proper scopes

compiler/ModuleGraph.cs

@@ -180,7 +180,7 @@ public class ModuleGraph
 
             var astModuleCache = new Dictionary<Ast, Module>();
 
-            // First pass: Register modules from ast
+            // Second pass: Register modules from ast
             foreach (var ast in asts)
             {
                 if (!modules.ContainsKey(ast.ModuleName.Ident))
@@ -191,7 +191,7 @@ public class ModuleGraph
                 }
             }
 
-            // Second pass: Register struct types without fields
+            // Third pass: Register struct types without fields
             foreach (var ast in asts)
             {
                 var module = astModuleCache[ast];
@@ -204,7 +204,7 @@ public class ModuleGraph
                 }
             }
 
-            // Third pass: Resolve struct fields
+            // Fourth pass: Resolve struct fields
             foreach (var ast in asts)
             {
                 var module = astModuleCache[ast];
@@ -219,7 +219,7 @@ public class ModuleGraph
                 }
             }
 
-            // Fourth pass: Register identifiers
+            // Fifth pass: Register identifiers
             foreach (var ast in asts)
             {
                 var module = astModuleCache[ast];

compiler/TypeChecker.cs

@@ -19,7 +19,7 @@ public class TypeChecker
     private readonly string moduleName;
     private readonly NodeDefinitionFunc function;
     private readonly ModuleGraph moduleGraph;
-    private readonly Scope scope = new(null);
+    private readonly Scope scope = new();
 
     private TypedNodeDefinitionFunc? CheckFunction(out List<Diagnostic> diagnostics)
     {
@@ -30,48 +30,50 @@ public class TypeChecker
         TypedNodeStatement? body = null;
         NubType? returnType = null;
 
-        foreach (var parameter in function.Parameters)
+        using (scope.EnterScope())
         {
-            scope.DeclareIdentifier(parameter.Name.Ident, ResolveType(parameter.Type));
+            foreach (var parameter in function.Parameters)
+            {
+                NubType parameterType;
+
+                try
+                {
+                    parameterType = ResolveType(parameter.Type);
+                }
+                catch (CompileException e)
+                {
+                    diagnostics.Add(e.Diagnostic);
+                    invalidParameter = true;
+                    continue;
+                }
+
+                scope.DeclareIdentifier(parameter.Name.Ident, parameterType);
+                parameters.Add(new TypedNodeDefinitionFunc.Param(parameter.Tokens, parameter.Name, parameterType));
+            }
 
             try
             {
-                parameters.Add(CheckDefinitionFuncParameter(parameter));
+                body = CheckStatement(function.Body);
             }
             catch (CompileException e)
             {
                 diagnostics.Add(e.Diagnostic);
-                invalidParameter = true;
             }
-        }
 
-        try
-        {
-            body = CheckStatement(function.Body);
-        }
-        catch (CompileException e)
-        {
-            diagnostics.Add(e.Diagnostic);
-        }
+            try
+            {
+                returnType = ResolveType(function.ReturnType);
+            }
+            catch (CompileException e)
+            {
+                diagnostics.Add(e.Diagnostic);
+            }
 
-        try
-        {
-            returnType = ResolveType(function.ReturnType);
+            if (body == null || returnType == null || invalidParameter)
+                return null;
+
+            return new TypedNodeDefinitionFunc(function.Tokens, moduleName, function.Name, parameters, body, returnType);
         }
-        catch (CompileException e)
-        {
-            diagnostics.Add(e.Diagnostic);
-        }
-
-        if (body == null || returnType == null || invalidParameter)
-            return null;
-
-        return new TypedNodeDefinitionFunc(function.Tokens, moduleName, function.Name, parameters, body, returnType);
-    }
-
-    private TypedNodeDefinitionFunc.Param CheckDefinitionFuncParameter(NodeDefinitionFunc.Param node)
-    {
-        return new TypedNodeDefinitionFunc.Param(node.Tokens, node.Name, ResolveType(node.Type));
     }
 
     private TypedNodeStatement CheckStatement(NodeStatement node)
@@ -96,7 +98,11 @@ public class TypeChecker
 
     private TypedNodeStatementBlock CheckStatementBlock(NodeStatementBlock statement)
     {
-        return new TypedNodeStatementBlock(statement.Tokens, statement.Statements.Select(CheckStatement).ToList());
+        using (scope.EnterScope())
+        {
+            var statements = statement.Statements.Select(CheckStatement).ToList();
+            return new TypedNodeStatementBlock(statement.Tokens, statements);
+        }
     }
 
     private TypedNodeStatementFuncCall CheckStatementExpression(NodeStatementExpression statement)
@@ -406,20 +412,45 @@ public class TypeChecker
         return customType;
     }
 
-    private class Scope(Scope? parent)
+    private sealed class Scope
     {
-        private readonly Dictionary<string, NubType> identifiers = new();
+        private readonly Stack<Dictionary<string, NubType>> scopes = new();
+
+        public IDisposable EnterScope()
+        {
+            scopes.Push([]);
+            return new ScopeGuard(this);
+        }
 
         public void DeclareIdentifier(string name, NubType type)
         {
-            identifiers.Add(name, type);
+            scopes.Peek().Add(name, type);
         }
 
         public NubType? GetIdentifierType(string name)
         {
-            return identifiers.TryGetValue(name, out var type)
-                ? type
-                : parent?.GetIdentifierType(name);
+            foreach (var scope in scopes)
+            {
+                if (scope.TryGetValue(name, out var type))
+                {
+                    return type;
+                }
+            }
+
+            return null;
+        }
+
+        private void ExitScope()
+        {
+            scopes.Pop();
+        }
+
+        private sealed class ScopeGuard(Scope owner) : IDisposable
+        {
+            public void Dispose()
+            {
+                owner.ExitScope();
+            }
         }
     }
 }