Fix #17712 (#17873)

compiler/dfa.nim

@@ -696,9 +696,10 @@ proc skipTrivials(c: var Con, n: PNode): PNode =
 proc genUse(c: var Con; orig: PNode) =
   let n = c.skipTrivials(orig)
 
-  if n.kind == nkSym and n.sym.kind in InterestingSyms:
-    c.code.add Instr(n: orig, kind: use)
-  elif n.kind in nkCallKinds:
+  if n.kind == nkSym:
+    if n.sym.kind in InterestingSyms:
+      c.code.add Instr(n: orig, kind: use)
+  else:
     gen(c, n)
 
 proc genDef(c: var Con; orig: PNode) =

tests/arc/tarcmisc.nim

@@ -27,6 +27,7 @@ finalizer
 aaaaa
 hello
 ok
+true
 closed
 destroying variable: 20
 destroying variable: 10
@@ -422,3 +423,13 @@ proc test3 =
 
 static: test3() # was buggy
 test3()
+
+# bug #17712
+proc t17712 =
+  var ppv = new int
+  discard @[ppv]
+  var el: ref int
+  el = [ppv][0]
+  echo el != nil
+
+t17712()