...

compiler/NubLang/Generation/QBE/QBEGenerator.cs

@@ -487,6 +487,9 @@ public class QBEGenerator
             case AssignmentNode assignment:
                 EmitCopyInto(assignment.Value, EmitAddressOf(assignment.Target));
                 break;
+            case BlockNode block:
+                EmitBlock(block);
+                break;
             case BreakNode:
                 EmitScopeCleanup();
                 _writer.Indented($"jmp {_breakLabels.Peek()}");
@@ -510,15 +513,9 @@ public class QBEGenerator
             case VariableDeclarationNode variableDeclaration:
                 EmitVariableDeclaration(variableDeclaration);
                 break;
-            case DeferNode defer:
-                Scope.DeferredStatements.Push(defer.Statement);
-                break;
             case WhileNode whileStatement:
                 EmitWhile(whileStatement);
                 break;
-            case ForArrayNode forArray:
-                EmitForArray(forArray);
-                break;
             default:
                 throw new ArgumentOutOfRangeException(nameof(statement));
         }
@@ -526,11 +523,6 @@ public class QBEGenerator
 
     private void EmitScopeCleanup()
     {
-        while (Scope.DeferredStatements.TryPop(out var deferredStatement))
-        {
-            EmitStatement(deferredStatement);
-        }
-
         while (Scope.Variables.TryPop(out var variable))
         {
             if (variable.Type is NubStructType structType)
@@ -613,54 +605,6 @@ public class QBEGenerator
         _breakLabels.Pop();
     }
 
-    // todo(nub31): Implement index ident
-    private void EmitForArray(ForArrayNode forArray)
-    {
-        var target = EmitExpression(forArray.Target);
-
-        var arrayStart = TmpName();
-        _writer.Indented($"{arrayStart} =l add {target}, 8");
-
-        var size = TmpName();
-        _writer.Indented($"{size} =l loadl {target}");
-
-        var count = TmpName();
-        _writer.Indented($"{count} =l copy 0");
-
-        var loopLabel = LabelName();
-        _writer.WriteLine(loopLabel);
-
-        var condition = TmpName();
-        _writer.Indented($"{condition} =w cultl {count}, {size}");
-
-        var continueLabel = LabelName();
-        var endLabel = LabelName();
-        _writer.Indented($"jnz {condition}, {continueLabel}, {endLabel}");
-        _writer.WriteLine(continueLabel);
-
-        var arrayOffset = TmpName();
-        _writer.Indented($"{arrayOffset} =l mul {count}, {SizeOf(forArray.ArrayType.ElementType)}");
-        var elementAddress = TmpName();
-        _writer.Indented($"{elementAddress} =l add {arrayStart}, {arrayOffset}");
-
-        if (forArray.ArrayType.ElementType is NubStructType)
-        {
-            _writer.Indented($"%{forArray.ElementIdent} =l copy {elementAddress}");
-        }
-        else
-        {
-            var element = EmitLoad(forArray.ArrayType.ElementType, elementAddress);
-            _writer.Indented($"%{forArray.ElementIdent} {QBEAssign(forArray.ArrayType.ElementType)} copy {element}");
-        }
-
-        EmitBlock(forArray.Body);
-
-        _writer.Indented($"{count} =l add {count}, 1");
-        _writer.Indented($"jmp {loopLabel}");
-
-        _writer.WriteLine(endLabel);
-    }
-
     private string EmitExpression(ExpressionNode expr)
     {
         return expr switch
@@ -1338,7 +1282,6 @@ public class QBEGenerator
 
 public class Scope
 {
-    public readonly Stack<StatementNode> DeferredStatements = [];
     public readonly Stack<Variable> Variables = [];
 }
 

compiler/NubLang/Parsing/Parser.cs

@@ -241,8 +241,6 @@ public sealed class Parser
                     return ParseIf(startIndex);
                 case Symbol.While:
                     return ParseWhile(startIndex);
-                case Symbol.For:
-                    return ParseFor(startIndex);
                 case Symbol.Let:
                     return ParseVariableDeclaration(startIndex);
                 case Symbol.Defer:
@@ -332,23 +330,6 @@ public sealed class Parser
         return new WhileSyntax(GetTokens(startIndex), condition, body);
     }
 
-    private ForSyntax ParseFor(int startIndex)
-    {
-        var elementIdent = ExpectIdentifier().Value;
-
-        string? indexIndent = null;
-        if (TryExpectSymbol(Symbol.Comma))
-        {
-            indexIndent = ExpectIdentifier().Value;
-        }
-
-        ExpectSymbol(Symbol.In);
-        var target = ParseExpression();
-        var body = ParseBlock();
-
-        return new ForSyntax(GetTokens(startIndex), elementIdent, indexIndent, target, body);
-    }
-
     private ExpressionSyntax ParseExpression(int precedence = 0)
     {
         var startIndex = _tokenIndex;

compiler/NubLang/Parsing/Syntax/StatementSyntax.cs

@@ -23,5 +23,3 @@ public record BreakSyntax(IEnumerable<Token> Tokens) : StatementSyntax(Tokens);
 public record DeferSyntax(IEnumerable<Token> Tokens, StatementSyntax Statement) : StatementSyntax(Tokens);
 
 public record WhileSyntax(IEnumerable<Token> Tokens, ExpressionSyntax Condition, BlockSyntax Body) : StatementSyntax(Tokens);
-
-public record ForSyntax(IEnumerable<Token> Tokens, string ElementIdent, string? IndexIdent, ExpressionSyntax Target, BlockSyntax Body) : StatementSyntax(Tokens);

compiler/NubLang/TypeChecking/Node/StatementNode.cs

@@ -22,8 +22,4 @@ public record ContinueNode : TerminalStatementNode;
 
 public record BreakNode : TerminalStatementNode;
 
