Merge commit '6204bb245b4a05e0f4f00bb48d83b76ebcd899e2' into zig0-0.15.2

stage0/astgen_test.zig

@@ -325,6 +325,11 @@ fn expectEqualData(
                 .shl_with_overflow,
                 .restore_err_ret_index,
                 .branch_hint,
+                // Container decl Small packed structs have undefined padding bits.
+                .struct_decl,
+                .enum_decl,
+                .union_decl,
+                .opaque_decl,
                 => true,
                 else => false,
             };