Simples fixes to the parser, add is_valid_start_symbol and updated parse_json.

json/scanner/json_parser.e

@@ -63,11 +63,17 @@ feature -- Commands
 
 	parse_json: ?JSON_VALUE is
 		    -- Parse JSON data `representation'
+		    -- start ::= object | array
 		do
+		    	if is_valid_start_symbol then
 		   	    Result := parse
 		        if extra_elements then
 		            is_parsed := False
 		        end
+		    else
+		        is_parsed := False
+		        report_error ("Syntax error unexpected token, expecting `{' or `['")
+		    end
 		end
 
 	parse: ?JSON_VALUE is
@@ -422,6 +428,12 @@ feature {NONE} -- Implementation
 			Result := has_next
 		end
 
+	is_valid_start_symbol : BOOLEAN
+		-- expecting `{' or `[' as start symbol
+		do
+			Result := representation.starts_with ("{") or representation.starts_with ("[")
+		end
+
 feature {NONE} -- Constants
 
 	false_id: STRING is "false"