Allow terminal symbols to be used anywhere in the grammar rules

Fixes: #182

Author: ydah

lib/racc/grammarfileparser.rb

@@ -200,6 +200,7 @@ def parse(src, filename = '-', lineno = 1)
       @grammar = Grammar.new
       @result = Result.new(@grammar)
       @embedded_action_seq = 0
+      @current_rule_target = nil
       yyparse @scanner, :yylex
       parse_user_code
       @result.grammar.init
@@ -228,11 +229,21 @@ def location
     end
 
     def add_rule_block(list)
-      target = list.shift
-      case target
-      when OrMark, OptionMark, ManyMark, Many1Mark, GroupStartMark, GroupEndMark, UserAction, Prec
-        raise CompileError, "#{target.lineno}: unexpected symbol #{target.name}"
+      if !list.empty? && list[0].is_a?(OrMark)
+        list.shift
+        target = @current_rule_target
+        if target.nil?
+          raise CompileError, "#{location()}: no target for rule continuation"
+        end
+      else
+        target = list.shift
+        case target
+        when OrMark, OptionMark, ManyMark, Many1Mark, GroupStartMark, GroupEndMark, UserAction, Prec
+          raise CompileError, "#{target.lineno}: unexpected symbol #{target.name}"
+        end
+        @current_rule_target = target
       end
+
       enum = list.each.with_index
       _, sym, idx = _add_rule_block(target, enum)
       if idx

test/assets/term.y

@@ -0,0 +1,11 @@
+class Parse
+rule
+  target    : term
+                { p 'target:term' }
+  term      : :TERM1
+                { p 'term:TERM1' }
+            | :TERM2
+                { p 'term:TERM2' }
+            | term :TERM3
+                { p 'term:TERM3' }
+end

test/regress/term

@@ -0,0 +1,126 @@
+#
+# DO NOT MODIFY!!!!
+# This file is automatically generated by Racc 1.8.1
+# from Racc grammar file "term.y".
+#
+
+require 'racc/parser.rb'
+class Parse < Racc::Parser
+##### State transition tables begin ###
+
+racc_action_table = [
+     3,     4,     5,     6,     7 ]
+
+racc_action_check = [
+     0,     0,     0,     1,     6 ]
+
+racc_action_pointer = [
+    -2,     3,   nil,   nil,   nil,   nil,     4,   nil ]
+
+racc_action_default = [
+    -4,    -6,    -1,    -2,    -3,    -5,    -6,     8 ]
+
+racc_goto_table = [
+     1,     2 ]
+
+racc_goto_check = [
+     1,     2 ]
+
+racc_goto_pointer = [
+   nil,     0,     1 ]
+
+racc_goto_default = [
+   nil,   nil,   nil ]
+
+racc_reduce_table = [
+  0, 0, :racc_error,
+  1, 6, :_reduce_1,
+  1, 7, :_reduce_2,
+  1, 7, :_reduce_3,
+  0, 7, :_reduce_none,
+  1, 7, :_reduce_5 ]
+
+racc_reduce_n = 6
+
+racc_shift_n = 8
+
+racc_token_table = {
+  false => 0,
+  :error => 1,
+  :TERM1 => 2,
+  :TERM2 => 3,
+  :TERM3 => 4 }
+
+racc_nt_base = 5
+
+racc_use_result_var = true
+
+Racc_arg = [
+  racc_action_table,
+  racc_action_check,
+  racc_action_default,
+  racc_action_pointer,
+  racc_goto_table,
+  racc_goto_check,
+  racc_goto_default,
+  racc_goto_pointer,
+  racc_nt_base,
+  racc_reduce_table,
+  racc_token_table,
+  racc_shift_n,
+  racc_reduce_n,
+  racc_use_result_var ]
+Ractor.make_shareable(Racc_arg) if defined?(Ractor)
+
+Racc_token_to_s_table = [
+  "$end",
+  "error",
+  "TERM1",
+  "TERM2",
+  "TERM3",
+  "$start",
+  "target",
+  "term" ]
+Ractor.make_shareable(Racc_token_to_s_table) if defined?(Ractor)
+
+Racc_debug_parser = false
+
+##### State transition tables end #####
+
+# reduce 0 omitted
+
+module_eval(<<'.,.,', 'term.y', 3)
+  def _reduce_1(val, _values, result)
+     p 'target:term'
+    result
+  end
+.,.,
+
+module_eval(<<'.,.,', 'term.y', 5)
+  def _reduce_2(val, _values, result)
+     p 'term:TERM1'
+    result
+  end
+.,.,
+
+module_eval(<<'.,.,', 'term.y', 7)
+  def _reduce_3(val, _values, result)
+     p 'term:TERM2'
+    result
+  end
+.,.,
+
+# reduce 4 omitted
+
+module_eval(<<'.,.,', 'term.y', 9)
+  def _reduce_5(val, _values, result)
+     p 'term:TERM3'
+    result
+  end
+.,.,
+
+def _reduce_none(val, _values, result)
+  val[0]
+end
+
+end   # class Parse

test/test_racc_command.rb

@@ -374,5 +374,11 @@ def test_group
       assert_debugfile 'group.y', [0, 0, 0, 0]
       assert_output_unchanged 'group.y'
     end
+
+    def test_term
+      assert_compile 'term.y'
+      assert_debugfile 'term.y', [0, 0, 0, 0]
+      assert_output_unchanged 'term.y'
+    end
   end
 end