xamarin/Xamarin.Forms

Binding compiler fails with indexers on Arrays

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#4,524 opened on Nov 23, 2018

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a/Xaml </>a/binding ⛓e/5 :clock5:help wantedin-progressinactivet/bug :bug:up-for-grabs

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Description

Description

I was creating the repro for #4516, and found out that this Xaml fail compilation.

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage
		xmlns="http://xamarin.com/schemas/2014/forms"
		xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
		xmlns:local="using:Xamarin.Forms.Xaml.UnitTests"
		x:Class="Xamarin.Forms.Xaml.UnitTests.Gh4516"
		x:DataType="local:Gh4516VM">
	<Image x:Name="image" Source="{Binding Images[0]}" />
</ContentPage>

Expected Behavior

should compile, and works

Actual Behavior

throw a NRE at compilation

Basic Information

  • Version with issue: master

Contributor guide

Research direction
Reproduce the NullReferenceException using the provided XAML snippet. Then trace the binding compiler code path to find where array indexing is handled. Debug to identify the null reference source.
Tech stack
csharp
Domain
mobile
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.
Half day
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
C#XAMLXamarin.Forms
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40