Properly handle scopes

Upsilon/Binder/Binder.cs

@@ -94,24 +94,19 @@ namespace Upsilon.Binder
         private BoundExpression BindLiteralExpression(LiteralExpressionSyntax e)
         {
             var value = e.Value;
-            var type = Type.Nil;
             LuaType outValue = null;
             switch (value)
             {
                 case double d:
-                    type     = Type.Number;
                     outValue = new NumberDouble(d);
                     break;
                 case long l:
-                    type     = Type.Number;
                     outValue = new NumberLong(l);
                     break;
                 case bool b:
-                    type = Type.Boolean;
                     outValue = new LuaBoolean(b);
                     break;
                 case null:
-                    type     = Type.Nil;
                     outValue = new LuaNull();
                     break;
                 default:
@@ -129,7 +124,7 @@ namespace Upsilon.Binder
         private BoundExpression BindVariableExpression(VariableExpressionSyntax e)
         {
             var name = e.Identifier.Name;
-            if (!_scope.TryGetVariable(name, out var variable))
+            if (!_scope.TryGetVariable(name, true, out var variable))
             {
                 _diagnostics.LogUnknownVariable(e.Identifier.Span, name);
                 return new BoundLiteralExpression(new LuaNull());
@@ -149,10 +144,11 @@ namespace Upsilon.Binder
             var name            = e.Identifier.Name;
             var boundExpression = BindExpression(e.Expression);
 
-            if (!_scope.TryGetVariable(name, out var variable))
+            var isLocal = e.LocalToken != null;
+            if (!_scope.TryGetVariable(name, !isLocal, out var variable))
             {
-                variable = new VariableSymbol(name, boundExpression.Type);
+                variable = new VariableSymbol(name, boundExpression.Type, isLocal);
-                if (e.LocalToken != null)
+                if (isLocal)
                     _scope.SetVariable(variable);
                 else
                     _scope.SetGlobalVariable(variable);
@@ -181,9 +177,10 @@ namespace Upsilon.Binder
         private BoundStatement BindBlockStatement(BlockStatementSyntax e)
         {
             var arr = ImmutableArray.CreateBuilder<BoundStatement>();
+            var innerBinder = new Binder(_scope, _diagnostics);
             foreach (var statementSyntax in e.Statements)
             {
-                var bound = BindStatement(statementSyntax);
+                var bound = innerBinder.BindStatement(statementSyntax);
                 arr.Add(bound);
             }
             return new BoundBlockStatement(arr.ToImmutable());

Upsilon/Binder/BoundScope.cs

@@ -41,15 +41,15 @@ namespace Upsilon.Binder
         }
 
 
-        public bool TryGetVariable(string key, out VariableSymbol result)
+        public bool TryGetVariable(string key, bool allowUpperScopes, out VariableSymbol result)
         {
             if (_variables.TryGetValue(key, out result))
             {
                 return true;
             }
-            if (_parentScope != null)
+            if (_parentScope != null && allowUpperScopes)
             {
-                return _parentScope.TryGetVariable(key, out result);
+                return _parentScope.TryGetVariable(key, true, out result);
             }
             return false;
         }

Upsilon/Binder/VariableSymbol.cs

@@ -4,13 +4,15 @@ namespace Upsilon.Binder
 {
     public class VariableSymbol
     {
-        public VariableSymbol(string name, Type type)
+        public VariableSymbol(string name, Type type, bool local)
         {
             Type = type;
+            Local = local;
             Name = name;
         }
 
         public Type Type { get; set; }
+        public bool Local { get; }
         public string Name { get; }
     }
 }

Upsilon/Evaluator/EvaluationScope.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using Upsilon.BaseTypes;
+using Upsilon.Binder;
+
+namespace Upsilon.Evaluator
+{
+    public class EvaluationScope
+    {
+        private readonly EvaluationScope _parentScope;
+        private readonly Dictionary<VariableSymbol, LuaType> _variables;
+
+        internal EvaluationScope(EvaluationScope parentScope)
+        {
+            _parentScope = parentScope;
+            _variables = new Dictionary<VariableSymbol, LuaType>();
+        }
+        internal EvaluationScope(Dictionary<VariableSymbol, LuaType> vars)
+        {
+            _variables = vars;
+        }
+
+        public void Set(VariableSymbol symbol, LuaType obj)
+        {
+            if (_variables.ContainsKey(symbol))
+            {
+                _variables[symbol] = obj;
+            }
+            else
+            {
+                _variables.Add(symbol, obj);
+            }
+        }
+
+        public void SetGlobal(VariableSymbol symbol, LuaType obj)
+        {
+            if (_parentScope != null)
+                _parentScope.SetGlobal(symbol, obj);
+            else
+            {
+                Set(symbol, obj);
+            }
+        }
+
+        public bool TryGet(VariableSymbol symbol, out LuaType obj)
+        {
+            if (_variables.TryGetValue(symbol, out obj))
+                return true;
+            if (_parentScope != null)
+                if (_parentScope.TryGet(symbol, out obj))
+                    return true;
+            return false;
+        }
+    }
+}

