Avoid caching compilation data and use value equality for SyntaxNodes

src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/VirtualMethodIndexData.cs

@@ -8,7 +8,7 @@ namespace Microsoft.Interop
     /// <summary>
     /// VirtualMethodIndexAttribute data
     /// </summary>
-    internal sealed record VirtualMethodIndexData(int Index) : InteropAttributeData
+    internal sealed record VirtualMethodIndexData(int Index) : InteropAttributeCompilationData
     {
         public bool ImplicitThisParameter { get; init; }
 

src/libraries/System.Runtime.InteropServices/gen/Common/DefaultMarshallingInfoParser.cs

@@ -8,7 +8,7 @@ namespace Microsoft.Interop
 {
     internal static class DefaultMarshallingInfoParser
     {
-        public static MarshallingInfoParser Create(StubEnvironment env, IGeneratorDiagnostics diagnostics, IMethodSymbol method, InteropAttributeData interopAttributeData, AttributeData unparsedAttributeData)
+        public static MarshallingInfoParser Create(StubEnvironment env, IGeneratorDiagnostics diagnostics, IMethodSymbol method, InteropAttributeCompilationData interopAttributeData, AttributeData unparsedAttributeData)
         {
 
             // Compute the current default string encoding value.

src/libraries/System.Runtime.InteropServices/gen/LibraryImportGenerator/Analyzers/ConvertToLibraryImportAnalyzer.cs

@@ -146,9 +146,9 @@ private static bool HasUnsupportedMarshalAsInfo(TypePositionInfo info)
                 || unmanagedType == UnmanagedType.SafeArray;
         }
 
-        private static InteropAttributeData CreateInteropAttributeDataFromDllImport(DllImportData dllImportData)
+        private static InteropAttributeCompilationData CreateInteropAttributeDataFromDllImport(DllImportData dllImportData)
         {
-            InteropAttributeData interopData = new();
+            InteropAttributeCompilationData interopData = new();
             if (dllImportData.SetLastError)
             {
                 interopData = interopData with { IsUserDefined = interopData.IsUserDefined | InteropAttributeMember.SetLastError, SetLastError = true };

src/libraries/System.Runtime.InteropServices/gen/LibraryImportGenerator/LibraryImportData.cs

@@ -1,16 +1,31 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
-using System.Runtime.InteropServices;
-using Microsoft.CodeAnalysis;
-
 namespace Microsoft.Interop
 {
     /// <summary>
-    /// LibraryImportAttribute data
+    /// Contains the data related to a LibraryImportAttribute, without references to Roslyn symbols.
+    /// See <seealso cref="LibraryImportCompilationData"/> for a type with a reference to the StringMarshallingCustomType
     /// </summary>
     internal sealed record LibraryImportData(string ModuleName) : InteropAttributeData
+    {
+        public string EntryPoint { get; init; }
+
+        public static LibraryImportData From(LibraryImportCompilationData libraryImport)
+            => new LibraryImportData(libraryImport.ModuleName) with
+            {
+                EntryPoint = libraryImport.EntryPoint,
+                IsUserDefined = libraryImport.IsUserDefined,
+                SetLastError = libraryImport.SetLastError,
+                StringMarshalling = libraryImport.StringMarshalling
+            };
+    }
+
+    /// <summary>
+    /// Contains the data related to a LibraryImportAttribute, with references to Roslyn symbols.
+    /// Use <seealso cref="LibraryImportData"/> instead when using for incremental compilation state to avoid keeping a compilation alive
+    /// </summary>
+    internal sealed record LibraryImportCompilationData(string ModuleName) : InteropAttributeCompilationData
     {
         public string EntryPoint { get; init; }
     }

src/libraries/System.Runtime.InteropServices/gen/LibraryImportGenerator/LibraryImportGenerator.cs

@@ -7,7 +7,6 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Runtime.InteropServices;
-using System.Text;
 using System.Threading;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -181,7 +180,7 @@ private static MemberDeclarationSyntax PrintGeneratedSource(
                 .WithBody(stubCode);
         }
 
-        private static LibraryImportData? ProcessLibraryImportAttribute(AttributeData attrData)
+        private static LibraryImportCompilationData? ProcessLibraryImportAttribute(AttributeData attrData)
         {
             // Found the LibraryImport, but it has an error so report the error.
             // This is most likely an issue with targeting an incorrect TFM.
@@ -198,7 +197,7 @@ private static MemberDeclarationSyntax PrintGeneratedSource(
             ImmutableDictionary<string, TypedConstant> namedArguments = ImmutableDictionary.CreateRange(attrData.NamedArguments);
 
             string? entryPoint = null;
-            if (namedArguments.TryGetValue(nameof(LibraryImportData.EntryPoint), out TypedConstant entryPointValue))
+            if (namedArguments.TryGetValue(nameof(LibraryImportCompilationData.EntryPoint), out TypedConstant entryPointValue))
             {
                 if (entryPointValue.Value is not string)
                 {
@@ -207,7 +206,7 @@ private static MemberDeclarationSyntax PrintGeneratedSource(
                 entryPoint = (string)entryPointValue.Value!;
             }
 