-public record DeferNode(StatementNode Statement) : StatementNode;
-
 public record WhileNode(ExpressionNode Condition, BlockNode Body) : StatementNode;
-
-public record ForArrayNode(NubArrayType ArrayType, string ElementIdent, string? IndexIdent, ExpressionNode Target, BlockNode Body) : StatementNode;

compiler/NubLang/TypeChecking/TypeChecker.cs

@@ -1,4 +1,5 @@
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using NubLang.Diagnostics;
 using NubLang.Modules;
@@ -125,7 +126,7 @@ public sealed class TypeChecker
         }
 
         _funcReturnTypes.Push(ResolveType(function.Signature.ReturnType));
-        var body = CheckBlock(function.Body, CurrentScope);
+        var body = CheckBlock(function.Body);
         _funcReturnTypes.Pop();
         return new StructFuncNode(function.Name, function.Hook, CheckFuncSignature(function.Signature), body);
     }
@@ -143,10 +144,9 @@ public sealed class TypeChecker
 
     private FuncNode CheckFuncDefinition(FuncSyntax node)
     {
-        var scope = new Scope();
         foreach (var parameter in node.Signature.Parameters)
         {
-            scope.DeclareVariable(new Variable(parameter.Name, ResolveType(parameter.Type), VariableKind.RValue));
+            CurrentScope.DeclareVariable(new Variable(parameter.Name, ResolveType(parameter.Type), VariableKind.RValue));
         }
 
         var signature = CheckFuncSignature(node.Signature);
@@ -156,7 +156,7 @@ public sealed class TypeChecker
         {
             _funcReturnTypes.Push(signature.ReturnType);
 
-            body = CheckBlock(node.Body, scope);
+            body = CheckBlock(node.Body);
 
             if (!AlwaysReturns(body))
             {
@@ -179,24 +179,6 @@ public sealed class TypeChecker
         return new FuncNode(CurrentModule, node.Name, node.ExternSymbol, signature, body);
     }
 
-    private StatementNode CheckStatement(StatementSyntax node)
-    {
-        return node switch
-        {
-            AssignmentSyntax statement => CheckAssignment(statement),
-            BreakSyntax => new BreakNode(),
-            ContinueSyntax => new ContinueNode(),
-            IfSyntax statement => CheckIf(statement),
-            ReturnSyntax statement => CheckReturn(statement),
-            StatementExpressionSyntax statement => CheckStatementExpression(statement),
-            VariableDeclarationSyntax statement => CheckVariableDeclaration(statement),
-            DeferSyntax statement => CheckDefer(statement),
-            WhileSyntax statement => CheckWhile(statement),
-            ForSyntax statement => CheckFor(statement),
-            _ => throw new ArgumentOutOfRangeException(nameof(node))
-        };
-    }
-
     private AssignmentNode CheckAssignment(AssignmentSyntax statement)
     {
         var target = CheckExpression(statement.Target);
@@ -272,11 +254,6 @@ public sealed class TypeChecker
         return new VariableDeclarationNode(statement.Name, Optional.OfNullable(assignmentNode), type);
     }
 
-    private DeferNode CheckDefer(DeferSyntax statement)
-    {
-        return new DeferNode(CheckStatement(statement.Statement));
-    }
-
     private WhileNode CheckWhile(WhileSyntax statement)
     {
         var condition = CheckExpression(statement.Condition, new NubBoolType());
@@ -284,31 +261,6 @@ public sealed class TypeChecker
         return new WhileNode(condition, body);
     }
 
-    private StatementNode CheckFor(ForSyntax statement)
-    {
-        var target = CheckExpression(statement.Target);
-
-        switch (target.Type)
-        {
-            case NubArrayType arrayType:
-            {
-                var scope = CurrentScope.SubScope();
-                scope.DeclareVariable(new Variable(statement.ElementIdent, arrayType.ElementType, VariableKind.RValue));
-                if (statement.IndexIdent != null)
-                {
-                    scope.DeclareVariable(new Variable(statement.ElementIdent, new NubIntType(true, 64), VariableKind.RValue));
-                }
-
-                var body = CheckBlock(statement.Body, scope);
-                return new ForArrayNode(arrayType, statement.ElementIdent, statement.IndexIdent, target, body);
-            }
-            default:
-            {
-                throw new TypeCheckerException(Diagnostic.Error($"Type {target.Type} is not an iterable target").At(statement.Target).Build());
-            }
-        }
-    }
-
     private FuncSignatureNode CheckFuncSignature(FuncSignatureSyntax statement)
     {
         var parameters = new List<FuncParameterNode>();
@@ -802,42 +754,98 @@ public sealed class TypeChecker
         return new StructInitializerNode(structType, initializers);
     }
 
