roslyn: Method Returns string[] But var types as string[]?
Version Used:
See below
Steps to Reproduce:
- Clone this repo https://github.com/MelbourneDeveloper/Urls @ 0497258a6f99e78af43b50c9bacb8ec926019bce
- Open in Visual Studio
- Open this code and hover over tokens
UrlExtensions -> ToRelativeUrl
Expected Behavior:
tokens should be string[]
Actual Behavior:
tokens is string[]?
Microsoft Visual Studio Professional 2019 Version 16.9.2 VisualStudio.16.Release/16.9.2+31112.23 Microsoft .NET Framework Version 4.8.04084
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Visual F# Tools 16.9.0-beta.21102.9+7ce7132f1459095e635194d09d6f73265352029a Microsoft Visual F# Tools
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VisualStudio.DeviceLog 1.0 Information about my package
VisualStudio.Foo 1.0 Information about my package
VisualStudio.Mac 1.0 Mac Extension for Visual Studio
Xamarin 16.9.000.273 (d16-9@1bba9e0) Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.
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Xamarin.iOS and Xamarin.Mac SDK 14.14.2.5 (3836759d4) Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.
About this issue
- Original URL
- State: closed
- Created 3 years ago
- Comments: 42 (22 by maintainers)
@Youssef1313 @CyrusNajmabadi
In a nutshell, the reason why I will always use the explicit type instead of var in the future is this compiles:
Up until now, I assumed it wouldn’t, and I believe that this opens up a lot of possible issues. So, I will change code like this, in order to stop anyone from setting the variable to null:
I would like to see an opt-in code rule that forces this.
@CyrusNajmabadi
NRT is about expressing intent.
If some construct is going to make a variable nullable, I need to know about it. I should be forced to decide.
I mean, yes
varwill change the type tostring[]?. But it’s not a problem for such a case (to me at least).To be explicit about
tokensbeingstring[], I think IDE0007 needs to be adjusted for that.Tagging @CyrusNajmabadi @sharwell for thoughts about IDE0007. I tend to agree that IDE0007 could be relaxed not to warn if the nullable annotation is different.
I was one of the people who advocated for “expressing intent” to be considered in this design. My argument was based on a claim that a developer writing
varis intending to say “use flow analysis to choose an appropriate static type for this variable that works throughout the method”. Since nullability is a flow analysis concept, it’s always safe to choose the nullable form wherevaris used and it works in strictly more cases than the non-nullable form. A developer interested in an exact static type is more likely to prefer an explicit type instead ofvar, so a design decision that optimizesvarfor the flow analysis scenario is unlikely to negatively impact users who prefer explicit types.As with any decision of this scale, there are always going to be a few users that don’t fit cleanly on one side or the other. However, I do believe that the current design does a great job of optimizing
varfor the “choose the best static type from flow analysis” intent and optimizing explicit local types for the “use this specific static type” intent.@CyrusNajmabadi Based on this discussion, I think you’ll disagree with https://github.com/dotnet/docs/issues/22997. You may want to put your thoughts their so that the docs don’t get updated badly.