Add support for backed enums (class SortOrder: string { ... })

Author: thekid

src/main/php/lang/ast/emit/PHP.class.php

@@ -363,7 +363,7 @@ protected function emitEnum($result, $enum) {
     array_unshift($result->meta, []);
     $result->locals= [[], []];
 
-    $result->out->write('final class '.$this->declaration($enum->name).' implements \UnitEnum');
+    $result->out->write('final class '.$this->declaration($enum->name).' implements \\'.($enum->base ? 'BackedEnum' : 'UnitEnum'));
     $enum->implements && $result->out->write(', '.implode(', ', $enum->implements));
     $result->out->write('{');
 
@@ -373,8 +373,28 @@ protected function emitEnum($result, $enum) {
       $this->emitOne($result, $member);
     }
 
-    // Name and constructor
-    $result->out->write('public $name; private function __construct($name) { $this->name= $name; }');
+    // Constructors
+    if ($enum->base) {
+      $result->out->write('public $name, $value;');
+      $result->out->write('private static $values= [];');
+      $result->out->write('private function __construct($name, $value) {
+        $this->name= $name;
+        $this->value= $value;
+        self::$values[$value]= $this;
+      }');
+      $result->out->write('public static function tryFrom($value) {
+        return self::$values[$value] ?? null;
+      }');
+      $result->out->write('public static function from($value) {
+        if ($r= self::$values[$value] ?? null) return $r;
+        throw new \ValueError("Not an enum value: ".\util\Objects::stringOf($value));
+      }');
+    } else {
+      $result->out->write('public $name;');
+      $result->out->write('private function __construct($name) {
+        $this->name= $name;
+      }');
+    }
 
     // Enum cases
     $result->out->write('public static function cases() { return [');
@@ -385,8 +405,16 @@ protected function emitEnum($result, $enum) {
 
     // Initializations
     $result->out->write('static function __init() {');
-    foreach ($cases as $case) {
-      $result->out->write('self::$'.$case->name.'= new self("'.$case->name.'");');
+    if ($enum->base) {
+      foreach ($cases as $case) {
+        $result->out->write('self::$'.$case->name.'= new self("'.$case->name.'", ');
+        $this->emitOne($result, $case->expression);
+        $result->out->write(');');
+      }
+    } else {
+      foreach ($cases as $case) {
+        $result->out->write('self::$'.$case->name.'= new self("'.$case->name.'");');
+      }
     }
     $this->emitInitializations($result, $result->locals[0]);
     $this->emitMeta($result, $enum->name, $enum->annotations, $enum->comment);

src/test/php/lang/ast/unittest/emit/EnumTest.class.php

@@ -51,6 +51,67 @@ public static function run($order= self::ASC) {
     Assert::equals('ASC', $t->getMethod('run')->invoke(null));
   }
 
+  #[Test]
+  public function value_property_of_backed_enum() {
+    $t= $this->type('enum <T>: string {
+      case ASC  = "asc";
+      case DESC = "desc";
+
+      public static function run() {
+        return self::DESC->value;
+      }
+    }');
+
+    Assert::equals('desc', $t->getMethod('run')->invoke(null));
+  }
+
+  #[Test, Values([['asc', 'ASC'], ['desc', 'DESC']])]
+  public function backed_enum_from($arg, $expected) {
+    $t= $this->type('enum <T>: string {
+      case ASC  = "asc";
+      case DESC = "desc";
+
+      public static function run($arg) {
+        return self::from($arg)->name;
+      }
+    }');
+
+    Assert::equals($expected, $t->getMethod('run')->invoke(null, [$arg]));
+  }
+
+  #[Test]
+  public function backed_enum_from_nonexistant() {
+    $t= $this->type('enum <T>: string {
+      case ASC  = "asc";
+      case DESC = "desc";
+
+      public static function run() {
+        try {
+          self::from("illegal");
+          throw new \lang\IllegalStateException("No exception raised");
+        } catch (\ValueError $expected) {
+          return $expected->getMessage();
+        }
+      }
+    }');
+
+    Assert::equals('Not an enum value: "illegal"', $t->getMethod('run')->invoke(null));
+  }
+
+  #[Test, Values([['asc', 'ASC'], ['desc', 'DESC'], ['illegal', null]])]
+  public function backed_enum_tryFrom($arg, $expected) {
+    $t= $this->type('enum <T>: string {
+      case ASC  = "asc";
+      case DESC = "desc";
+
+      public static function run($arg) {
+        return self::tryFrom($arg)?->name;
+      }
+    }');
+
+    Assert::equals($expected, $t->getMethod('run')->invoke(null, [$arg]));
+  }
+
   #[Test]
   public function enum_values() {
     $t= $this->type('use lang\Enum; enum <T> {