config: exclude multiple inheritance from JSON loading typing#4178
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behrmann merged 1 commit intosystemd:mainfrom Feb 18, 2026
Merged
config: exclude multiple inheritance from JSON loading typing#4178behrmann merged 1 commit intosystemd:mainfrom
behrmann merged 1 commit intosystemd:mainfrom
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As pointed out in [1], the reason that ty cannot infer that the assignment of the dict instance s to the dict j when loading JSON after checking that s is instance of dict, is because multiple inheritance is a thing and the passed in object could be a dict that doesn't have string keys, but does have a read method. So let's be explicit and disallow these unhandled cases. This also fixes that the order of these branches is not stable against reordering with pyright and type checking fails if e.g. the check for the read attribute is moved above the dict instance check. [1] astral-sh/ty#1475 (comment) [2] astral-sh/ty#1578
daandemeyer
approved these changes
Feb 18, 2026
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As pointed out in [1], the reason that ty cannot infer that the assignment of the dict instance s to the dict j when loading JSON after checking that s is instance of dict, is because multiple inheritance is a thing and the passed in object could be a dict that doesn't have string keys, but does have a read method. So let's be explicit and disallow these unhandled cases. This also fixes that the order of these branches is not stable against reordering with pyright and type checking fails if e.g. the check for the read attribute is moved above the dict instance check.
[1] astral-sh/ty#1475 (comment)
[2] astral-sh/ty#1578