From 879429889357374071de96576984c4f01529be6d Mon Sep 17 00:00:00 2001
From: Owen Mansel-Chan <owen-mc@github.com>
Date: Fri, 29 May 2026 15:57:08 +0100
Subject: [PATCH] Fix empty switch statements

---
 .../go/controlflow/ControlFlowGraphShared.qll | 38 ++++++-------------
 1 file changed, 12 insertions(+), 26 deletions(-)

diff --git a/go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll b/go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll
index 72d7da2e851..992cef0ffeb 100644
--- a/go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll
+++ b/go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll
@@ -1231,6 +1231,14 @@ module GoCfg {
       exprSwitch(n1, n2) or typeSwitch(n1, n2) or caseClause(n1, n2)
     }
 
+    private predicate switchCasesStartOrAfter(Go::SwitchStmt sw, PreControlFlowNode n) {
+      n.isBefore(sw.getNonDefaultCase(0))
+      or
+      not exists(sw.getANonDefaultCase()) and n.isBefore(sw.getDefault())
+      or
+      not exists(sw.getACase()) and n.isAfter(sw)
+    }
+
     private predicate exprSwitch(PreControlFlowNode n1, PreControlFlowNode n2) {
       exists(Go::ExpressionSwitchStmt sw |
         n1.isBefore(sw) and
@@ -1241,14 +1249,7 @@ module GoCfg {
           (
             n2.isBefore(sw.getExpr())
             or
-            not exists(sw.getExpr()) and
-            (
-              n2.isBefore(sw.getNonDefaultCase(0))
-              or
-              not exists(sw.getANonDefaultCase()) and n2.isBefore(sw.getDefault())
-              or
-              not exists(sw.getACase()) and n2.isAfter(sw)
-            )
+            not exists(sw.getExpr()) and switchCasesStartOrAfter(sw, n2)
           )
         )
         or
@@ -1256,20 +1257,10 @@ module GoCfg {
         (
           n2.isBefore(sw.getExpr())
           or
-          not exists(sw.getExpr()) and
-          (
-            n2.isBefore(sw.getNonDefaultCase(0))
-            or
-            not exists(sw.getANonDefaultCase()) and n2.isBefore(sw.getDefault())
-          )
+          not exists(sw.getExpr()) and switchCasesStartOrAfter(sw, n2)
         )
         or
-        n1.isAfter(sw.getExpr()) and
-        (
-          n2.isBefore(sw.getNonDefaultCase(0))
-          or
-          not exists(sw.getANonDefaultCase()) and n2.isBefore(sw.getDefault())
-        )
+        n1.isAfter(sw.getExpr()) and switchCasesStartOrAfter(sw, n2)
       )
     }
 
@@ -1284,12 +1275,7 @@ module GoCfg {
         or
         n1.isAfter(sw.getInit()) and n2.isBefore(sw.getTest())
         or
-        n1.isAfter(sw.getTest()) and
-        (
-          n2.isBefore(sw.getNonDefaultCase(0))
-          or
-          not exists(sw.getANonDefaultCase()) and n2.isBefore(sw.getDefault())
-        )
+        n1.isAfter(sw.getTest()) and switchCasesStartOrAfter(sw, n2)
       )
     }