implicit-any-empty-container raised on chained assignment

[pkerichang]

Describe the Bug

pyrefly is able to infer the empty container type in the following code:

key: str = "foo"
table: dict[str, dict[str, int]] = {}
foo = table.get(key, None)
if foo is None:
    foo = {}
    table[key] = foo

however, if chained assignment is used to save one line, then pyrefly now reports an implicit-any-empty-container error:

key: str = "foo"
table: dict[str, dict[str, int]] = {}
foo = table.get(key, None)
if foo is None:
    foo = table[key] = {}  # pyrefly reports error here

The chain assignment order does not matter, this also fails:

key: str = "foo"
table: dict[str, dict[str, int]] = {}
foo = table.get(key, None)
if foo is None:
    table[key] = foo = {}  # pyrefly reports error here

Sandbox Link

No response

(Only applicable for extension issues) IDE Information

No response

[ak4-sh]

I can take a look at this! #claim

[github-actions]

@ak4-sh you've claimed this issue — it's now assigned to you. Thanks for picking it up! 🎉