diff --git a/Upsilon/BaseTypes/ScriptFunction.cs b/Upsilon/BaseTypes/ScriptFunction.cs
index b4d0a2b..4c15a78 100644
--- a/Upsilon/BaseTypes/ScriptFunction.cs
+++ b/Upsilon/BaseTypes/ScriptFunction.cs
@@ -28,10 +28,10 @@ namespace Upsilon.BaseTypes
     internal class ScriptInternalFunction : ScriptFunction, IScopeOwner
     {
         public BoundBlockStatement Block           { get; }
-        public ImmutableArray<VariableSymbol> Parameters { get; }
+        public ImmutableArray<BoundVariableSymbol> Parameters { get; }
         public EvaluationScope EvaluationScope { get; }
 
-        public ScriptInternalFunction(ImmutableArray<VariableSymbol> parameters, BoundBlockStatement block,
+        public ScriptInternalFunction(ImmutableArray<BoundVariableSymbol> parameters, BoundBlockStatement block,
             EvaluationScope evaluationScope)
         {
             Parameters = parameters;
@@ -46,7 +46,7 @@ namespace Upsilon.BaseTypes
             {
                 var parameterVariable = Parameters[i];
                 var parameterValue    = variables[i];
-                innerEvaluator.Scope.CreateLocal(parameterVariable, parameterValue);
+                innerEvaluator.Scope.CreateLocal(parameterVariable.VariableSymbol, parameterValue);
             }
             return innerEvaluator.EvaluateNode(Block);
         }
diff --git a/Upsilon/Binder/Binder.cs b/Upsilon/Binder/Binder.cs
index de4b621..94a6cd9 100644
--- a/Upsilon/Binder/Binder.cs
+++ b/Upsilon/Binder/Binder.cs
@@ -44,7 +44,7 @@ namespace Upsilon.Binder
                 Scope = new BoundScope(Scope);
                 foreach (var valueParameter in unboundFunctionStatement.Value.Parameters)
                 {
-                    Scope.AssignToNearest(valueParameter);
+                    Scope.AssignToNearest(valueParameter.VariableSymbol);
                 }
                 unboundFunctionStatement.Value.Block =
                     (BoundBlockStatement) BindBlockStatement(unboundFunctionStatement.Value.UnboundBlock);
@@ -377,11 +377,11 @@ namespace Upsilon.Binder
         private BoundExpression BindFunctionExpression(FunctionExpressionSyntax e, string variableSymbol = null)
         {
             var innerScope = new BoundScope(Scope);
-            var parameters = ImmutableArray.CreateBuilder<VariableSymbol>();
+            var parameters = ImmutableArray.CreateBuilder<BoundVariableSymbol>();
             foreach (var identifierToken in e.Parameters)
             {
                 var vari = new VariableSymbol(identifierToken.Name, Type.Unknown, true);
-                parameters.Add(vari);
+                parameters.Add(new BoundVariableSymbol(vari, identifierToken.Span));
                 innerScope.DefineLocalVariable(vari);
             }
 
@@ -417,9 +417,9 @@ namespace Upsilon.Binder
             var func       = (BoundFunctionExpression)BindFunctionExpression(e.FunctionExpression, name);
             var parameters = ImmutableArray.CreateBuilder<VariableSymbol>();
 
-            foreach (var identifierToken in func.Parameters)
+            foreach (var parameter in func.Parameters)
             {
-                var vari = new VariableSymbol(identifierToken.Name, Type.Unknown, true);
+                var vari = new VariableSymbol(parameter.VariableSymbol.Name, Type.Unknown, true);
                 parameters.Add(vari);
                 innerScope.DefineLocalVariable(vari);
             }
diff --git a/Upsilon/Binder/BoundExpressions/BoundFunctionExpression.cs b/Upsilon/Binder/BoundExpressions/BoundFunctionExpression.cs
index 68f3e58..24716be 100644
--- a/Upsilon/Binder/BoundExpressions/BoundFunctionExpression.cs
+++ b/Upsilon/Binder/BoundExpressions/BoundFunctionExpression.cs
@@ -6,10 +6,10 @@ namespace Upsilon.Binder
 {
     public class BoundFunctionExpression : BoundExpression
     {
-        public ImmutableArray<VariableSymbol> Parameters { get; }
+        public ImmutableArray<BoundVariableSymbol> Parameters { get; }
         public BoundBlockStatement Block { get; set; }
 
