Improve Array.appendOne and remove SingleChildBuilder

Author: TimLariviere

CHANGELOG.md

@@ -9,6 +9,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 _No unreleased changes_
 
+## [3.0.0-pre16] - 2024-11-22
+
+### Changed
+- Small optimization when building for AOT by @TimLariviere
+
+### Removed
+- Removed `SingleChildBuilder` due to its big impact on AOT compilation compared to the low benefits on development experience by @TimLariviere
+
 ## [3.0.0-pre15] - 2024-11-21
 
 ### Added
@@ -192,7 +200,8 @@ _No unreleased changes_
 ### Changed
 - Fabulous.XamarinForms & Fabulous.MauiControls have been moved been out of the Fabulous repository. Find them in their own repositories: [https://github.com/fabulous-dev/Fabulous.XamarinForms](https://github.com/fabulous-dev/Fabulous.XamarinForms) / [https://github.com/fabulous-dev/Fabulous.MauiControls](https://github.com/fabulous-dev/Fabulous.MauiControls)
 
-[unreleased]: https://github.com/fabulous-dev/Fabulous/compare/3.0.0-pre15...HEAD
+[unreleased]: https://github.com/fabulous-dev/Fabulous/compare/3.0.0-pre16...HEAD
+[3.0.0-pre16]: https://github.com/fabulous-dev/Fabulous/releases/tag/3.0.0-pre16
 [3.0.0-pre15]: https://github.com/fabulous-dev/Fabulous/releases/tag/3.0.0-pre15
 [3.0.0-pre14]: https://github.com/fabulous-dev/Fabulous/releases/tag/3.0.0-pre14
 [3.0.0-pre13]: https://github.com/fabulous-dev/Fabulous/releases/tag/3.0.0-pre13

src/Fabulous/Array.fs

@@ -49,7 +49,7 @@ module ArraySlice =
 module Array =
     let inline appendOne (v: 'v) (arr: 'v array) =
         let res = Array.zeroCreate(arr.Length + 1)
-        Array.blit arr 0 res 0 arr.Length
+        res[..arr.Length - 1] <- arr
         res[arr.Length] <- v
         res
 

src/Fabulous/Builders.fs

@@ -279,52 +279,3 @@ type AttributeCollectionBuilder<'msg, 'marker, 'itemMarker when 'msg: equality>
 
             res
     end
-
-type SingleChildBuilderStep<'msg, 'marker when 'msg: equality> = delegate of unit -> WidgetBuilder<'msg, 'marker>
-
-[<Struct>]
-type SingleChildBuilder<'msg, 'marker, 'childMarker when 'msg: equality> =
-    val WidgetKey: WidgetKey
-    val Attr: WidgetAttributeDefinition
-    val AttributesBundle: AttributesBundle
-
-    new(widgetKey: WidgetKey, attr: WidgetAttributeDefinition) =
-        { WidgetKey = widgetKey
-          Attr = attr
-          AttributesBundle = AttributesBundle(StackList.empty(), ValueNone, ValueNone, ValueNone) }
-
-    new(widgetKey: WidgetKey, attr: WidgetAttributeDefinition, attributesBundle: AttributesBundle) =
-        { WidgetKey = widgetKey
-          Attr = attr
-          AttributesBundle = attributesBundle }
-
-    member inline this.Yield(widget: WidgetBuilder<'msg, 'childMarker>) =
-        SingleChildBuilderStep(fun () -> widget)
-
-    member inline this.Combine
-        ([<InlineIfLambda>] a: SingleChildBuilderStep<'msg, 'childMarker>, [<InlineIfLambda>] _b: SingleChildBuilderStep<'msg, 'childMarker>)
-        =
-        SingleChildBuilderStep(fun () ->
-            // We only want one child, so we ignore the second one
-            a.Invoke())
-
-    member inline this.Delay([<InlineIfLambda>] fn: unit -> SingleChildBuilderStep<'msg, 'childMarker>) =
-        SingleChildBuilderStep(fun () -> fn().Invoke())
-
-    member inline this.Run([<InlineIfLambda>] result: SingleChildBuilderStep<'msg, 'childMarker>) =
-        let childAttr = this.Attr.WithValue(result.Invoke().Compile())
-
-        let struct (scalars, widgets, widgetCollections, environments) =
-            this.AttributesBundle
-
-        WidgetBuilder<'msg, 'marker>(
-            this.WidgetKey,
-            AttributesBundle(
-                scalars,
-                (match widgets with
-                 | ValueNone -> ValueSome [| childAttr |]
-                 | ValueSome widgets -> ValueSome(Array.appendOne childAttr widgets)),
-                widgetCollections,
-                environments
-            )
-        )

src/Fabulous/Components/ComponentContext.fs

@@ -48,7 +48,7 @@ type ComponentContext(initialSize: int) =
         if values.Length < count then
             let newLength = max (values.Length * 2) count
             let newArray = Array.zeroCreate newLength
-            Array.blit values 0 newArray 0 values.Length
+            newArray[..values.Length - 1] <- values
             values <- newArray
 
     member this.TryGetValue<'T>(key: int) =