This project provides compile-time support for pure (const) C# functions. A pure function has no side-effects.

Annotating a method with the Const attribute declares it as a pure function. The diagnostics in this project will then report on any side-effects.

• CConst1: A pure function may not contain an assignment to a non-local variable.

  using FonsDijkstra.CConst;
  
  class C
  {
      int i;
      
      [Const]
      int F()
      {
          i = 3; // reports diagnostic CConst1
          return 0;
      }
  }

• CConst2: A pure function may not call a non-pure function.

  using FonsDijkstra.CConst;
  
  class C
  {
      [Const]
      int F()
      {
          G(); // reports diagnostic CConst2
          return 0;
      }
  
      void G()
      {
      }
  }

• CConst51: An override of a pure function must be declared a pure function itself.

  using FonsDijkstra.CConst;
  
  class A
  {
      [Const]
      public abstract bool F();
  }
  
  class B : A
  {
      public override bool F() // reports diagnostic CConst51
      {
          return false;
      }
  }

• CConst52: An interface implementation of a pure function must be declared a pure function itself.

  using FonsDijkstra.CConst;
  
  interface I
  {
      [Const]
      bool F();
  }
  
  class C : I
  {
      public bool F() // reports diagnostic CConst52
      {
          return false;
      }
  }