From 14d7a9b9c12a9279618680e1efaf840df942b137 Mon Sep 17 00:00:00 2001
From: Mark <markjordanthom@gmail.com>
Date: Mon, 20 Nov 2023 13:40:58 -0700
Subject: [PATCH] fix dif:vars_remove_goal/2 (#2175), untabify forms.rs to
 appease format check

---
 src/forms.rs     | 10 +++++-----
 src/lib/dif.pl   | 12 +++++++-----
 src/tests/dif.pl |  7 +++++++
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/src/forms.rs b/src/forms.rs
index 3a2b743f2..d18d41f15 100644
--- a/src/forms.rs
+++ b/src/forms.rs
@@ -744,11 +744,11 @@ impl Number {
             Number::Float(f) => Number::Float(OrderedFloat(f.signum())),
             _ => {
                 if self.is_positive() {
-		    if self.is_zero() {
-			Number::Fixnum(Fixnum::build_with(0))
-		    } else {
-			Number::Fixnum(Fixnum::build_with(1))
-		    }
+                    if self.is_zero() {
+                        Number::Fixnum(Fixnum::build_with(0))
+                    } else {
+                        Number::Fixnum(Fixnum::build_with(1))
+                    }
                 } else if self.is_negative() {
                     Number::Fixnum(Fixnum::build_with(-1))
                 } else {
diff --git a/src/lib/dif.pl b/src/lib/dif.pl
index 8efb42710..c344e1d75 100644
--- a/src/lib/dif.pl
+++ b/src/lib/dif.pl
@@ -33,11 +33,13 @@
 
 vars_remove_goal([], _).
 vars_remove_goal([Var|Vars], Goal0) :-
-    get_atts(Var, +dif(Goals0)),
-    remove_goal(Goals0, Goal0, Goals),
-    (   Goals = [] ->
-        put_atts(Var, -dif(_))
-    ;   put_atts(Var, +dif(Goals))
+    (  get_atts(Var, +dif(Goals0)) ->
+       remove_goal(Goals0, Goal0, Goals),
+       (   Goals = [] ->
+           put_atts(Var, -dif(_))
+       ;   put_atts(Var, +dif(Goals))
+       )
+    ;  true
     ),
     vars_remove_goal(Vars, Goal0).
 
diff --git a/src/tests/dif.pl b/src/tests/dif.pl
index 752f14054..1696c64a3 100644
--- a/src/tests/dif.pl
+++ b/src/tests/dif.pl
@@ -207,6 +207,13 @@
     \+ E=[]
 )).
 
+% https://github.com/mthom/scryer-prolog/issues/2175
+test("scryer-prolog#2175",(
+    dif(A,B),
+    A=C*[],
+    A=[]*D*B,D=[]
+)).
+
 main :-
     findall(test(Name, Goal), test(Name, Goal), Tests),
     run_tests(Tests, Failed),