Add check for duplicate local ident

compiler/Generator.cs

@@ -167,6 +167,9 @@ public class Generator
 
                     static inline void string_rc_dec(struct nub_core_string *string)
                     {
+                        if (string == NULL)
+                            return;
+
                         if (string->flags & FLAG_STRING_LITERAL)
                             return;
 
@@ -362,10 +365,8 @@ public class Generator
         if (statement.Value != null)
         {
             var value = EmitExpression(statement.Value);
-            var variableName = TmpName();
-            writer.WriteLine($"{CType(statement.Value.Type, variableName)} = {value};");
             EmitCleanupAllScopes();
-            writer.WriteLine($"return {variableName};");
+            writer.WriteLine($"return {value};");
         }
         else
         {
@@ -481,7 +482,7 @@ public class Generator
 
     private string EmitExpression(TypedNodeExpression node)
     {
-        var value = node switch
+        return node switch
         {
             TypedNodeExpressionBinary expression => EmitExpressionBinary(expression),
             TypedNodeExpressionUnary expression => EmitExpressionUnary(expression),
@@ -498,10 +499,6 @@ public class Generator
             TypedNodeExpressionFuncCall expression => EmitExpressionFuncCall(expression),
             _ => throw new ArgumentOutOfRangeException(nameof(node), node, null)
         };
-
-        var tmp = TmpName();
-        writer.WriteLine($"{CType(node.Type, tmp)} = {value};");
-        return tmp;
     }
 
     private string EmitExpressionBinary(TypedNodeExpressionBinary expression)
@@ -509,15 +506,16 @@ public class Generator
         var left = EmitExpression(expression.Left);
         var right = EmitExpression(expression.Right);
 
+        var name = Tmp();
+
         if (expression.Operation == TypedNodeExpressionBinary.Op.Add && expression.Left.Type is NubTypeString && expression.Right.Type is NubTypeString)
         {
-            var name = TmpName();
             scopes.Peek().DeconstructableNames.Add((name, expression.Type));
             writer.WriteLine($"{CType(NubTypeString.Instance, name)} = string_concat({left}, {right});");
             return name;
         }
 
-        return expression.Operation switch
+        var op =  expression.Operation switch
         {
             TypedNodeExpressionBinary.Op.Add => $"({left} + {right})",
             TypedNodeExpressionBinary.Op.Subtract => $"({left} - {right})",
@@ -536,30 +534,40 @@ public class Generator
             TypedNodeExpressionBinary.Op.LogicalOr => $"({left} || {right})",
             _ => throw new ArgumentOutOfRangeException()
         };
+
+        writer.WriteLine($"{CType(expression.Type, name)} = {op};");
+
+        return name;
     }
 
     private string EmitExpressionUnary(TypedNodeExpressionUnary expression)
     {
         var target = EmitExpression(expression.Target);
 
-        return expression.Operation switch
+        var name = Tmp();
+
+        var op = expression.Operation switch
         {
             TypedNodeExpressionUnary.Op.Negate => $"(-{target})",
             TypedNodeExpressionUnary.Op.Invert => $"(!{target})",
             _ => throw new ArgumentOutOfRangeException()
         };
+
+        writer.WriteLine($"{CType(expression.Type, name)} = {op};");
+
+        return name;
     }
 
     private string EmitExpressionStringLiteral(TypedNodeExpressionStringLiteral expression)
     {
-        var name = TmpName();
+        var name = Tmp();
         referencedStringLiterals.Add(name, expression.Value.Value);
         return $"&{name}";
     }
 
     private string EmitExpressionStructLiteral(TypedNodeExpressionStructLiteral expression)
     {
-        var name = TmpName();
+        var name = Tmp();
         scopes.Peek().DeconstructableNames.Add((name, expression.Type));
 
         var initializerValues = new Dictionary<string, string>();
@@ -580,7 +588,7 @@ public class Generator
 
     private string EmitExpressionEnumLiteral(TypedNodeExpressionEnumLiteral expression)
     {
-        var name = TmpName();
+        var name = Tmp();
         scopes.Peek().DeconstructableNames.Add((name, expression.Type));
 
