use early return; improve comment

Author: ianhoffman

src/Codegen/Constraints/BaseBuilder.php

@@ -95,60 +95,62 @@ protected function addEnumConstraintCheck(HackBuilder $hb): void {
 
   protected function addHackEnumConstraintCheck(HackBuilder $hb): void {
     $schema = type_assert_type($this->typed_schema, TSchema::class);
-    if (Shapes::keyExists($schema, 'hackEnum')) {
-      try {
-        $rc = new \ReflectionClass($schema['hackEnum']);
-      } catch (\ReflectionException $e) {
-        throw new \Exception(Str\format("Hack enum '%s' does not exist", $schema['hackEnum']));
-      }
+    if (!Shapes::keyExists($schema, 'hackEnum')) {
+      return;
+    }
 
-      invariant($rc->isEnum(), "'%s' is not an enum", $schema['hackEnum']);
+    try {
+      $rc = new \ReflectionClass($schema['hackEnum']);
+    } catch (\ReflectionException $e) {
+      throw new \Exception(Str\format("Hack enum '%s' does not exist", $schema['hackEnum']));
+    }
 
-      $schema_type = $schema['type'] ?? null;
-      $hack_enum_values = keyset[];
-      foreach ($rc->getConstants() as $hack_enum_value) {
-        if ($schema_type === TSchemaType::INTEGER_T) {
-          $hack_enum_value = $hack_enum_value ?as int;
-        } else {
-          $hack_enum_value = $hack_enum_value ?as string;
-        }
-        invariant(
-          $hack_enum_value is nonnull,
-          "'%s' must contain only values of type %s",
-          $rc->getName(),
-          $schema_type === TSchemaType::INTEGER_T ? 'int' : 'string'
-        );
-        $hack_enum_values[] = $hack_enum_value;
-      }
+    invariant($rc->isEnum(), "'%s' is not an enum", $schema['hackEnum']);
 
-      if (Shapes::keyExists($schema, 'enum')) {
-        // If both `enum` and `hackEnum` are specified, assert that `enum` is a subset of
-        // `hackEnum` values.
-        foreach ($schema['enum'] as $enum_value) {
-          invariant(
-            $enum_value is string,
-            "Enum value '%s' is not a valid value for '%s'",
-            \print_r($enum_value, true),
-            $rc->getName()
-          );
-          invariant(
-            C\contains_key($hack_enum_values, $enum_value),
-            "Enum value '%s' is unexpectedly not present in '%s'",
-            \print_r($enum_value, true),
-            $rc->getName()
-          );
-        }
+    $schema_type = $schema['type'] ?? null;
+    $hack_enum_values = keyset[];
+    foreach ($rc->getConstants() as $hack_enum_value) {
+      if ($schema_type === TSchemaType::INTEGER_T) {
+        $hack_enum_value = $hack_enum_value ?as int;
+      } else {
+        $hack_enum_value = $hack_enum_value ?as string;
       }
-
-      $hb->addMultilineCall(
-        '$typed = Constraints\HackEnumConstraint::check',
-        vec[
-          '$typed',
-          Str\format('\%s::class', $rc->getName()),
-          '$pointer'
-        ]
+      invariant(
+        $hack_enum_value is nonnull,
+        "'%s' must contain only values of type %s",
+        $rc->getName(),
+        $schema_type === TSchemaType::INTEGER_T ? 'int' : 'string'
       );
+      $hack_enum_values[] = $hack_enum_value;
     }
+
+    if (Shapes::keyExists($schema, 'enum')) {
+      // If both `enum` and `hackEnum` are specified, assert that `enum` is a subset of
+      // `hackEnum` values. Any value not also in `hackEnum` can't be valid.
+      foreach ($schema['enum'] as $enum_value) {
+        invariant(
+          $enum_value is string,
+          "Enum value '%s' is not a valid value for '%s'",
+          \print_r($enum_value, true),
+          $rc->getName()
+        );
+        invariant(
+          C\contains_key($hack_enum_values, $enum_value),
+          "Enum value '%s' is unexpectedly not present in '%s'",
+          \print_r($enum_value, true),
+          $rc->getName()
+        );
+      }
+    }
+
+    $hb->addMultilineCall(
+      '$typed = Constraints\HackEnumConstraint::check',
+      vec[
+        '$typed',
+        Str\format('\%s::class', $rc->getName()),
+        '$pointer'
+      ]
+    );
   }
 
   public function addBuilderClass(CodegenClass $class): void {