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Area-NullnessIssues related to handling of Nullable Reference TypesIssues related to handling of Nullable Reference TypesBug
Description
Issue description
A method of implementing INotifyPropertyChanged by publishing an Event now seems impossible to make compile cleanly (?)
namespace Nullness
open System.ComponentModel
type XViewModel() =
let propertyChanged = Event<PropertyChangedEventHandler, PropertyChangedEventArgs>()
//let propertyChanged = Event<PropertyChangedEventHandler|null, PropertyChangedEventArgs>()
interface INotifyPropertyChanged with
[<CLIEvent>]
member this.PropertyChanged = propertyChanged.Publish
generates this warning:
1>C:\git\temp\Nullness\Nullness\XViewModel.fs(10,39): warning FS3261: Nullness warning: The types 'System.Delegate' and 'System.Delegate | null' do not have compatible nullability.. See also C:\git\temp\Nullness\Nullness\XViewModel.fs(10,38)-(10,61).
And there doesn't seem to be a way to avoid this.
Choose one or more from the following categories of impact
- Unexpected nullness warning (false positive in nullness checking, code uses --checknulls and langversion:preview).Missing nullness warning in a case which can produce nulls (false negative, code uses --checknulls and langversion:preview).Breaking change related to older
null
constructs in code not using the checknulls switch.Breaking change related to generic code and explicit type constraints (null
,not null
).Type inference issue (i.e. code worked without type annotations before, and applying the --checknulls enforces type annotations).C#/F# interop issue related to nullness metadata.Other (none of the categories above apply).To pick up a draggable item, press the space bar. While dragging, use the arrow keys to move the item. Press space again to drop the item in its new position, or press escape to cancel.
Operating System
Windows (Default)
What .NET runtime/SDK kind are you seeing the issue on
.NET SDK (.NET Core, .NET 5+)
.NET Runtime/SDK version
Net SD 9.0.200
Reproducible code snippet and actual behavior
namespace Nullness
open System.ComponentModel
type XViewModel() =
let propertyChanged = Event<PropertyChangedEventHandler, PropertyChangedEventArgs>()
//let propertyChanged = Event<PropertyChangedEventHandler|null, PropertyChangedEventArgs>()
interface INotifyPropertyChanged with
[<CLIEvent>]
member this.PropertyChanged = propertyChanged.Publish
Possible workarounds
No response
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Area-NullnessIssues related to handling of Nullable Reference TypesIssues related to handling of Nullable Reference TypesBug
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Activity
abonie commentedon Mar 17, 2025
Seems like duplicate of #18349 likely