-            return new LibraryImportData(attrData.ConstructorArguments[0].Value!.ToString())
+            return new LibraryImportCompilationData(attrData.ConstructorArguments[0].Value!.ToString())
             {
                 EntryPoint = entryPoint,
             }.WithValuesFromNamedArguments(namedArguments);
@@ -261,9 +260,9 @@ private static IncrementalStubGenerationContext CalculateStubInformation(
             var generatorDiagnostics = new GeneratorDiagnostics();
 
             // Process the LibraryImport attribute
-            LibraryImportData libraryImportData =
+            LibraryImportCompilationData libraryImportData =
                 ProcessLibraryImportAttribute(generatedDllImportAttr!) ??
-                new LibraryImportData("INVALID_CSHARP_SYNTAX");
+                new LibraryImportCompilationData("INVALID_CSHARP_SYNTAX");
 
             if (libraryImportData.IsUserDefined.HasFlag(InteropAttributeMember.StringMarshalling))
             {
@@ -302,7 +301,7 @@ private static IncrementalStubGenerationContext CalculateStubInformation(
                 methodSyntaxTemplate,
                 new MethodSignatureDiagnosticLocations(originalSyntax),
                 new SequenceEqualImmutableArray<AttributeSyntax>(additionalAttributes.ToImmutableArray(), SyntaxEquivalentComparer.Instance),
-                libraryImportData,
+                LibraryImportData.From(libraryImportData),
                 LibraryImportGeneratorHelpers.CreateGeneratorFactory(environment, options),
                 new SequenceEqualImmutableArray<Diagnostic>(generatorDiagnostics.Diagnostics.ToImmutableArray())
                 );

src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/InteropAttributeData.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Immutable;
-using System.Runtime.InteropServices;
 using Microsoft.CodeAnalysis;
 
 namespace Microsoft.Interop
@@ -22,9 +21,24 @@ public enum InteropAttributeMember
     }
 
     /// <summary>
-    /// Common data for all source-generated-interop trigger attributes
+    /// Common data for all source-generated-interop trigger attributes.
+    /// This type and derived types should not have any reference that would keep a compilation alive.
     /// </summary>
     public record InteropAttributeData
+    {
+        /// <summary>
+        /// Value set by the user on the original declaration.
+        /// </summary>
+        public InteropAttributeMember IsUserDefined { get; init; }
+        public bool SetLastError { get; init; }
+        public StringMarshalling StringMarshalling { get; init; }
+    }
+
+    /// <summary>
+    /// Common data for all source-generated-interop trigger attributes that also includes a reference to the Roslyn symbol for StringMarshallingCustomType.
+    /// See <seealso cref="InteropAttributeData"/> for a type that doesn't keep a compilation alive.
+    /// </summary>
+    public record InteropAttributeCompilationData
     {
         /// <summary>
         /// Value set by the user on the original declaration.
@@ -37,14 +51,14 @@ public record InteropAttributeData
 
     public static class InteropAttributeDataExtensions
     {
-        public static T WithValuesFromNamedArguments<T>(this T t, ImmutableDictionary<string, TypedConstant> namedArguments) where T : InteropAttributeData
+        public static T WithValuesFromNamedArguments<T>(this T t, ImmutableDictionary<string, TypedConstant> namedArguments) where T : InteropAttributeCompilationData
         {
             InteropAttributeMember userDefinedValues = InteropAttributeMember.None;
             bool setLastError = false;
             StringMarshalling stringMarshalling = StringMarshalling.Custom;
             INamedTypeSymbol? stringMarshallingCustomType = null;
 
-            if (namedArguments.TryGetValue(nameof(InteropAttributeData.SetLastError), out TypedConstant setLastErrorValue))
+            if (namedArguments.TryGetValue(nameof(InteropAttributeCompilationData.SetLastError), out TypedConstant setLastErrorValue))
             {
                 userDefinedValues |= InteropAttributeMember.SetLastError;
                 if (setLastErrorValue.Value is not bool)
@@ -53,7 +67,7 @@ public static T WithValuesFromNamedArguments<T>(this T t, ImmutableDictionary<st
                 }
                 setLastError = (bool)setLastErrorValue.Value!;
             }
-            if (namedArguments.TryGetValue(nameof(InteropAttributeData.StringMarshalling), out TypedConstant stringMarshallingValue))
+            if (namedArguments.TryGetValue(nameof(InteropAttributeCompilationData.StringMarshalling), out TypedConstant stringMarshallingValue))
             {
                 userDefinedValues |= InteropAttributeMember.StringMarshalling;
                 // TypedConstant's Value property only contains primitive values.
@@ -64,7 +78,7 @@ public static T WithValuesFromNamedArguments<T>(this T t, ImmutableDictionary<st
                 // A boxed primitive can be unboxed to an enum with the same underlying type.
                 stringMarshalling = (StringMarshalling)stringMarshallingValue.Value!;
             }
-            if (namedArguments.TryGetValue(nameof(InteropAttributeData.StringMarshallingCustomType), out TypedConstant stringMarshallingCustomTypeValue))
+            if (namedArguments.TryGetValue(nameof(InteropAttributeCompilationData.StringMarshallingCustomType), out TypedConstant stringMarshallingCustomTypeValue))
             {
                 userDefinedValues |= InteropAttributeMember.StringMarshallingCustomType;
                 if (stringMarshallingCustomTypeValue.Value is not INamedTypeSymbol)

