This is different from 'recover' (which was previously named 'consume'):

```
  (1)	consume <name | attr> [ with <expr> ]
```

- The operand can either be a *name* an *attribute*.

- if the operand is a cypclass or a pointer the value NULL
  is assigned to it; else the operand keeps its old value.

- The resulting value of 'consume' is the old value of the operand.

- The resulting type is the type of the operand seen as an rvalue,
  i.e. the same type except for 'iso' which is seen as 'iso~'.