feat(closure): implement proper lexical scope handling for closures

- Add genNewClosure method to handle closure creation with correct scope
- Preserve lexical class scope and late static binding for closures
- Handle trait method flattening correctly when creating closures in traits
- Update arrow function and fiber generator closure creation to use new method
- Fix strict scalar parameter checking to run inside argument expressions
- Correct trait name resolution in class definition processing
- Add comprehensive test coverage for closure lexical scope behavior

src/Build/FileScanner.php

@@ -90,9 +90,8 @@ class FileScanner
 
         foreach ($iterator as $file) {
             if ($file->isFile()) {
-                if (self::isPhpFile($file) || self::isNativeSourceFile($file)) {
-                    $filePath = $file->getPathname();
-                } else {
+                $filePath = $file->getPathname();
+                if (!self::isPhpFile($filePath) && !self::isNativeSourceFile($filePath)) {
                     continue;
                 }
                 if (!$this->isExcluded($filePath)) {

src/Generator/ClosureGenerator.php

@@ -23,6 +23,22 @@ use PhpParser\Node\Expr\Variable;
 
 trait ClosureGenerator
 {
+    protected function genNewClosure(string $callback, string $uses, bool $hasThis): string
+    {
+        $thisArg = $hasThis ? 'this_' : '{}';
+        if ($this->classDef?->trait !== null) {
+            // PHP flattens a trait method into the consuming class. A closure
+            // declared in that method therefore uses the consuming class as
+            // its lexical scope, never the trait's own class entry.
+            $scope = 'php_get_called_ce(this_)';
+        } else {
+            $scope = $this->class
+                ? $this->getClassEntryPtr($this->getFullClassName())
+                : 'nullptr';
+        }
+        return 'php::newClosure(' . $callback . ', ' . $uses . ', ' . $thisArg . ', ' . $scope . ')';
+    }
+
     protected function parseArrowFunction(Expr\ArrowFunction $expr): string
     {
         $nodeFinder = new NodeFinder();
@@ -211,11 +227,14 @@ trait ClosureGenerator
         $this->context = $oriContext;
         $this->context->beforeStmtLines[] = $code;
 
-        if ($this->methodDef && !$expr->static) {
-            return 'php::newClosure(' . $tmpVar . ', { ' . implode(', ', $useVars) . ' }, this_)';
-        } else {
-            return 'php::newClosure(' . $tmpVar . ', { ' . implode(', ', $useVars) . ' })';
-        }
+        // Even a static closure inherits the outer called scope for late
+        // static binding. It still cannot access $this because it was not
+        // registered in the closure compilation context above.
+        return $this->genNewClosure(
+            $tmpVar,
+            '{ ' . implode(', ', $useVars) . ' }',
+            $this->methodDef !== null
+        );
     }
 
     protected function closureContainsYield(Expr\ArrowFunction|Expr\Closure $expr): bool
@@ -325,9 +344,7 @@ trait ClosureGenerator
 
         $code .= $this->getIndent() . '};' . PHP_EOL;
         $args = $capturedArgs ? '{ ' . implode(', ', $capturedArgs) . ' }' : '{}';
-        $callback = $this->methodDef
-            ? 'php::newClosure(' . $callbackVar . ', ' . $args . ', this_)'
-            : 'php::newClosure(' . $callbackVar . ', ' . $args . ')';
+        $callback = $this->genNewClosure($callbackVar, $args, $this->methodDef !== null);
         $code .= $this->getIndent() . 'return typephp_new_fiber_generator(' . $callback . ');' . PHP_EOL;
         return $code;
     }

