suppress incorrect var T destructor warnings for newFinalizer in stdl…

…ib (#22810)

in `std/nre`
```nim
proc initRegex(pattern: string, flags: int, study = true): Regex =
  new(result, destroyRegex)
```
gives incorrect warnings like

```
C:\Users\blue\Documents\Nim\lib\impure\nre.nim(252, 6) Error: A custom '=destroy' hook which takes a 'var T' parameter is deprecated; it should take a 'T' parameter [Deprecated
```

compiler/semmagic.nim

@@ -526,7 +526,9 @@ proc semNewFinalize(c: PContext; n: PNode): PNode =
           selfPtr.add transFormedSym.ast[bodyPos][1]
           selfPtr.typ = selfSymbolType
           transFormedSym.ast[bodyPos][1] = c.semExpr(c, selfPtr)
-        bindTypeHook(c, transFormedSym, n, attachedDestructor)
+        # TODO: suppress var destructor warnings; if newFinalizer is not
+        # TODO: deprecated, try to implement plain T destructor
+        bindTypeHook(c, transFormedSym, n, attachedDestructor, suppressVarDestructorWarning = true)
   result = addDefaultFieldForNew(c, n)
 
 proc semPrivateAccess(c: PContext, n: PNode): PNode =

compiler/semstmts.nim

@@ -1904,7 +1904,7 @@ proc bindDupHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp) =
   incl(s.flags, sfUsed)
   incl(s.flags, sfOverridden)
 
-proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp) =
+proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp; suppressVarDestructorWarning = false) =
   let t = s.typ
   var noError = false
   let cond = case op
@@ -1923,7 +1923,7 @@ proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp) =
       elif obj.kind == tyGenericInvocation: obj = obj[0]
       else: break
     if obj.kind in {tyObject, tyDistinct, tySequence, tyString}:
-      if op == attachedDestructor and t[1].kind == tyVar:
+      if (not suppressVarDestructorWarning) and op == attachedDestructor and t[1].kind == tyVar:
         message(c.config, n.info, warnDeprecated, "A custom '=destroy' hook which takes a 'var T' parameter is deprecated; it should take a 'T' parameter")
       obj = canonType(c, obj)
       let ao = getAttachedOp(c.graph, obj, op)