C# improvements

[romamihalich]

Summary

Found some issues in C# doc generation and decided to fix it.
Number 4. of changes list fixes #181.

Changes

1. Fix "returns" insertion

1.1 Method returning void

Not insert if void. Currently checks for first child in ret.return_statement, but it's not enough, because it modifiers like public, static etc can be put before return type.

before:

class TestClass
{
   /// <summary>
   /// 
   /// </summary>
   /// <param name="p1"></param>
   /// <returns></returns>
   public void TestMethod(int p1)
   {
   }
}

after:

class TestClass
{
   /// <summary>
   /// 
   /// </summary>
   /// <param name="p1"></param>
   public void TestMethod(int p1)
   {
   }
}

1.2 Constructor

Not insert at all. Currently inserts every time.

before:

class TestClass
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="p"></param>
    /// <returns></returns>
    public TestClass(int p)
    {
    }
}

after:

class TestClass
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="p"></param>
    public TestClass(int p)
    {
    }
}

1.3 Indexer

Change logic from search for return statement to checking if getter is present, because get might not contain return statement, but instead =>, also might not contain body at all in interfaces.
before:

interface IndexerTest
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    public IndexerTest this[int i] { set; }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    public IndexerTest this[int i] { get; }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    public IndexerTest this[int i] { get; set; }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    public IndexerTest this[int i] { get => null; set { } }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    /// <returns></returns>
    public IndexerTest this[int i] { get { return null; } }
}

after:

interface IndexerTest
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    public IndexerTest this[int i] { set; }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    /// <returns></returns>
    public IndexerTest this[int i] { get; }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    /// <returns></returns>
    public IndexerTest this[int i] { get; set; }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    /// <returns></returns>
    public IndexerTest this[int i] { get => null; set { } }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="i"></param>
    /// <returns></returns>
    public IndexerTest this[int i] { get { return null; } }
}

2. Fix parameter generation when attribute is attached to it

Currently gets 2-nd position of children in parameter. Changed it to take last child instead.

before:

class AttributeTest
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="string"></param>
    /// <param name="p2"></param>
    /// <returns></returns>
    private string TestAttribute([Attr] string p, int p2)
    {
    }
}

after:

class AttributeTest
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="p"></param>
    /// <param name="p2"></param>
    /// <returns></returns>
    private string TestAttribute([Attr] string p, int p2)
    {
    }
}

3. Added support for primary constructors

before:

/// <summary>
/// 
/// </summary>
class PrimaryConstructorTest(int p1, string p2)
{
}

after:

/// <summary>
/// 
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
class PrimaryConstructorTest(int p1, string p2)
{
}

4. Added support for records, record structs, structs

Same logic as for classes is applied.

/// <summary>
/// 
/// </summary>
/// <typeparam name="T1"></typeparam>
/// <typeparam name="T2"></typeparam>
/// <typeparam name="T3"></typeparam>
/// <param name="P1"></param>
record RecordTest<T1, T2, T3>(int P1);

/// <summary>
/// 
/// </summary>
/// <typeparam name="T1"></typeparam>
/// <typeparam name="T2"></typeparam>
/// <typeparam name="T3"></typeparam>
/// <param name="P1"></param>
/// <param name="P2"></param>
record struct RecordStructTest<T1, T2, T3>(string P1, int P2);

/// <summary>
/// 
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="a"></param>
/// <param name="b"></param>
struct StructTest<T>(Type1 a, int b)
{
}

5. Change parameters and type parameters order for xmldoc (type parameters should go first)

before:

class TypeParametersOrder
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="p1"></param>
    /// <param name="p2"></param>
    /// <typeparam name="T1"></typeparam>
    /// <typeparam name="T2"></typeparam>
    /// <returns></returns>
    public void Test<T1, T2>(string p1, string p2)
    {
    }
}

after:

class TypeParametersOrder
{
    /// <summary>
    /// 
    /// </summary>
    /// <typeparam name="T1"></typeparam>
    /// <typeparam name="T2"></typeparam>
    /// <param name="p1"></param>
    /// <param name="p2"></param>
    public void Test<T1, T2>(string p1, string p2)
    {
    }
}

[romamihalich]

Also "doxygen" is default annotation convention for C#. Most of C# devs use "xmldoc". Maybe it makes sense to set "xmldoc" as default?