[Analyzer]: Flagging unexpected `UnsafeAccessorAttribute` usage

[AaronRobinsonMSFT]

The UnsafeAccessorAttribute feature has some non-obvious issues in some scenarios. The most recent example is captured in #91740.

Example:

using System.Runtime.CompilerServices;

class Program
{
    static void Main()
    {
        // Crashes at runtime with System.MissingMethodException:
        // Method not found: 'System.Object.<Main>g__MemberwiseClone|0_0'.
        _ = MemberwiseClone(new object());

        [UnsafeAccessor(UnsafeAccessorKind.Method)] // Analyzer should warn when applied to local function without defining "Name" property.
        static extern object MemberwiseClone(object obj);
    }
}

Additional cases for analyzer to consider: #91740 (comment)

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Issue Details

---

Background and motivation

The UnsafeAccessorAttribute feature has some non-obvious issues in some scenarios. The most recent example is captured in #91740.

using System.Runtime.CompilerServices;

class Program
{
    static void Main()
    {
        // Crashes at runtime with System.MissingMethodException:
        // Method not found: 'System.Object.<Main>g__MemberwiseClone|0_0'.
        _ = MemberwiseClone(new object());

        [UnsafeAccessor(UnsafeAccessorKind.Method)] // Analyzer should warn when applied to local function without defining "Name" property.
        static extern object MemberwiseClone(object obj);
    }
}

API Proposal

f

API Usage

f

Alternative Designs

No response

Risks

No response

Author:	AaronRobinsonMSFT
Assignees:	-
Labels:	api-suggestion, area-System.Runtime.CompilerServices, help wanted, source-generator
Milestone:	Future

[DaZombieKiller]

Would it make sense to expose an attribute similar to [CallerMemberName] for this scenario? If we could just mark string parameters and properties of attributes with [AttributedMemberName] or something similar, then these scenarios would "just work" for local functions without the need of an analyzer.