make @:hlNative impure (close #5661)

src/optimization/analyzerTexpr.ml

@@ -1045,7 +1045,7 @@ module Purity = struct
 				| None ->
 					if not (is_pure c cf) then taint node
 				(* TODO: The function code check shouldn't be here I guess. *)
-				| Some _ when (Meta.has Meta.Extern cf.cf_meta || Meta.has Meta.FunctionCode cf.cf_meta) ->
+				| Some _ when (Meta.has Meta.Extern cf.cf_meta || Meta.has Meta.FunctionCode cf.cf_meta || Meta.has (Meta.Custom ":hlNative") cf.cf_meta) ->
 					if not (is_pure c cf) then taint node
 				| Some e ->
 					try