dotnet/roslyn

VB parsing string-interpolation in erroneous code has poor error recovery

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#3,617 opened on Jun 22, 2015

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 (15 comments) (0 reactions) (1 assignee)C# (4,257 forks)batch import
Area-CompilersBugConcept-Diagnostic Clarityhelp wanted

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Description

Watch this video: string-interpolation-parsing

I get into this situation often when I'm copying+pasting code around, or breaking a method up into smaller methods by deleting "sub" and then re-adding a bunch of "sub" and "end sub" statements where appropriate.

WHAT I OBSERVE: When there's a valid statement, regular strings and interpolated string parse fine.

When there's an invalid statement, regular strings parse fine, but interpolated strings don't recognize their terminating quote, so the remainder of the entire file gets "stringed out".

WHAT I EXPECT: interpolated strings should believe themselves terminated at the terminating quote, just like regular strings do.

Contributor guide

Research direction
Investigate the parsing of string interpolation in Visual Basic when there are syntax errors. Focus on the error recovery logic and how it currently fails to terminate interpolated strings properly. Trace through the parser code for interpolated strings and compare with regular strings to identify the missing or incorrect interaction with error recovery.
Tech stack
csharp
Domain
compilers
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.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30