Add `mrb_get_arg1()` that retrieves single (and only) argument.

`mrb_get_arg1()` raises `ArgumentError` if the method does not receive one
argument.

And replaces all `mrb_get_args(mrb, "o", &arg)` by the new function.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/symbol.c b/src/symbol.c
index f55e09b7b..992848797 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -564,10 +564,9 @@ mrb_sym_dump(mrb_state *mrb, mrb_sym sym)
 static mrb_value
 sym_cmp(mrb_state *mrb, mrb_value s1)
 {
-  mrb_value s2;
+  mrb_value s2 = mrb_get_arg1(mrb);
   mrb_sym sym1, sym2;
 
-  mrb_get_args(mrb, "o", &s2);
   if (!mrb_symbol_p(s2)) return mrb_nil_value();
   sym1 = mrb_symbol(s1);
   sym2 = mrb_symbol(s2);