public Prop1 : int { get; private set; }
public Prop2 : int { get; set; }

using System.Console;

public class A
{
  public this(i : int) { Prop1 = i; }
  public Prop1 : int { get; private set; }
  public Prop2 : int { get; set; }
}
 
module Program
{
  Main() : void
  {
    def a = A(123);
    a.Prop2 = 789;
    WriteLine($"a.Prop1=$(a.Prop1); a.Prop2=$(a.Prop2);");
    _ = ReadLine();
  }
}

// Support autoproperty (see C# 3.0 specification).
// убеждаемся, что это не абстракное или extern- свойсво, что это не индексер (т.е. нет параметров) и не член интерфейса.
when (!(propertyAst.Attributes %&& (NemerleAttributes.Abstract | NemerleAttributes.Extern)) 
      && !IsIndexer && !par.IsInterface)
  match (propertyAst.get, propertyAst.set)
  {
    | (Some(PT.ClassMember.Function(_, _, FunBody.Abstract) as getr), // распознаем, что getter и setter абстрактны (не имеют тел)
       Some(PT.ClassMember.Function(_, _, FunBody.Abstract) as setr)) => // за одно "выцепляем" ссылки на сами getter и setter.

      def field = Macros.NewSymbol("field"); // Генерируем новое имя для поля, которое будет хранить значение свойства
      par.Define(<[ decl: mutable $(field : name) : $(propertyAst.ty); ]>); // Добавляем поле это поле

      // Формируем тела getter-а и setter-а, так чтобы они использовали добавленное выше поле.
      getr.Body = <[ $(field : name) ]>;
      setr.Body = <[ $(field : name) = value ]>;

    | _ => ()
  }

_FR>get { return field ?? String.Empty; }
_FR>

[NullValue("")]
public Foo : string { get; set; }

$("ViewState" : usesite)

ViewState

when (!(propertyAst.Attributes %&& (NemerleAttributes.Abstract | NemerleAttributes.Extern)))
    match (propertyAst.get, propertyAst.set)
    {
        | (Some(PT.ClassMember.Function(_, _, FunBody.Abstract) as getr), 
             Some(PT.ClassMember.Function(_, _, FunBody.Abstract) as setr)) =>
            
            def ctx = Nemerle.Macros.ImplicitCTX();
            ctx.Env.Manager.MacroColors.PushUseSiteColor();
            try
            {
                getr.Body = <[
                    def val = ViewState[$(propertyAst.Name : string)];
                    if (val == null) $defaulteValue else (val :> $(propertyAst.ty))
                ]>;
                setr.Body = <[ ViewState[$(propertyAst.Name : string)] = value ]>;
            }
            finally { ctx.Env.Manager.MacroColors.PopColor(); }
            
        | _ => Message.Error(propertyAst.Location, "Property should have empty getter and setter!")
    }  
}

\Projects\Nemerle\ncc\hierarchy\TypeInfo.n(80,24,80,27): error : interface method cannot have body
\Projects\Nemerle\ncc\hierarchy\TypeInfo.n(80,29,80,32): error : interface method cannot have body
\Projects\Nemerle\ncc\hierarchy\TypeInfo.n(95,28,95,31): error : interface method cannot have body
\Projects\Nemerle\ncc\hierarchy\TypeInfo.n(95,33,95,36): error : interface method cannot have body
\Projects\Nemerle\tools\msbuild-task\Compiler.MSBuild.targets(167,9): error : interface members are not allowed to have any attributes specified, except 'new'
\Projects\Nemerle\tools\msbuild-task\Compiler.MSBuild.targets(167,9): error : fields cannot be defined inside interface
\Projects\Nemerle\tools\msbuild-task\Compiler.MSBuild.targets(167,9): error : interface members are not allowed to have any attributes specified, except 'new'
\Projects\Nemerle\tools\msbuild-task\Compiler.MSBuild.targets(167,9): error : fields cannot be defined inside interface

R>Обновился с репозитория, ошибка компиляции во второй фазе, эти изменения могут вызвать такую ошибку?

