Auto merge of rust-lang#16285 - lnicola:repr-packed-unaligned, r=Veykril

fix: Fix panic on unaligned packed attribute

Closes rust-lang#16284

Author: bors

crates/hir-def/src/data/adt.rs

@@ -128,7 +128,7 @@ fn parse_repr_tt(tt: &Subtree) -> Option<ReprOptions> {
                     } else {
                         0
                     };
-                    let pack = Align::from_bytes(pack).unwrap();
+                    let pack = Align::from_bytes(pack).unwrap_or(Align::ONE);
                     min_pack =
                         Some(if let Some(min_pack) = min_pack { min_pack.min(pack) } else { pack });
                     ReprFlags::empty()

crates/hir-ty/src/layout/tests.rs

@@ -220,6 +220,36 @@ fn recursive() {
     );
 }
 
+#[test]
+fn repr_packed() {
+    size_and_align! {
+        #[repr(packed)]
+        struct Goal;
+    }
+    size_and_align! {
+        #[repr(packed(2))]
+        struct Goal;
+    }
+    size_and_align! {
+        #[repr(packed(4))]
+        struct Goal;
+    }
+    size_and_align! {
+        #[repr(packed)]
+        struct Goal(i32);
+    }
+    size_and_align! {
+        #[repr(packed(2))]
+        struct Goal(i32);
+    }
+    size_and_align! {
+        #[repr(packed(4))]
+        struct Goal(i32);
+    }
+
+    check_size_and_align("#[repr(packed(5))] struct Goal(i32);", "", 4, 1);
+}
+
 #[test]
 fn generic() {
     size_and_align! {