dotnet/roslyn

'Use pattern-matching' should be missing on writes from local function captures

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#29,512 opened on Aug 24, 2018

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Area-IDEBughelp wanted

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Description

From https://github.com/dotnet/roslyn/pull/26097#discussion_r210728805

We should look for writes that are logically within the span, but syntactically are not.

var s = field as string;
WriteField();
if (s != null) { ... }

void WriteField () => field = null;

/cc @sharwell

Contributor guide

Research direction
Investigate the pattern matching analyzer's handling of writes from local function captures. Trace the data flow analysis for the 'Use pattern matching' diagnostic in the context of local functions.
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.
1-3 hours
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.
Mostly clear
Prerequisites
C#Roslyn internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30