Small updates to help with linker->aot port (#2873)

* Move GetDiagnosticCategory into shared code
* Describe the intent around usage of DiagnosticContext in a comment
* Minor fix in MessageOrigin GetHasCode
* Add tests for patterns which NativeAOT had trouble with

Linker changes made for https://github.com/dotnet/runtime/pull/71485

4 files changed, 76 insertions, 10 deletions

diff --git a/test/Mono.Linker.Tests.Cases/DataFlow/AttributeConstructorDataflow.cs b/test/Mono.Linker.Tests.Cases/DataFlow/AttributeConstructorDataflow.cs
index 7f73071d4..46120679c 100644
--- a/test/Mono.Linker.Tests.Cases/DataFlow/AttributeConstructorDataflow.cs
+++ b/test/Mono.Linker.Tests.Cases/DataFlow/AttributeConstructorDataflow.cs
@@ -16,8 +16,10 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 	{
 		[KeptAttributeAttribute (typeof (KeepsPublicConstructorAttribute))]
 		[KeptAttributeAttribute (typeof (KeepsPublicMethodsAttribute))]
+		[KeptAttributeAttribute (typeof (TypeArrayAttribute))]
 		[KeepsPublicConstructor (typeof (ClassWithKeptPublicConstructor))]
 		[KeepsPublicMethods ("Mono.Linker.Tests.Cases.DataFlow.AttributeConstructorDataflow+ClassWithKeptPublicMethods")]
+		[TypeArray (new Type[] { typeof (AttributeConstructorDataflow) })]
 		// Trimmer only for now - https://github.com/dotnet/linker/issues/2273
 		[ExpectedWarning ("IL2026", "--ClassWithKeptPublicMethods--", ProducedBy = ProducedBy.Trimmer)]
 		public static void Main ()
@@ -109,5 +111,15 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 				public int Field;
 			}
 		}
+
+		[Kept]
+		[KeptBaseType (typeof (Attribute))]
+		class TypeArrayAttribute : Attribute
+		{
+			[Kept]
+			public TypeArrayAttribute (Type[] types) // This should not trigger data flow analysis of the parameter
+			{
+			}
+		}
 	}
 }
diff --git a/test/Mono.Linker.Tests.Cases/DataFlow/AttributeFieldDataflow.cs b/test/Mono.Linker.Tests.Cases/DataFlow/AttributeFieldDataflow.cs
index 44c857b74..2cac037c5 100644
--- a/test/Mono.Linker.Tests.Cases/DataFlow/AttributeFieldDataflow.cs
+++ b/test/Mono.Linker.Tests.Cases/DataFlow/AttributeFieldDataflow.cs
@@ -16,8 +16,10 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 	{
 		[KeptAttributeAttribute (typeof (KeepsPublicConstructorsAttribute))]
 		[KeptAttributeAttribute (typeof (KeepsPublicMethodsAttribute))]
+		[KeptAttributeAttribute (typeof (TypeArrayAttribute))]
 		[KeepsPublicConstructors (Type = typeof (ClassWithKeptPublicConstructor))]
-		[KeepsPublicMethods ("Mono.Linker.Tests.Cases.DataFlow.AttributeFieldDataflow+ClassWithKeptPublicMethods")]
+		[KeepsPublicMethods (Type = "Mono.Linker.Tests.Cases.DataFlow.AttributeFieldDataflow+ClassWithKeptPublicMethods")]
+		[TypeArray (Types = new Type[] { typeof (AttributeFieldDataflow) })]
 		// Trimmer only for now - https://github.com/dotnet/linker/issues/2273
 		[ExpectedWarning ("IL2026", "--ClassWithKeptPublicMethods--", ProducedBy = ProducedBy.Trimmer)]
 		public static void Main ()
@@ -46,12 +48,14 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 		class KeepsPublicMethodsAttribute : Attribute
 		{
 			[Kept]
-			public KeepsPublicMethodsAttribute (
-				[KeptAttributeAttribute (typeof (DynamicallyAccessedMembersAttribute))]
-				[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicMethods)]
-				string type)
+			public KeepsPublicMethodsAttribute ()
 			{
 			}
+
+			[Kept]
+			[KeptAttributeAttribute (typeof (DynamicallyAccessedMembersAttribute))]
+			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicMethods)]
+			public string Type;
 		}
 
