Add CollectionBuilderAttribute polyfill

README.md

@@ -50,6 +50,7 @@ Here's an example of some of the new features that **PolySharp** can enable down
 - `[StringSyntax]` (needed to enable [syntax highlight in the IDE](https://github.com/dotnet/runtime/issues/62505))
 - `[ModuleInitializer]` (needed to enable [custom module initializers](https://learn.microsoft.com/dotnet/csharp/language-reference/proposals/csharp-9.0/module-initializers))
 - `[RequiresLocation]` (needed to enable [ref readonly parameters](https://github.com/dotnet/csharplang/issues/6010))
+- `[CollectionBuilder]` (needed for [collection expressions](https://github.com/dotnet/csharplang/issues/5354))
 
 To leverage them, make sure to bump your C# language version. You can do this by setting the `<LangVersion>` MSBuild property in your project. For instance, by adding `<LangVersion>11.0</LangVersion>` (or your desired C# version) to the first `<PropertyGroup>` of your .csproj file. For more info on this, [see here](https://sergiopedri.medium.com/enabling-and-using-c-9-features-on-older-and-unsupported-runtimes-ce384d8debb), but remember that you don't need to manually copy polyfills anymore: simply adding a reference to **PolySharp** will do this for you automatically.
 

src/PolySharp.Package/README.md

@@ -48,6 +48,7 @@ Here's an example of some of the new features that **PolySharp** can enable down
 - `[StringSyntax]` (needed to enable [syntax highlight in the IDE](https://github.com/dotnet/runtime/issues/62505))
 - `[ModuleInitializer]` (needed to enable [custom module initializers](https://learn.microsoft.com/dotnet/csharp/language-reference/proposals/csharp-9.0/module-initializers))
 - `[RequiresLocation]` (needed to enable [ref readonly parameters](https://github.com/dotnet/csharplang/issues/6010))
+- `[CollectionBuilder]` (needed for [collection expressions](https://github.com/dotnet/csharplang/issues/5354))
 
 To leverage them, make sure to bump your C# language version. You can do this by setting the `<LangVersion>` MSBuild property in your project. For instance, by adding `<LangVersion>11.0</LangVersion>` (or your desired C# version) to the first `<PropertyGroup>` of your .csproj file. For more info on this, [see here](https://sergiopedri.medium.com/enabling-and-using-c-9-features-on-older-and-unsupported-runtimes-ce384d8debb), but remember that you don't need to manually copy polyfills anymore: simply adding a reference to **PolySharp** will do this for you automatically.
 

src/PolySharp.SourceGenerators/EmbeddedResources/System.Runtime.CompilerServices.CollectionBuilderAttribute.cs

@@ -0,0 +1,48 @@
+// <auto-generated/>
+#pragma warning disable
+#nullable enable annotations
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Runtime.CompilerServices
+{
+    [global::System.AttributeUsage(
+        global::System.AttributeTargets.Class |
+        global::System.AttributeTargets.Struct |
+        global::System.AttributeTargets.Interface,
+        Inherited = false)]
+    [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    internal sealed class CollectionBuilderAttribute : Attribute
+    {
+        /// <summary>
+        /// Initialize the attribute to refer to the <paramref name="methodName"/> method on the <paramref name="builderType"/> type.
+        /// </summary>
+        /// <param name="builderType">The type of the builder to use to construct the collection.</param>
+        /// <param name="methodName">The name of the method on the builder to use to construct the collection.</param>
+        /// <remarks>
+        /// <paramref name="methodName"/> must refer to a static method that accepts a single parameter of
+        /// type <see cref="ReadOnlySpan{T}"/> and returns an instance of the collection being built containing
+        /// a copy of the data from that span.  In future releases of .NET, additional patterns may be supported.
+        /// </remarks>
+        public CollectionBuilderAttribute(Type builderType, string methodName)
+        {
+            BuilderType = builderType;
+            MethodName = methodName;
+        }
+
+        /// <summary>
+        /// Gets the type of the builder to use to construct the collection.
+        /// </summary>
+        public Type BuilderType { get; }
+
+        /// <summary>
+        /// Gets the name of the method on the builder to use to construct the collection.
+        /// </summary>
+        /// <remarks>
+        /// This should match the metadata name of the target method.
+        /// For example, this might be ".ctor" if targeting the type's constructor.
+        /// </remarks>
+        public string MethodName { get; }
+    }
+}

src/PolySharp.SourceGenerators/EmbeddedResources/System.Runtime.CompilerServices.ModuleInitializerAttribute.cs

@@ -31,8 +31,5 @@ namespace System.Runtime.CompilerServices
     [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
     internal sealed class ModuleInitializerAttribute : global::System.Attribute
     {
-        public ModuleInitializerAttribute()
-        {
-        }
     }
 }

src/PolySharp.SourceGenerators/EmbeddedResources/System.Runtime.Versioning.RequiresPreviewFeaturesAttribute.cs

@@ -26,7 +26,9 @@ internal sealed class RequiresPreviewFeaturesAttribute : global::System.Attribut
         /// <summary>
         /// Initializes a new instance of the <see cref="global::System.Runtime.Versioning.RequiresPreviewFeaturesAttribute"/> class.
         /// </summary>
-        public RequiresPreviewFeaturesAttribute() { }
+        public RequiresPreviewFeaturesAttribute()
+        {
+        }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="global::System.Runtime.Versioning.RequiresPreviewFeaturesAttribute"/> class with the specified message.