Fix parsing of mutiple assignment with rescue modifier

Single assignment with rescue modifier applies rescue to the RHS:

  a = raise rescue 1 # a = (raise rescue 1)

Previously, multiple assignment with rescue modifier applied rescue
to the entire expression:

  a, b = raise rescue [1, 2] # (a, b = raise) rescue [1, 2]

This makes multiple assignment with rescue modifier consistent with
single assignment with rescue modifier, applying rescue to the RHS:

  a, b = raise rescue [1, 2] # a, b = (raise rescue [1, 2])

Implements [Feature #8239]
Fixes [Bug #8279]

parse.y

@@ -1387,6 +1387,15 @@ stmt		: keyword_alias fitem {SET_LEX_STATE(EXPR_FNAME|EXPR_FITEM);} fitem
 		    /*% %*/
 		    /*% ripper: assign!($1, $3) %*/
 		    }
+                | mlhs '=' mrhs_arg modifier_rescue stmt
+                    {
+                    /*%%%*/
+                        YYLTYPE loc = code_loc_gen(&@4, &@5);
+                        value_expr($3);
+			$$ = node_assign(p, $1, NEW_RESCUE($3, NEW_RESBODY(0, remove_begin($5), 0, &loc), 0, &@$), &@$);
+                    /*% %*/
+                    /*% ripper: massign!($1, rescue_mod!($3, $5)) %*/
+                    }
 		| mlhs '=' mrhs_arg
 		    {
 		    /*%%%*/

test/ruby/test_assignment.rb

@@ -92,6 +92,11 @@ class TestAssignment < Test::Unit::TestCase
     a,b,*c = *[*[1,2]]; assert_equal([1,2,[]], [a,b,c])
   end
 
+  def test_assign_rescue
+    a = raise rescue 2; assert_equal(2, a)
+    a, b = raise rescue [3,4]; assert_equal([3, 4], [a, b])
+  end
+
   def test_assign_abbreviated
     bug2050 = '[ruby-core:25629]'
     a = Hash.new {[]}