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Showing content from https://github.com/dotnet/csharplang/issues/4037 below:

Allow nameof to always access instance members from static context (VS 17.7, .NET 8) · Issue #4037 · dotnet/csharplang · GitHub

• Proposed
• Prototype: Done
• Implementation: Done
• Specification: Not Started

For background see dotnet/roslyn#48754

The current compiler has some interesting behavior with regards to accessing instance members from a static context:

using System;
public struct C {
    public string P;
    public static string M1() => nameof(P); // Legal
    public static string M2() => nameof(P.Length); // error CS0120: An object reference is required for the non-static field, method, or property 'C.P'
}

Where even though P is an instance member you can access it from a static context, but you can't access P.Length.

The relevant part of the spec is this:

The meaning of the named_entity of a nameof_expression is the meaning of it as an expression; that is, either as a simple_name, a base_access or a member_access. However, where the lookup described in Simple names and Member access results in an error because an instance member was found in a static context, a nameof_expression produces no such error.

This is somewhat ambiguous, but can be interpreted as saying only the top level lookup ignores errors where an instance member was found in a static context, but nested lookups do not. See here dotnet/roslyn#48754 (comment).

My request here is twofold:

1. Firstly can the LDT clarify the meaning of the spec here.
2. If the current behavior is not a bug, can we allow this in a future language version.

1. Remove a strange and confusing inconsistency in what's allowed.
2. Attribute arguments are considered a static context, and accessing instance members is often useful in them, e.g. when using the ForeignKeyAttribute.

Update the spec from:

The meaning of the named_entity of a nameof_expression is the meaning of it as an expression; that is, either as a simple_name, a base_access or a member_access. However, where the lookup described in Simple names and Member access results in an error because an instance member was found in a static context, a nameof_expression produces no such error.

To

The meaning of a named_entity is the meaning of it as an expression; that is, either as a simple_name, a base_access or a member_access. However, where the lookup described in Simple names and Member access results in an error because an instance member was found in a static context, a nameof_expression produces no such error.

This is not a particularly common scenario, and so probably not worth changing the spec for, if it's decided that the current implementation is not a bug.

https://github.com/dotnet/csharplang/blob/master/meetings/2020/LDM-2020-11-11.md#allow-nameof-to-access-instance-members-from-static-contexts

alrz, yaakov-h, Unknown6656, PathogenDavid, nil4 and 25 more

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