API Proposal: Unsafe.IsNullRef(ref readonly)

[hez2010]

Background and motivation

Currently we cannot test whether a ref readonly is null ref or not because Unsafe.IsNullRef() takes a ref parameter instead of ref readonly parameter.
Given that Unsafe.IsNullRef doesn’t need mutability, the signature should be changed from IsNullRef(ref) to IsNullRef(ref readonly).

API Proposal

namespace System.Runtime.CompilerServices;

public static class Unsafe
{
-    public bool IsNullRef(ref value);
+    public bool IsNullRef(ref readonly value); // or in value
}

API Usage

ref readonly int Foo() {…}
ref readonly int x = ref Foo();
Unsafe.IsNullRef(in x);

Alternative Designs

No response

Risks

No response

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Issue Details

---

Background and motivation

Currently we cannot test whether a ref readonly is null ref or not because Unsafe.IsNullRef() takes a ref parameter instead of ref readonly parameter.
Given that Unsafe.IsNullRef doesn’t need the ability of mutability, the signature should be changed from IsNullRef(ref) to IsNullRef(ref readonly).

API Proposal

namespace System.Runtime.CompilerServices;

public static class Unsafe
{
-    public bool IsNullRef(ref value);
+    public bool IsNullRef(ref readonly value); // or in value
}

API Usage

ref readonly int Foo() {…}
ref readonly int x = ref Foo();
Unsafe.IsNullRef(in x);

Alternative Designs

No response

Risks

No response

Author:	hez2010
Assignees:	-
Labels:	api-suggestion, area-System.Runtime.CompilerServices
Milestone:	-

[sakno]

@hez2010 , you can but with a bit more verbose code:

ref readonly int x = ref Foo();
Unsafe.IsNullRef(ref Unsafe.AsRef(in x));

[stephentoub]

the signature should be changed from IsNullRef(ref) to IsNullRef(ref readonly).

The language doesn't currently support that, changing the current signature to in instead of ref would be breaking, and we can't overload on ref vs in.

This would require dotnet/csharplang#6010, at which point there are a bunch of methods including this one we'd be looking to change over.

[jkotas]

Superseded by #73608.

[hez2010]

I think you mean by #85911?