Revert "fixes #22923; fixes =dup issues (#23182)"

This reverts commit fbb9ce4d5c.

compiler/ccgexprs.nim

@@ -2642,8 +2642,6 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
   of mTrace: discard "no code to generate"
   of mEnsureMove:
     expr(p, e[1], d)
-  of mDup:
-    expr(p, e[1], d)
   else:
     when defined(debugMagics):
       echo p.prc.name.s, " ", p.prc.id, " ", p.prc.flags, " ", p.prc.ast[genericParamsPos].kind

compiler/liftdestructors.nim

@@ -287,7 +287,7 @@ proc boolLit*(g: ModuleGraph; info: TLineInfo; value: bool): PNode =
 
 proc getCycleParam(c: TLiftCtx): PNode =
   assert c.kind in {attachedAsgn, attachedDup}
-  if c.fn.typ.len == 3 + ord(c.kind == attachedAsgn):
+  if c.fn.typ.len == 4:
     result = c.fn.typ.n.lastSon
     assert result.kind == nkSym
     assert result.sym.name.s == "cyclic"
@@ -322,14 +322,6 @@ proc newOpCall(c: var TLiftCtx; op: PSym; x: PNode): PNode =
   if sfNeverRaises notin op.flags:
     c.canRaise = true
 
-  if c.kind == attachedDup and op.typ.len == 3:
-    assert x != nil
-    if c.fn.typ.len == 3:
-      result.add getCycleParam(c)
-    else:
-      # assume the worst: A cycle is created:
-      result.add boolLit(c.g, x.info, true)
-
 proc newDeepCopyCall(c: var TLiftCtx; op: PSym; x, y: PNode): PNode =
   result = newAsgnStmt(x, newOpCall(c, op, y))
 

compiler/semmagic.nim

@@ -624,16 +624,6 @@ proc magicsAfterOverloadResolution(c: PContext, n: PNode,
     let op = getAttachedOp(c.graph, t, attachedTrace)
     if op != nil:
       result[0] = newSymNode(op)
-  of mDup:
-    result = n
-    let t = n[1].typ.skipTypes(abstractVar)
-    let op = getAttachedOp(c.graph, t, attachedDup)
-    if op != nil:
-      result[0] = newSymNode(op)
-      if op.typ.len == 3:
-        let boolLit = newIntLit(c.graph, n.info, 1)
-        boolLit.typ = getSysType(c.graph, n.info, tyBool)
-        result.add boolLit
   of mWasMoved:
     result = n
     let t = n[1].typ.skipTypes(abstractVar)