Prevent duplicates when overriding or shadowing methods

The current code will insert multiple definitions of a method when that method has been overridden or shadowed.

The approach is the same as that already used for property deduplication, which is to group by the method definition.

AutomaticInterface/AutomaticInterface/Builder.cs

@@ -64,6 +64,11 @@ private static void AddMethodsToInterface(
         InterfaceBuilder codeGenerator
     )
     {
+        var methodDisplayFormatForDeduplication = new SymbolDisplayFormat(
+            memberOptions: SymbolDisplayMemberOptions.IncludeParameters,
+            parameterOptions: SymbolDisplayParameterOptions.IncludeType
+        );
+
         classSymbol
             .GetAllMembers()
             .Where(x => x.Kind == SymbolKind.Method)
@@ -72,6 +77,8 @@ InterfaceBuilder codeGenerator
             .Where(x => x.MethodKind == MethodKind.Ordinary)
             .Where(x => !x.IsStatic)
             .Where(x => x.ContainingType.Name != nameof(Object))
+            .GroupBy(x => x.ToDisplayString(methodDisplayFormatForDeduplication))
+            .Select(x => x.First())
             .ToList()
             .ForEach(method =>
             {

AutomaticInterface/Tests/GeneratorTests.cs

@@ -2211,4 +2211,102 @@ public partial interface ISecondClass
             """;
         GenerateCode(code).Should().Be(expected);
     }
+
+    [Fact]
+    public void WorksWithMethodOverrides()
+    {
+        const string code = """
+
+            using AutomaticInterfaceAttribute;
+
+            namespace AutomaticInterfaceExample;
+
+            public class BaseClass
+            {
+                public virtual bool AMethod();
+            }
+
+            [GenerateAutomaticInterface]
+            public class DemoClass : BaseClass
+            {
+                public override bool AMethod() => return true;
+            }
+
+            """;
+
+        const string expected = """
+            //--------------------------------------------------------------------------------------------------
+            // <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>
+            //--------------------------------------------------------------------------------------------------
+
+            using System.CodeDom.Compiler;
+            using AutomaticInterfaceAttribute;
+
+            namespace AutomaticInterfaceExample
+            {
+                [GeneratedCode("AutomaticInterface", "")]
+                public partial interface IDemoClass
+                {
+                    /// <inheritdoc />
+                    bool AMethod();
+                    
+                }
+            }
+
+            """;
+        GenerateCode(code).Should().Be(expected);
+    }
+
+    [Fact]
+    public void WorksWithMethodShadowing()
+    {
+        const string code = """
+
+            using AutomaticInterfaceAttribute;
+
+            namespace AutomaticInterfaceExample;
+
+            public class BaseClass
+            {
+                public bool AMethod();
+            }
+
+            [GenerateAutomaticInterface]
+            public class DemoClass : BaseClass
+            {
+                public new bool AMethod() => return true;
+            }
+
+            """;
+
+        const string expected = """
+            //--------------------------------------------------------------------------------------------------
+            // <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>
+            //--------------------------------------------------------------------------------------------------
+
+            using System.CodeDom.Compiler;
+            using AutomaticInterfaceAttribute;
+
+            namespace AutomaticInterfaceExample
+            {
+                [GeneratedCode("AutomaticInterface", "")]
+                public partial interface IDemoClass
+                {
+                    /// <inheritdoc />
+                    bool AMethod();
+                    
+                }
+            }
+
+            """;
+        GenerateCode(code).Should().Be(expected);
+    }
 }