dotnet/roslyn

Strange behaviour in async method

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#32,276 创建于 2019年1月9日

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 (5 评论) (0 反应) (0 负责人)C# (20,414 star) (4,257 fork)batch import
Area-InteractiveBugDeveloper CommunityInteractive-Debugginghelp wanted

描述

I have a solution targeting NetCoreApp2.0.

Lately I've seen that when running an async method, the debugger shows me variables that are non allocated (out of scope).

If this variable is an IQueryable<string> it will show show up in the 'Locals window' as NullReferenceException.

If I manually set the 'next statement' to first statement in the block containing this IQueryable<string>, a NullReferenceException will be thrown when accessing the variable.

This issue has been moved from https://developercommunity.visualstudio.com/content/problem/238451/strange-behaviour-in-async-method.html VSTS ticketId: 604787 These are the original issue comments: (no comments) These are the original issue solutions: (no solutions)

贡献者指南

技术栈
csharp
领域
tooling
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
5
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
over 1 week
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
needs investigation
前置要求
C# async/awaitRoslyn compiler internalsDebugging symbol generation
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
15
研究方向
Investigate the async state machine transformation in Roslyn, specifically in the AsyncRewriter class. Look at how local variables are mapped to closures and whether the debugger scoping information is correctly emitted. Check relevant tests for async debugging. No linked PRs found; this issue may require deep analysis of the compiler's code generation for async methods.