...

src/compiler/NubLang/Syntax/Binding/Binder.cs

@@ -6,15 +6,14 @@ using NubLang.Syntax.Tokenization;
 
 namespace NubLang.Syntax.Binding;
 
-// TODO: Currently anonymous function does not get a new scope
 public sealed class Binder
 {
     private readonly SyntaxTree _syntaxTree;
     private readonly DefinitionTable _definitionTable;
 
-    // TODO: Implement proper variable tracking and scoping
-    private readonly Dictionary<string, NubType> _variables = [];
+    private readonly Stack<Variable> _variables = [];
     private readonly Stack<NubType> _funcReturnTypes = [];
+    private readonly Stack<int> _variableScopes = [];
 
     public Binder(SyntaxTree syntaxTree, DefinitionTable definitionTable)
     {
@@ -26,6 +25,7 @@ public sealed class Binder
     {
         _variables.Clear();
         _funcReturnTypes.Clear();
+        _variableScopes.Clear();
 
         var diagnostics = new List<Diagnostic>();
         var definitions = new List<BoundDefinition>();
@@ -66,13 +66,7 @@ public sealed class Binder
         foreach (var func in node.Functions)
         {
             var signature = BindFuncSignature(func.Signature);
-
-            foreach (var parameter in signature.Parameters)
-            {
-                _variables[parameter.Name] = parameter.Type;
-            }
-
-            var body = BindFuncBody(func.Body, signature.ReturnType);
+            var body = BindFuncBody(func.Body, signature.ReturnType, signature.Parameters);
 
             functions.Add(new BoundTraitFuncImpl(func.Tokens, func.Name, signature, body));
         }
@@ -121,13 +115,7 @@ public sealed class Binder
         _variables.Clear();
 
         var signature = BindFuncSignature(node.Signature);
-
-        foreach (var parameter in signature.Parameters)
-        {
-            _variables[parameter.Name] = parameter.Type;
-        }
-
-        var body = BindFuncBody(node.Body, signature.ReturnType);
+        var body = BindFuncBody(node.Body, signature.ReturnType, signature.Parameters);
 
         return new BoundLocalFunc(node.Tokens, node.Namespace, node.Name, signature, body);
     }
@@ -220,7 +208,7 @@ public sealed class Binder
             throw new NotImplementedException("Diagnostics not implemented");
         }
 
-        _variables[statement.Name] = type;
+        _variables.Push(new Variable(statement.Name, type));
 
         return new BoundVariableDeclaration(statement.Tokens, statement.Name, assignment, type);
     }
@@ -280,11 +268,9 @@ public sealed class Binder
             var expectedParameterType = funcType.Parameters[i];
             var parameter = expression.Parameters[i];
             parameters.Add(new BoundFuncParameter(parameter.Tokens, parameter.Name, expectedParameterType));
-
-            _variables[parameter.Name] = expectedParameterType;
         }
 
-        var body = BindFuncBody(expression.Body, funcType.ReturnType);
+        var body = BindFuncBody(expression.Body, funcType.ReturnType, parameters);
 
         return new BoundAnonymousFunc(expression.Tokens, new NubFuncType(funcType.ReturnType, parameters.Select(x => x.Type).ToList()), parameters, funcType.ReturnType, body);
     }
@@ -371,7 +357,11 @@ public sealed class Binder
 
         if (!expression.Namespace.HasValue)
         {
-            return new BoundVariableIdent(expression.Tokens, _variables[expression.Name], expression.Name);
+            var variable = _variables.FirstOrDefault(x => x.Name == expression.Name);
+            if (variable != null)
+            {
+                return new BoundVariableIdent(expression.Tokens, variable.Type, variable.Name);
+            }
         }
 
         throw new BindException(Diagnostic.Error($"No identifier with then name {(expression.Namespace.HasValue ? $"{expression.Namespace.Value}::" : "")}{expression.Name} exists").Build());
@@ -583,8 +573,17 @@ public sealed class Binder
         };
     }
 
-    private BoundBlock BindBlock(BlockSyntax node)
+    private BoundBlock BindBlock(BlockSyntax node, IEnumerable<Variable>? variables = null)
     {
+        _variableScopes.Push(_variables.Count);
+        if (variables != null)
+        {
+            foreach (var variable in variables)
+            {
+                _variables.Push(variable);
+            }
+        }
+
         var statements = new List<BoundStatement>();
 
         foreach (var statement in node.Statements)
@@ -592,18 +591,50 @@ public sealed class Binder
             statements.Add(BindStatement(statement));
         }
 
+        var count = _variableScopes.Pop();
+        while (_variableScopes.Count > count)
+        {
+            _variableScopes.Pop();
+        }
+
         return new BoundBlock(node.Tokens, statements);
     }
 
-    private BoundBlock BindFuncBody(BlockSyntax block, NubType returnType)
+    private BoundBlock BindFuncBody(BlockSyntax block, NubType returnType, IEnumerable<BoundFuncParameter> parameters)
     {
         _funcReturnTypes.Push(returnType);
-        var body = BindBlock(block);
+        var body = BindBlock(block, parameters.Select(x => new Variable(x.Name, x.Type)));
         _funcReturnTypes.Pop();
         return body;
     }
 }
 
+public record Variable(string Name, NubType Type);
+
+public class Scope(Scope? parent)
+{
+    private List<Variable> _variables = [];
+
+    public Variable Lookup(string name)
+    {
+        var variable = _variables.FirstOrDefault(x => x.Name == name);
+        if (variable == null)
+        {
+            if (parent != null)
+            {
+                return parent.Lookup(name);
+            }
+        }
+
+        throw new BindException(Diagnostic.Error($"Variable {name} is not available in the current scope").Build());
+    }
+
+    public Scope SubScope()
+    {
+        return new Scope(this);
+    }
+}
+
 public class BindException : Exception
 {
     public Diagnostic Diagnostic { get; }