From bd166a244f078d34a55fe1f7df7dd9fd73f44a99 Mon Sep 17 00:00:00 2001
From: Mitya Lyubarskiy <mityal@fb.com>
Date: Mon, 10 Feb 2020 05:29:51 -0800
Subject: [PATCH] [nullsafe][easy] fix the wrong comment about order of
 arguments in `instanceof`

Summary:
This was introduced in D19770219, and skcho caught it, but for some
reason I seemed to have a blind spot and confused the semantics of `instanceof`.

Reviewed By: skcho

Differential Revision: D19813031

fbshipit-source-id: d939b981b
---
 infer/src/nullsafe/typeCheck.ml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/infer/src/nullsafe/typeCheck.ml b/infer/src/nullsafe/typeCheck.ml
index e19fe1d46..76f328dd7 100644
--- a/infer/src/nullsafe/typeCheck.ml
+++ b/infer/src/nullsafe/typeCheck.ml
@@ -665,8 +665,8 @@ let rec check_condition_for_sil_prune tenv idenv calls_this find_canonical_dupli
     | _ ->
         None
   in
-  (* check if the expression is coming from (`a` instanceof `b`), and returns `b`, if it is the case *)
-  let extract_argument_from_instanceof expr =
+  (* check if the expression is coming from (`a` instanceof `b`), and returns `a`, if it is the case *)
+  let extract_first_argument_from_instanceof expr =
     match extract_arguments_from_call ComplexExpressions.procname_instanceof expr with
     | Some [argument; _] ->
         Some argument
@@ -805,9 +805,9 @@ let rec check_condition_for_sil_prune tenv idenv calls_this find_canonical_dupli
               accumulated_typestate )
           arguments
     | None -> (
-      match extract_argument_from_instanceof expr with
+      match extract_first_argument_from_instanceof expr with
       | Some argument ->
-          (* ([argument] instanceof [expr] == true) implies (expr != null) *)
+          (* ([argument] instanceof <anything> == true) implies (argument != null) *)
           set_original_pvar_to_nonnull_in_typestate ~with_cond_redundant_check:false argument
             typestate
       | None ->