prog.cs(15,24): error CS1644: Feature `pattern matching' cannot be used because it is not part of the C# 7.0 language specification
prog.cs(20,14): error CS0589: Internal compiler error during parsingSystem.NotImplementedException: type pattern matching
at Mono.CSharp.CSharpParser.case_963 () <0x7fe8a77cd800 + 0x0007f> in <6d1f622b5bed41cf94a26e291798f831#da64574cc157543f8213a54ad5b33bb2>:0
at Mono.CSharp.CSharpParser.yyparse (Mono.CSharp.yyParser.yyInput yyLex) <0x7fe8a77a52c0 + 0x02096> in <6d1f622b5bed41cf94a26e291798f831#da64574cc157543f8213a54ad5b33bb2>:0
at Mono.CSharp.CSharpParser.parse () <0x7fe8a77d77a0 + 0x00069> in <6d1f622b5bed41cf94a26e291798f831#da64574cc157543f8213a54ad5b33bb2>:0
Compilation failed: 2 error(s), 0 warnings