dotnet/roslyn

VB Editor IntelliSense does not show Task's members in ContinueWith

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#8,482 opened on Feb 9, 2016

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Area-CompilersBughelp wanted

Description

This item was filed by a customer. Please communicate and close the loop with your customer via the customer tab inside TFS.

Problem Description

Description: I have the following VB code:

 Public Class Form1 

 Private Sub OnTest() Handles Button1.Click 

 Dim t = Task.Factory.StartNew(Function() 5) 
 t.ContinueWith(Sub(ant) MsgBox(ant.Result)) 

 End Sub 

 End Class

This code compiles perfectly, but there's one bug: as soon as I type MsgBox(ant., then IntelliSense treats ant as Object - and hence doesn't show me Task's members - only Object's one.

Repro Steps:Code

 Private Sub OnTest() Handles Button1.Click 

 Dim t = Task.Factory.StartNew(Function() 5) 
 t.ContinueWith(Sub(ant) MsgBox(ant.Result)) 

 End Sub

Impact:IntelliSense treats "ant" variable as Object.

Contributor guide

Tech stack
None
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.
1-2 days
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.
clear
Prerequisites
Understanding VB.NET type inferenceFamiliarity with Roslyn completion provider
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate how Roslyn's IntelliSense handles lambda parameters in VB.NET, specifically for ContinueWith. Look at the completion provider for lambda parameter types, possibly in src/Features/LanguageServer or src/EditorFeatures. Check if the parameter 'ant' is correctly inferred as Task(Of Integer) from the antecedent. The issue may involve the type inference of lambda parameters in VB when chaining Task methods. Start by searching for relevant code in the Roslyn repository that handles VB completion for lambda expressions.