-        public BoundFunctionExpression(ImmutableArray<VariableSymbol> parameters, BoundBlockStatement block, TextSpan span) : base(span)
+        public BoundFunctionExpression(ImmutableArray<BoundVariableSymbol> parameters, BoundBlockStatement block, TextSpan span) : base(span)
         {
             Parameters = parameters;
             Block = block;
@@ -18,6 +18,11 @@ namespace Upsilon.Binder
         public override BoundKind Kind => BoundKind.BoundFunctionExpression;
         public override BoundNode GetNodeAtPosition(int characterPosition)
         {
+            foreach (var parameter in Parameters)
+            {
+                if (characterPosition >= parameter.Span.Start && characterPosition <= parameter.Span.End)
+                    return parameter.GetNodeAtPosition(characterPosition);
+            }
             if (characterPosition >= Block.Span.Start && characterPosition <= Block.Span.End)
                 return Block.GetNodeAtPosition(characterPosition);
             return this;
diff --git a/Upsilon/Binder/BoundExpressions/UnboundFunctionExpression.cs b/Upsilon/Binder/BoundExpressions/UnboundFunctionExpression.cs
deleted file mode 100644
index 98d5e50..0000000
--- a/Upsilon/Binder/BoundExpressions/UnboundFunctionExpression.cs
+++ /dev/null
@@ -1,19 +0,0 @@
-using System.Collections.Immutable;
-using Upsilon.Parser;
-using Upsilon.Text;
-
-namespace Upsilon.Binder
-{
-    public class UnboundFunctionExpression : BoundFunctionExpression
-    {
-        public UnboundFunctionExpression(ImmutableArray<VariableSymbol> parameters,
-            BlockStatementSyntax unboundBlock, TextSpan span) : base(parameters, null, span)
-        {
-            UnboundBlock = unboundBlock;
-        }
-
-        public override BoundKind Kind => BoundKind.BoundPromise;
-
-        public BlockStatementSyntax UnboundBlock { get; }
-    }
-}
\ No newline at end of file
diff --git a/Upsilon/Binder/BoundStatements/UnboundFunctionExpression.cs b/Upsilon/Binder/BoundStatements/UnboundFunctionExpression.cs
new file mode 100644
index 0000000..6ffa9af
--- /dev/null
+++ b/Upsilon/Binder/BoundStatements/UnboundFunctionExpression.cs
@@ -0,0 +1,36 @@
+using System.Collections.Immutable;
+using Upsilon.Parser;
+using Upsilon.Text;
+
+namespace Upsilon.Binder
+{
+    public class UnboundFunctionExpression : BoundFunctionExpression
+    {
+        public UnboundFunctionExpression(ImmutableArray<BoundVariableSymbol> parameters,
+            BlockStatementSyntax unboundBlock, TextSpan span) : base(parameters, null, span)
+        {
+            UnboundBlock = unboundBlock;
+        }
+
+        public override BoundKind Kind => BoundKind.BoundPromise;
+
+        public BlockStatementSyntax UnboundBlock { get; }
+
+        public override BoundNode GetNodeAtPosition(int characterPosition)
+        {
+            foreach (var parameter in Parameters)
+            {
+                if (characterPosition >= parameter.Span.Start && characterPosition <= parameter.Span.End)
+                    return parameter.GetNodeAtPosition(characterPosition);
+            }
+
+            if (Block != null)
+            {
+                if (characterPosition >= Block.Span.Start && characterPosition <= Block.Span.End)
+                    return Block.GetNodeAtPosition(characterPosition);
+
+            }
+            return this;
+        }
+    }
+}
\ No newline at end of file
diff --git a/Upsilon/Binder/BoundVariableSymbol.cs b/Upsilon/Binder/BoundVariableSymbol.cs
index f13e970..91402f0 100644
--- a/Upsilon/Binder/BoundVariableSymbol.cs
+++ b/Upsilon/Binder/BoundVariableSymbol.cs
@@ -8,7 +8,6 @@ namespace Upsilon.Binder
         public BoundVariableSymbol(VariableSymbol variableSymbol, TextSpan span) : base(span)
         {
             VariableSymbol = variableSymbol;
-            Type = variableSymbol.Type;
         }
 
         public VariableSymbol VariableSymbol { get; }
@@ -18,6 +17,6 @@ namespace Upsilon.Binder
             return this;
         }
 
-        public override Type Type { get; }
+        public override Type Type => VariableSymbol.Type;
     }
 }
\ No newline at end of file
diff --git a/Upsilon/Evaluator/Evaluator.cs b/Upsilon/Evaluator/Evaluator.cs
index 10ca704..93961bc 100644
--- a/Upsilon/Evaluator/Evaluator.cs
+++ b/Upsilon/Evaluator/Evaluator.cs
@@ -66,7 +66,7 @@ namespace Upsilon.Evaluator
             {
                 var parameter = parameters[index];
                 var parameterName = function.Parameters[index];
-                innerEvaluator.Scope.CreateLocal(parameterName, parameter);
+                innerEvaluator.Scope.CreateLocal(parameterName.VariableSymbol, parameter);
             }
 
             var result = innerEvaluator.EvaluateNode(function.Block);