Add InlineArrayAttribute polyfill

README.md

@@ -75,6 +75,7 @@ It also includes the following optional runtime-supported polyfills:
 - `[SuppressGCTransition]` (see [here](https://devblogs.microsoft.com/dotnet/improvements-in-native-code-interop-in-net-5-0/))
 - `[DisableRuntimeMarshalling]` (see [here](https://learn.microsoft.com/dotnet/standard/native-interop/disabled-marshalling))
 - `[UnsafeAccessor]` (see [here](https://github.com/dotnet/runtime/issues/81741))
+- `[InlineArray]` (see [here](https://learn.microsoft.com/dotnet/csharp/language-reference/proposals/csharp-12.0/inline-arrays))
 
 # Options ⚙️
 

src/PolySharp.Package/README.md

@@ -73,6 +73,7 @@ It also includes the following optional runtime-supported polyfills:
 - `[SuppressGCTransition]` (see [here](https://devblogs.microsoft.com/dotnet/improvements-in-native-code-interop-in-net-5-0/))
 - `[DisableRuntimeMarshalling]` (see [here](https://learn.microsoft.com/dotnet/standard/native-interop/disabled-marshalling))
 - `[UnsafeAccessor]` (see [here](https://github.com/dotnet/runtime/issues/81741))
+- `[InlineArray]` (see [here](https://learn.microsoft.com/dotnet/csharp/language-reference/proposals/csharp-12.0/inline-arrays))
 
 # Options ⚙️
 

src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Runtime.CompilerServices.InlineArrayAttribute.cs

@@ -0,0 +1,44 @@
+// <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.CompilerServices2
+{
+    /// <summary>
+    /// Indicates that the instance's storage is sequentially replicated "length" times.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This attribute can be used to annotate a <see langword="struct"/> type with a single field.
+    /// The runtime will replicate that field in the actual type layout as many times as is specified.
+    /// </para>
+    /// <para>
+    /// Here's an example of how an inline array type with 8 <see cref="float"/> values can be declared:
+    /// <code lang="csharp">
+    /// [InlineArray(8)]
+    /// struct Float8InlineArray
+    /// {
+    ///     private float _value;
+    /// }
+    /// </code>
+    /// </para>
+    /// </remarks>
+    [global::System.AttributeUsage(global::System.AttributeTargets.Struct, AllowMultiple = false)]
+    [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    [global::System.Diagnostics.Conditional("MULTI_TARGETING_SUPPORT_ATTRIBUTES")]
+    public sealed class InlineArrayAttribute : global::System.Attribute
+    {
+        /// <summary>Creates a new <see cref="global::System.Runtime.CompilerServices2.InlineArrayAttribute"/> instance with the specified length.</summary>
+        /// <param name="length">The number of sequential fields to replicate in the inline array type.</param>
+        public InlineArrayAttribute(int length)
+        {
+            Length = length;
+        }
+
+        /// <summary>Gets the number of sequential fields to replicate in the inline array type.</summary>
+        public int Length { get; }
+    }
+}

src/PolySharp.SourceGenerators/Models/SyntaxFixupType.cs

@@ -27,5 +27,11 @@ internal enum SyntaxFixupType
     /// Generates the <c>[UnmanagedCallersOnly]</c> type in the <c>InteropServices2</c> dummy namespace.
     /// </summary>
     /// <remarks>This is needed when methods annotated with the attribute have to be assigned to delegates, which Roslyn will otherwise block.</remarks>
-    UseInteropServices2ForUnmanagedCallersOnlyAttribute = 1 << 2
+    UseInteropServices2ForUnmanagedCallersOnlyAttribute = 1 << 2,
+
+    /// <summary>
+    /// Generates a global using for the <c>[InlineArray]</c> type in the dummy namespace.
+    /// </summary>
+    /// <remarks>This is always needed when the type is used, as the usage is entirely blocked in the normal namespace.</remarks>
+    EmitGlobalUsingForInlineArrayAttribute = 1 << 3
 }

src/PolySharp.SourceGenerators/PolyfillsGenerator.Polyfills.cs

@@ -153,6 +153,13 @@ static SyntaxFixupType GetSyntaxFixupType(Compilation compilation, string name)
                 fixupType |= SyntaxFixupType.RemoveMethodImplAttributes;
             }
 
+            // Emit the global using for the dummy [InlineArray] type, if allowed
+            if (name is "System.Runtime.CompilerServices.InlineArrayAttribute" &&
+                compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp10))
+            {
+                fixupType |= SyntaxFixupType.EmitGlobalUsingForInlineArrayAttribute;
+            }
+
             return fixupType;
         }
 
@@ -287,6 +294,18 @@ private void EmitGeneratedType(SourceProductionContext context, GeneratedType ty
                         "System.Runtime.InteropServices2");
                 }
 
+                if ((type.FixupType & SyntaxFixupType.EmitGlobalUsingForInlineArrayAttribute) != 0)
+                {
+                    // Generate a global using for [InlineArray]
+                    adjustedSource = adjustedSource.Replace(
+                        "namespace System.Runtime.CompilerServices2",
+                        """
+                        global using InlineArrayAttribute = global::System.Runtime.CompilerServices2.InlineArrayAttribute;
+
+                        namespace System.Runtime.CompilerServices2
+                        """);
+                }
+
                 sourceText = SourceText.From(adjustedSource, Encoding.UTF8);
             }
             else

tests/PolySharp.Tests/RuntimeSupport.cs

@@ -88,9 +88,9 @@ public void ReferenceSomeAssemblyFile()
 
 internal class AccessorApis
 {
-#pragma warning disable IDE0044
+#pragma warning disable CS0169, IDE0044
     private int field;
-#pragma warning restore IDE0044
+#pragma warning restore CS0169, IDE0044
 
     [StackTraceHidden]
     public void HideMe()
@@ -99,4 +99,12 @@ public void HideMe()
 
     [UnsafeAccessor(UnsafeAccessorKind.Field, Name = nameof(field))]
     public static extern ref int GetField(RandomApis obj);
+}
+
+[InlineArray(16)]
+internal struct Int8
+{
+#pragma warning disable CS0169, IDE0044, IDE0051
+    private int value0;
+#pragma warning restore CS0169, IDE0044, IDE0051
 }