...

src/compiler/NubLang/Generation/QBE/QBEGenerator.cs

@@ -12,14 +12,13 @@ public partial class QBEGenerator
     private readonly BoundDefinitionTable _definitionTable;
     private readonly QBEWriter _writer;
 
-    private List<CStringLiteral> _cStringLiterals = [];
-    private List<StringLiteral> _stringLiterals = [];
-    private Stack<string> _breakLabels = [];
-    private Stack<string> _continueLabels = [];
-    private Queue<(BoundAnonymousFunc Func, string Name)> _anonymousFunctions = [];
-    private Dictionary<BoundTraitFuncImpl, string> _implFunctions = [];
-    private Stack<Variable> _variables = [];
-    private Stack<int> _variableScopes = [];
+    private readonly List<CStringLiteral> _cStringLiterals = [];
+    private readonly List<StringLiteral> _stringLiterals = [];
+    private readonly Stack<string> _breakLabels = [];
+    private readonly Stack<string> _continueLabels = [];
+    private readonly Queue<(BoundAnonymousFunc Func, string Name)> _anonymousFunctions = [];
+    private readonly Dictionary<BoundTraitFuncImpl, string> _implFunctions = [];
+    private readonly Stack<Scope> _scopes = [];
     private int _tmpIndex;
     private int _labelIndex;
     private int _anonymousFuncIndex;
@@ -28,6 +27,8 @@ public partial class QBEGenerator
     private int _implFuncNameIndex;
     private bool _codeIsReachable = true;
 
+    private Scope Scope => _scopes.Peek();
+
     public QBEGenerator(BoundSyntaxTree syntaxTree, BoundDefinitionTable definitionTable, string file)
     {
         _syntaxTree = syntaxTree;
@@ -37,14 +38,13 @@ public partial class QBEGenerator
 
     public string Emit()
     {
-        _cStringLiterals = [];
-        _stringLiterals = [];
-        _breakLabels = [];
-        _continueLabels = [];
-        _anonymousFunctions = [];
-        _implFunctions = [];
-        _variables = [];
-        _variableScopes = [];
+        _cStringLiterals.Clear();
+        _stringLiterals.Clear();
+        _breakLabels.Clear();
+        _continueLabels.Clear();
+        _anonymousFunctions.Clear();
+        _implFunctions.Clear();
+        _scopes.Clear();
         _tmpIndex = 0;
         _labelIndex = 0;
         _anonymousFuncIndex = 0;
@@ -347,18 +347,15 @@ public partial class QBEGenerator
         return "l";
     }
 
-    private void EmitFuncDefinition(string name, IEnumerable<BoundFuncParameter> parameters, NubType returnType, BoundBlock body)
+    private void EmitFuncDefinition(string name, IReadOnlyList<BoundFuncParameter> parameters, NubType returnType, BoundBlock body)
     {
-        var parameterArray = parameters.ToArray();
-
-        _variables.Clear();
-        _variableScopes.Clear();
         _labelIndex = 0;
         _tmpIndex = 0;
 
         var builder = new StringBuilder();
 
         builder.Append("export function ");
+
         if (returnType is not NubVoidType)
         {
             builder.Append(FuncQBETypeName(returnType) + ' ');
@@ -366,15 +363,16 @@ public partial class QBEGenerator
 
         builder.Append(name);
 
-        var parameterStrings = parameterArray.Select(x => FuncQBETypeName(x.Type) + $" %{x.Name}");
-
-        builder.Append($"({string.Join(", ", parameterStrings)})");
+        builder.Append($"({string.Join(", ", parameters.Select(x => FuncQBETypeName(x.Type) + $" %{x.Name}"))})");
 
         _writer.StartFunction(builder.ToString());
 
-        var parameterVars = parameterArray.Select(parameter => new Variable(parameter.Name, new Val("%" + parameter.Name, parameter.Type, ValKind.Direct))).ToList();
+        var scope = new Scope();
 
-        EmitBlock(body, parameterVars);
+        foreach (var parameter in parameters)
+        {
+            scope.Declare(parameter.Name, new Val("%" + parameter.Name, parameter.Type, ValKind.Direct));
+        }
 
         if (body.Statements.LastOrDefault() is not BoundReturn)
         {
@@ -445,6 +443,20 @@ public partial class QBEGenerator
         _writer.WriteLine("}");
     }
 
+    private void EmitBlock(BoundBlock block, Scope? scope = null)
+    {
+        _scopes.Push(scope ?? Scope.SubScope());
+
+        foreach (var statement in block.Statements.Where(_ => _codeIsReachable))
+        {
+            EmitStatement(statement);
+        }
+
+        _scopes.Pop();
+
+        _codeIsReachable = true;
+    }
+
     private string EmitUnwrap(Val val)
     {
         return val.Kind switch
@@ -525,29 +537,49 @@ public partial class QBEGenerator
     #endregion
 }
 
-internal class StringLiteral(string value, string name)
+public class StringLiteral(string value, string name)
 {
     public string Value { get; } = value;
     public string Name { get; } = name;
 }
 
-internal class CStringLiteral(string value, string name)
+public class CStringLiteral(string value, string name)
 {
     public string Value { get; } = value;
     public string Name { get; } = name;
 }
 
-internal class Variable(string name, Val val)
+public record Val(string Name, NubType Type, ValKind Kind, MethodCallContext? FuncCallContext = null);
+
+public class Scope(Scope? parent = null)
 {
-    public string Name { get; } = name;
-    public Val Val { get; } = val;
+    private readonly Dictionary<string, Val> _variables = [];
+
+    public Val Lookup(string name)
+    {
+        var variable = _variables.GetValueOrDefault(name);
+        if (variable != null)
+        {
+            return variable;
+        }
+
+        return parent?.Lookup(name) ?? throw new UnreachableException($"Variable '{name}' not found");
+    }
+
+    public void Declare(string name, Val value)
+    {
+        _variables.Add(name, value);
+    }
+
+    public Scope SubScope()
+    {
+        return new Scope(this);
+    }
 }
 
-internal record Val(string Name, NubType Type, ValKind Kind, MethodCallContext? FuncCallContext = null);
+public record MethodCallContext(Val ThisArg);
 
-internal record MethodCallContext(Val ThisArg);
-
-internal enum ValKind
+public enum ValKind
 {
     Pointer,
     Direct,