QUndoStack does not execute obsolete undo command despite what the docs say

The docs for QUndoStack::undo says:

 After the command is undone, if QUundoCommand::isObsolete() returns true, then the command will be deleted from the stack.

But that doesn't line up with the source code:

if (!cmd->isObsolete())

    cmd->undo()

which means that the command is not undone at all if it's obsolete.

It's useful to be able to undo and delete a command in one step. One example use case for this is when you're creating a macro and something goes wrong in the middle.