         var enumVariantType = (NubTypeEnumVariant)expression.Type;
@@ -638,7 +646,10 @@ public class Generator
     {
         var name = EmitExpression(expression.Target);
         var parameterValues = expression.Parameters.Select(EmitExpression).ToList();
-        return $"{name}({string.Join(", ", parameterValues)})";
+
+        var tmp = Tmp();
+        writer.WriteLine($"{CType(expression.Type, tmp)} = {name}({string.Join(", ", parameterValues)});");
+        return tmp;
     }
 
     public string CType(NubType node, string? varName = null)
@@ -667,7 +678,7 @@ public class Generator
         return $"struct {NameMangler.Mangle("anonymous", "struct", type)}{(varName != null ? $" {varName}" : "")}";
     }
 
-    private string TmpName()
+    private string Tmp()
     {
         return $"_tmp{tmpNameIndex++}";
     }

compiler/TypeChecker.cs

@@ -24,7 +24,7 @@ public class TypeChecker
     private readonly NodeDefinitionFunc function;
     private NubType functionReturnType = null!;
     private readonly ModuleGraph moduleGraph;
-    private readonly Scope scope = new();
+    private readonly Stack<Dictionary<string, NubType>> scopes = new();
 
     private TypedNodeDefinitionFunc? CheckFunction(out List<Diagnostic> diagnostics)
     {
@@ -51,7 +51,7 @@ public class TypeChecker
             }
         }
 
-        using (scope.EnterScope())
+        using (EnterScope())
         {
             foreach (var parameter in function.Parameters)
             {
@@ -60,6 +60,7 @@ public class TypeChecker
                 try
                 {
                     parameterType = ResolveType(parameter.Type);
+                    DeclareLocalIdentifier(parameter.Name, parameterType);
                 }
                 catch (CompileException e)
                 {
@@ -68,7 +69,6 @@ public class TypeChecker
                     continue;
                 }
 
-                scope.DeclareIdentifier(parameter.Name.Ident, parameterType);
                 parameters.Add(new TypedNodeDefinitionFunc.Param(parameter.Tokens, parameter.Name, parameterType));
             }
 
@@ -114,7 +114,7 @@ public class TypeChecker
 
     private TypedNodeStatementBlock CheckStatementBlock(NodeStatementBlock statement)
     {
-        using (scope.EnterScope())
+        using (EnterScope())
         {
             var statements = statement.Statements.Select(CheckStatement).ToList();
             return new TypedNodeStatementBlock(statement.Tokens, statements);
@@ -137,8 +137,19 @@ public class TypeChecker
         if (!condition.Type.IsAssignableTo(NubTypeBool.Instance))
             throw BasicError("Condition part of if statement must be a boolean", condition);
 
-        var thenBlock = CheckStatement(statement.ThenBlock);
-        var elseBlock = statement.ElseBlock == null ? null : CheckStatement(statement.ElseBlock);
+        TypedNodeStatement thenBlock;
+
+        using (EnterScope())
+        {
+            thenBlock = CheckStatement(statement.ThenBlock);
+        }
+
+        TypedNodeStatement? elseBlock;
+
+        using (EnterScope())
+        {
+            elseBlock = statement.ElseBlock == null ? null : CheckStatement(statement.ElseBlock);
+        }
 
         return new TypedNodeStatementIf(statement.Tokens, condition, thenBlock, elseBlock);
     }
@@ -175,7 +186,7 @@ public class TypeChecker
 
         type ??= value.Type;
 
-        scope.DeclareIdentifier(statement.Name.Ident, type);
+        DeclareLocalIdentifier(statement.Name, type);
 
         return new TypedNodeStatementVariableDeclaration(statement.Tokens, statement.Name, type, value);
     }
@@ -186,9 +197,11 @@ public class TypeChecker
         if (!condition.Type.IsAssignableTo(NubTypeBool.Instance))
             throw BasicError("Condition part of if statement must be a boolean", condition);
 
