AppVer.Development.CodeAnalyzer.VisualBasic 1.1.1

AppVer.Development.CodeAnalyzer.VisualBasic

Roslyn analyzers for Visual Basic projects.

Explicit return statements

Enforces explicit Return or Throw statements in all functions to help prevent hidden fall-through paths.

• Reports missing return paths as warnings by default (configurable via .editorconfig).
• Supports Visual Basic projects targeting .NET Framework and .NET Core.

Function CalculateValue(x As Integer) As Integer
    If x > 10 Then
        Return 5
    End If
    ' Missing explicit Return or Throw
End Function

Ref-struct safety for VB.NET

Visual Basic can consume ref-like types such as Span(Of T), ReadOnlySpan(Of T), and C# ref struct types through a compiler workaround, but the VB compiler does not enforce C# ref-struct lifetime rules. These analyzers restore that safety at compile time.

The VB workaround

Apply a non-error Obsolete attribute to members (or types) that use ref-like types:

Imports System

<Obsolete("Allow ref structs", False)>
Public Sub ReadSecondValue()
    Dim values As New Span(Of Integer)({1, 2, 3})
    Console.WriteLine(values(1))
End Sub

For fields and properties, apply the attribute at class level:

<Obsolete("Allow ref structs", False)>
Public Class BufferView
    Private _span As Span(Of Integer)
End Class

The analyzer treats every ref-like use as safety-sensitive. See RefStructSafetyPlan.md for full design details.

Diagnostics

Async and iterator safety is covered entirely by VBRS0004/0005 (conservative retention at declaration). There are no separate use-after-Await/Yield rules.

ByRef parameters

Passing a ref-like value ByRef is not diagnosed at the call site. Dangerous callee behavior is caught inside the callee by the rules above:

• Field or auto-property storage → VBRS0003
• Boxing or reference conversion → VBRS0001
• Lambda capture → VBRS0002

ByRef parameters cannot appear in Async or Iterator methods (compiler error BC36926), so retention rules do not apply to that path.

For compiled C# APIs (BCL, NuGet libraries), ref-like ByRef parameters were checked by C#'s ref-safety analysis at compile time. For other VB assemblies compiled with the same Obsolete workaround and consumed only as metadata, passing ref-like values ByRef is caller-beware — the analyzer cannot see those bodies.

Example violations

' VBRS0001: boxing
Dim s As Span(Of Integer)
Dim o As Object = s

' VBRS0002: lambda capture
Dim f = Function() s.Length

' VBRS0003: field storage
Private _span As Span(Of Integer)

' VBRS0004: ref-like local in Async method
Public Async Function M() As Task
    Dim s As Span(Of Integer)
End Function

Configuration

Configure severity per diagnostic in .editorconfig. Example:

dotnet_diagnostic.VBRS0001.severity = error
dotnet_diagnostic.VBRS0002.severity = warning
dotnet_diagnostic.VBRS0003.severity = none

Usage

Install the NuGet package for your VB project. Visual Studio and dotnet build will run the analyzers automatically under Analyzers in Solution Explorer.

dotnet add package AppVer.Development.CodeAnalyzer.VisualBasic