Support expect! declaration in Racc grammar file

`expect` warns the difference between expected S/R conflicts count
and actual count however racc command exits with success.
racc command will exit with failure if `expect!` declaration
is specified therefore build process of racc user will also fail.

bin/racc

@@ -193,6 +193,9 @@ def main
     end
 
     profiler.report
+    if states.should_raise_unexpected_number_of_srconflicts?
+      raise Racc::CompileError, "#{states.grammar.n_expected_srconflicts} shift/reduce conflicts are expected but #{states.n_srconflicts} shift/reduce conflicts exist"
+    end
   rescue Racc::Error, Errno::ENOENT, Errno::EPERM => err
     raise if $DEBUG or debug_flags.any?
     lineno = err.message.slice(/\A\d+:/).to_s

lib/racc/grammar.rb

@@ -27,6 +27,7 @@ def initialize(debug_flags = DebugFlags.new)
       @rules   = []  # :: [Rule]
       @start   = nil
       @n_expected_srconflicts = nil
+      @raise_unexpected_number_of_srconflicts = nil
       @prec_table = []
       @prec_table_closed = false
       @closed = false
@@ -36,6 +37,7 @@ def initialize(debug_flags = DebugFlags.new)
     attr_reader :start
     attr_reader :symboltable
     attr_accessor :n_expected_srconflicts
+    attr_accessor :raise_unexpected_number_of_srconflicts
 
     def [](x)
       @rules[x]

lib/racc/grammarfileparser.rb

@@ -73,9 +73,17 @@ module Racc
                     }\
                   | seq(:EXPECT, :DIGIT) {|_, num|
                       if @grammar.n_expected_srconflicts
-                        raise CompileError, "`expect' seen twice"
+                        raise CompileError, "`expect and/or expect!' seen twice"
                       end
                       @grammar.n_expected_srconflicts = num
+                      @grammar.raise_unexpected_number_of_srconflicts = false
+                    }\
+                  | seq(:EXPECT!, :DIGIT) {|_, num|
+                      if @grammar.n_expected_srconflicts
+                        raise CompileError, "`expect and/or expect!' seen twice"
+                      end
+                      @grammar.n_expected_srconflicts = num
+                      @grammar.raise_unexpected_number_of_srconflicts = true
                     }
 
     g.convdef     = seq(:symbol, :STRING) {|sym, code|
@@ -439,7 +447,7 @@ def yylex0
             break
           elsif /\A\/\*/ =~ @line
             skip_comment
-          elsif s = reads(/\A[a-zA-Z_]\w*/)
+          elsif s = reads(/\A[a-zA-Z_]\w*!?/)
             yield [atom_symbol(s), s.intern]
           elsif s = reads(/\A\d+/)
             yield [:DIGIT, s.to_i]
@@ -493,6 +501,7 @@ def next_line
       'options'  => :OPTION,
       'start'    => :START,
       'expect'   => :EXPECT,
+      'expect!'  => :EXPECT!,
       'class'    => :CLASS,
       'rule'     => :RULE,
       'end'      => :END

lib/racc/state.rb

@@ -73,6 +73,10 @@ def should_report_srconflict?
           (n_srconflicts() != @grammar.n_expected_srconflicts)
     end
 
+    def should_raise_unexpected_number_of_srconflicts?
+      should_report_srconflict? && @grammar.raise_unexpected_number_of_srconflicts
+    end
+
     def srconflict_exist?
       n_srconflicts() != 0
     end

test/assets/expect_bang.y

@@ -0,0 +1,7 @@
+class E
+  expect! 0
+rule
+  list: inlist inlist
+  inlist:
+        | A
+end

test/test_racc_command.rb

@@ -108,6 +108,13 @@ def test_expect_y
       assert_debugfile 'expect.y', [1,0,0,0,1]
     end
 
+    def test_expect_bang_y
+      assert_raise_with_message(Test::Unit::AssertionFailedError, /0 shift\/reduce conflicts are expected but 1 shift\/reduce conflicts exist/) {
+        assert_compile 'expect_bang.y'
+      }
+      assert_debugfile 'expect_bang.y', [1,0,0,0,0]
+    end
+
     def test_nullbug1_y
       assert_compile 'nullbug1.y'
       assert_debugfile 'nullbug1.y', [0,0,0,0]