From 8f797bab845830fed3e3da7c417ff611a6efe7f1 Mon Sep 17 00:00:00 2001
From: Akos Hajdu <akoshajdu@fb.com>
Date: Wed, 21 Jul 2021 09:10:56 -0700
Subject: [PATCH] [erl-frontend] Support xor expressions

Summary: Add support for the xor operator by reducing `(X xor Y)` to `(X and not Y) or (not X and Y)`. Alternatively, `(X != Y)` could have been used but that might not be safe since SIL models Booleans with integers.

Reviewed By: skcho

Differential Revision: D29816793

fbshipit-source-id: 2496b718b
---
 infer/src/erlang/ErlangTranslator.ml          |  9 +++++++
 .../codetoanalyze/erlang/features/issues.exp  |  2 ++
 .../erlang/features/src/logic.erl             | 26 ++++++++++++++++++-
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/infer/src/erlang/ErlangTranslator.ml b/infer/src/erlang/ErlangTranslator.ml
index c1efab9e5..12313d3d0 100644
--- a/infer/src/erlang/ErlangTranslator.ml
+++ b/infer/src/erlang/ErlangTranslator.ml
@@ -418,6 +418,15 @@ and translate_expression env {Ast.line; simple_expression} =
             make_simple_eager Mod (* TODO: check semantics of Rem vs Mod *)
         | Sub ->
             make_simple_eager (MinusA None)
+        | Xor ->
+            let expr =
+              Exp.BinOp
+                ( LOr
+                , Exp.BinOp (LAnd, Var id1, Exp.UnOp (LNot, Var id2, None))
+                , Exp.BinOp (LAnd, Exp.UnOp (LNot, Var id1, None), Var id2) )
+            in
+            let op_block = Block.make_load env ret_var expr any in
+            Block.all env [block1; block2; op_block]
         | todo ->
             L.debug Capture Verbose
               "@[todo ErlangTranslator.translate_expression(BinaryOperator) %s@."
diff --git a/infer/tests/codetoanalyze/erlang/features/issues.exp b/infer/tests/codetoanalyze/erlang/features/issues.exp
index 87c599ed9..990ba1fef 100644
--- a/infer/tests/codetoanalyze/erlang/features/issues.exp
+++ b/infer/tests/codetoanalyze/erlang/features/issues.exp
@@ -36,6 +36,8 @@ codetoanalyze/erlang/features/src/logic.erl, test_andalso10_Bad/0, 1, NO_TRUE_BR
 codetoanalyze/erlang/features/src/logic.erl, test_or00_Bad/0, 1, NO_TRUE_BRANCH_IN_IF, no_bucket, ERROR, [no true branch in if expression here]
 codetoanalyze/erlang/features/src/logic.erl, test_orelse00_Bad/0, 1, NO_TRUE_BRANCH_IN_IF, no_bucket, ERROR, [no true branch in if expression here]
 codetoanalyze/erlang/features/src/logic.erl, test_unot_Bad/0, 1, NO_TRUE_BRANCH_IN_IF, no_bucket, ERROR, [no true branch in if expression here]
+codetoanalyze/erlang/features/src/logic.erl, test_xor00_Bad/0, 1, NO_TRUE_BRANCH_IN_IF, no_bucket, ERROR, [no true branch in if expression here]
+codetoanalyze/erlang/features/src/logic.erl, test_xor11_Bad/0, 1, NO_TRUE_BRANCH_IN_IF, no_bucket, ERROR, [no true branch in if expression here]
 codetoanalyze/erlang/features/src/short_circuit.erl, accepts_one/1, 0, NO_MATCHING_FUNCTION_CLAUSE, no_bucket, ERROR, [*** LATENT ***,no matching function clause here]
 codetoanalyze/erlang/features/src/short_circuit.erl, test_and_Bad/0, -7, NO_MATCHING_FUNCTION_CLAUSE, no_bucket, ERROR, [calling context starts here,in call to `accepts_one/1`,no matching function clause here]
 codetoanalyze/erlang/features/src/short_circuit.erl, test_andalso_Bad/0, -15, NO_MATCHING_FUNCTION_CLAUSE, no_bucket, ERROR, [calling context starts here,in call to `accepts_one/1`,no matching function clause here]
diff --git a/infer/tests/codetoanalyze/erlang/features/src/logic.erl b/infer/tests/codetoanalyze/erlang/features/src/logic.erl
index a056cbdaa..df6c0dceb 100644
--- a/infer/tests/codetoanalyze/erlang/features/src/logic.erl
+++ b/infer/tests/codetoanalyze/erlang/features/src/logic.erl
@@ -27,7 +27,11 @@
     test_orelse10_Ok/0,
     test_orelse11_Ok/0,
     test_unot_Ok/0,
-    test_unot_Bad/0
+    test_unot_Bad/0,
+    test_xor00_Bad/0,
+    test_xor01_Ok/0,
+    test_xor10_Ok/0,
+    test_xor11_Bad/0
 ]).
 
 test_and00_Bad() ->
@@ -119,3 +123,23 @@ test_unot_Bad() ->
     if
         not ?T -> ok
     end.
+
+test_xor00_Bad() ->
+    if
+        ?F xor ?F -> ok
+    end.
+
+test_xor01_Ok() ->
+    if
+        ?F xor ?T -> ok
+    end.
+
+test_xor10_Ok() ->
+    if
+        ?T xor ?F -> ok
+    end.
+
+test_xor11_Bad() ->
+    if
+        ?T xor ?T -> ok
+    end.