stage2 更多的工具库 stage1 修复问题

stage2/utils/source.spl

@@ -173,7 +173,10 @@ fn set_at(set: *Sources, index: usize): *Source {
 
 fn set_find(set: *Sources, fname: ByteView): FindResult {
     var out: usize = 0;
-    if Map.get(&set.by_name, &fname as *u8, &out as *u8) { ret .Found(out); }
+    match Map.get(&set.by_name, &fname as *u8, &out as *u8) {
+        .Found => { ret .Found(out); },
+        .NotFound => {},
+    }
     ret .NotFound;
 }