add while loop compilation and fix a few issues with execution

Qrakhen.Qamp.Core/Compilation/Builders/FunctionBuilder.cs

@@ -9,6 +9,8 @@ public class FunctionBuilder
     public int OuterCount;
     public int ArgumentCount;
 
+    public long CurrentInstruction => Segment.Instructions.Count;
+
     public Function Build()
     {
         return new Function(Name, Segment.Build(), OuterCount, ArgumentCount);

Qrakhen.Qamp.Core/Compilation/Digester.cs

@@ -183,12 +183,53 @@ public class Digester : ISteppable<Token>
         }
 
         if (canAssign && Match(T.Equal)) 
-            ErrorAtCurrent("Invalid assignment target");        
+            ErrorAtCurrent("Invalid assignment target.");        
     }
 
     internal void DeclareClass()
     {
         _logger.Method();
+        Consume(T.Identifier, "Expected a class name.");
+        // we need both a global name constant and a local declaration for this class
+        string name = Previous.Value!;
+        long identifier = IdentifierConstant(name);
+        DeclareLocal(name);
+        EmitDynamic(Op.Class, identifier);
+        DefineVariable(identifier);
+        ClassBuilder = new ClassBuilder { 
+            Outer = ClassBuilder, 
+            Name = name,
+            IsDerived = false 
+        };
+
+        if (Match(T.Colon))
+        {
+            Consume(T.Identifier, "Expected base class name.", false);
+            ExpressionParser.Variable(this, false);
+            if (name == Previous.Value!)
+                ErrorAtPrevious($"Class {name} can not inherit from itself!");
+
+            // Add base reference by injecting a synthetic base variable into a virtual scope
+            BeginScope();
+            AddLocal("base");
+            DefineVariable(0);
+            
+            ExpressionParser.Variable(this, name, false);
+            ClassBuilder.IsDerived = true;
+        }
+
+        ExpressionParser.Variable(this, name, false);
+        Consume(T.ContextOpen, "Expected '{' for class body declaration.", false);
+        while (!Check(T.ContextClose) && !Check(T.Eof))
+            DeclareMethod();
+
+        Consume(T.ContextClose, "Expected '}' to end class body declaration.", false);
+        Emit(Op.Pop);
+
+        if (ClassBuilder.IsDerived)
+            EndScope();
+
+        ClassBuilder = ClassBuilder.Outer;
     }
 
     internal void DeclareFunction()
@@ -203,13 +244,13 @@ public class Digester : ISteppable<Token>
     internal void DeclareMethod()
     {
         _logger.Method();
-        Consume(T.Identifier, "Expected method name", false);
+        Consume(T.Identifier, "Expected method name.", false);
-        long name = IdentifierConstant(Previous.Value!);
+        long identifier = IdentifierConstant(Previous.Value!);
         FunctionType type = FunctionType.Method;
         if (Previous.Value == ClassBuilder?.Name)
             type = FunctionType.Constructor;
         CreateFunction(type);
-        EmitDynamic(Op.Method, name);
+        EmitDynamic(Op.Method, identifier);
     }
 
     internal void DeclareVariable()
@@ -259,17 +300,29 @@ public class Digester : ISteppable<Token>
     internal void Else()
     {
         _logger.Method();
-        ErrorAtPrevious("Unexpected solitary 'else'");
+        ErrorAtPrevious("This 'else' is very alone :( Have you meant to place it after an 'if'?");
     }
 
     internal void While()
     {
         _logger.Method();
+        long start = Function.CurrentInstruction;
+        Consume(T.GroupOpen, "Expected while condition to be placed inside parentheses. Missing '('.", false);
+        Expression();
+        Consume(T.GroupClose, "Expected while condition to be placed inside parentheses. Missing ')'.", false);
+        long exit = EmitJump(Op.JumpIfFalse);
+        Emit(Op.Pop);
+        Statement();
+        EmitLoop(start);
+        PatchJump(exit);
+        Emit(Op.Pop);
     }
 
     internal void Do()
     {
         _logger.Method();
+        // todo: just do a while loop here with synthetic counter variables checked at end
+        throw new NotImplementedException();
     }
 
     internal void For()
@@ -285,7 +338,7 @@ public class Digester : ISteppable<Token>
             StatementExpression();
         }
 
-        long start = Function.Segment.Instructions.Count;
+        long start = Function.CurrentInstruction;
         long exit = -1;
         if (!Match(T.Semicolon)) {
             Expression();

Qrakhen.Qamp.Core/Compilation/ExpressionParser.cs

@@ -166,7 +166,7 @@ public static class ExpressionParser
         digester.EmitConstant(Values.Objects.String.Make(digester.Previous.Value));
     }
 
-    static void Variable(Digester digester, string name, bool canAssign)
+    public static void Variable(Digester digester, string name, bool canAssign)
     {
         OpCode Get, Set;
         long variable = digester.ResolveLocal(digester.Builder, name);
@@ -192,7 +192,7 @@ public static class ExpressionParser
         }
     }
 
-    static void Variable(Digester digester, bool canAssign)
+    public static void Variable(Digester digester, bool canAssign)
     {
         Variable(digester, digester.Previous.Value!, canAssign);
     }

Qrakhen.Qamp.Core/Execution/Runner.cs

@@ -62,9 +62,7 @@ public class InstructionPtr : Pointer<Instruction>
         Ptr++;
         byte[] data = new byte[8];
         for (int i = 0; i < length; i++)        
-        {
             data[i] = Segment.Read(Ptr++);
-        }
         return data.ToInt64();
     }
 
@@ -211,7 +209,7 @@ public class Runner : IDisposable
                 // todo: add closure
 
                 case Op.GetGlobal: {
-                    string? name = call.Ptr.GetString(call.Ptr.NextLong())?.Value;
+                    string? name = call.Ptr.GetString(call.Ptr.NextDynamic())?.Value;
                     if (string.IsNullOrEmpty(name))
                         throw new ExecutionException($"tried to set global variable with empty name");
                     if (!Globals.Has(name))