Properly initialize the SaprusMessage fromBytes

Will actually use the provided packet type inline.

src/main.zig

@@ -84,7 +84,13 @@ const SaprusMessage = union(SaprusPacketType) {
     }
 };
 
-inline fn toBytesAux(comptime Header: type, header: Header, payload: []const u8, w: std.ArrayList(u8).Writer, allocator: Allocator) !void {
+inline fn toBytesAux(
+    comptime Header: type,
+    header: Header,
+    payload: []const u8,
+    w: std.ArrayList(u8).Writer,
+    allocator: Allocator,
+) !void {
     const payload_list = try encodeToList(payload, allocator);
     defer payload_list.deinit();
 
@@ -93,26 +99,20 @@ inline fn toBytesAux(comptime Header: type, header: Header, payload: []const u8,
     try w.writeAll(payload_list.items);
 }
 
-inline fn fromBytesAux(comptime Packet: SaprusPacketType, comptime Header: type, r: StringReader, allocator: Allocator) !SaprusMessage {
+inline fn fromBytesAux(
+    comptime packet: SaprusPacketType,
+    comptime Header: type,
+    r: StringReader,
+    allocator: Allocator,
+) !SaprusMessage {
     const header = try r.readStructEndian(Header, .big);
     const len = try r.readInt(u16, .big);
     const payload = try decodeFromReader(r, len, allocator);
 
-    return switch (Packet) {
+    return @unionInit(SaprusMessage, @tagName(packet), .{
-        .relay => SaprusMessage{
+        .header = header,
-            .relay = .{
+        .payload = payload,
-                .header = header,
+    });
-                .payload = payload,
-            },
-        },
-        .connection => SaprusMessage{
-            .connection = .{
-                .header = header,
-                .payload = payload,
-            },
-        },
-        else => unreachable,
-    };
 }
 
 pub fn main() !void {