dotnet/roslyn

VB - wrong execution flow while debugging

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#48,575 opened on Oct 13, 2020

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Area-InteractiveBugLanguage-VBhelp wanted

Description

Version Used: current - VS 16.7.6 Steps to Reproduce:

    Function Test() As Boolean
        Dim sobj = New Object
        Dim o = 1

        SyncLock sobj
            If o = 1 Then
            Else
                Return False
            End If
        End SyncLock

        Return True
    End Function

Expected Behavior: Should not reach 'Return False' section of If statement Actual Behavior: Debugger reaches 'Return False' section of If statement, but without returning from function

Contributor guide

Tech stack
csharp
Domain
developer experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic understanding of Visual Basic syntaxFamiliarity with Roslyn compiler architecture
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
The bug involves incorrect step by step execution in the VB debugger. Look into the Roslyn debugger implementation, specifically the expression evaluator and stepping logic for VB. The issue might be in the handling of SyncLock and conditional branches. Check files under '/src/Compilers/VisualBasic/' related to debugging and emit.