 		[Kept]
@@ -74,5 +78,18 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 			public static void KeptMethod () { }
 			static void Method () { }
 		}
+
+		[Kept]
+		[KeptBaseType (typeof (Attribute))]
+		class TypeArrayAttribute : Attribute
+		{
+			[Kept]
+			public TypeArrayAttribute ()
+			{
+			}
+
+			[Kept]
+			public Type[] Types;
+		}
 	}
 }
diff --git a/test/Mono.Linker.Tests.Cases/DataFlow/AttributePropertyDataflow.cs b/test/Mono.Linker.Tests.Cases/DataFlow/AttributePropertyDataflow.cs
index e6848fa5d..1b10390ea 100644
--- a/test/Mono.Linker.Tests.Cases/DataFlow/AttributePropertyDataflow.cs
+++ b/test/Mono.Linker.Tests.Cases/DataFlow/AttributePropertyDataflow.cs
@@ -16,8 +16,10 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 	{
 		[KeptAttributeAttribute (typeof (KeepsPublicConstructorsAttribute))]
 		[KeptAttributeAttribute (typeof (KeepsPublicMethodsAttribute))]
+		[KeptAttributeAttribute (typeof (TypeArrayAttribute))]
 		[KeepsPublicConstructors (Type = typeof (ClassWithKeptPublicConstructor))]
-		[KeepsPublicMethods ("Mono.Linker.Tests.Cases.DataFlow.AttributePropertyDataflow+ClassWithKeptPublicMethods")]
+		[KeepsPublicMethods (Type = "Mono.Linker.Tests.Cases.DataFlow.AttributePropertyDataflow+ClassWithKeptPublicMethods")]
+		[TypeArray (Types = new Type[] { typeof (AttributePropertyDataflow) })]
 		// Trimmer only for now - https://github.com/dotnet/linker/issues/2273
 		[ExpectedWarning ("IL2026", "--ClassWithKeptPublicMethods--", ProducedBy = ProducedBy.Trimmer)]
 		public static void Main ()
@@ -47,12 +49,15 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 		class KeepsPublicMethodsAttribute : Attribute
 		{
 			[Kept]
-			public KeepsPublicMethodsAttribute (
-				[KeptAttributeAttribute (typeof (DynamicallyAccessedMembersAttribute))]
-				[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicMethods)]
-				string type)
+			public KeepsPublicMethodsAttribute ()
 			{
 			}
+
+			[field: Kept]
+			[Kept]
+			[KeptAttributeAttribute (typeof (DynamicallyAccessedMembersAttribute))]
+			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicMethods)]
+			public string Type { get; [Kept] set; }
 		}
 
 		[Kept]
@@ -75,5 +80,19 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 			public static void KeptMethod () { }
 			static void Method () { }
 		}
+
+		[Kept]
+		[KeptBaseType (typeof (Attribute))]
+		class TypeArrayAttribute : Attribute
+		{
+			[Kept]
+			public TypeArrayAttribute ()
+			{
+			}
+
+			[field: Kept]
+			[Kept]
+			public Type[] Types { get; [Kept] set; }
+		}
 	}
 }
diff --git a/test/Mono.Linker.Tests.Cases/DataFlow/ByRefDataflow.cs b/test/Mono.Linker.Tests.Cases/DataFlow/ByRefDataflow.cs
index 0b05ededc..a16c455e8 100644
--- a/test/Mono.Linker.Tests.Cases/DataFlow/ByRefDataflow.cs
+++ b/test/Mono.Linker.Tests.Cases/DataFlow/ByRefDataflow.cs
@@ -126,10 +126,28 @@ namespace Mono.Linker.Tests.Cases.DataFlow
 			static IntPtr GetDangerous () { return IntPtr.Zero; }
 
 			[Kept]
+			[ExpectedWarning ("IL2070")]
+			static unsafe void LocalStackAllocDeref (Type t)
+			{
+				// Code pattern from CoreLib which caused problems in AOT port
+				// so making sure we handle this correctly (that is without failing)
+				int buffSize = 256;
+				byte* stackSpace = stackalloc byte[buffSize];
+				byte* buffer = stackSpace;
+
+				byte* toFree = buffer;
+				buffer = null;
+
+				// IL2070 - this is to make sure that DataFlow ran on the method's body
+				t.GetProperties ();
+			}
+
+			[Kept]
 			[ExpectedWarning ("IL2026")]
 			public static void Test ()
 			{
 				IntPtrDeref ();
+				LocalStackAllocDeref (null);
 			}
 		}
 	}