Fixed shift width for `MRB_ENV_SET_BIDX()`

ref c07f24cd and close #5035

include/mruby/proc.h

@@ -34,7 +34,7 @@ struct REnv {
 #define MRB_ENV_HEAP_P(e) ((e)->flags & MRB_ENV_HEAPED)
 #define MRB_ENV_ONSTACK_P(e) (((e)->flags & MRB_ENV_CLOSED) == 0)
 #define MRB_ENV_BIDX(e) (((e)->flags >> 8) & 0xff)
-#define MRB_ENV_SET_BIDX(e,idx) ((e)->flags = (((e)->flags & ~(0xff<<8))|((unsigned int)(idx) & 0xff)<<10))
+#define MRB_ENV_SET_BIDX(e,idx) ((e)->flags = (((e)->flags & ~(0xff<<8))|((unsigned int)(idx) & 0xff)<<8))
 
 void mrb_env_unshare(mrb_state*, struct REnv*);
 

test/t/kernel.rb

@@ -116,6 +116,13 @@ assert('Kernel#block_given?', '15.3.1.3.6') do
       "block"
     end
   end
+
+  def bg_try_in_block
+    -> { block_given? }[]
+  end
+
+  assert_false bg_try_in_block
+  assert_true bg_try_in_block{}
 end
 
 assert('Kernel#class', '15.3.1.3.7') do