Change UnpackError with UnpackDefect (#14457)

* Change `UnpackError` with `UnpackDefect`

The deprecation warning for `UnpackError` exception raised by some
`inline` procedures in the Nim standard library propagates to the user
code. If the user code has a requirement for building without warnings
this is a problem for the successful execution of the tests. In order
to resolve this, all occurrences of `UnpackError` in the Nim code base
are changed to `UnpackDefect`. Only the type alias is retained to not
break other people's user code since `UnpackError` is exported type.

* Remove the catching of `UnpackDefect`

Defect exceptions should not be cached, because they indicate problem in
the API usage. The code in `nimblesocket.nim` is rewritten to first
check whether there is a value set into the `knownDomain` variable from
the `Option` type before usage.

lib/pure/nativesockets.nim

@@ -445,9 +445,10 @@ proc getSockDomain*(socket: SocketHandle): Domain =
   if getsockname(socket, cast[ptr SockAddr](addr(name)),
                  addr(namelen)) == -1'i32:
     raiseOSError(osLastError())
-  try:
-    result = toKnownDomain(name.sin6_family.cint).get()
-  except UnpackError:
+  let knownDomain = toKnownDomain(name.sin6_family.cint)
+  if knownDomain.isSome:
+    result = knownDomain.get()
+  else:
     raise newException(IOError, "Unknown socket family in getSockDomain")
 
 proc getAddrString*(sockAddr: ptr SockAddr): string =

lib/pure/options.nim

@@ -40,7 +40,7 @@
 ##    assert found.isSome and found.get() == 2
 ##
 ## The `get` operation demonstrated above returns the underlying value, or
-## raises `UnpackError` if there is no value. Note that `UnpackError`
+## raises `UnpackDefect` if there is no value. Note that `UnpackDefect`
 ## inherits from `system.Defect`, and should therefore never be caught.
 ## Instead, rely on checking if the option contains a value with
 ## `isSome <#isSome,Option[T]>`_ and `isNone <#isNone,Option[T]>`_ procs.
@@ -178,11 +178,11 @@ proc get*[T](self: Option[T]): lent T {.inline.} =
       a = some(42)
       b = none(string)
     assert a.get == 42
-    doAssertRaises(UnpackError):
+    doAssertRaises(UnpackDefect):
       echo b.get
 
   if self.isNone:
-    raise newException(UnpackError, "Can't obtain a value from a `none`")
+    raise newException(UnpackDefect, "Can't obtain a value from a `none`")
   result = self.val
 
 proc get*[T](self: Option[T], otherwise: T): T {.inline.} =
@@ -208,11 +208,11 @@ proc get*[T](self: var Option[T]): var T {.inline.} =
       a = some(42)
       b = none(string)
     assert a.get == 42
-    doAssertRaises(UnpackError):
+    doAssertRaises(UnpackDefect):
       echo b.get
 
   if self.isNone:
-    raise newException(UnpackError, "Can't obtain a value from a `none`")
+    raise newException(UnpackDefect, "Can't obtain a value from a `none`")
   return self.val
 
 proc map*[T](self: Option[T], callback: proc (input: T)) {.inline.} =
@@ -411,7 +411,7 @@ when isMainModule:
       check some("a").isSome
 
     test "none":
-      expect UnpackError:
+      expect UnpackDefect:
         discard none(int).get()
       check(none(int).isNone)
       check(not none(string).isSome)