It's a csharp compile error to use optional parameters before ref par…

…ameters - fixes #1057
icsharpcode · Dec 10, 2023 · 8d57a1c · 8d57a1c
1 parent 4861f98
commit 8d57a1c
Show file tree

Hide file tree

Showing 3 changed files with 19 additions and 1 deletion.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ### VB -> C#
 
+* Convert optional parameters before ref parameters using attributes to avoid compile error [#1057](https://github.com/icsharpcode/CodeConverter/issues/1057)
 * Remove square brackets when escaping labels and identifiers [#1043](https://github.com/icsharpcode/CodeConverter/issues/1043) and [#1044](https://github.com/icsharpcode/CodeConverter/issues/1044)
 * Exit Property now returns value assigned to return variable [#1051](https://github.com/icsharpcode/CodeConverter/issues/1051)
 * Avoid stack overflow for very deeply nested binary expressions [#1033](https://github.com/icsharpcode/CodeConverter/issues/1033)

diff --git a/CodeConverter/CSharp/ExpressionNodeVisitor.cs b/CodeConverter/CSharp/ExpressionNodeVisitor.cs
@@ -1403,7 +1403,7 @@ public override async Task<CSharpSyntaxNode> VisitParameter(VBSyntax.ParameterSy
                     attributes.Insert(0,
                         SyntaxFactory.AttributeList(SyntaxFactory.SeparatedList(optionalDateTimeAttributes)));
                 }
-            } else if (node.Modifiers.Any(m => m.IsKind(VBasic.SyntaxKind.ByRefKeyword))) {
+            } else if (node.Modifiers.Any(m => m.IsKind(VBasic.SyntaxKind.ByRefKeyword)) || HasRefParametersAfterThisOne()) {
                 var defaultExpression = await node.Default.Value.AcceptAsync<ExpressionSyntax>(TriviaConvertingExpressionVisitor);
                 var arg = CommonConversions.CreateAttributeArgumentList(SyntaxFactory.AttributeArgument(defaultExpression));
                 _extraUsingDirectives.Add("System.Runtime.InteropServices");
@@ -1432,6 +1432,8 @@ public override async Task<CSharpSyntaxNode> VisitParameter(VBSyntax.ParameterSy
             id,
             @default
         );
+
+        bool HasRefParametersAfterThisOne() => vbSymbol is not null && baseParameters is {} bp && bp.Skip(vbSymbol.Ordinal + 1).Any(x => x.RefKind != RefKind.None);
     }
 
     private async Task<TypeSyntax> SyntaxOnlyConvertParamAsync(VBSyntax.ParameterSyntax node)

diff --git a/Tests/CSharp/ExpressionTests/ByRefTests.cs b/Tests/CSharp/ExpressionTests/ByRefTests.cs
@@ -343,6 +343,21 @@ public static bool CallingFunc()
 }");
     }
 
+    [Fact]
+    public async Task RefAfterOptionalArgumentAsync()
+    {
+        await TestConversionVisualBasicToCSharpAsync(@"
+    Sub S(Optional a As Integer = 0, Optional ByRef b As Integer = 0)
+        S()
+    End Sub
+", @"
+public void S([Optional, DefaultParameterValue(0)] int a, [Optional, DefaultParameterValue(0)] ref int b)
+{
+    int argb = 0;
+    S(b: ref argb);
+}");
+    }
+
     [Fact]
     public async Task OutOptionalArgumentAsync()
     {