More specific inline dict type inference can fail on 1.17.0

Bug Report

More specific inline dict type inference can fail on 1.17.0.

To Reproduce

The following fails on 1.17.0 but is fine on 1.16.1 (the playground link uses master as 1.17.0 isn't available there):
https://mypy-play.net/?mypy=master&python=3.13&gist=7e77b89fe5f9cb7e548c4ef83b3783c1

Revealing the type for the inline dict gives:

• 1.16.1: builtins.dict[builtins.str, Union[typing.Collection[builtins.str], None]]
• 1.17.0: builtins.dict[builtins.str, builtins.dict[builtins.str, builtins.list[Any] | None] | builtins.dict[builtins.str, builtins.str] | builtins.str | None]

Expected Behavior

No mypy errors.

Actual Behavior

main.py:11: error: Dict entry 0 has incompatible type "str": "None"; expected "str": "str"  [dict-item]
main.py:12: error: Dict entry 1 has incompatible type "str": "list[Never]"; expected "str": "str"  [dict-item]
Found 2 errors in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.17.0
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.13.5

Inizia con la riproduzione collegata in mypy playground e confronta il suo comportamento su 1.16.1, 1.17.0 e master. L’issue non indica alcun file o test del repository, quindi segui il percorso di inferenza dei tipi dei dizionari inline a partire dagli errori riprodotti; il lavoro è completato quando l’esempio non produce errori mantenendo il tipo inferito previsto.