add phpt tests

tests/compiler/static/late-static-class-return.phpt

@@ -0,0 +1,82 @@
+--TEST--
+static::class resolves to the called class through string-typed methods
+--FILE--
+<?php
+declare(strict_types=1);
+
+trait LsbClassTrait
+{
+    public function traitClass(): string
+    {
+        return static::class;
+    }
+}
+
+class LsbBase
+{
+    use LsbClassTrait;
+
+    public static function staticClass(): string
+    {
+        return static::class;
+    }
+
+    public function instanceClass(): string
+    {
+        return static::class;
+    }
+
+    public static function viaVar(): string
+    {
+        $name = static::class;
+        return $name;
+    }
+
+    public static function untypedClass()
+    {
+        return static::class;
+    }
+}
+
+class LsbChild extends LsbBase
+{
+}
+
+final class LsbGrandChild extends LsbChild
+{
+}
+
+function main(): void
+{
+    // Called class is the declaring class.
+    var_dump(LsbBase::staticClass());
+    var_dump((new LsbBase())->instanceClass());
+
+    // Late static binding through a static call.
+    var_dump(LsbChild::staticClass());
+    var_dump(LsbGrandChild::staticClass());
+
+    // Late static binding through an inherited instance method.
+    var_dump((new LsbChild())->instanceClass());
+    var_dump((new LsbGrandChild())->instanceClass());
+
+    // The result assigned to a local variable and returned.
+    var_dump(LsbChild::viaVar());
+
+    // static::class in a trait body resolves to the consuming class.
+    var_dump((new LsbChild())->traitClass());
+
+    // Untyped return keeps the runtime value intact.
+    var_dump(LsbGrandChild::untypedClass());
+}
+?>
+--EXPECT--
+string(7) "LsbBase"
+string(7) "LsbBase"
+string(8) "LsbChild"
+string(13) "LsbGrandChild"
+string(8) "LsbChild"
+string(13) "LsbGrandChild"
+string(8) "LsbChild"
+string(8) "LsbChild"
+string(13) "LsbGrandChild"