Merge pull request #15087 from michaelnebel/csharp/stubgenrefreadonly

C#: Stub generator support for `ref readonly` parameters.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp.StubGenerator/StubVisitor.cs

@@ -534,6 +534,9 @@ private void StubParameters(ICollection<IParameterSymbol> parameters)
                 case RefKind.In:
                     stubWriter.Write("in ");
                     break;
+                case RefKind.RefReadOnlyParameter:
+                    stubWriter.Write("ref readonly ");
+                    break;
                 default:
                     stubWriter.Write($"/* TODO: {parameter.RefKind} */");
                     break;
@@ -884,4 +887,4 @@ public override void VisitProperty(IPropertySymbol symbol)
         if (explicitInterfaceImplementations.Length == 0)
             StubProperty(symbol, null);
     }
-}
+}

csharp/extractor/Semmle.Extraction.Tests/StubGenerator.cs

@@ -42,7 +42,7 @@ public void StubGeneratorMethodTest()
         // Setup
         const string source = @"
 public class MyTest {
-    public int M1(string arg1) { return 0;}
+    public int M1(string arg1) { return 0; }
 }";
 
         // Execute
@@ -56,6 +56,26 @@ public class MyTest {
         Assert.Equal(expected, stub);
     }
 
+    [Fact]
+    public void StubGeneratorRefReadonlyParameterTest()
+    {
+        // Setup
+        const string source = @"
+public class MyTest {
+    public int M1(ref readonly Guid guid) { return 0; }
+}";
+
+        // Execute
+        var stub = GenerateStub(source);
+
+        // Verify
+        const string expected = @"public class MyTest {
+public int M1(ref readonly Guid guid) => throw null;
+}
+";
+        Assert.Equal(expected, stub);
+    }
+
     private static string GenerateStub(string source)
     {
         var st = CSharpSyntaxTree.ParseText(source);