`Type.FullName` behavior diverges from documentation

[Youssef1313]

Description

https://learn.microsoft.com/en-us/dotnet/api/system.type.fullname?view=net-10.0

null if the current instance represents a generic type parameter, an array type, pointer type

using System;

var m = typeof(C).GetMethod("M")!;
foreach (var p in m.GetParameters())
{
    Console.WriteLine($"{p.Name}: {p.ParameterType.FullName}");
}

public class C
{
    public unsafe void M<T>(int* x, int[] y, T z) { }
}

This prints:

x: System.Int32*
y: System.Int32[]
z:

So it doesn't seem to be null for points and array types?

Reproduction Steps

See above.

Expected behavior

Implementation and docs are aligned.

Actual behavior

They are not aligned.

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[KalleOlaviNiemitalo]

Full text of the "Property Value" section:

The fully qualified name of the type, including its namespace but not its assembly; or null if the current instance represents a generic type parameter, an array type, pointer type, or byref type based on a type parameter, or a generic type that is not a generic type definition but contains unresolved type parameters.

Could be rewritten as:

The fully qualified name of the type, including its namespace but not its assembly; or null if the current instance represents one of the following:

• a generic type parameter (example: typeof(List<object>).GetGenericTypeDefinition().GetGenericArguments()[0])
• a generic type that is not a generic type definition but contains unresolved type parameters (example: typeof(List<object>).GetGenericTypeDefinition().MakeGenericType(typeof(Dictionary<object, object>).GetGenericTypeDefinition()))
• an array type, pointer type, or byref type based on a type whose Type.FullName is null

[Youssef1313]

Oh, I see.
The bullet points makes it much clearer. This is a doc clarification request then.

[jkotas]

This can return null for all sorts of custom types. How about this?

The fully qualified name of the type, including its namespace but not its assembly; or null if the type cannot be represented by a fully qualified name. Types that cannot be represented by a fully qualified name include types that contain unresolved generic parameters (Type.ContainsGenericParameters is true) and types that contain function pointers.