UnionBy stub had a wrong parameter type

src/ExpressiveSharp/Extensions/ExpressiveQueryableLinqExtensions.cs

@@ -408,7 +408,7 @@ public static IExpressiveQueryable<T> IntersectBy<T, TKey>(
         [EditorBrowsable(EditorBrowsableState.Never)]
         public static IExpressiveQueryable<T> UnionBy<T, TKey>(
             this IExpressiveQueryable<T> source,
-            IEnumerable<TKey> second,
+            IEnumerable<T> second,
             Func<T, TKey> keySelector)
             => throw new UnreachableException(InterceptedMessage);
 
@@ -551,7 +551,7 @@ public static IExpressiveQueryable<T> IntersectBy<T, TKey>(
         [EditorBrowsable(EditorBrowsableState.Never)]
         public static IExpressiveQueryable<T> UnionBy<T, TKey>(
             this IExpressiveQueryable<T> source,
-            IEnumerable<TKey> second,
+            IEnumerable<T> second,
             Func<T, TKey> keySelector,
             IEqualityComparer<TKey>? comparer)
             => throw new UnreachableException(InterceptedMessage);

tests/ExpressiveSharp.Generator.Tests/PolyfillInterceptorGenerator/SetOperationTests.UnionBy_GeneratesInterceptor.verified.txt

@@ -8,7 +8,7 @@ namespace ExpressiveSharp.Generated.Interceptors
         [global::System.Runtime.CompilerServices.InterceptsLocationAttribute(/* scrubbed */)]
         internal static global::ExpressiveSharp.IExpressiveQueryable<global::TestNs.Order> __Polyfill_UnionBy_361d_10_18(
             this global::ExpressiveSharp.IExpressiveQueryable<global::TestNs.Order> source,
-            global::System.Collections.Generic.IEnumerable<string> second,
+            global::System.Collections.Generic.IEnumerable<global::TestNs.Order> second,
                     global::System.Func<global::TestNs.Order, string> __func)
         {
             // Source: o => o.Tag

tests/ExpressiveSharp.Generator.Tests/PolyfillInterceptorGenerator/SetOperationTests.cs

@@ -75,7 +75,7 @@ namespace TestNs
                 class Order { public string Tag { get; set; } }
                 class TestClass
                 {
-                    public void Run(System.Linq.IQueryable<Order> query, System.Collections.Generic.IEnumerable<string> extra)
+                    public void Run(System.Linq.IQueryable<Order> query, System.Collections.Generic.IEnumerable<Order> extra)
                     {
                         query.AsExpressive()
                              .UnionBy(extra, o => o.Tag)

tests/ExpressiveSharp.IntegrationTests/Tests/SetOperationInterceptorTests.cs

@@ -0,0 +1,60 @@
+using ExpressiveSharp.IntegrationTests.Scenarios.Store.Models;
+
+namespace ExpressiveSharp.IntegrationTests.Tests;
+
+[TestClass]
+public class SetOperationInterceptorTests
+{
+    private static readonly List<Order> _orders = new()
+    {
+        new Order { Id = 1, Tag = "A", Price = 100, Quantity = 2 },
+        new Order { Id = 2, Tag = "B", Price = 50, Quantity = 1 },
+        new Order { Id = 3, Tag = "C", Price = 25, Quantity = 4 },
+    };
+
+    [TestMethod]
+    public void UnionBy_WithElementSequence_CompilesAndRuns()
+    {
+        var source = _orders.AsQueryable();
+        var extra = new List<Order>
+        {
+            new() { Id = 4, Tag = "B", Price = 999, Quantity = 9 },
+            new() { Id = 5, Tag = "D", Price = 10, Quantity = 1 },
+        };
+
+        var results = source.AsExpressive()
+            .UnionBy(extra, o => o.Tag)
+            .ToList();
+
+        var tags = results.Select(o => o.Tag).ToList();
+        Assert.AreEqual(4, results.Count);
+        CollectionAssert.AreEquivalent(new[] { "A", "B", "C", "D" }, tags);
+        Assert.AreEqual(2, results.Single(o => o.Tag == "B").Id);
+    }
+
+    [TestMethod]
+    public void ExceptBy_WithKeySequence_CompilesAndRuns()
+    {
+        var source = _orders.AsQueryable();
+        var excluded = new[] { "B" };
+
+        var results = source.AsExpressive()
+            .ExceptBy(excluded, o => o.Tag)
+            .ToList();
+
+        CollectionAssert.AreEquivalent(new[] { "A", "C" }, results.Select(o => o.Tag).ToList());
+    }
+
+    [TestMethod]
+    public void IntersectBy_WithKeySequence_CompilesAndRuns()
+    {
+        var source = _orders.AsQueryable();
+        var included = new[] { "B", "C", "X" };
+
+        var results = source.AsExpressive()
+            .IntersectBy(included, o => o.Tag)
+            .ToList();
+
+        CollectionAssert.AreEquivalent(new[] { "B", "C" }, results.Select(o => o.Tag).ToList());
+    }
+}