dotnet/roslyn

Parse await expression in VB when method is not async

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#10,320 opened on Apr 4, 2016

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Area-CompilersBugConcept-Diagnostic ClarityLanguage-VBhelp wanted

Description

If you use an await expression in VB when the enclosing method is not async, you get an error that you cannot use await in a non-async method, and you also get a syntax error. In most cases we could drop the syntax error and just report the former error message.

We could also check that we bind properly if we relax the parser. See C# issue #10232.

Contributor guide

Tech stack
csharp
Domain
tooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
basic understanding of Roslyn parserVB.NET languageerror handling in compilers
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Examine the VB parser code in the Roslyn repository, particularly the part that parses await expressions. Review the linked C# issue #10232 for a similar fix pattern. Identify where the syntax error is emitted and ensure that only the semantic error (await in non async method) is reported, dropping the redundant syntax error.