[release/10.0.2xx] Fix CA1859 improperly handling default interface implementations

src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.NetCore.Analyzers/Performance/UseConcreteTypeAnalyzer.cs

@@ -268,12 +268,19 @@ void Evaluate(ISymbol affectedSymbol, ITypeSymbol fromType, PooledConcurrentSet<
                     return;
                 }
 
-                // if any of the methods that are invoked on toType are explicit implementations of interface methods, then we don't want
-                // to recommend upgrading the type otherwise it would break those call sites
                 if (targets != null)
                 {
                     foreach (var t in targets)
                     {
+                        // if any of the methods that are invoked on fromType are default implementations of interface methods,
+                        // then we don't want to recommend upgrading the type because it would break those call sites.
+                        if (!t.IsAbstract && fromType.TypeKind is TypeKind.Interface)
+                        {
+                            return;
+                        }
+
+                        // if any of the methods that are invoked on toType are explicit implementations of interface methods,
+                        // then we don't want to recommend upgrading the type because it would break those call sites.
                         var check = toType;
                         while (check != null)
                         {

src/Microsoft.CodeAnalysis.NetAnalyzers/tests/Microsoft.CodeAnalysis.NetAnalyzers.UnitTests/Microsoft.NetCore.Analyzers/Performance/UseConcreteTypeTests.cs

@@ -662,6 +662,32 @@ static int Bar()
             await TestCSAsync(Source);
         }
 
+        [Fact]
+        [WorkItem(50328, "https://github.com/dotnet/sdk/issues/50328")]
+        public static async Task ShouldNotTrigger6()
+        {
+            const string Source = @"
+#nullable enable
+                interface IFoo
+                {
+                    int M() => 42;
+                }
+                public class C : IFoo
+                {
+                }
+                public class Use
+                {
+                    static int Bar()
+                    {
+                        IFoo f = new C();
+                        return f.M();
+                    }
+                }
+                ";
+
+            await TestCSAsync(Source);
+        }
+
         [Fact]
         public static async Task ShouldTrigger_InterpolatedString_Mameof()
         {