Make transpiled enums string-backed

Author: grebaldi

src/Transpiler/Php/Transpiler.php

@@ -100,11 +100,11 @@ public function transpileEnumDeclaration(EnumDeclarationNode $enumDeclaration):
         $lines[] = '';
         $lines[] = 'namespace Vendor\\Project\\Component;';
         $lines[] = '';
-        $lines[] = 'enum ' . $enumDeclaration->enumName;
+        $lines[] = 'enum ' . $enumDeclaration->enumName . ': string';
         $lines[] = '{';
 
         foreach ($enumDeclaration->memberDeclarations->items as $memberDeclarationNode) {
-            $lines[] = '    case ' . $memberDeclarationNode->name . ';';
+            $lines[] = '    case ' . $memberDeclarationNode->name . ' = \'' . $memberDeclarationNode->name . '\';';
         }
 
         $lines[] = '}';

test/Integration/Examples/Enum/Enum.php

@@ -4,13 +4,13 @@
 
 namespace Vendor\Project\Component;
 
-enum DayOfWeek
+enum DayOfWeek: string
 {
-    case MONDAY;
-    case TUESDAY;
-    case WEDNESDAY;
-    case THURSDAY;
-    case FRIDAY;
-    case SATURDAY;
-    case SUNDAY;
+    case MONDAY = 'MONDAY';
+    case TUESDAY = 'TUESDAY';
+    case WEDNESDAY = 'WEDNESDAY';
+    case THURSDAY = 'THURSDAY';
+    case FRIDAY = 'FRIDAY';
+    case SATURDAY = 'SATURDAY';
+    case SUNDAY = 'SUNDAY';
 }