {
+                return Err(Error::new(
+                    // TODO join meta.path span with prim span
+                    // but the function is currently nightly only
+                    meta.path.span(),
+                    "conflicting representation hints",
+                ));
+            }
+            prim = Some(meta.path);
             Ok(())
-        });
+        })?;
     }
     match prim {
         Some(prim) => Ok(prim),

diff --git a/safe-discriminant/tests/fail/multi_repr.stderr b/safe-discriminant/tests/fail/multi_repr.stderr
@@ -1,3 +1,9 @@
+error: conflicting representation hints
+ --> tests/fail/multi_repr.rs:4:15
+  |
+4 | #[repr(C, u8, i8)]
+  |               ^^
+
 error[E0566]: conflicting representation hints
  --> tests/fail/multi_repr.rs:4:8
   |