`String#lines` with a block is deprecated style.

mrbgems/mruby-string-ext/src/string.c

@@ -320,36 +320,16 @@ static mrb_value
 mrb_str_lines(mrb_state *mrb, mrb_value self)
 {
   mrb_value result;
-  mrb_value blk;
   int ai;
   mrb_int len;
-  mrb_value arg;
   char *b = RSTRING_PTR(self);
   char *p = b, *t;
   char *e = b + RSTRING_LEN(self);
 
-  mrb_get_args(mrb, "&", &blk);
+  mrb_get_args(mrb, "");
 
   result = mrb_ary_new(mrb);
   ai = mrb_gc_arena_save(mrb);
-  if (!mrb_nil_p(blk)) {
-    while (p < e) {
-      t = p;
-      while (p < e && *p != '\n') p++;
-      if (*p == '\n') p++;
-      len = (mrb_int) (p - t);
-      arg = mrb_str_new(mrb, t, len);
-      mrb_yield_argv(mrb, blk, 1, &arg);
-      mrb_gc_arena_restore(mrb, ai);
-      if (b != RSTRING_PTR(self)) {
-        ptrdiff_t diff = p - b;
-        b = RSTRING_PTR(self);
-        p = b + diff;
-      }
-      e = b + RSTRING_LEN(self);
-    }
-    return self;
-  }
   while (p < e) {
     t = p;
     while (p < e && *p != '\n') p++;