Added VB scenarios.

VB does not have this particular bug and corresponding scenario works correctly.
There are however other bugs beyond the scope of what is fixed in this PR.

src/Compilers/VisualBasic/Test/Emit/CodeGen/CodeGenRefReturnTests.vb

@@ -2325,6 +2325,136 @@ BC31143: Method 'Public Overloads ByRef Function F() As Integer' does not have a
 </expected>)
         End Sub
 
+        <Fact>
+        <WorkItem(17706, "https://github.com/dotnet/roslyn/issues/17706")>
+        Public Sub SpillingByrefCall_NoSpilling()
+            Dim comp1 = CreateCSharpCompilation(
+"
+using System;
+
+public class TestClass
+{
+    int x = 0;
+
+    public ref int Save(int y)
+    {
+        x = y;
+        return ref x;
+    }
+
+    public void Write(ref int y)
+    {
+        Console.WriteLine(y);
+    }
+
+    public void Write(ref int y, int z)
+    {
+        Console.WriteLine(y);
+    }
+}")
+            comp1.VerifyDiagnostics()
+
+            Dim comp2 = CreateVisualBasicCompilation(
+                Nothing,
+"
+Imports System.Threading.Tasks
+
+Module Module1
+
+    Sub Main()
+        TestMethod().Wait()
+    End Sub
+
+    Async Function TestMethod() As Task
+        Dim inst = New TestClass
+
+        ' this is OK. `ref` call is not spilled.
+        ' prints: 10    (last value)
+        inst.Write(inst.Save(Await Task.FromResult(10)))
+
+
+        ' this is OK. `ref` call is not spilled.
+        ' prints: 22    (last value)
+        inst.Write(inst.Save(Await Task.FromResult(20)), inst.Save(22))
+    End Function
+
+End Module
+",
+                referencedCompilations:={comp1},
+                referencedAssemblies:=LatestVbReferences,
+                compilationOptions:=TestOptions.DebugExe)
+
+            comp2.AssertTheseDiagnostics()
+            Dim verifier = CompileAndVerify(comp2, expectedOutput:=
+"
+10
+22
+")
+            verifier.VerifyDiagnostics()
+        End Sub
+
+        <Fact(Skip:="https://github.com/dotnet/roslyn/issues/24275")>
+        <WorkItem(24275, "https://github.com/dotnet/roslyn/issues/24275")>
+        Public Sub SpillingByrefCall_Spilling()
+            Dim comp1 = CreateCSharpCompilation(
+"
+using System;
+
+public class TestClass
+{
+    int x = 0;
+
+    public ref int Save(int y)
+    {
+        x = y;
+        return ref x;
+    }
+
+    public void Write(ref int y)
+    {
+        Console.WriteLine(y);
+    }
+
+    public void Write(ref int y, int z)
+    {
+        Console.WriteLine(y);
+    }
+}")
+            comp1.VerifyDiagnostics()
+
+            Dim comp2 = CreateVisualBasicCompilation(
+                Nothing,
+"
+Imports System.Threading.Tasks
+
+Module Module1
+
+    Sub Main()
+        TestMethod().Wait()
+    End Sub
+
+    Async Function TestMethod() As Task
+        Dim inst = New TestClass
+
+        ' ERROR?
+        ' currently `ref` is spilled 'by-value' and assert fires.
+        inst.Write(inst.Save(Await Task.FromResult(30)), inst.Save(Await Task.FromResult(33)))
+    End Function
+
+End Module
+",
+                referencedCompilations:={comp1},
+                referencedAssemblies:=LatestVbReferences,
+                compilationOptions:=TestOptions.DebugExe)
+
+            comp2.AssertTheseDiagnostics()
+            Dim verifier = CompileAndVerify(comp2, expectedOutput:=
+"
+??
+")
+            verifier.VerifyDiagnostics()
+        End Sub
+
     End Class
 
 End Namespace