Bind Variables

Upsilon/Binder/Binder.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Runtime.InteropServices;
 using Upsilon.BaseTypes.Number;
 using Upsilon.Parser;
 using Type = Upsilon.BaseTypes.Type;
@@ -38,7 +37,7 @@ namespace Upsilon.Binder
                 case SyntaxKind.AssignmentExpression:
                     return BindAssignmentExpression((AssignmentExpressionSyntax) e);
                 case SyntaxKind.VariableExpression:
-                    break;
+                    return BindVariableExpression((VariableExpressionSyntax) e);
                 case SyntaxKind.BadExpression:
                     break;
                 case SyntaxKind.ScriptUnit:
@@ -130,5 +129,17 @@ namespace Upsilon.Binder
 
             return new BoundAssignmenExpression(variable, boundExpression);
         }
+
+        private BoundExpression BindVariableExpression(VariableExpressionSyntax e)
+        {
+            var name = e.Identifier.Name;
+            if (!_scope.TryGetVariable(name, out var variable))
+            {
+                _diagnostics.LogUnknownVariable(e.Identifier.Span, name);
+                return new BoundLiteralExpression(null, Type.Nil);
+            }
+
+            return new BoundVariableExpression(variable);
+        }
     }
 }

Upsilon/Binder/BoundKind.cs

@@ -7,6 +7,7 @@ namespace Upsilon.Binder
         BoundLiteralExpression,
         BoundBinaryExpression,
         BoundUnaryExpression,
-        BoundAssignmentExpression
+        BoundAssignmentExpression,
+        VariableExpression
     }
 }

Upsilon/Binder/BoundVariableExpression.cs

@@ -0,0 +1,17 @@
+using System;
+using Type = Upsilon.BaseTypes.Type;
+
+namespace Upsilon.Binder
+{
+    public class BoundVariableExpression : BoundExpression
+    {
+        public BoundVariableExpression(VariableSymbol variable)
+        {
+            Variable = variable;
+        }
+
+        public VariableSymbol Variable { get; }
+        public override BoundKind Kind => BoundKind.VariableExpression;
+        public override Type      Type => Variable.Type;
+    }
+}