HackLint5649: Exempt internal classnames in __Sealed attributes

Summary:
## LLM-generated Summary:
Exempts internal classnames referenced in __Sealed user attributes from HackLint5649, while preserving the lint for usage elsewhere. This reduces false positives when sealing APIs that intentionally reference internal types and is validated with tests for class, interface, and method attributes plus an outside-attribute case.
 ---
Session: DEV53002705

Reviewed By: enetsee

Differential Revision: D92219643

fbshipit-source-id: fcdc391056830d19b13dc79f1e29d98dbe0a0b2a

Author: nmaue

hphp/hack/src/lints/linter_internal_class.ml

@@ -13,6 +13,8 @@ module Env = Tast_env
 module Cls = Folded_class
 module SN = Naming_special_names
 
+let in_sealed_attribute = ref false
+
 let check_internal_classname pos ci env =
   let class_result =
     match ci with
@@ -33,9 +35,21 @@ let handler =
   object
     inherit Tast_visitor.handler_base
 
+    method! at_user_attribute _env ua =
+      match ua.ua_name with
+      | (_, name) when String.equal name SN.UserAttributes.uaSealed ->
+        in_sealed_attribute := true
+      | _ -> in_sealed_attribute := false
+
+    method! at_class_ _env _c = in_sealed_attribute := false
+
+    method! at_method_ _env _m = in_sealed_attribute := false
+
+    method! at_fun_def _env _fd = in_sealed_attribute := false
+
     method! at_expr env (_, _, expr) =
       match expr with
       | Class_const ((_, p, ci), pstr) when String.equal (snd pstr) "class" ->
-        check_internal_classname p ci env
+        if not !in_sealed_attribute then check_internal_classname p ci env
       | _ -> ()
   end

hphp/hack/test/lint/lint_internal_class.php

@@ -20,3 +20,20 @@ public function test(): void {
   }
 
 }
+
+internal class InternalForSealed {}
+
+<<__Sealed(InternalForSealed::class)>>
+interface SealedInterface {}
+
+<<__Sealed(InternalForSealed::class, Foo::class)>>
+abstract class SealedClass {}
+
+class ClassWithSealedMethod {
+  <<__Sealed(InternalForSealed::class)>>
+  public function sealedMethod(): void {}
+}
+
+function uses_internal_outside_sealed(): void {
+  $x = InternalForSealed::class;
+}

hphp/hack/test/lint/lint_internal_class.php.exp

@@ -4,3 +4,5 @@ File "lint_internal_class.php--use.php", line 8, characters 8-13:
 This is a classname of an `internal` class. Internal classnames are dangerous because they are effectively raw strings. Please avoid them, or make sure that they are never used outside of the module. (Lint[5649])
 File "lint_internal_class.php--use.php", line 14, characters 10-15:
 This is a classname of an `internal` class. Internal classnames are dangerous because they are effectively raw strings. Please avoid them, or make sure that they are never used outside of the module. (Lint[5649])
+File "lint_internal_class.php--use.php", line 33, characters 8-24:
+This is a classname of an `internal` class. Internal classnames are dangerous because they are effectively raw strings. Please avoid them, or make sure that they are never used outside of the module. (Lint[5649])