Make sure all types are fully qualified before rewriting parameter

AutomaticInterface/DotnetAutomaticInterface/Builder.cs

@@ -202,8 +202,13 @@ bool nullableContextEnabled
         )
         {
             var addNullable = new AddNullableAnnotationSyntaxRewriter();
+            // Modify the full parameter display string to add the nullable annotation
             return addNullable
-                .Visit(param.DeclaringSyntaxReferences.First().GetSyntax())
+                .Visit(
+                    SyntaxFactory.ParseParameterList(
+                        param.ToDisplayString(FullyQualifiedDisplayFormat)
+                    )
+                )
                 .ToFullString();
         }
         return param.ToDisplayString(FullyQualifiedDisplayFormat);

AutomaticInterface/Tests/Methods/Methods.FullyQualifyOptionalNullableGenericTypes.verified.txt

@@ -0,0 +1,20 @@
+//--------------------------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if the code is regenerated.
+// </auto-generated>
+//--------------------------------------------------------------------------------------------------
+
+#nullable enable
+namespace AutomaticInterfaceExample
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("DotnetAutomaticInterface", "")]
+    public partial interface IDemoClass
+    {
+        /// <inheritdoc cref="AutomaticInterfaceExample.DemoClass.TryStartTransaction(int?, AutomaticInterfaceExample.Types.Model{AutomaticInterfaceExample.Types.Model2})" />
+        bool TryStartTransaction(int? param, global::AutomaticInterfaceExample.Types.Model<global::AutomaticInterfaceExample.Types.Model2>? modelParam = null);
+
+    }
+}
+#nullable restore

AutomaticInterface/Tests/Methods/Methods.cs

@@ -99,6 +99,37 @@ public bool TryStartTransaction(int? param, int param2 = 0, string data = null,
         await Verify(Infrastructure.GenerateCode(code));
     }
 
+    [Fact]
+    public async Task FullyQualifyOptionalNullableGenericTypes()
+    {
+        const string code = """
+
+            using DotnetAutomaticInterface;
+
+
+            namespace AutomaticInterfaceExample {
+
+                namespace Types {
+                    public class Model<T>;
+                    public class Model2;
+                }
+
+                [GenerateAutomaticInterface]
+                public class DemoClass
+                {
+                    public bool TryStartTransaction(int? param, Types.Model<Types.Model2> modelParam = null)
+                    {
+                        return true;
+                    }
+                }
+
+            }
+
+
+            """;
+        await Verify(Infrastructure.GenerateCode(code));
+    }
+
     [Fact]
     public async Task AddsPublicMethodToInterface()
     {