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[ty] Guard recursive constructor bindings by receiver - #27958
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Track active constructor receiver types while resolving call bindings and recover with a gradual signature when a receiver repeats. Preserve descriptor-sensitive and finite generic constructor chains, along with downstream argument checks. Add regression coverage for decorator-induced, mutual, and generic constructor cycles and the finite cases that must not be truncated. Fixes astral-sh/ty#4347.
Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 97.68%. The percentage of expected errors that received a diagnostic held steady at 93.44%. The number of fully passing files held steady at 109/136. |
Memory usage reportMemory usage unchanged ✅ |
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charliermarsh
approved these changes
Aug 21, 2026
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Summary
Fixes astral-sh/ty#4347.
Constructor signature expansion can revisit the same receiver through class-valued
__new__,__init__, or metaclass__call__, recursively expanding bindings until ty overflows the stack. A generic decorator that replaces__new__withtype[C]is one way to trigger this.Track active constructor receivers during binding expansion and return a gradual signature when an exact receiver repeats, letting the enclosing constructor supply the instance return type. Comparing full receiver types preserves finite generic chains and descriptor overloads that distinguish
Cfromtype[C].Test plan
Extend the constructor mdtests to cover:
__init__, metaclass__call__, and callable instances.__init__argument validation and known non-instance return types from__new__or metaclass__call__.The full
ty_python_semantictest suite, Clippy, and applicable repository hooks pass.