Upsilon/Evaluator/Evaluator.cs

@@ -10,19 +10,18 @@ namespace Upsilon.Evaluator
     {
         private readonly Diagnostics _diagnostics;
         private LuaType _value;
-        private Script Script { get; }
+        private readonly EvaluationScope _scope;
-        private readonly Dictionary<VariableSymbol, LuaType> _variables = new Dictionary<VariableSymbol, LuaType>();
 
-        public Evaluator(Script script, Diagnostics diagnostics)
+        public Evaluator(Diagnostics diagnostics, Dictionary<VariableSymbol, LuaType> vars)
         {
             _diagnostics = diagnostics;
-            Script       = script;
+            _scope = new EvaluationScope(vars);
         }
-        public Evaluator(Script script, Diagnostics diagnostics, Dictionary<VariableSymbol, LuaType> vars)
+
+        private Evaluator(Diagnostics diagnostics, EvaluationScope parentScope)
         {
             _diagnostics = diagnostics;
-            Script       = script;
+            _scope       = new EvaluationScope(parentScope);
-            _variables = vars;
         }
 
         public LuaType Evaluate(BoundScript e)
@@ -115,21 +114,36 @@ namespace Upsilon.Evaluator
         private void EvaluateAssignmentStatement(BoundVariableAssignment e)
         {
             var val = EvaluateExpression(e.BoundExpression);
-            _variables[e.Variable] = val;
+            if (e.Variable.Local)
+            {
+                _scope.Set(e.Variable, val);
+            }
+            else
+            {
+                _scope.SetGlobal(e.Variable, val);
+            }
             _value = val;
         }
 
         private LuaType EvaluateVariableExpression(BoundVariableExpression e)
         {
-            return _variables[e.Variable];
+            if (_scope.TryGet(e.Variable, out var val))
+            {
+                return val;
+            }
+            throw new Exception($"Cannot find variable: '{e.Variable.Name}'");
         }
 
         private void EvaluateBoundBlockStatement(BoundBlockStatement boundBlockStatement)
         {
+            var innerEvaluator = new Evaluator(_diagnostics, _scope);
             foreach (var boundStatement in boundBlockStatement.Statements)
             {
-                EvaluateStatement(boundStatement);
+                innerEvaluator.EvaluateStatement(boundStatement);
             }
+
+            if (innerEvaluator._value != null)
+                _value = innerEvaluator._value;
         }
 
         private void EvaluateBoundIfStatement(BoundIfStatement boundBlockStatement)

Upsilon/Evaluator/Script.cs

@@ -22,7 +22,7 @@ namespace Upsilon.Evaluator
             if (variables == null)
                 variables = new Dictionary<VariableSymbol, LuaType>();
             Binder = new Binder.Binder(new BoundScope(variables, null), Diagnostics);
-            Evaluator = new Evaluator(this, Diagnostics, variables);
+            Evaluator = new Evaluator( Diagnostics, variables);
         }
 
         public BoundScript Bind()

UpsilonTests/ScopeTests.cs

@@ -0,0 +1,44 @@
+using Upsilon.BaseTypes.Number;
+using Upsilon.Evaluator;
+using Xunit;
+
+namespace UpsilonTests
+{
+    public class ScopeTests
+    {
+        [Fact]
+        public void LocalInnerScopeDoesNotOverrideGlobal()
+        {
+            const string input = @"
+a = 10
+if true then
+    local a = 100
+end
+b = a
+";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            var evaluate = script.Evaluate<NumberLong>();
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal((long)10, evaluate);
+        }
+
+        [Fact]
+        public void InnerScopeDoesOverrideGlobal()
+        {
+            const string input = @"
+a = 10
+if true then
+    a = 100
+end
+b = a
+";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            var evaluate = script.Evaluate<NumberLong>();
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal((long)100, evaluate);
+        }
+
+    }
+}

UpsilonTests/UpsilonTests.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
         <TargetFramework>netcoreapp2.1</TargetFramework>