Don't emit "XDeclaredButNotUsed" hint for instances of types with custom destructor

[arnetheduck]

Description

Destructors are useful for RAII-style scope-based utilities. As such, they can be seen as a better and more flexible defer, given that they are reusable.

However, to use them as such, one needs to create an instance somewhere whose only purpose is to go out of scope at the right moment and that variable will never be used by regular code - the custom destructor itself is the usage.

type Defer = object

proc `=destroy`(x: X) = echo "this is the meaningful part of using Defer"

proc f() =
  var x: Defer # this should result in no hint

As an alternative, a separate hint could be given for the code above - this would allow applications to turn the normal "XDeclaredButNotUsed" hint into an error while leaving this usecase alone.

Nim Version

2.2.0

Current Output

Expected Output

Known Workarounds

No response

Additional Information

No response

[Araq]

Shouldn't this code be:

proc f() =
  var _: Defer