src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/ManagedTypeInfo.cs

@@ -4,9 +4,6 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using System;
-using System.Collections.Generic;
-using System.Text;
 
 namespace Microsoft.Interop
 {
@@ -18,6 +15,19 @@ public abstract record ManagedTypeInfo(string FullTypeName, string DiagnosticFor
         private TypeSyntax? _syntax;
         public TypeSyntax Syntax => _syntax ??= SyntaxFactory.ParseTypeName(FullTypeName);
 
+        public virtual bool Equals(ManagedTypeInfo? other)
+        {
+            return other is not null
+                && Syntax.IsEquivalentTo(other.Syntax)
+                && FullTypeName == other.FullTypeName
+                && DiagnosticFormattedName == other.DiagnosticFormattedName;
+        }
+
+        public override int GetHashCode()
+        {
+            return FullTypeName.GetHashCode() ^ DiagnosticFormattedName.GetHashCode();
+        }
+
         protected ManagedTypeInfo(ManagedTypeInfo original)
         {
             FullTypeName = original.FullTypeName;

src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/ManualTypeMarshallingHelper.cs

@@ -24,6 +24,24 @@ public readonly record struct CustomTypeMarshallerData(
     public readonly record struct CustomTypeMarshallers(
         ImmutableDictionary<MarshalMode, CustomTypeMarshallerData> Modes)
     {
+        public bool Equals(CustomTypeMarshallers other)
+        {
+            // Check for equal count, then check if any KeyValuePairs exist in one 'Modes'
+            // but not the other (i.e. set equality on the set of items in the dictionary)
+            return Modes.Count == other.Modes.Count
+                && !Modes.Except(other.Modes).Any();
+        }
+
+        public override int GetHashCode()
+        {
+            int hash = 0;
+            foreach (KeyValuePair<MarshalMode, CustomTypeMarshallerData> mode in Modes)
+            {
+                hash ^= mode.Key.GetHashCode() ^ mode.Value.GetHashCode();
+            }
+            return hash;
+        }
+
         public CustomTypeMarshallerData GetModeOrDefault(MarshalMode mode)
         {
             CustomTypeMarshallerData data;

src/libraries/System.Runtime.InteropServices/tests/LibraryImportGenerator.UnitTests/CodeSnippets.cs

@@ -964,7 +964,7 @@ public static partial void Method(
             + CustomCollectionMarshallingCodeSnippets<CodeSnippets>.Stateless.In
             + CustomCollectionMarshallingCodeSnippets<CodeSnippets>.CustomIntMarshaller;
 
-    public static string RecursiveCountElementNameOnReturnValue => $@"
+        public static string RecursiveCountElementNameOnReturnValue => $@"
 using System.Runtime.InteropServices;
 using System.Runtime.InteropServices.Marshalling;
 {DisableRuntimeMarshalling}

src/libraries/System.Runtime.InteropServices/tests/LibraryImportGenerator.UnitTests/IncrementalGenerationTests.cs

@@ -1,17 +1,15 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.CSharp;
-using Microsoft.CodeAnalysis.Text;
-using Microsoft.Interop.UnitTests;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using System.Text;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.Interop.UnitTests;
 using Xunit;
 using static Microsoft.Interop.LibraryImportGenerator;
 
@@ -217,8 +215,7 @@ public static IEnumerable<object[]> CompilationObjectLivenessSources()
             // Basic stub
             yield return new[] { CodeSnippets.BasicParametersAndModifiers<int>() };
             // Stub with custom string marshaller
-            // TODO: Compilation is held alive by the CustomStringMarshallingType property in LibraryImportData
-            // yield return new[] { CodeSnippets.CustomStringMarshallingParametersAndModifiers<string>() }; 
+            yield return new[] { CodeSnippets.CustomStringMarshallingParametersAndModifiers<string>() };
         }
 
         // This test requires precise GC to ensure that we're accurately testing that we aren't