5 files changed, 106 insertions, 0 deletions
diff --git a/tool/lrama/lib/lrama/state/reduce.rb b/tool/lrama/lib/lrama/state/reduce.rb
new file mode 100644
index 0000000000..a2b7c26cfe
--- /dev/null
+++ b/tool/lrama/lib/lrama/state/reduce.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Lrama
+  class State
+    class Reduce
+      # https://www.gnu.org/software/bison/manual/html_node/Default-Reductions.html
+      attr_reader :item, :look_ahead, :not_selected_symbols
+      attr_accessor :default_reduction
+
+      def initialize(item)
+        @item = item
+        @look_ahead = nil
+        @not_selected_symbols = []
+      end
+
+      def rule
+        @item.rule
+      end
+
+      def look_ahead=(look_ahead)
+        @look_ahead = look_ahead.freeze
+      end
+
+      def add_not_selected_symbol(sym)
+        @not_selected_symbols << sym
+      end
+
+      def selected_look_ahead
+        if @look_ahead
+          # @type ivar @look_ahead: Array<Grammar::Symbol>
+          @look_ahead - @not_selected_symbols
+        else
+          []
+        end
+      end
+    end
+  end
+end
diff --git a/tool/lrama/lib/lrama/state/reduce_reduce_conflict.rb b/tool/lrama/lib/lrama/state/reduce_reduce_conflict.rb
new file mode 100644
index 0000000000..736d08376a
--- /dev/null
+++ b/tool/lrama/lib/lrama/state/reduce_reduce_conflict.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Lrama
+  class State
+    class ReduceReduceConflict < Struct.new(:symbols, :reduce1, :reduce2, keyword_init: true)
+      def type
+        :reduce_reduce
+      end
+    end
+  end
+end
diff --git a/tool/lrama/lib/lrama/state/resolved_conflict.rb b/tool/lrama/lib/lrama/state/resolved_conflict.rb
new file mode 100644
index 0000000000..3bb3d1446e
--- /dev/null
+++ b/tool/lrama/lib/lrama/state/resolved_conflict.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module Lrama
+  class State
+    # * symbol: A symbol under discussion
+    # * reduce: A reduce under discussion
+    # * which: For which a conflict is resolved. :shift, :reduce or :error (for nonassociative)
+    class ResolvedConflict < Struct.new(:symbol, :reduce, :which, :same_prec, keyword_init: true)
+      def report_message
+        s = symbol.display_name
+        r = reduce.rule.precedence_sym&.display_name
+        case
+        when which == :shift && same_prec
+          msg = "resolved as #{which} (%right #{s})"
+        when which == :shift
+          msg = "resolved as #{which} (#{r} < #{s})"
+        when which == :reduce && same_prec
+          msg = "resolved as #{which} (%left #{s})"
+        when which == :reduce
+          msg = "resolved as #{which} (#{s} < #{r})"
+        when which == :error
+          msg = "resolved as an #{which} (%nonassoc #{s})"
+        else
+          raise "Unknown direction. #{self}"
+        end
+
+        "Conflict between rule #{reduce.rule.id} and token #{s} #{msg}."
+      end
+    end
+  end
+end
diff --git a/tool/lrama/lib/lrama/state/shift.rb b/tool/lrama/lib/lrama/state/shift.rb
new file mode 100644
index 0000000000..81ef013a17
--- /dev/null
+++ b/tool/lrama/lib/lrama/state/shift.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module Lrama
+  class State
+    class Shift
+      attr_reader :next_sym, :next_items
+      attr_accessor :not_selected
+
+      def initialize(next_sym, next_items)
+        @next_sym = next_sym
+        @next_items = next_items
+      end
+    end
+  end
+end
diff --git a/tool/lrama/lib/lrama/state/shift_reduce_conflict.rb b/tool/lrama/lib/lrama/state/shift_reduce_conflict.rb
new file mode 100644
index 0000000000..fd66834539
--- /dev/null
+++ b/tool/lrama/lib/lrama/state/shift_reduce_conflict.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Lrama
+  class State
+    class ShiftReduceConflict < Struct.new(:symbols, :shift, :reduce, keyword_init: true)
+      def type
+        :shift_reduce
+      end
+    end
+  end
+end