From e412f6be55f9ba2b45c020a240ed467cce5ac28f Mon Sep 17 00:00:00 2001
From: florian <florian@freepascal.org>
Date: Fri, 19 Apr 2024 23:43:05 +0200
Subject: [PATCH]   + in on an empty set is always false, resolves #40745

---
 compiler/nset.pas       | 10 ++++++++++
 tests/webtbs/tw40745.pp | 17 +++++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 tests/webtbs/tw40745.pp

diff --git a/compiler/nset.pas b/compiler/nset.pas
index c0f06e5c1b..fa321aa9ed 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -350,6 +350,7 @@ implementation
         t : tnode;
       begin
          result:=nil;
+
          { constant evaluation }
          if (left.nodetype=ordconstn) then
            begin
@@ -400,6 +401,15 @@ implementation
              typecheckpass(t);
              result:=t;
              exit;
+           end
+         { ... in [] is always false }
+         else if is_emptyset(right) and
+           not(might_have_sideeffects(left,[mhs_exceptions])) then
+           begin
+             t:=cordconstnode.create(1, pasbool1type, false);
+             typecheckpass(t);
+             result:=t;
+             exit;
            end;
       end;
 
diff --git a/tests/webtbs/tw40745.pp b/tests/webtbs/tw40745.pp
new file mode 100644
index 0000000000..85bf7c596b
--- /dev/null
+++ b/tests/webtbs/tw40745.pp
@@ -0,0 +1,17 @@
+program test;
+{$mode objfpc}
+type
+  TSetOfChar = set of char;
+  TMyObject=class
+    class function Method(setofchar: TSetOfChar): Boolean; inline;
+  end;
+
+class function TMyObject.Method(setofchar: TSetOfChar): Boolean;
+var sym: char=#0;
+begin
+  Result:=sym in setofchar;
+end;
+
+begin
+  TMyObject.Method([]);
+end.
\ No newline at end of file