Rudimentary in modifier support

src/PublicApiGenerator/ApiGenerator.cs

@@ -417,6 +417,7 @@ static string ConvertAttributeToCode(Func<CodeTypeReference, CodeTypeReference>
             "System.Runtime.CompilerServices.ExtensionAttribute",
             "System.Runtime.CompilerServices.RuntimeCompatibilityAttribute",
             "System.Runtime.CompilerServices.IteratorStateMachineAttribute",
+            "System.Runtime.CompilerServices.IsReadOnlyAttribute",
             "System.Reflection.DefaultMemberAttribute",
             "System.Diagnostics.DebuggableAttribute",
             "System.Diagnostics.DebuggerNonUserCodeAttribute",
@@ -589,9 +590,16 @@ static bool IsExtensionMethod(ICustomAttributeProvider method)
                 else if (parameter.ParameterType.IsByReference)
                     direction |= FieldDirection.Ref;
 
-                var parameterType = parameter.ParameterType.IsByReference
-                    ? ((ByReferenceType)parameter.ParameterType).ElementType
-                    : parameter.ParameterType;
+                var parameterType = parameter.ParameterType;
+                if (parameterType is RequiredModifierType requiredModifierType)
+                {
+                    parameterType = requiredModifierType.ElementType;
+                }
+                // order is crucial because a RequiredModifierType can be a ByReferenceType
+                if (parameterType is ByReferenceType byReferenceType)
+                {
+                    parameterType = byReferenceType.ElementType;
+                }
 
                 var type = CreateCodeTypeReference(parameterType);
 
@@ -601,6 +609,15 @@ static bool IsExtensionMethod(ICustomAttributeProvider method)
                     isExtension = false;
                 }
 
+                // special case of ref is in
+                // TODO: Move CustomAttributes.Any(a => a.AttributeType.FullName == "System.Runtime.CompilerServices.IsReadOnlyAttribute") to extension method once other PR is merged
+                if (parameter.CustomAttributes.Any(a =>
+                        a.AttributeType.FullName == "System.Runtime.CompilerServices.IsReadOnlyAttribute"))
+                {
+                    type = ModifyCodeTypeReference(type, "in");
+                    direction = FieldDirection.In;
+                }
+
                 var name = parameter.HasConstant
                     ? string.Format(CultureInfo.InvariantCulture, "{0} = {1}", parameter.Name, FormatParameterConstant(parameter))
                     : parameter.Name;

src/PublicApiGeneratorTests/Class_constructors.cs

@@ -73,7 +73,7 @@ public void Should_output_constructor_parameters()
 {
     public class ClassWithConstructorWithParameters
     {
-        public ClassWithConstructorWithParameters(int intValue, string stringValue, PublicApiGeneratorTests.Examples.ComplexType complexType, PublicApiGeneratorTests.Examples.GenericType<int> genericType) { }
+        public ClassWithConstructorWithParameters(int intValue, string stringValue, PublicApiGeneratorTests.Examples.ComplexType complexType, PublicApiGeneratorTests.Examples.GenericType<int> genericType, ref int intValueByRef, in int intValueByIn) { }
     }
 }");
         }
@@ -147,7 +147,7 @@ public ClassWithPublicConstructor()
 
         public class ClassWithConstructorWithParameters
         {
-            public ClassWithConstructorWithParameters(int intValue, string stringValue, ComplexType complexType, GenericType<int> genericType)
+            public ClassWithConstructorWithParameters(int intValue, string stringValue, ComplexType complexType, GenericType<int> genericType, ref int intValueByRef, in int intValueByIn)
             {
             }
         }

src/PublicApiGeneratorTests/Interface_method_parameters.cs

@@ -148,6 +148,19 @@ public interface IMethodWithRefParameter
 }");
         }
 
+        [Fact]
+        void Should_output_in_parameters()
+        {
+            AssertPublicApi<IMethodWithInParameter>(
+                @"namespace PublicApiGeneratorTests.Examples
+{
+    public interface IMethodWithInParameter
+    {
+        void Method(in string value);
+    }
+}");
+        }
+
         [Fact]
         void Should_output_out_parameters()
         {
@@ -230,6 +243,11 @@ public interface IMethodWithRefParameter
             void Method(ref string value);
         }
 
+        public interface IMethodWithInParameter
+        {
+            void Method(in string value);
+        }
+
         public interface IMethodWithOutParameter
         {
             void Method(out string value);

src/PublicApiGeneratorTests/Method_parameters.cs

@@ -75,6 +75,34 @@ public class MethodWithGenericTypeParameter
 }");
         }
 
+        [Fact]
+        public void Should_output_generic_ref_type()
+        {
+            AssertPublicApi<MethodWithGenericRefTypeParameter>(
+                @"namespace PublicApiGeneratorTests.Examples
+{
+    public class MethodWithGenericRefTypeParameter
+    {
+        public MethodWithGenericRefTypeParameter() { }
+        public void Method(ref PublicApiGeneratorTests.Examples.GenericType<int> value) { }
+    }
+}");
+        }
+
+        [Fact]
+        public void Should_output_generic_in_type()
+        {
+            AssertPublicApi<MethodWithGenericInTypeParameter>(
+                @"namespace PublicApiGeneratorTests.Examples
+{
+    public class MethodWithGenericInTypeParameter
+    {
+        public MethodWithGenericInTypeParameter() { }
+        public void Method(in PublicApiGeneratorTests.Examples.GenericType<int> value) { }
+    }
+}");
+        }
+
         [Fact]
         public void Should_output_fully_qualified_type_name_for_generic_parameter()
         {
@@ -159,6 +187,20 @@ public class MethodWithRefParameter
 }");
         }
 
+        [Fact]
+        public void Should_output_in_parameters()
+        {
+            AssertPublicApi<MethodWithInParameter>(
+                @"namespace PublicApiGeneratorTests.Examples
+{
+    public class MethodWithInParameter
+    {
+        public MethodWithInParameter() { }
+        public void Method(in string value) { }
+    }
+}");
+        }
+
         [Fact]
         public void Should_output_out_parameters()
         {
@@ -265,6 +307,20 @@ public void Method(GenericType<int> value)
             }
         }
 
+        public class MethodWithGenericRefTypeParameter
+        {
+            public void Method(ref GenericType<int> value)
+            {
+            }
+        }
+
+        public class MethodWithGenericInTypeParameter
+        {
+            public void Method(in GenericType<int> value)
+            {
+            }
+        }
+
         public class MethodWithGenericTypeOfComplexTypeParameter
         {
             public void Method(GenericType<ComplexType> value)
@@ -307,6 +363,13 @@ public void Method(ref string value)
             }
         }
 
+        public class MethodWithInParameter
+        {
+            public void Method(in string value)
+            {
+            }
+        }
+
         public class MethodWithOutParameter
         {
             public void Method(out string value)

src/PublicApiGeneratorTests/PublicApiGeneratorTests.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFrameworks>netcoreapp2.1;net452</TargetFrameworks>
     <NoWarn>$(NoWarn);CS0067</NoWarn>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>