Add Parser::LexerError

lib/rbs/parser.y

@@ -1425,7 +1425,11 @@ def next_token
     s = input.matched.yield_self {|s| s[1, s.length - 2] }.gsub(/\\'/, "'")
     new_token(:tSTRING, s)
   else
-    raise "Unexpected token: #{input.peek(10)}..."
+    text = input.peek(10)
+    start_index = charpos(input)
+    end_index = start_index + text.length
+    location = RBS::Location.new(buffer: buffer, start_pos: start_index, end_pos: end_index)
+    raise LexerError.new(input: text, location: location)
   end
 end
 
@@ -1457,4 +1461,15 @@ class SemanticsError < ParsingError
   end
 end
 
+class LexerError < ParsingError
+  attr_reader :location, :input
+
+  def initialize(input:, location:)
+    @input = input
+    @location = location
+
+    super "Unexpected string: #{input}..."
+  end
+end
+
 ---- footer

sig/parser.rbs

@@ -8,6 +8,13 @@ module RBS
       def initialize: (token_str: String, error_value: untyped, ?value_stack: untyped?) -> void
     end
 
+    class LexerError < ParsingError
+      attr_reader input: String
+      attr_reader location: Location
+
+      def initialize: (input: String, location: Location) -> void
+    end
+
     class SemanticsError < ParsingError
       attr_reader subject: untyped
       attr_reader location: Location