fix optional block arguments in rhs

define optional block arguments as argument variables in the rhs
default expressions, as same as mere assignment expressions.

Import ruby/ruby@01740f0c273c89f7bcff3d5014d73c8ff6fb1986

2 files changed, 6 insertions, 3 deletions

diff --git a/src/parse.y b/src/parse.y
index a8bee8237..43c0c7321 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -3065,10 +3065,9 @@ f_opt           : f_opt_asgn arg_value
                     }
                 ;
 
-f_block_opt     : tIDENTIFIER '=' primary_value
+f_block_opt     : f_opt_asgn primary_value
                     {
-                      local_add_f(p, $1);
-                      $$ = cons(nsym($1), $3);
+                      $$ = cons(nsym($1), $2);
                     }
                 ;
 
diff --git a/test/t/syntax.rb b/test/t/syntax.rb
index 245c5c099..83243a99f 100644
--- a/test/t/syntax.rb
+++ b/test/t/syntax.rb
@@ -289,3 +289,7 @@ assert('optional argument in the rhs default expressions') do
   assert_nil(o.t)
   assert_equal("method called", o.t2)
 end
+
+assert('optional block argument in the rhs default expressions') do
+  assert_nil(proc {|foo = foo| foo}.call)
+end