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NilPy: @property and @x.setter inside a class

Hangs off [[feature-nilpy-corpus-uforth]]. uforth's wall as of 2026-07-20, at uforth.py:384, after float()/None-local landed.

@property
def base(self) -> int:
    b = self.memory[SYS_BASE_ADDR:SYS_BASE_ADDR + 8]
    return int.from_bytes(b, "little", signed=True)

@base.setter
def base(self, value: int) -> None:
    ...

Currently PyParseClass's body loop errors on any @ inside a class: unsupported decorator inside class (only @dataclass on classes) (pyparser.inc, search that message).

Census

Exactly 2 properties, each with a getter AND a setter (compiling, base), plus the 11 @dataclass uses that already work. Both map a Python attribute onto uforth's byte memory, so both directions are genuinely used — a read-only implementation does not get past this.

Recommended shape — reuse Pascal's real properties

The dialect already has class properties, and the shared parser already dispatches a named property's READ and WRITE through its accessor methods (FindUProp in parser.inc, e.g. the self.x path). So the frontend only has to REGISTER one:

That gets self.base and self.base = v working with no new lowering.

The one real obstacle — the name collision

Python names the getter and the setter both base. Pascal needs two distinct methods, so the accessors must be mangled (e.g. base -> __prop_get_base / __prop_set_base) and the property itself keeps the plain name base.

PyParseMethod(ci) takes no name override and reads the name from the token stream, and PyRegisterClassMembers (the member PRE-PASS, pyparser.inc:4795) independently registers method names the same way. Both have to learn the mangled name or they will disagree — the pre-pass registering base twice is what makes the second def base collide today. Threading an optional name-override through those two is the bulk of the work; the property registration itself is a few lines.

Do NOT try to avoid the mangling by registering a method base and a property base together: the getter/setter pair still collides with each other, and member lookup order between properties and methods becomes load-bearing.

Gate

make test-nilpy green with a .npy case diffed against CPython covering BOTH directions (a read and a write, and a write whose effect is observed through a later read) + --tier quick + self-host byte-identical + make fpc-check clean relative to HEAD.

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