Add missing case for including interface members.

Add tests to verify interface members get included.
Add test for interface type constraints, but needs more investigation.

Author: carlossanlop

src/Compatibility/ApiDiff/Microsoft.DotNet.ApiDiff/MemoryOutputDiffGenerator.cs

@@ -176,6 +176,7 @@ private async Task<string> ProcessAfterAssemblyAsync(IAssemblySymbol afterAssemb
             MetadataReferences = loader.MetadataReferences,
             DiagnosticOptions = _diagnosticOptions,
             SyntaxRewriters = [
+                // IMPORTANT: The order of these elements matters!
                 new TypeDeclarationCSharpSyntaxRewriter(_addPartialModifier), // This must be visited BEFORE GlobalPrefixRemover as it depends on the 'global::' prefix to be found
                 GlobalPrefixRemover.Singleton, // And then call this ASAP afterwards so there are fewer identifiers to visit
                 PrimitiveSimplificationRewriter.Singleton,
@@ -643,7 +644,11 @@ m is EnumMemberDeclarationSyntax ||
 
     private static IEnumerable<T> GetMembersOfType<T>(SyntaxNode node) where T : MemberDeclarationSyntax => node
         .ChildNodes()
-        .Where(n => n is T m && IsEnumMemberOrHasPublicOrProtectedModifierOrIsDestructor(m))
+        .Where(n => n is T m &&
+                    // Interface members have no visibility modifiers
+                    (node.IsKind(SyntaxKind.InterfaceDeclaration) ||
+                     // For the rest of the types, analyze each member directly
+                     IsEnumMemberOrHasPublicOrProtectedModifierOrIsDestructor(m)))
         .Cast<T>();
 
     private string GetAttributeDocId(IMethodSymbol attributeConstructorSymbol, AttributeSyntax attribute, SemanticModel model)

test/Microsoft.DotNet.ApiDiff.Tests/Diff.Interface.Tests.cs

@@ -25,6 +25,8 @@ public struct MyStruct
                     }
                     public interface IMyInterface
                     {
+                        int MyMethod();
+                        long MyProperty { get; }
                     }
                 }
                 """,
@@ -33,6 +35,8 @@ namespace MyNamespace
                   {
                 +     public interface IMyInterface
                 +     {
+                +         int MyMethod();
+                +         long MyProperty { get; }
                 +     }
                   }
                 """);
@@ -44,6 +48,8 @@ namespace MyNamespace
                 {
                     public interface IMyBeforeInterface
                     {
+                        int MyMethod();
+                        long MyProperty { get; }
                     }
                 }
                 """,
@@ -52,6 +58,8 @@ namespace MyNamespace
                 {
                     public interface IMyAfterInterface
                     {
+                        int MyMethod();
+                        long MyProperty { get; }
                     }
                 }
                 """,
@@ -60,9 +68,13 @@ namespace MyNamespace
                   {
                 -     public interface IMyBeforeInterface
                 -     {
+                -         int MyMethod();
+                -         long MyProperty { get; }
                 -     }
                 +     public interface IMyAfterInterface
                 +     {
+                +         int MyMethod();
+                +         long MyProperty { get; }
                 +     }
                   }
                 """);
@@ -77,6 +89,8 @@ public struct MyStruct
                     }
                     public interface IMyInterface
                     {
+                        int MyMethod();
+                        long MyProperty { get; }
                     }
                 }
                 """,
@@ -93,9 +107,46 @@ namespace MyNamespace
                   {
                 -     public interface IMyInterface
                 -     {
+                +         int MyMethod();
+                +         long MyProperty { get; }
                 -     }
                   }
                 """);
 
+    [Fact(Skip = "The resulting inheritance shows more than expected but not wrong, and does not show the nullability constraing")]
+    // Shows: public interface IMyInterface<TKey, TValue> : System.Collections.Generic.IDictionary<TKey, TValue>, System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey, TValue>>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey, TValue>>, System.Collections.IEnumerable, System.Collections.Generic.IReadOnlyDictionary<TKey, TValue>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey, TValue>>
+    public Task InterfaceAddWithTypeConstraints() => RunTestAsync(
+                beforeCode: """
+                using System.Collections.Generic;
+                namespace MyNamespace
+                {
+                    public struct MyStruct
+                    {
+                    }
+                }
+                """,
+                afterCode: """
+                using System.Collections.Generic;
+                namespace MyNamespace
+                {
+                    public struct MyStruct
+                    {
+                    }
+                    public interface IMyInterface<TKey, TValue> : IDictionary<TKey, TValue>, IReadOnlyDictionary<TKey, TValue> where TKey : notnull
+                    {
+                        bool ContainsValue(TValue value);
+                    }
+                }
+                """,
+                expectedCode: """
+                  namespace MyNamespace
+                  {
+                +     public interface IMyInterface<TKey, TValue> : System.Collections.Generic.IDictionary<TKey, TValue>, System.Collections.Generic.IReadOnlyDictionary<TKey, TValue> where TKey : notnull
+                +     {
+                +         bool ContainsValue(TValue value);
+                +     }
+                  }
+                """);
+
     #endregion
 }