Things to do for the REPL support in MCS:

Documentation for the REPL mode for MCS can be found here:

	      http://mono-project.com/CsharpRepl

* Embedding API

	* Booting the compiler without Main ()
	* Expose LoadAssembly/LoadPackage
	* Register fields?
	* Register a lookup function for fields?
	* Register classes to expose to REPL

* Embedded Library

	* Run a REPL on a socket (from Joe Shaw)
	* Host a REPL on XSP (from Nat).

* TODO

	Clear struct fields inside the clearing code.

* Other ideas:

	MD addin for "csharp"

* Supporting class-level declarations

	Currently the evaluator has this feature disabled, to enable
	it edit the eval.cs file and make this be the default:

-				parser.Lexer.putback_char = Tokenizer.EvalUsingDeclarationsParserCharacter;
-				//parser.Lexer.putback_char = Tokenizer.EvalCompilationUnitParserCharacter;
+				//parser.Lexer.putback_char = Tokenizer.EvalUsingDeclarationsParserCharacter;
+				parser.Lexer.putback_char = Tokenizer.EvalCompilationUnitParserCharacter;

	
	It currently has a few problems:

	* Support for overwritting existing defined
	  classes is not supported.

	* The usability is not as useful, since the defaults
	  for C# are still to make members private, we should
	  change this default to be public in those cases.

	* The error lookup system lacks information from types, for
          example this causes an unsupported call into a TypeBuilder:

	  csharp>class D { void DD () {} }
	  csharp>var d = new D ();
	  csharp>d.DD ();

		Internal compiler error at Internal(1,1):: exception caught while emitting MethodBuilder [Class0::Host]
		System.NotSupportedException: The invoked member is not supported in a dynamic module.
		  at System.Reflection.Emit.AssemblyBuilder.get_Location () [0x00000] in <filename unknown>:0 
		  at Mono.CSharp.Report.SymbolRelatedToPreviousError (System.Reflection.MemberInfo mi) [0x00000] in
		  at Mono.CSharp.MethodGroupExpr.NoExactMatch (Mono.CSharp.ResolveContext ec, 
					    Mono.CSharp.Arguments& Arguments, IDictionary`2 c


	  The above is caused by TypeManager.LookupDeclSpace (dt)
	  failing to return a value (it returns null) so our code
	  assumes we have an Assembly instead of an assemblybuilder.

	  

* Declaring a class twice produces an internal parse error:

  class X {}
  class X {}

  The second declaration will no longer be parsed, so it could even
  contain junk, and wont be flagged.   We probably need to allow for
  type redefinition in REPL modes, the exception from the second is:

  csharp -v -v
  > class X {}
  > class X {}

    System.ArgumentException: An element with the same key already exists in the dictionary.
      at System.Collections.Generic.Dictionary`2[System.String,Mono.CSharp.DeclSpace].Add (System.String key, Mono.CSharp.DeclSpace value) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.Namespace.AddDeclSpace (System.String name, Mono.CSharp.DeclSpace ds) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.ModuleCompiled.AddMemberType (Mono.CSharp.DeclSpace ds) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.TypeContainer.AddTypeContainer (Mono.CSharp.TypeContainer tc) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.CSharpParser.push_current_class (Mono.CSharp.TypeContainer tc, System.Object partial_token) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.CSharpParser.yyparse (yyInput yyLex) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.CSharpParser.yyparse (yyInput yyLex, System.Object yyd) [0x00000] in <filename unknown>:0 
      at Mono.CSharp.CSharpParser.parse () [0x00000] in <filename unknown>:0 
    
* Mix statements with other top-level declarations.

csharp> class Y {static void Main () {Console.WriteLine ("Foo"); }}
csharp> typeof (Y);
Y
csharp> Y.Main ();
Exception caught by the compiler while compiling:
   Block that caused the problem begin at: Internal(1,1):
                     Block being compiled: [<interactive>(1,2):,<interactive>(1,11):]
System.NotSupportedException: The invoked member is not supported in a dynamic module.
Internal compiler error at Internal(1,1):: exception caught while emitting MethodBuilder [Class2::Host]
System.NotSupportedException: The invoked member is not supported in a dynamic module.
  at System.Reflection.Emit.AssemblyBuilder.get_Location () [0x00000] in /second/home/cvs/mcs/class/corlib/System.Reflection.Emit/AssemblyBuilder.cs:214 
  at Mono.CSharp.Report.SymbolRelatedToPreviousError (System.Reflection.MemberInfo mi) [0x00036] in /second/home/cvs/mcs/mcs/report.cs:664 
  at Mono.CSharp.Expression.Error_MemberLookupFailed (System.Type container_type, System.Type qualifier_type, System.Type queried_type, System.String name, System.String class_name, MemberTypes mt, BindingFlags bf) [0x00121] in /second/home/cvs/mcs/mcs/ecore.cs:857 
  at Mono.CSharp.MemberAccess.DoResolve (Mono.CSharp.EmitContext ec, Mono.CSharp.Expression right_side) [0x00230] in /second/home/cvs/mcs/mcs/expression.cs:7426 
  at Mono.CSharp.MemberAccess.DoResolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/expression.cs:7494 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec, ResolveFlags flags) [0x00075] in /second/home/cvs/mcs/mcs/ecore.cs:479 
  at Mono.CSharp.Invocation.DoResolve (Mono.CSharp.EmitContext ec) [0x0000d] in /second/home/cvs/mcs/mcs/expression.cs:4725 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec, ResolveFlags flags) [0x00075] in /second/home/cvs/mcs/mcs/ecore.cs:479 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/ecore.cs:506 
  at Mono.CSharp.OptionalAssign.DoResolve (Mono.CSharp.EmitContext ec) [0x00013] in /second/home/cvs/mcs/mcs/repl.cs:681 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec, ResolveFlags flags) [0x00075] in /second/home/cvs/mcs/mcs/ecore.cs:479 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/ecore.cs:506 
  at Mono.CSharp.ExpressionStatement.ResolveStatement (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/ecore.cs:1307 
  at Mono.CSharp.StatementExpression.Resolve (Mono.CSharp.EmitContext ec) [0x0000b] in /second/home/cvs/mcs/mcs/statement.cs:743 
  at Mono.CSharp.Block.Resolve (Mono.CSharp.EmitContext ec) [0x000f0] in /second/home/cvs/mcs/mcs/statement.cs:2254 
  at Mono.CSharp.ExplicitBlock.Resolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/statement.cs:2550 
  at Mono.CSharp.EmitContext.ResolveTopBlock (Mono.CSharp.EmitContext anonymous_method_host, Mono.CSharp.ToplevelBlock block, Mono.CSharp.Parameters ip, IMethodData md, System.Boolean& unreachable) [0x00087] in /second/home/cvs/mcs/mcs/codegen.cs:796 
csharp>  

