Add support for InlineArrayConversion

ICSharpCode.Decompiler.Tests/TestCases/Correctness/Conversions.cs

@@ -19,6 +19,7 @@
 // #include "../../../ICSharpCode.Decompiler/Util/CSharpPrimitiveCast.cs"
 
 using System;
+using System.Runtime.CompilerServices;
 
 using ICSharpCode.Decompiler.Util;
 
@@ -111,6 +112,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 
 			Console.WriteLine(ReadZeroTerminatedString("Hello World!".Length));
 			C1.Test();
+#if ROSLYN2 && !NET40
+			C3.Run();
+#endif
 		}
 
 		static void RunTest(bool checkForOverflow)
@@ -199,4 +203,32 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			return new C1();
 		}
 	}
+
+#if ROSLYN2 && !NET40
+	class C3
+	{
+		[InlineArray(4)] struct MyArray { private int elem; }
+
+		static void Foo(object o)
+		{
+			Console.WriteLine("Foo(object) called");
+		}
+
+		static void Foo(ReadOnlySpan<int> o)
+		{
+			Console.WriteLine("Foo(ReadOnlySpan<int>) called");
+		}
+
+		static void Test(MyArray arr)
+		{
+			Foo((object)arr);
+		}
+
+		public static void Run()
+		{
+			Console.WriteLine("C3.Run() called");
+			Test(default);
+		}
+	}
+#endif
 }

ICSharpCode.Decompiler.Tests/TestCases/Pretty/InlineArrayTests.cs

@@ -91,9 +91,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			Byte16 buffer2 = GetByte16();
 			Receiver((ReadOnlySpan<byte>)buffer2);
 			Byte16 buffer3 = GetByte16();
-			ReceiverSpan((Span<byte>)buffer3);
+			ReceiverSpan(buffer3);
 			Byte16 buffer4 = GetByte16();
-			ReceiverReadOnlySpan((ReadOnlySpan<byte>)buffer4);
+			ReceiverReadOnlySpan(buffer4);
 		}
 
 		public Byte16 GetByte16()

ICSharpCode.Decompiler/CSharp/Resolver/CSharpConversions.cs

@@ -230,12 +230,20 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 				if (c != Conversion.None)
 					return c;
 			}
+			if ((toType.IsKnownType(KnownTypeCode.SpanOfT) || toType.IsKnownType(KnownTypeCode.ReadOnlySpanOfT))
+				&& fromType.IsInlineArrayType())
+			{
+				var @field = fromType.GetFields(f => !f.IsStatic, GetMemberOptions.IgnoreInheritedMembers).FirstOrDefault();
+				var spanElementType = toType.TypeArguments[0];
+				if (field != null && IdentityConversion(field.ReturnType, spanElementType))
+					return Conversion.InlineArrayConversion;
+			}
 			return Conversion.None;
 		}
 
 		/// <summary>
 		/// Gets whether the type 'fromType' is convertible to 'toType'
-		/// using one of the conversions allowed when satisying constraints (§4.4.4)
+		/// using one of the conversions allowed when satisfying constraints (§4.4.4)
 		/// </summary>
 		public bool IsConstraintConvertible(IType fromType, IType toType)
 		{

ICSharpCode.Decompiler/TypeSystem/Implementation/KnownAttributes.cs

@@ -112,11 +112,14 @@ namespace ICSharpCode.Decompiler.TypeSystem
 
 		// C# 11 attributes:
 		RequiredAttribute,
+
+		// C# 12 attributes:
+		InlineArray,
 	}
 
 	public static class KnownAttributes
 	{
-		internal const int Count = (int)KnownAttribute.RequiredAttribute + 1;
+		internal const int Count = (int)KnownAttribute.InlineArray + 1;
 
 		static readonly TopLevelTypeName[] typeNames = new TopLevelTypeName[Count]{
 			default,
@@ -186,6 +189,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			new TopLevelTypeName("System.Runtime.CompilerServices", "PreserveBaseOverridesAttribute"),
 			// C# 11 attributes:
 			new TopLevelTypeName("System.Runtime.CompilerServices", "RequiredMemberAttribute"),
+			// C# 12 attributes:
+			new TopLevelTypeName("System.Runtime.CompilerServices", "InlineArrayAttribute"),
 		};
 
 		public static ref readonly TopLevelTypeName GetTypeName(this KnownAttribute attr)

ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs

@@ -306,6 +306,16 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			}
 		}
 
+		public static bool IsInlineArrayType(this IType type)
+		{
+			if (type.Kind != TypeKind.Struct)
+				return false;
+			var td = type.GetDefinition();
+			if (td == null)
+				return false;
+			return td.HasAttribute(KnownAttribute.InlineArray);
+		}
+
 		/// <summary>
 		/// Gets whether the type is the specified known type.
 		/// For generic known types, this returns true for any parameterization of the type (and also for the definition itself).