T? is not allowed as a type pattern

Version Used: master

Steps to Reproduce:

using System;
public class C {
    void M(object g) {
        _ = g is Nullable<int>; // ok
        _ = g is int?; // ok
        _ = g switch { Nullable<int> => 0 }; // CS8116
        _ = g switch { int? => 0 }; // syntax error
        switch (g) { case Nullable<int>: break; } // CS8116
        switch (g) { case int?: break; } // syntax error  
    }
}

Expected Behavior: either

• No error in all cases
• CS8116 for int? type patterns as well.

[sharwell]

I see two areas for improvement:

1. Report CS8116 for use of int? when the same would be reported for Nullable<int>
2. Add a code fix for this error to change int? to int

[HaloFour]

@Youssef1313

Oh, yes, I’d agree, it should be added as a warning wave if it is not currently. Note that SharpLab does not run in “strict” mode so you might need to check elsewhere.