-        var body = CheckStatement(statement.Body);
-
-        return new TypedNodeStatementWhile(statement.Tokens, condition, body);
+        using (EnterScope())
+        {
+            var body = CheckStatement(statement.Body);
+            return new TypedNodeStatementWhile(statement.Tokens, condition, body);
+        }
     }
 
     private TypedNodeStatementMatch CheckStatementMatch(NodeStatementMatch statement)
@@ -214,14 +227,14 @@ public class TypeChecker
 
             uncoveredCases.Remove(@case.Variant.Ident);
 
-            using (scope.EnterScope())
+            using (EnterScope())
             {
                 if (@case.VariableName != null)
                 {
                     if (variant.Type is null)
                         throw BasicError("Cannot capture variable for enum variant without type", @case.VariableName);
 
-                    scope.DeclareIdentifier(@case.VariableName.Ident, variant.Type);
+                    DeclareLocalIdentifier(@case.VariableName, variant.Type);
                 }
 
                 var body = CheckStatement(@case.Body);
@@ -416,14 +429,14 @@ public class TypeChecker
     {
         if (expression.Sections.Count == 1)
         {
-            var name = expression.Sections[0].Ident;
+            var name = expression.Sections[0];
 
-            var localType = scope.GetIdentifierType(name);
+            var localType = GetIdentifierType(name.Ident);
             if (localType is not null)
-                return new TypedNodeExpressionLocalIdent(expression.Tokens, localType, name);
+                return new TypedNodeExpressionLocalIdent(expression.Tokens, localType, name.Ident);
 
-            if (moduleGraph.TryResolveIdentifier(currentModule, name, true, out var ident))
-                return new TypedNodeExpressionGlobalIdent(expression.Tokens, ident.Type, currentModule, name);
+            if (moduleGraph.TryResolveIdentifier(currentModule, name.Ident, true, out var ident))
+                return new TypedNodeExpressionGlobalIdent(expression.Tokens, ident.Type, currentModule, name.Ident);
         }
         else if (expression.Sections.Count == 2)
         {
@@ -755,45 +768,44 @@ public class TypeChecker
         return new CompileException(Diagnostic.Error(message).At(fileName, node).Build());
     }
 
-    private sealed class Scope
+    public void DeclareLocalIdentifier(TokenIdent name, NubType type)
     {
-        private readonly Stack<Dictionary<string, NubType>> scopes = new();
+        var existing = GetIdentifierType(name.Ident);
+        if (existing is not null)
+            throw BasicError($"Local identifier '{name.Ident}' is already defined", name);
 
-        public IDisposable EnterScope()
-        {
-            scopes.Push([]);
-            return new ScopeGuard(this);
-        }
+        scopes.Peek().Add(name.Ident, type);
+    }
 
-        public void DeclareIdentifier(string name, NubType type)
+    public NubType? GetIdentifierType(string name)
+    {
+        foreach (var scope in scopes)
         {
-            scopes.Peek().Add(name, type);
-        }
-
-        public NubType? GetIdentifierType(string name)
-        {
-            foreach (var scope in scopes)
+            if (scope.TryGetValue(name, out var type))
             {
-                if (scope.TryGetValue(name, out var type))
-                {
-                    return type;
-                }
+                return type;
             }
-
-            return null;
         }
 
-        private void ExitScope()
-        {
-            scopes.Pop();
-        }
+        return null;
+    }
 
-        private sealed class ScopeGuard(Scope owner) : IDisposable
+    public IDisposable EnterScope()
+    {
+        scopes.Push([]);
+        return new ScopeGuard(this);
+    }
+
+    private void ExitScope()
+    {
+        scopes.Pop();
+    }
+
+    private sealed class ScopeGuard(TypeChecker owner) : IDisposable
+    {
+        public void Dispose()
         {
-            public void Dispose()
-            {
-                owner.ExitScope();
-            }
+            owner.ExitScope();
         }
     }
 }

examples/program/main.nub

@@ -21,9 +21,9 @@ func main(): i32 {
         {
             core::println("quit")
         }
-        Say message
+        Say msg
         {
-            core::println(message)
+            core::println(msg)
         }
     }