Null-forgiving operator results in nullable type-CodePudding

I've a .NET 6.0 C# console project with the property <Nullable>enable</Nullable>. In it, I've the following, where Span is a primitive data type:

sealed class PrivateParser {
   private void FatalError(int msgId, Span span /*, ...*/) {
       /* ... */
   }
}

When I call FatalError(), immediately forgiving null in the second agument:

FatalError(0x80A0400, id.Span!);

The compiler outputs:

error CS1503: Argument 2: cannot convert from
'ShockBasic.Semantics.SourceData.Span?' to
'ShockBasic.Semantics.SourceData.Span' [C:\Users\hando\Documents\shockbasic\sb\ShockBasic.Compiler.csproj]

See Microsoft docs, the operator should return the non-nullable type, thus I'm a bit lost.

To reproduce it, the full project is in this GitHub commit. Run dotnet build and you can look at the last error. Locations

CodePudding user response：

From the docs that you have added in the question:

you use the null-forgiving operator to declare that expression x of a reference type isn't null.

Span is a value type. To change "Nullable value type" (in your case (Nullable<Span>/Span?) To non nullable, when calling the method you should use FatalError(0x80A0400, id.Span.Value);, but that may throw InvalidOperationException (docs) when the id.Span will be null