On 2020-11-27 01:12, Ned Batchelder wrote:
On 11/26/20 6:44 AM, 3mi...@gmail.com wrote:
Add something like Move type hint to typing module. It will tell the analyzer
that the input parameter of the function is moved and can not be used after.
For example:
```
def f(d: Move[dict]) -> dict:
d['a'] = 2
return d
d = {1: 2}
f(d)
print(d[1]) # mistake, using of moved value
Maybe I'm behind the times on the latest thinking in programming
languages. I'm not familiar with "move semantics". Can someone explain
what is wrong with the code above? What is the mistake? `print(d[1])`
will work perfectly fine. The function changes the 'a' key, and then we
access the 1 key. Should the example have used the same key in both places?
d is moved into function f. f does return d when it exits, moving it out
back again, but as the caller doesn't bind to it, it's discarded.
Move semantics is a way of ensuring that there's only one "owner", which
makes garbage collection simpler; when an object is discarded
(dereferenced) by its the owner, it can be garbage-collected.
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