account for nil return type in tyProc sumGeneric (#23250)

fixes #23249

2 files changed, 19 insertions, 1 deletions

diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index b4d875981..a0de33ed5 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -246,7 +246,8 @@ proc sumGeneric(t: PType): int =
           result += sumGeneric(a)
       break
     of tyProc:
-      result += sumGeneric(t.returnType)
+      if t.returnType != nil:
+        result += sumGeneric(t.returnType)
       for _, a in t.paramTypes:
         result += sumGeneric(a)
       break
diff --git a/tests/overload/t23249.nim b/tests/overload/t23249.nim
new file mode 100644
index 000000000..f4657833b
--- /dev/null
+++ b/tests/overload/t23249.nim
@@ -0,0 +1,17 @@
+# issue #23249
+
+type Control* = object
+proc onAction*(c: Control, handler: proc(e: int) {.gcsafe.}) = discard
+proc onAction*(c: Control, handler: proc() {.gcsafe.}) = discard
+
+template setControlHandlerBlock(c: Control, p: untyped, a: untyped) =
+    when compiles(c.p(nil)):
+        c.p() do() {.gcsafe.}: a
+    else:
+        c.p = proc() {.gcsafe.} =
+            a
+
+proc mkLayout() =
+  var b: Control
+  setControlHandlerBlock(b, onAction):
+    echo "hi"