From c95fa10824a1f9d05de165a08b87d1ffa82783b2 Mon Sep 17 00:00:00 2001
From: Ivan Bondarev <ibond84@googlemail.com>
Date: Sun, 12 Dec 2021 15:26:45 +0100
Subject: [PATCH] bug fix #2572

---
 TestSuite/diapasons3.pas | 17 +++++++++--------
 TestSuite/diapasons4.pas |  6 ++++++
 bin/Lib/PABCSystem.pas   | 15 ++++++++++++++-
 3 files changed, 29 insertions(+), 9 deletions(-)
 create mode 100644 TestSuite/diapasons4.pas

diff --git a/TestSuite/diapasons3.pas b/TestSuite/diapasons3.pas
index 1e8a6d743..bb99cfb62 100644
--- a/TestSuite/diapasons3.pas
+++ b/TestSuite/diapasons3.pas
@@ -1,11 +1,12 @@
-var a : 1..4;
+var
+  a: 1..4;
 
 begin
-a := 2;
-a += 1;
-assert(a=3);
-a -= 1;
-assert(a=2);
-a *= 2;
-assert(a=4);
+  a := 2;
+  a += 1;
+  assert(a = 3);
+  a -= 1;
+  assert(a = 2);
+  a *= 2;
+  assert(a = 4);
 end.
\ No newline at end of file
diff --git a/TestSuite/diapasons4.pas b/TestSuite/diapasons4.pas
new file mode 100644
index 000000000..74788c3ea
--- /dev/null
+++ b/TestSuite/diapasons4.pas
@@ -0,0 +1,6 @@
+begin
+  var r := 1..2;
+  assert(r <> nil);
+  r := nil;
+  assert(r = nil);
+end.
\ No newline at end of file
diff --git a/bin/Lib/PABCSystem.pas b/bin/Lib/PABCSystem.pas
index 8bcffc9f0..015ddde21 100644
--- a/bin/Lib/PABCSystem.pas
+++ b/bin/Lib/PABCSystem.pas
@@ -637,7 +637,20 @@ type
 
     static function operator in(x: integer; r: IntRange): boolean := (x >= r.l) and (x <= r.h); 
     static function operator in(x: real; r: IntRange): boolean := (x >= r.l) and (x <= r.h); 
-    static function operator=(r1,r2: IntRange): boolean := (r1.l = r2.l) and (r1.h = r2.h);
+    static function operator=(r1,r2: IntRange): boolean;
+    begin
+      var o1: object := r1;
+      var o2: object := r2;
+      if (o1 = nil) and (o2 = nil) then
+        Result := true
+      else if (o1 <> nil) and (o2 = nil) then
+        Result := false
+      else if (o1 = nil) and (o2 <> nil) then
+        Result := false
+      else
+        Result := (r1.l = r2.l) and (r1.h = r2.h);
+    end;
+    
     /// Возвращает True если диапазон пуст
     function IsEmpty: boolean := l>h;