src/Generator/FiberGenerator.php

@@ -301,9 +301,7 @@ trait FiberGenerator
 
         $code .= $this->getIndent() . '};' . PHP_EOL;
         $args = $uses ? '{ ' . implode(', ', $uses) . ' }' : '{}';
-        $closureExpr = $this->class
-            ? 'php::newClosure(' . $closureVar . ', ' . $args . ', this_)'
-            : 'php::newClosure(' . $closureVar . ', ' . $args . ')';
+        $closureExpr = $this->genNewClosure($closureVar, $args, $this->class !== '');
         $code .= $this->getIndent() . 'return typephp_new_fiber_generator(' . $closureExpr . ');' . PHP_EOL;
         $this->indentLevel--;
         $code .= '}' . PHP_EOL;

src/Translator.php

@@ -2604,7 +2604,7 @@ CODE;
             }
 
             foreach ($classStmt->traits as $trait1) {
-                $traitFullName = $this->getNamespacedClassName($trait1);
+                $traitFullName = $this->getNamespacedClassName($trait1->toString());
                 if (!$this->hasClass($traitFullName)) {
                     $this->fatalError($classStmt, "Trait `{$traitFullName}` not found");
                 }

src/TypeSystem/NativeTypeCompatibilityTrait.php

@@ -188,15 +188,20 @@ trait NativeTypeCompatibilityTrait
         if (($type === Type::VAR || $type === Type::REF) && $this->isStrictScalarType($argInfo->type)) {
             // A native scalar ABI value has already lost its zval type. Preserve
             // the dynamic value until strict_types validation has completed.
-            $tmpVar = $this->addTmpVar(Type::VAR);
-            $this->context->beforeStmtLines[] = $tmpVar . ' = (' . $expr . ');';
-            $this->context->beforeStmtLines[] = rtrim($this->genStrictScalarParamCheck(
+            // Keep the check inside the argument expression: beforeStmtLines
+            // may run before an enclosing assignment or comma expression has
+            // initialized a compiler-generated argument temporary.
+            $checkedArg = 'typephp_checked_arg';
+            $check = rtrim($this->genStrictScalarParamCheck(
                 $argInfo,
-                $tmpVar,
+                $checkedArg,
                 $callableName,
                 (string) ($argIndex + 1)
             ));
-            $expr = $tmpVar;
+            $expr = '([&](php::Var ' . $checkedArg . ') -> php::Var {' . PHP_EOL
+                . $check . PHP_EOL
+                . $this->getIndent() . 'return ' . $checkedArg . ';' . PHP_EOL
+                . $this->getIndent() . '})(' . $expr . ')';
         }
 
         $this->checkVarAssignExpr($arg, $argInfo->type, $type);

tests/compiler/closure/lexical-scope.phpt

@@ -0,0 +1,55 @@
+--TEST--
+closures preserve lexical class scope and late static binding scope
+--FILE--
+<?php
+
+class ClosureScopeParent
+{
+    private static string $secret = 'private';
+
+    public function callbacks(): array
+    {
+        return [
+            fn(): string => self::$secret,
+            static fn(): string => self::$secret,
+            static fn(): string => static::class,
+        ];
+    }
+}
+
+class ClosureScopeChild extends ClosureScopeParent
+{
+}
+
+trait ClosureScopeTrait
+{
+    public function traitCallback(): Closure
+    {
+        return static fn(): string => self::$traitSecret;
+    }
+}
+
+class ClosureScopeTraitUser
+{
+    use ClosureScopeTrait;
+
+    private static string $traitSecret = 'trait-private';
+}
+
+function main(): void
+{
+    foreach ((new ClosureScopeChild())->callbacks() as $callback) {
+        $scope = (new ReflectionFunction($callback))->getClosureScopeClass();
+        echo $scope?->getName(), ':', $callback(), "\n";
+    }
+
+    $traitCallback = (new ClosureScopeTraitUser())->traitCallback();
+    $traitScope = (new ReflectionFunction($traitCallback))->getClosureScopeClass();
+    echo $traitScope?->getName(), ':', $traitCallback(), "\n";
+}
+?>
+--EXPECT--
+ClosureScopeParent:private
+ClosureScopeParent:private
+ClosureScopeParent:ClosureScopeChild
+ClosureScopeTraitUser:trait-private