COMPILE [stage2] Nemerle.Compiler.dll
______......................................................
hierarchy/TypeInfo.n:80:24:80:27: ←[01;31merror←[0m: interface method cannot hav
e body
hierarchy/TypeInfo.n:80:29:80:32: ←[01;31merror←[0m: interface method cannot hav
e body
hierarchy/TypeInfo.n:95:28:95:31: ←[01;31merror←[0m: interface method cannot hav
e body
hierarchy/TypeInfo.n:95:33:95:36: ←[01;31merror←[0m: interface method cannot hav
e body
←[01;31merror←[0m: interface members are not allowed to have any attributes spec
ified, except 'new'
←[01;31merror←[0m: fields cannot be defined inside interface
←[01;31merror←[0m: interface members are not allowed to have any attributes spec
ified, except 'new'
←[01;31merror←[0m: fields cannot be defined inside interface
make[3]: *** [out.stage2/Nemerle.Compiler.stage2.dll] Error 1
make[3]: Leaving directory `/work/nemerle/ncc'
make[2]: *** [aux-stage] Error 2
make[2]: Leaving directory `/work/nemerle/ncc'
make[1]: *** [stage2] Error 2
make[1]: Leaving directory `/work/nemerle/ncc'
make: *** [all] Error 2

get { return field ?? String.Empty; }

[ImmutableProperty]
public Prop1 : int { public get; };

ИД>Зачем write-only представить не могу, а вот immutable в принципе могу

ИД>[ImmutableProperty]
ИД>public Prop1 : int { public get; };
ИД>

public Prop1 : int { get; private set; }

public PageNo : int
{
    get { ViewState["PageNo"] :> (int?) ?? 0; }
    private set { ViewState["PageNo"] = value; }
}

[Storage(ViewState), DefaultValue(0)] public PageNo : int { get; private set;}

[Storage(ViewState), DefaultValue(0)] public PageNo : int { get; private set;}

[ViewState(0)] public PageNo : int { get; private set; }

using Nemerle; 
using Nemerle.Compiler;
using Nemerle.Collections;
using Nemerle.Utility;
using Nemerle.Compiler.Parsetree;

using System;

namespace MacroLibrary2
{
  [MacroUsage(MacroPhase.BeforeTypedMembers, MacroTargets.Property, Inherited = true)]
  macro ViewState(_ : TypeBuilder, propertyAst : ParsedProperty, defaulteValue)
  {
    when (!(propertyAst.Attributes %&& (NemerleAttributes.Abstract | NemerleAttributes.Extern)))
      match (propertyAst.get, propertyAst.set)
      {
        | (Some(PT.ClassMember.Function(_, _, FunBody.Abstract) as getr), 
           Some(PT.ClassMember.Function(_, _, FunBody.Abstract) as setr)) =>
          
          def ctx = Nemerle.Macros.ImplicitCTX();
          ctx.Env.Manager.MacroColors.PushUseSiteColor();
          try
          {
            getr.Body = <[
              def val = $("ViewState" : usesite)[$(propertyAst.Name : string)];
              if (val == null) $defaulteValue else (val :> $(propertyAst.ty))
            ]>;
            setr.Body = <[ $("ViewState" : usesite)[$(propertyAst.Name : string)] = value ]>;
          }
          finally { ctx.Env.Manager.MacroColors.PopColor(); }
          
        | _ => Message.Error(propertyAst.Location, "Property should have empty getter and setter!")
      }  
  }
}

using System;
using Nemerle.Collections;
using System.Console;
using Nemerle.Utility;
using MacroLibrary2;

public class A
{
  ViewState : System.Collections.Hashtable = System.Collections.Hashtable();
  
  [ViewState(0)]
  public Prop1 : int { get; set; }

  [ViewState("<empty>")]
  public Prop2 : string { get; set; }
}

module Program
{
  Main() : void
  {
    def a = A();
    WriteLine($"a.Prop1=$(a.Prop1)");
    WriteLine($"a.Prop2=$(a.Prop2)");
    a.Prop1 = 123;
    a.Prop2 = "test";
    WriteLine($"a.Prop1=$(a.Prop1)");
    WriteLine($"a.Prop2=$(a.Prop2)");
    
    Write("..."); _ = ReadLine();
  }
}

a.Prop1=0
a.Prop2=<empty>
a.Prop1=123
a.Prop2=test

[MacroUsage(MacroPhase.BeforeTypedMembers, MacroTargets.Property, Inherited = true)]
macro ViewState(_ : TypeBuilder, propertyAst : ParsedProperty, defaulteValue)
{
  Helper.PersistState("ViewState", Nemerle.Macros.ImplicitCTX(), propertyAst, defaulteValue);
}

public Foo { get; } : Foo = Foo();

private _foo : Foo = Foo();
public   Foo : Foo { get { _foo; } }

private _foo : Foo;
public   Foo : Foo{ get { _foo ?? (_foo = Foo()); } }

public Foo : int
{ get; private set;}

// нежели так
[Accessor(WantSetter = true)] _foo;