* Another one:

csharp> class X { X (){ Console.WriteLine ("Called"); } }              
csharp> new X ();
Exception caught by the compiler while compiling:
   Block that caused the problem begin at: Internal(1,1):
                     Block being compiled: [<interactive>(1,2):,<interactive>(1,10):]
System.NotSupportedException: The invoked member is not supported in a dynamic module.
Internal compiler error at Internal(1,1):: exception caught while emitting MethodBuilder [Class0::Host]
System.NotSupportedException: The invoked member is not supported in a dynamic module.
  at System.Reflection.Emit.AssemblyBuilder.get_Location () [0x00000] in /second/home/cvs/mcs/class/corlib/System.Reflection.Emit/AssemblyBuilder.cs:214 
  at Mono.CSharp.Report.SymbolRelatedToPreviousError (System.Reflection.MemberInfo mi) [0x00036] in /second/home/cvs/mcs/mcs/report.cs:664 
  at Mono.CSharp.Expression.Error_MemberLookupFailed (System.Type container_type, System.Type qualifier_type, System.Type queried_type, System.String name, System.String class_name, MemberTypes mt, BindingFlags bf) [0x00121] in /second/home/cvs/mcs/mcs/ecore.cs:857 
  at Mono.CSharp.Expression.MemberLookupFinal (Mono.CSharp.EmitContext ec, System.Type qualifier_type, System.Type queried_type, System.String name, MemberTypes mt, BindingFlags bf, Location loc) [0x0002f] in /second/home/cvs/mcs/mcs/ecore.cs:804 
  at Mono.CSharp.New.DoResolve (Mono.CSharp.EmitContext ec) [0x002ad] in /second/home/cvs/mcs/mcs/expression.cs:5486 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec, ResolveFlags flags) [0x00075] in /second/home/cvs/mcs/mcs/ecore.cs:479 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/ecore.cs:506 
  at Mono.CSharp.OptionalAssign.DoResolve (Mono.CSharp.EmitContext ec) [0x00013] in /second/home/cvs/mcs/mcs/repl.cs:687 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec, ResolveFlags flags) [0x00075] in /second/home/cvs/mcs/mcs/ecore.cs:479 
  at Mono.CSharp.Expression.Resolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/ecore.cs:506 
  at Mono.CSharp.ExpressionStatement.ResolveStatement (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/ecore.cs:1307 
  at Mono.CSharp.StatementExpression.Resolve (Mono.CSharp.EmitContext ec) [0x0000b] in /second/home/cvs/mcs/mcs/statement.cs:743 
  at Mono.CSharp.Block.Resolve (Mono.CSharp.EmitContext ec) [0x000f0] in /second/home/cvs/mcs/mcs/statement.cs:2254 
  at Mono.CSharp.ExplicitBlock.Resolve (Mono.CSharp.EmitContext ec) [0x00000] in /second/home/cvs/mcs/mcs/statement.cs:2550 
  at Mono.CSharp.EmitContext.ResolveTopBlock (Mono.CSharp.EmitContext anonymous_method_host, Mono.CSharp.ToplevelBlock block, Mono.CSharp.Parameters ip, IMethodData md, System.Boolean& unreachable) [0x00087] in /second/home/cvs/mcs/mcs/codegen.cs:796 
csharp>  

* Important: we need to replace TypeBuidlers with Types after things
  have been emitted, or stuff like this happens:

csharp> public class y  {}
csharp> typeof (y); 
Class1


* Clearing data

	TODO: when clearing data for variables that have been overwritten
	we need to check for structs and clear all the fields that contain
	reference types.

* DEBATABLE: Implement auto-insert-semicolon

	This is easy to implement, just retry the parse with a
	semicolon, the question is whether this is a good idea to do
	in the first place or not.