Overview

After investigating this issue: https://developercommunity.visualstudio.com/t/Conditional-breakpoint-is-not-respecting/11063626

I determined that for evaluations inside ref-returning frames, the expression compiler would generate query method signatures indicating that the return type is T& (ref T), while the query method itself still returned T (as expected).

In particular, this bug breaks breakpoint conditions in VS; typical conditions rely on comparisons, which return Int32 and the debugger can make the implicit conversion from Int32 to the method signature bool return type. In ref-returning methods, the debugger cannot make the implicit conversion when the signature indicates bool&.

Details

Clearly this is an oversight on the C# expression compiler side; the VB EE already handles this correctly (EEMethodSymbol.vb)

Public Overrides ReadOnly Property ReturnsByRef As Boolean
    Get
        Return False
    End Get
End Property

The change is to make EEMethodSymbol not inherit RefKind and instead return RefKind.None.

Testing

Added unit test; deployed changes to experimental instance and verified the linked original issue is fixed.

Microsoft Reviewers: Open in CodeFlow