-    private BlockNode CheckBlock(BlockSyntax node, Scope? scope = null)
+    private BlockNode CheckBlock(BlockSyntax node)
     {
         var statements = new List<StatementNode>();
 
-        _scopes.Push(scope ?? CurrentScope.SubScope());
-
         var reachable = true;
         var warnedUnreachable = false;
 
+        BeginScope(false);
+
         foreach (var statement in node.Statements)
         {
-            var checkedStatement = CheckStatement(statement);
+            if (statement is DeferSyntax deferStmt)
-
-            if (reachable)
             {
-                statements.Add(checkedStatement);
+                CurrentScope.PushDefer(deferStmt);
-                if (checkedStatement is TerminalStatementNode)
-                {
-                    reachable = false;
-                }
             }
             else
             {
-                if (!warnedUnreachable)
+                var checkedStatement = CheckStatement(statement);
+
+                if (reachable)
                 {
-                    Diagnostics.Add(Diagnostic.Warning("Statement is unreachable").At(statement).Build());
+                    if (checkedStatement is TerminalStatementNode)
-                    warnedUnreachable = true;
+                    {
+                        while (CurrentScope.TryPopDefer(out var defer))
+                        {
+                            var checkedDeferredStatement = CheckStatement(defer.Statement);
+                            if (checkedDeferredStatement is TerminalStatementNode)
+                            {
+                                throw new TypeCheckerException(Diagnostic
+                                    .Error("Cannot defer terminal statements")
+                                    .WithHelp("Avoid using defer with terminal statements such as 'return', 'break', 'continue' etc.")
+                                    .At(defer)
+                                    .Build());
+                            }
+
+                            statements.Add(checkedDeferredStatement);
+                        }
+
+                        reachable = false;
+                    }
+
+                    statements.Add(checkedStatement);
+                }
+                else
+                {
+                    if (!warnedUnreachable)
+                    {
+                        Diagnostics.Add(Diagnostic.Warning("Statement is unreachable").At(statement).Build());
+                        warnedUnreachable = true;
+                    }
                 }
             }
         }
 
-        _scopes.Pop();
+        while (CurrentScope.TryPopDefer(out var defer))
+        {
+            var checkedDeferredStatement = CheckStatement(defer.Statement);
+            if (checkedDeferredStatement is TerminalStatementNode)
+            {
+                throw new TypeCheckerException(Diagnostic
+                    .Error("Cannot defer terminal statements")
+                    .WithHelp("Avoid using defer with terminal statements such as 'return', 'break', 'continue' etc.")
+                    .At(defer)
+                    .Build());
+            }
+
+            statements.Add(checkedDeferredStatement);
+        }
+
+        EndScope();
 
         return new BlockNode(statements);
     }
 
+    private StatementNode CheckStatement(StatementSyntax statement)
+    {
+        return statement switch
+        {
+            AssignmentSyntax assignmentStmt => CheckAssignment(assignmentStmt),
+            BlockSyntax blockStmt => CheckBlock(blockStmt),
+            BreakSyntax => new BreakNode(),
+            ContinueSyntax => new ContinueNode(),
+            IfSyntax ifStmt => CheckIf(ifStmt),
+            ReturnSyntax retStmt => CheckReturn(retStmt),
+            StatementExpressionSyntax stmtExpr => CheckStatementExpression(stmtExpr),
+            VariableDeclarationSyntax varDeclStmt => CheckVariableDeclaration(varDeclStmt),
+            WhileSyntax whileStmt => CheckWhile(whileStmt),
+            DeferSyntax => throw new InvalidOperationException($"Compiler bug: defer statement should not have reached {nameof(CheckStatement)}"),
+            _ => throw new ArgumentOutOfRangeException(nameof(statement))
+        };
+    }
+
     private bool AlwaysReturns(StatementNode statement)
     {
         switch (statement)
@@ -949,6 +957,7 @@ public record Variable(string Name, NubType Type, VariableKind Kind);
 
 public class Scope(Scope? parent = null)
 {
+    private readonly Stack<DeferSyntax> _defers = [];
     private readonly List<Variable> _variables = [];
 
     public Variable? LookupVariable(string name)
@@ -967,6 +976,16 @@ public class Scope(Scope? parent = null)
         _variables.Add(variable);
     }
 
+    public void PushDefer(DeferSyntax defer)
+    {
+        _defers.Push(defer);
+    }
+
+    public bool TryPopDefer([NotNullWhen(true)] out DeferSyntax? defer)
+    {
+        return _defers.TryPop(out defer);
+    }
+
     public Scope SubScope()
     {
         return new Scope(this);

example/src/main.nub

@@ -12,9 +12,7 @@ struct Human
 extern "main" func main(args: []cstring): i64
 {
     let x: ref<Human> = {}
-
     test(x)
-
     return 0
 }